Document xdM9L6127owzrrX7ZNj92YRG1

+Human Toxicol. (1989). 8. 173-203 U N P 010376 b l / 2 7S33I2EH Polychlorinated Dibenzo-p-dioxlns and Polychlorinated Dibenzorurans: The Risks to Human Health. A Review -V > \ ^ S.A. Skene, I.C. Dewhurst & M. Greenberg Department of Health, Medical Toxicology and Environmental Health Division, Hannibal House. Elephant and Castle, London, SE1 6TE, UK 1 PCDDs and PCDFs are ubiquitous and persistent in the environment. They are to be found in body tissues of both humans and animals. 2 The most extensively studied PCDD is 2,3,7.8-TCDD. It has been shown to produce a wide range of effects and is considered to be a (non-gcnoloxic) carcinogen in animals. 3 Studies into the mechanisms of toxicity so far reveal that there is involvement of a specific receptor (Ah), however further work is required to elucidate (he mechanisms of the various effects. 4 Reports on a number of human exposures to PCDDs and PCDFs are described. Results from human epidemiological studies are difficult to interpret: there have been problems in methodology: there has been inadequate information on intake, and exposures have often been to mixtures of PCDDs and/or PCDFs together with other related compounds. 5 Many regulatory authorities faced with the problem of providing an index of risk from exposure to mixtures of PCDDs and PCDFs have employed the concept of `TCDD equivalents'. 6 Whether or not PCDDs and PCDFs pose a significant human health risk at current levels of exposure they remain of considerable interest to the toxicologist. hco V" CO 00 b* - Chemistry, sources and environmental fate of PCDDs and PCDFs Chemistry The polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are two series of tricyclic aromatic compounds. PCDDs and PCDFs can loosely be described as chlorodibenzo derivatives of the basic chemical structures p-dioxin and furan, respectively (Figure ]). Related bromine substituted dibenzo-p-dioxins and diben zofurans also exist as contaminants of commercial chemicals, but are not discussed in this paper. The number of chlorine atoms can vary between one and eight and there are many positional isomers with 75 PCDDs and 135 PCDFs, in the latter case, the large number is due to the asymmetry of the basic dibenzofuran molecule. The information available .on the chemical and physical properties of PCDDs and PCDFs suggests that both series of compounds are extremely stable, in pure form, even on heating up to 70CPC. There are some general trends regarding volaiility and solubility in polar solutions - both decreasing with a* cty ct* x + Cly S 8 Flfurt I Structures of PCDDs and PCDFs ay the increase in number of chlorine atoms. The most extensively studied isomer is 2,3,7,8-TCDD. This isomer has a melting point of about 305*C and a boiling point of 421'C. 2,3,7,8-TCDD is lipophilic and is almost insoluble in water. The vapour `pressure is very low and therefore it tends not to s'ttMize readily.1 There are no current technical uses for PCDDs or PCDFs, although they have been synthesized In the laboratory in order to generate analytical standards.1 PCDDs and PCDFs very rarely occur in the environment as the only products from any one particular source. They often occur with other I 174 S.A. SKENE el ! related polyhalogenaled species such as poly charge ratio {ml2 ) (or the mass fragments delected) chlorinated biphenyls (PCBs) polychlorinated ter- and quantitative information (front the magnitude phenyb (PCTs). chlorinated phenols (e g tri- of the response) chlorophenol (TCP) and pcnlachlotophenol (PCP)). The use of immunoassay techniques have been and phenoxy acetic acid herbicides (e g. 2,4-D and described in the literature and although still - ' ' requiring some further development, they show -v */ The advances achieved in analytical techniques considerable potential Fishbein' described a radio over recent years have allowed for much improved immunoassay technique for the determination of detection limits for both PCDDs and PCDFs 2.3,7.8-TCDF in biological tissues Ihe detection Environmental samples can now be analysed down limits of this assay are reported to range between to the parts per trillion level (ppt) or 1 in 10,i. or in 20 pg/g (ppt) to 4 0 ng'g (ppb) for this particular some cases down to the parts per quadrillion level isomer. Values for TCDF in various Aroclors (ppq) or I in 1015. (PCBs) and tissues dcictmincd by radioimmuno There are essentially three stages in the assay are reported to correlate with those obtained analytical determination of PCDDs and PCDFs in by GC/MS environmental and biological samples. Stage I Because it is necessary to measure PCDDs and involves the extraction of the chemicals from the PCDFs at extremely low concentrations and matrix. The technique used will depend upon the because these chemicals often occur in very matrix involved. For example adipose tissue or complex mixtures, the analytical technique often human breast milk samples require a simple solvent requires extraction and concentration by factors of extraction procedure: but for municipal incinerator several thousand in order to brine the concentra By-ash. where the chemicals are more strongly tion of PCDDs and PCDFs up to measurable bound to the matrix, it is more usual to treat the levels. Other organic compounds that are present matrix with acid prior to soxhlet extraction with (often at much higher concentrations) can interfere toluene.' with their determination " Stage 2 of the procedure is to clean-up the The determination of PCDDs and PCDFs in extracts obtained from stage I. The degree of other chlorinated organic samples, such as clean-up required depends upon the sample matrix, phenoxyalkanoic herbicides presents a number of the subsequent analytical instrumentation used, analytical problems.7 * The presence of predioxins- and personal preference of the analyst. The effic in such chemicals can lead to the formation of iency of the extraction jnd clean up procedures -an PCDDs duimg the .tii..;ti:.il proceiliite. thus be determined by the use of "C internal standards resulting in increases in the apparent amounts and calculating the percentage recovery of the present. Special adaptations to the analytical tech material to correct for PCDDs and PCDFs which nique are required when chemicals which are may have been lost during the procedure. The total structurally related to PCDDs and PCDFs are recovery of both PCDDs and PCDFs depends upon present, as such chemicals may have similar the particular isomer in question. The procedure extraction properties.7 may however be subject to certain inaccuracies, The importance of quantitative analysis of either because of the PCDD or PCDF isomer used PCDCs and PCDFs has increased over recent or because of adsorption of the standard onto the years. The problems involved are very complex matrix, thereby decreasing the extraction effic- because of the large number of interfering iency.1,4 chemicals present; the extremely low detection The final stage in the process is to analyse limits often required: and the large number of quantitatively the cleaned-up extract for the isomers, representing a wide range of toxicological presence of PCDDs and PCDFs The procedure properties and potencies At present quantitative used will depend upon the accuracy required for determinations of PCDDs and PCDFs have mostly the final result: for detection of PCDDs and PCDFs been conducted on total isomers (homologues) e g down to the ppt concentration, the usual procedure total TCDDs, TCDFs. PeCDDs. PeCDFs. etc., is gas chromatography coupled to a mass spectro with only selective isomer analyses conducted on meter (GCVMS). The retention lime observed on those congeners specifically substituted at the the chromatogram provides the qualitative evi 2,3.7,8 positions Individual isomer analysis is dence for the presence of a particular isomer (i.e. extremely costly and therefore rarely carried out specific PCDD/PCDF) or homologue (i.e. total routinely. However, the results of collective isomer p . PCDDs/FCDFs with a specified number of chlorine analyses are none the less helpful in mapping out- atoms). The results obtained from the mass major areas of contamination, althoueh the task of T v !. . spectrometer (MS) provide both additional qualita- more accurate 'risk assessment- from such data 'i* '- .five information (from observation of the mass to becomes more difficult If 3 GENP 01037 / HI S i PCDDS AND PCDFS: RISKS TO HUMANS 175 Sources were key intermediates in the production of PCDDs and PCDFs have been delected in a phenoxv acetic acid herbicides (2.4-D and 2.4.5-T). number of emissions resulting from combustion Other chemicals of concern include PCBs. which sources. The detection of these chemicals in such a are known to contain high levels of PCDFs. wide range of samples led to the formulation of the 'trace chemistries of fire' hypothesis, which states Environmental fate o f PCDDs and PCDFs - that numerous products arise in trace amounts Environmental and biological monitoring has during the many chemical reactions that occur revealed that PCDDs and PCDFs occur fairly during combustion Identified sources that have ubiquitously. 2.3.7.8-TCDD has tended to be the aroused a great deal of public concern include most widely studied of these chemicals, however emissions from municipal waste incinerators, indus because of the chemical and physical similarities trial waste incinerators, in particular PCB waste within the group of PCDDs and PCDFs. it is likely and also PCB fires Other identified sources of that a general trend will be seen with the other PCDDs and PCDFs include exhaust emissions from PCDDs and PCDFs. diesel and petrol fueled vehicles.10'11 The latter is Because of their chemical nature. PCDDs and associated with the lead content of fuels (particu PCDFs are strongly bound to particulate matter, larly as these contain a dichloroethane scavenger, a this will influence the way they move through the precursor of both PCDDs and PCDFs) and is much environment. 2.3.7.8-TCDD is tightly bound to reduced in vehicles with catalytic converters.15 peaty soils high in organic matter and usually Very small amounts have also been delected in remains tn the upper layers of such soil types, cigarette smoke and charcoal-grilled steaks 13 undergoing very little vertical migration 17 There Research into the formation of PCDDs and PCDFs fore transport of 2.3.7.8-TCDD in this environment from combustion sources has indicated that the will generally occur by mobilization of soil particles presence of these chemicals will depend upon the Levels of PCDDs and PCDFs in water per se are conditions of the combustion process. In particular, thought to be very low, since adsorption to the molecular structure and chlorine content of the particulate sediment seems to predominate. How fuel, the presence of precursors and contaminants, ever, suspension of paniculate matter may occur. the reaction temperature within the combustion Animals living in this environment may acquire zone and post combustion zone, the residence lime these chemicals directly through the ingestion of of re ir'an! and intermediate products in the high sediment or indirectly from the tro 'Me food chain itn.pcijture zone, mixing etfiuency ol air with There arc few data on levels of PlD D s/IC D Fs in fuel, airfuel ratio, fuel-feed size and finally the air. Information so far available indicates that the presence of metals in the process acting as levels in this medium (as for water) are low. It is catalysts.1' generally believed that uptake of PCDDs/PCDFs The possibility of formation of PCDDs and by inhalation may not be an important source of PCDFs from municipal waste incineration has been exposure.1* recognized for some years, following their deter- It has been suggested that (he primary source of ^ mination in fiv ash1' and subsequently, in emissions exposure to man of PCDDs and PCDFs is from from such sources They may occur as a result of combustion and that uptake occurs from the V chemical precursors in the fuel supply e g. PCBs or consumption of foods such as fish, dairy produce chlorophenols and/or via de-novo synthesis from and meat.1* Levels of PCDD and PCDFs in the pyrolysis of chemically unrelated chlorinated vegetable matter are reported to be generally very compounds It has been suggested that chlorine- low. and where contamination has been found, it is containing plastic materials such as PVC may largely on the surfaces, arising from surface deposi provide the largest source of organic chlorine, and tion rather than by uptake from the soil 10 this has resulted in concern over other possible The main degradation process for dioxins and PCDD/PCDF sources such as hospital waste incin- presumably dibenzofurans is by photolysis, involv 1 erators. which burn large quantities of PVC.'* ing surface exposure to UV light, in the presence of The presence of PCDDs and PCDFs as a hydrogen donor. Such donors include natural unwanted by-products in a number of commercially substances such as leaf waxes, natural organic films available industrial chemicals has added to the on water surfaces, pesticides or formulating agents general public concern over these substances, in as well as the presence of otherwise undesirable particular their presence as impurities from the pollutants such as spilled oils.51'25 The half-life of manufacture of many industrial and agricultural 2.3.7.8-TCDD in soil, in the absence of UV light is chemicals based upon chlorophenols and chlor estimated at 10 years.13 thus indicating that any inated aromatic hydrocarbons Chlorophenols have other degradation processes take place at a much been used as fungicides, herbicides, slimicides. and slower rate. __ X m S.A. SKENE et al. Qjoxns do gradually volatilize fretti soil and receiving 0.05-0.1% of the administered intra plant surfaces, but the importance of this route to peritoneal dose. Changing the route of administra 'dear* dioxins Troni the environment is unknown. tion to oral or sub-cuiancous apparently decreased Tbe rate of volatilisation depends upon several the amount in the fetus, but did not alter the environmental properties, as.well as on the degree. .distribution pattern, demonstrating the majority of 0 r chlorination of the molecule." A few fungal and the dose to be In the fetal liver. In a further study bacterial (pedes hove been found to be capable of 2.3.7.8- TCDD was also shown to transfer to the degrading dioxins, although their importance rela pup via the milk.41 tive to other degradation processes is A dietary study with PCDF mixtures demon unknown ." *3i strated the ability ol these substances to cross the placenta in female ddN mice, bui the greatest Animal studies uptake was shown in the suckling pup. indicating milk to be ihe major vector.41 The majority of the Absorption, distribution and excretion absorbed dose in the dam was found in the liver. Animal studies have demonstrated that absorption The relative isomer distributions in the pups were of 23,7,8-TCDD by the gastrointestinal tract and reported to differ from those in the diet, with through the skin depend upon the vehicle used.7* 23.7.8- TCDF and 2.3.4,7,8-PeCDF being prefer For other PCDDs and PCDFs, the isomer and entially stored. chlorination number will also be important. The 2,3,7,8-TCDD is metabolized to a very limited bioava lability of these chemicals from soil will extent, although glucuronide conjugates44,41 and depend upon the soil type and has been said to vary hydroxy derivatives*'1 have been identified. Tbe between 1 and 70% when contaminated soil was metabolism of 2.3.7.6-TCDD has been related to administered to guinea pigs.7* PCDDs and PCDFs cytochrome P-450 monooxygenase activity and are strongly adsorbed onto incinerator fly ash and there is evidence to suggest P-45Q/P-448 inducers, they are more readily absorbed by animals admin such as phnobarbital may influence (he rale of istered solvent extracts of fly ash than by those 2.3.7.8- TCDD meiabolism. The rate of 23,7.8- receiving fly ash itself.70 TCDD meiabolism by rat liver microsomes has The tissue distribution of 2,3,7,8-TCDD varies been reported to be I04-fold slower than that of with species," J l dose11, time after dosing and Benzo[a]pyre ne.1* Metabolites of 2,3,7,8-TCDD previous exposure to 2,3,7,8-TCDD.11 Monkeys (2-hydroxy-3.7,8-lrichlnrrutibcnzo-p'dioxtn and 2- and guinea pigs concentrate ' ,J,7.S-TCDD in the IniW xy-l ,.' ,?..vl..li.nim iit.:.ibi:nzo*;M!iv,\in) a rt fat, muscle and skin, whereas other species concen considered to be over 100 times less potent than Ihe trate TCDD to a greater extent in the liver." parent compound.41 For other dioxins, mono- and Radio-labelled TCDD administered intravenously di-hydroxy derivaiives of dibenzo-p-dioxin; to mice and rats" *" has been found to concentrate 1-CDD; 2-CDD; 23.-D CD D ; 2,7-DCDD; 1.2,4- in the nasal turbinates; a site of 2,3,7,8-TCDD- Tri-CDD and 1,2,3,4-TCDD have been reported to induced tumours in rats. be excreted by rats,4' however no metabolites of The majority of 2,3,7,8-TCDD in the liver is OCDD have been detected.4*,M A scheme has associated with the microsomal fraction.11 Tbe been proposed with a 23-epoxide intermediate, distribution of .2,3,7,8-TCDF differs from 2,3,7,8- which cannot be readily formed bv compounds TCDD in that it concentrates in fat and skin more substituted at the 2.3.7,8-posilions. Unidentified than liver, although the distribution varies with polar metabolites of 23,7,6-TCDF have been time, repeated dosing'1 and sire o f dose." reported in the urine of monkeys, rats and guinea Tbe retention of PCDDs and PCDFs by the liver pigs.11*" -51 No metabolites of other PCDFs have increases with chlorination (between four and six been reported in the (issues ol treated animals, chlorines), with PCDFs being retained longer than which would indicate metabolites are readily PCDDs. The retention in fat however, is longer for excreted. PCDDs1* indirating differing rates of metabolism. Tbe excretory half-life of 2,3,7,8-TCDD has Nishirumi & Masuda40 demonstrated liver accumu been found to vary with species and is not always lation in rats of 1,2,3,4,7,8-HxCDF and 23.4,7,6- related lo its relative toxicity [or that species." The PeCDF to be dose-dependent, with an increased half-life values in rodents have been found to range proportion of the dose retained at low dose levels. between 10 and 36 days" and in monkeys a value 2,3,7,8-TCDD has been delected in the fetuses of 1000 days has been proposed.51 Biliary excretion of dosed female rats41 although the concentration has been proposed as a major route of 2,3,7,8- was lower than in the mothers. Nau & Bass41 TCDD elimination:51 2,3.7.8-TCDD is also reported the transfer of ,4C 2,3,7,8-TCDD from excreted in the milk.41 The excretion of 23.7,8- pregnant NMRI mice to the fetus, with the fetuses TCDF also varies with species, but is comparatively v iv o /o PCDDS AND PCDFS: RISKS TO HUMANS 177 rapid, wilh half-lire values of 2 days in rats and 8 studies indicate that the total dose administered is days in the monkey.**"51 Metabolites of 2.3,7,8- probably more important than the size of a single TCDF generally appeared in ihe urine and bile, dose o r frequency of administration.57 The most *- whilst the faeces contained mainly unaltered extensively reported sub-acute study of 2,3,7,8- -2,3,7.8-TCDF------------- TCDD yet-published is ihat of'K o d b i'er of.5* This .. t-1 . v j'i. i , j... was a 13-week study in which young adult Sprague I V' Acute'toxicity '' The acute toxicity of 2,3,7,8-TCDD varies widely both quantitatively and qualitatively with species/ slrain/sex of the animals, the administration pro tocol, and even, between research groups. How ever. certain aspects are common to all animals studied: progressive body weight loss; thymic atrophy (especially of the cortex), a considerable delay from administration to death (up to 43 days) and gastrointestinal haemorrhages. Various signs which have been seen in one or more species administered a single dose of 2,3,7,8-TCDD in clude: reduction in food consumption (although this is not primarily responsible for the decrease in body weight); rough coat; dehydration; muscular necrosis; loss of fat deposits; hypocellular bone- marrow; haemolysis; changes in overall serum protein levels and their ratios; testicular degener ation, particularly of the seminiferous tubules which develop mull nucleated giant cells; necrotic spermatocytes and spermatozoa; distention of the gall bladder; bile duct proliferation; an increase in hepatocyte size together with a temporary prolifer ation of their rough endoplasmic reticulum and increase in Ihe prominence of the nucleolus (indicative of protein synthesis); fluorescence of liver and bones, indicating excess porphyrin deposi tion; fatty droplets In the phetatocyiei; ascites; hyperplasia of the renal pelvis and inflammatory infiltration of organs.11 LDjo values for 2,3,7,8-TCDD In animals, when administered by gavage, have been repotted to vary between 0.6 pg k g '1 in Hartley guinea pjgs (the most susceptible species) to 5031 pg k g "' in Ihe Golden Syrian hamster.1* 2,3,7,8-TCDD is undoubtedly the most toxic and most extensively studied of all PCDDs and PCDFs, although the limited information available on the others indicate that the clinico-pathological signs seen following acute administration were very simitar*0 5 but the potencies vary considerably, depending upon the isomer in question and also the species tested,*4 The most acutely toxic isomer studied In the PCDF series is 2,3,7.8-TCDF,,which has been reported to have an oral LDM of 5 pg kg"' in the guinea pig,*4 though recent work oh 2,3,4,7,8-PeCDF indicated this to be more potent in certain assays.54 Dawley rats were exposed to 2,3,7,8-TCDD at doses of 0.001, 0.01, 0.1 and 1 pg k g " ^ " 1, for 5 days per week, by gavage. At the end of the treatment some of the rats were killed and aulopsied, whilst others were allowed a 13-week recovery period. Female rats were more sensitive than males. A no-effect level was identified at 0.001 pg kg"1 (equivalent to a total dose of 0.065 pg kg"1) with a total dose or 0.63 pg kg-5 producing only small changes in relative liver weights. Effects observed at the highest dose levels for both male and female animals included severe weight loss, haematological changes, increase in urinary porphyrins, increased relative liver weights associated with gross changes, increased lipid content and changes in the size .and shape of hcpaiocyies. Other changes noted were decreased thymus weight, thymic involution and a decrease in food intake and females experienced uterine changes. Some reversal of these effects were shown following termination of treatment, in particular body weight (complete in females and partial in males) but no firm conclusions could be drawn from these findings. There are few published reports of sub-scute studies on other PCDDs. A 13-week study con ducted on a m ature of HxCDD isomen in rats and mice at doses of between 2.3 to 100 pg kg-1 body weight per week demonstrated weight loss, hepatotoxicity and thymic atrophy. H ie effects seen varied between species and between sexes in the rat.5* The production of chloracne-like lesions has been reported in hairless mice following dermal application of 2,3,7,8-TCDD.60 Four weeks follow ing treatment (O .lp g k g -1 in 0.1 ml acetone, three limes per week) the skin became hard and shiny with fine scales. Histologically, there was hyperkeratinization of the stratum coraeum, epi dermal hypetplasia. kcratinizaiion of ihe dermal cysts, reduction in sebaceous glands and lympho cytic infiltration of the dermis, A number of in vitro studies have also been used to study this effect.61-61 Schweiz el at.a studied the effects of several dioxins (2,7-DCDD, 1,2.3.4-TCDD, 2,3,7,8TCDD, HxCDDs and OCDD) on the production of comedone formation in rabbits' ears. The animals were exposed to the chemical for 5 days per week for 4 weeks. The most reactive of the chemicals was 2,3,7,8-TCDD (at a total dose of Sub acute toxicity 0.8 pg) followed by HxCDD (mixed isomers, at The responses of experimental animals in sub-acute dose of 200-1000 pg). The other chemicals failed *: o> & > I7S S.A. SKENE tl el. lo elicit Qresponse at the doses tested. However, as mucosa, bile ducts, pancreatic ducts, salivary ducts different solvents were used, valid comparisons are and most cpithclia; hyperplastic gastritis and ulcer not possible. ation of the gastric mucosa; squamous metaplasia Sub-acute effects of orally administered 2,3,7,8- and keralinization oi the sebaceous glands and hair TCDF in Rhesus monkeys, indicate that although follicles; keralinization of the meibomian glands; the signs of intoxication of this-PCDF-are similar to -- irregular "growlh- oITbe and'finger nails; haemor- 2.3.7.8- TCDD, it is 10-100 limes less toxic than its rhages in most tissues, dilation of the bile duct; an p c b fa equivalent,4* although a no-effect level increase in the number of mucus secreting cells of (NEL) has yet to be established. Mixtures of the gut, at the expense of the parietal and TCDFs. PeCDFs and HxCDFs, when administered zymogenic cells; cardiac enlargement; haemolysis in the diet to rats for 4 weeks, demonstrated and ascites. One monkey was essentially unaffec significant changes similar to those reported for ted; no changes in serum Itpid. cholesterol, protein, 2.3.7.8- TCDD, .globulin: albumin ratios or SGPT were found. Chronic toxicity Many of the non-eaicinogenie effects of chronic exposure of rodents to PCDDs are described in the studies relating to the carcinogenicity of these compounds. Results of these studies have been summarized in Table 1. A number of pathological effects typical of PCDD exposure have been described, although liver appears to be the major target organ. As vet it has not been possible to determine NELs for chronic toxicity of dibenzo-pdioxin, 2.7-DCDD. 2.3.7.8-TCDD and HxCDD. Administration of 0.001-1 pg k g ^ 'd " 1 of 2.3.7.8TCDD for 2 years caused an Increase in centrilobular fatly metamorphosis of the liver in male rats.64 Kodba el al.67 reported significant (PcO.OS) changes in the numbers of swollen hepatoevtet fincreases in females, decreases in males) in rats receiving 0.U0I pg k g ^ 'd "1 2,3,7,8-TCUD. flic lowest dose of HxCDD tnixlure (0.18 pg kg- , d " ') produced toxic hepatitis in both male and female rats.49 Dietary administration of 300 ppm of 2,7DCDD for 2 years in rats produced fatty metamor phosis of the liver and an increase in chronic murine pneumonia4* and 3000 ppm dibenzo-pdioxin in the diet for 2 years produced nephropathy in male rats and a fatty metamorphosis of the liver in females.4* The chronic effects of 2,3,7,8-TCDD and TCDF on non-human primates (Macaco muUata) have been described in a number of studies4*-90"93 with a number of similarities reported in the findings. Young Rhesus monkeys exposed to 2.3,7.8-TCDD in the diet (approximately 0.01 pg kg_ld _l) demonstrated periorbital oedema, loss of facial hair and eyelashes, accentuated hair follicles and dry scaly skin.91 After 6 months on this regimen, anaemia was also noted and by 9 months, haem orrhages and thrombocytopenia were detected. Between months 3-12, five of the original eight monkeys died, with death attributed lo the effects of pancytopenia. The following lesions were delec ted at autopsy; hypocellular bone marrow; hyper plasia; hypertrophy and metaplasia of the bronchial Carcinogenicily The available data on the carcinogenicity of PCDDs in rodents are summarized in Table 1. There appears to be very little, if any. data relating to carcinogenicity testing of PCDFs. Most dioxins tested demonstrated a carcinogenic potential, although dibenro-p-dioxin did not and preliminary reports of investigation* on OCDD would not be expected to show any tumour excess due to the short period of administration.'* The most potent rodent carcinogens yet tested appear to be 2J.7.8-TCDD and an HxCDD mixture. The commonest sites for tumour production are liver5*-49'4*'7* and also hard palate/nasal turbinates and longue for 2.3,7,8-TCDD.4, 2,3,7,8-TCDD is considered to be a very potent promoter95 however, other '-ulics on the nu-chanisin of 2,3,7,8-TCDD caicinogetiicily hate found it also to be a coca reinoxen,96 a weak carcinogen,9* a complete carcinogen, and an anlicarcinogen;'9 the effects varying with the model used. The current view on the mechanism of carcinogenicity oi 2.3,7,8-TCDD indicates that it is a nongenotoxic carcinogen, thereby justifying attempts lo identify a NEL. One suggested level comes from the rat feeding study reported by Kociba tt at.67 and is estimated at 0.001 pg k g ^ 'd '1. Mutagenicity 2,3,7,8-TCDD has been tested in a variety of mutagenicity test procedures with conflicting results and attempts at repealing positive studies have been unsuccessful. Detailed reviews of the muta genicity of 2,3,7,8-TCDD have been carried out by Wassom et al.10, EPA3* and Giri.*1 AH concluded that the results were equivocal and further studies were required. In a more recent review by Shu et of.*3 it was suggested that 2.3.7.8-TCDD Tails Into the category of 'non-genotoxic' carcinogens, which includes a number oi substances such as oesirogens, asbestos and compounds such as phno barbital and chlorinated hydrocarbons which have been shown to be carcinogenic in animals. The i I i , j i i ! . PCDDS AND PCDFS: RISKS TO HUMANS 17? Table I Chronic totlcilv end carcinopcnichy or PCDDi Compound D o if Spnift Tumour typf Other o b itn tsiota P lb fiiio -p :i l l o i l i L _ j ( n ) o r. ID OUDppm^ Mitt-----------NCI (WWJT* in diei N o n e------------------------------------------- _Dccitiii in bodrueifhi end -------decrease inaurvftal intop dote Caida. lateitiiiial renal fnOiminilion in remake. NCI 1U l" 5^Ktl of 10(Hlfiptn Rati in diet None Decrease inbodyeight end deciciic insurvival in inp date females. Incidence ol chronic murine pneumonia incicaicd end intrtaie in ncphrapalhv in male rail. J.TDCDD junior m ini ppm R ill NCI (lW ir indid None Decrease inbody eight. Hepalotie tctirni. Inclined chronic murine pneumonia and interstitial renal inflammation. Dettcise insurvival. NCI (I979j |" 50n0of 10Olflppm Femalemice None in did Dentate inbody atiiht. Hrpatofoak letton (focal netmhl NCI ItWal" fUDof 10(Oippm Mile mice mdiet Hepatocellular denomi ai both dfKcii leuLatmialimphrjma il .*1*It ppm Dent In body eight. HfcCDDmUlurr and M.J.7,1.9 NTPilWOr* 5 .J .J .I.3 n l, t' ~'/*eeV'1(iy M'P Ran Hepatocellular adenoma ind caic'cwm*ncoplattk oodulct it highdote in malt* nod all d w t in female. Foilriular cell adenorna ol thuoid inIon dtiu nulet, Occreate in body eight gain (dont 5.5 and 5 |if kg Lenf kriona (idenonutoai hyperplasia1. Icnic hepatitis. NTP (I9M>):I* 3.3 3. I J M l | bw",weck`, by Mile mice Hepatocellular idenomi and cateinoma/ncoplattk oodulei at high dote Nooven health effects. Fany tneumotphoiia and pifmentation ofBvti (highdote). \"n* irW * NTT [IVSO)*' in s.: 3 l i | l | bw" tek'1by l*P Skin painting Fini, le mice and S '1 n v rn health rfcr** Liver c-ttcinoma/neoptjuc noJiflcf in high K jrm aopoksrta duie group* Slice None None 1J.T.ITCDD NTP(IVS)" 0.001 p | the timet per eek ikin piinliny Mile mice None Survival rateafjghdy drrretieiL NTP(IVS)** 0.003p | three limn per onk skin p*intin| Female mice Rbrourcoma of integumentary intern Survive) rate* atightlpdecrraieda NIPCWSI)- 0.01,0.03.0.3. 1b**1"*V1 eek"l by !'* !* Slik riTt Thyroid loninlav ceHadenoma (high dote] Dcret inbode weighl gain. Toaicbcpaiiiii (high do) Other IKtr effectfocal cellularchange (highdote) and fatly roeiimorphotii. A denomatou bpctplatii ol King. Hipcrketaiiniiatton of tiomadi (U |hdQ K )t NTP 1191-1" 0.01.005,0.5 H I** tiw-Vmtck-'by Feraik rati Liver oeoplnik nodufe/careinomi (highdose) piiohaiy adrnoma (to* dove only) Decreaie Inbodyeight |iin. Tenichepatitis (high Am t). Other Gr i ettecii (local ccUulu chanyc andtattymetamotphents [tacepc a< highdote kvcij). Atknomalous hyperplasia of tuny. Derreate tn hyperplasia of bile duct. Increase in lymphocytic inflimmitonr infitratioqof lachrymal glind. Decrease inminceiliuiionol tenal pelrii. ISO S.A. SKENE fl flt Tabla I Continued Ctwnpoumd (M i Doit rn r(tw 2 r K V / UI '-*. .j * 0.01. 0.05, 0.5 b i ' L c x k '1by I*np rm -dw ar 0.04.0.1.US by P "P Kocitufta/. (I9B)*1 O.OOL 0 0 1 ,0 .1 pg Lg In Ihe diel Koribaeral. (isnsj*' .0.001,0.01,0.1 > | t | b * ',d ' *io lie diet Speda Turrutut frpe Other ohtfrreiio/u Male mice BcpalmDcdar adenoma/cairnomi (high dose). Atveolar/bioodUolar denoma (hijS dose] Increased local rakiftntioQ of brain decreased focal calcification of basal ganglia. Toiic hepatitis (high dose). Lymphocytie inflammatory iuuliatioa of hm| (including bronchui) salivary glanits and kidney. Female mice Hcpaiocellular denomVciteinomi (h lji dose). Thyioid follicular ceti adenoma (high dose). Ititiiocyiic lympbmi (hi|h dote). Increased local cafdficitioo of hram; decreased focal calcifeaiion of basal ganglia. Toiit hepatitis (high dose), Lvmphoeyiie inflimmaiory infillratioQ ol lung (Deluding bronchus) salivary glands and kidney Decrease in lymphocytic inflammatory infiltration of multiple organs Increased calcification of renal pelvis. M a te rna Squvpom celi calcinomi of hard ptlne/nitil littbinaic) end longue; adenoma of adrmal conta ai 0.1 None al lo*cr dosci. Reduced body eight gain (from 6 months to 2 vein) n a high dose llacmaiologtcal effects ai high dose including ansemi^pancyiopenia. Purphvrm and ALA let cl dictations (high lime), Liter damage (at lo highesr doses* less exientitc thin In females). Respiratory effects flciseitcoiive than females |hith do*e|) and cardiovascular effects; adrenal haematocysis (high dose). Female rata Hepatocellulai hyperpluiic nodulei. at Q,| ad 0.01 pg, SquiniMUcdl carcinoma of hard p |3 l(fiu u l (mhnilei and longue: bcpaliXiltular carcinoma; kcjiiimung sqoamous crii carcinoma o( lung at 0.1 u j Reduced body weigh) gain (from 6 months to 2 years) at high dose, MaonuoToficat eflecti at high dnv, including :macmiaf punc)-tot'eni'rorph)iin* ALA and creatinine alien lions (high dose). Liver damage (at two highest doses* more etttnske than in males). Swollen hepatocytes (tow dose) Thvmic or iptenic urophy (high dose). Respiratory system effects, (more eatentbe than males) and cardiovascular effects. Increased adrenal cortical haemorrhage and pancreatic atrophy and fibrosis mechanism by which such compoutTds induce Table 1 2,3,7.6-TCDD gcnoloiictiy studies in systems other carcinogenesis in animals varies depending upon than S.typhimunum, Adapted from Shu et of.*1 (he chemica). Mutagenicity assays have been conducted in a Teil Remit Reference number of strains of Salmonella lyphimurium. Mutagenicity: E, colt Sd-4 All studies have demonstrated negative results, Mutagenicity; S. ccrevisiee with the eicepiion of Hussain a al. and Settler*4 Mutagenicity: mouse lymphoma cells + 65 + 68 69 who reported positive results for the induction of Viral inactivation: 0 8 virus -- 90 rcverlants in one strain, TA 1532, sensitive to DNA binding; rat liver in vivo - 91 frameshift mutations. Attempts to repeal these studies using cither TA 1532 or other frameshiftsensitive strains were unsuccessful.**'4-*7 A summary of genotoxicity studies with test systems other than S.typhimurium has been des cribed by Shu t t c/.w and is presented in Table 2. Unscheduled DNA avnlhesis j hcpaiocvtci Unscheduled DNA svnthesis J in vitro Transformation: BHK cells Transformation; C3H/I0T, cells Sex-linked recessive lethal; Drosophila Dominant lethal; Rat - + - 92 93 95 96 97 W UiO380 PCDDS AND PCDF5: RISiK'TO'HCWDHVS-Trr A more detailed discussion o f some of these wjih 2,3,7,8-TCDD; the administered dose In one findings is summarized below. study was reported to be 1 pg k g '1 w e e k '1 by Hussain cl at.a reported 2,3,7,8-TCDD to gavage for 45 weeks. Two studies were reported as induce a reversion to streptomycin independence in giving weakly positive results for chromosomal E. colt Sd-4 at doses above 2 pg ml-1, however, at aberrations: Loprieno et al.n found a significant these concentrations, survival was below 20%. increase in chromosome aberrations in CD-I mouse Bronzetli cl af.n tested the mutagenic effect of bone marrow cells, when assaying at 96 h, but not 2,3,7,6-TCIJD In a suspension test in Saccharo- at 124 h after an i.p. Injection of 10 pg 2,3,7,8- myces cerevisiae. The author repotted a positive, TCDD k g '1. The second study (G reen et at., died dose-related response (over the range of 0.5-10 pg by Wassons et a/." ) reported a weakly positive TCDD ml-1) in mitotic gene conversion and re result for chromosomal aberrations in bone marrow verse point mutation in the presence of mouse liver cells from Osbornc-Mendel rats receiving 510 mix. The maximum increase was approximately 4 pg k g '1 twice weekly lor 13 weeks, no controls fourfold at 10 pg m l"1, with 15% survival; no were used and comparisons were made with cells changes were noted in the absence or S10 mix. This from animals receiving tower doses. In addition, no study has been criticized on the grounds that the details were given of the aberrations observed. No weak positive effect was observed only at higher conclusions can be drawn from this study. doses in (he presence of considerable toxicity and Abernethy ef at.96 demonstrated concentrations may have resulted from the selection of spontan of 2,3,7,8-TCDD above 4 pM to promote the eous mutant colonies, already present in the yeast transformation of mouse embryo fibroblasts cell population,11 Bronzetli el a/.** also reported on (C3H/HIT^) which had been pretreated with N- an imransanguinous host mediated assay on CD-I mcihjl-TV-nitro-A'-nitrosoguanidine (0.5 pg m l"1). mice, in which a maximal mutational effect was Comparison of maximal response with the promot noted in both liver and kidney, 20 days after ing agent TPA (12-0-telradecanoylphorbol-l3- administration of 25 pg of 2,3,7,6-TCDD by acetate), indicated that the dose required for gavage. 2,3,7,8-TCDD was 10* less than for TPA and Rogers ei of.*9 found mutation rates to increase suggested 2,3,7,8-TCDD was the most potent in LSI 78V mouse lymphoma cells exposed to promoter yet tested with C3H*nn\* cells. 2.3.7.8- TCDD when methotrexate, thymidine or The binding of [5HJ 2,3.7,B-TDD to liver thioguanme were used as the selective agents, but protein, RNA and DNA when administered i.p. to not when ouabain o r cytosine arabtnoside were Sprague Dawtey rats at a dose of 7.5 pg kg-1 was used. Cell survival was decreased at 2,3,7,8-TCDD determined by Poland & Glover.*1 The results concentrations of 0.1 mg m l"1 and above. Cb>ne demonstrated the majority of bound 2,3,7,8- morphology was reported to be changed by 2,3,7,8- TCDD to be associated with protein (0.01% of TCDD concentrations of 0.01 mg ml-1 and above, administered dose) with virtually none binding to but growth in TCDD-free medium for 36 h before nucleic adds. plating reversed this change. It is not possible to There is some evidence, from studies on yeasts, draw conclusions from this study as it has never to suggest that 2,3,7,8-TCDD has mutagenic poten been repealed, even though equivocal results were tial. However, (he data from bacterial gene muta obtained. It has been suggested that (he response tion assays, dastogenidty studies and DNA seen may have occurred by a mechanism other than damage assays were negative. Negative results were mutagenesis." also obtained in a sex-linked recessive lethal assay A negative dominant lethal effect in male Wistar in Drosophila and in a dominant-lethal assay In rats was reported by Khera & Ruddick.*4 Doses of rats. Whilst the balance of results are negative, 2.3.7.8- TCDD (4, 8 or 12 pg kg" 1) were admin there is evidence from cell transformation assays istered for 7 days before seven sequential mating that 2,3,7,8-TCDD has tumour promoting activity. trials over 35 days and produced tokic effects in Mulagenidty studies on other PCDDs have only some of the animals. been carried out on 2,7,-DCDD and OCDD. Meyne et o/.** found no evidence of an increase Dibenzo-p-dioxin has also been studied. Green & in chromosome aberrations, micronuclei or sister M oreland" reported (in abstract form only) no chromatid exchange (SCE) in bone marrow cells of increase in chromosome aberrations in rat bone C57BL/6J or DBA/2J mice exposed to 2,3,7,8- marrow cells following treatment with 10 pg k g '1 TCDD (0, 50, 100, 150 pg kg-1 i.p.). It was noted dibenzo-p-dioxin or 2,7-DCDD. by intubation for 5 that the doses administered proved to be hepato- days, however, it should be noted that no dose toxic to these strains of mice. A number of other range was used. Furthermore, It has been re studies (reported by EPAM) have found no evid ported" that using the same protocol, a negative ence of chromosomal abnormalities in rats treated result was also obtained for 2,3,7,8-TCDD, but 1BJ S.A. SKENE rr al. using a different protocol Greco * Moreland 2.3.7.8- TCDD may only be seen in highly obtained a positive result for 2,3,7.8-TCDD. No organized systems (possibly signifying a require other dioxins were tested in this revised system. ment for the Ah receptor), in vitro systems have Commoner'TM reported that dibenzo-p-dioxin however been used successfully in the investiga r,;iwd m demonstrate an increase in revcitasti tions of hyperkeratinization.*1 . _ - . .......... . .. whetT tester! at doses between 0 and' 100 fig p e r- In humans the most common effect of exposure - plate (h assays using S, typhlmurium strains TA 100, to PCDDs and PCDFs' is chloracne/ppidermal 1535, 1537 and 1538 with and without S9 mix. hyperplasia. Two cell culture systems, XB cells Finally, OCDD has been tested in a number of (epithelial cells, derived from a mouse teratoma) or strains of S. typhimurium,w The results indicated a neonatal human foreskin cells, have been found to negative response with strains TA 1S30, 1531 and exhibit hyperkeiatinizaiion when challenged with G46 and questionable results when tested in 2,3,7,8'TCDD.` , #! It is reported that XB cells TA 1532 and 1534 strains. No details of dosing or possess the Ah receptor protein and keratinization activation system were provided. response was proportional to the binding affinity of There appears to be little information on the the test compound for the receptor.01 mutagenicity of PCDFs. The mutagenic effects of four PCDFs (2,8-DCDF; 3,6-DCDF; 2,3,7,8-TCDF Reproductive toxicology and OCDF) and dibenzofuran have been studied in 2.3.7.8- TCDD is generally accepted as being one of various strains of S. lyphimurium with and without the most potent teratogens/fetotoxins in all the S9 mix. None of these dibenzafurans were found to common laboratory species studied. Mice present be mutagenic.101 leratological lesions, mainlv deft palate and kidney anomales/hydroneph^)sis.,,*"l,,' A number of feto- Cytotoxicity toxic effects have been reported in rats including A number of in vitro studies have been carried out intestinal haemorrhages and subcutaneous oedema, on 2,3,7,8-TCDD.,n *101 | n the majority of cell as well as kidney abnormalIies.'5'l"0,lllM,, Other lines challenged, no evidence of toxic effects were effects noted include decreased fetal weight1" and noted. This suggests either that the systems used also increased fetal death.'' Pups bom to mothers may be unsuitable or that the in vivo effects of receiving 2,3.7,8-TCDD in the diet also had Table 3 Reproductive ctier I* of 2,3,7.R-TfnD Pmram/Ur Mete fertility Ftmilc fertility Gcaen) reproductive performance Teratogenidly/ embryolcihalily Fetoloiidly Postnatal dcvtlopfTKQt Sptria *nd rtf. R.1*'' Rxl>" FUI Mookeyni,JO'* Ril'" Monkey71'1* Mouse'" Rat'* Ribbii'" Monkey71-'" Mousel*7''TM Ret1" Rebbii"' Monkey'" Monkey'" Ow rtqtdtfd fnj i | Effect Minimal tffut 00 |M) to (MGS) 2000 10 h i too* (11 mo) 2 [7mo) to' 2H r IMOS| 1000 1 [S-I5d of 500 1 pregnancy| too 1 (7toobefore + itt prcgnency| 100 [6~l5dof pregnancy} 50000 1 [6-ISd of 115 | pregnancy) too 0.72 (15-50mo before + ell pregnancy) - 0.12 |*Smobut ool for 10mobefore or during pregnancy) " w produtt So rffrtt too* 1 500 0.72 (17 mo| [MGS| lll Hr) 0.72* l !| to- | f6-l3dof pregnancy) 0 72 (15--30mobefore >11pregnancy) M00 1 |6-i5d of pregnancy] "0.12 ) 115-33mo before ill pr(|iunt)| * ladicerc* the basis for the figure h lentitive. - Indicates dm known. U W o l o duration o t doling, GS MoJtfgencrationiijdy, fr ife s fc GENP 010381 PCDDS AND PCDFS: RISKS TO UMANS J33 fr II' \ reduced survival rate and (he transfer of pups at monkeys to a total of 0.2, 1 or 5 pg k g '1 of birth to control foster mothers did not increase 2,3.7,8-TCDD given in nine doses, by gavage, survival, indicating the effects were probably due to between days 20-40 of gestation. The two animals in utero exposure rather than exposure via mother's receiving the 5 pg ltg"r dose aborted on days 47 milk.** Table 3 summarizes the data. .. and 48 of gestation and died on days 83 and 136. O f ' Maternal responses have included increased the four animals receiving I pg kg"1 three liver/body weight ratios in some mice studies and aborted, with only one animal showing overt signs vaginal haemorrhage, decreased fertility and body of maternal toxicity. None of the four animals weight gain in some of the rat studies. Fetuses of receiving the 0.2 pg kg-1 dose demonstrated signs New Zealand rabbits, demonstrated increases in of maternal toxicity, although one may have extra ribs and soft tissue abnormalities, in addition aborted. The signs of maternal toxicity found were to maternal toxicity at doses of 0.23 jig kg-1 and an initial thickening and reddening of the eyelids, above and malformations at 0.1 pg k g " . ' followed by weight loss, dry skin, loss of hair, There are few studies on the reproductive effects anaemia, purpura and bleeding from the nose and of 2,3.7,8-TCDD in the mal. 2J.7.8-TC D D mouth. V. autopsy, squamous metaplasia of (he (4 ug kg- , d - ' for 7 weeks) can cause inflam sebacer !s glands, hyperplasia of the bile duct, mation of the testes which may be secondary to ginc- and hypoplasia of the bone marrow were general toxicity in rats*1 and possible modifications . A parallel study giving I pg kg-1 of icstosierone hydroxylase activities follow!' rCDD as a single dose on days 25, 30, 35 single oral doses of 0.2. 1 or 5 pc Vp-1 or 40 of gestation produced similar results to the A number of authors h a su/ j v ' ie divided dose regimen. Of the three live fetuses NELs for teratogenic effects of 2.3.7 .B-'i .. <>D. but from both experiments in the I pg kg-1 groups many of these estimates are uncertain (Table 3). minor abnormalities of the palate and uvula were The lowest dose used in rodent reproductive noted. No abnormalities were noted in three toxicity studies was 0.001 pg kg^'d " 1. which pro fetuses from the 0.2 pg k g '1 group. Although the duced increases in the incidence of deft palate in a 0.2 pg kg-1 group (with an average intake of CF-1 mouse teratology study, although such effects approximately 0.01 pg per kg body weight per were not evident at the next higher dosage.100 day) did not differ significantly from control A tecent review of the reproductive toxicology of animals, it is not possible to draw any firm 2 ,' V.'t-TCDD Uv<tx that ihr range nf toxic conclu-ions from such small group sires. Animals effects of TCDD on the reproductive system is from higher dose groups exhibited signs of toxicity consistent with its toxicokinetics, distribution of the but aborted prior to these symptoms becoming Ah-receplor (and AHH enzyme induction) and obvious. No conclusions could be drawn on also suppression of immune function.114 2,3,7,6- whether abortions were due to maternal toxicity or TCDD mostly occurs in the environment as part of effects of 2,3.7,8-TCDD on the fetus. chemical mixtures (as indeed do other PCDDs and The direct administration of 2,3,7,6-TCDD (or PCDFs). There is evidence to suggest that in the indeed any other of the FCDDs or PCDFs) during presence of some other polychtorinated com gestation is not necessarily required to produce pounds, the teratogenic effects or 2,3,7,8-TCDD adverse effects on the offspring. Since 2,3,7,6- may be enhanced. A combination of 2,3,7,8-TCDD TCDD is lipophilic and accumulates In the adipose and 2,3,4,5,3`,4`-hexachlorobiphenyl (HCB) ad tissue, is poorly metabolized and has a long half- ministered by gavage to C57BL/6N mice on days life in most species, particularly in primates, 10-13 of gestation produce a tenfold increase in the maternal exposure before conception can lend to incidence of deft palate in pups compared to the ultimate mobilization from adipose stores and level produced by a dose of 2,7,8-TCD D thereby transfer to the developing offspring during alone.1" Hassoun & Denker,'10 reported that co- gestation and also lactation. In a study by Schantz administration of p-naplhoflavone, a microsomal et of.111 subtle effects on matemalfinfant behaviour mono-oxygenase inducer with no teratogenic action were noted when the animals were mated one year itself, was found to increase the incidence of after withdrawal of 2,3,7,8-TCDD administration 2,3,7.8-TCDD induced cleft palate in mice. Finally (5 ppt and 25 ppl) in the maternal diet for about 4 a mixture of 2,3,7.8-TCDD and 2J.7.8-TC D F years. There were no obvious toxicological effects administered by gavage by C57BL/6N mice on day of TCDD exposure on the offspring or the mother. 10 of gestation produced a more than additive The main finding was that TCDD-exposed mother- increase in cleft palate and small increases in infants dyads spent more time in close soda] kidney malformations."7 contact than did controls. The authors suggest that A few studies have been reported in non-human the infant exposure to TCDD may have been the primates. McNulty70 exposed pregnant Rhesus determining factor and that the effects were ! 1M S.A. SKENE tl at. probably mediated w the mother's milk. The 2,3.7,6-TCDF) treatment, although the actual authors noted little difference from control infants response varies with animal spccies/slrain/age and with regard to social or environmental exploration, the experimental protocol. In common with other self-directed behaviour, stereotypic behaviour or effects produced by PCDDs and PCDFs, the play behaviour and suggest the findings from this alterations in immune system functioning appear in study indicate mothers were responding to subtle, general to parallel the levels of Ah receptor and physical or behavioural cues in modifying their cate arylhydrocaibon hydroxylase (AHH) indudbility. o fT C D D offspring. Further reports of this study, Vccchi tt at.'23 determined the number of seen as abstracts only, noted changes (both positive haemolytic plaque forming ceils (PFC) produced in and negative) in learning tasks with increasing different strains or mice (differing in AHH levels of TCDD in the infants' fat. The authors responsiveness) after administration of 2.3.7.8- calculated a NEL of 0.05 ng TCDD kg bw ^'d" 1 TCDD or TCDF followed by i.p. injection of sheep based on transfer from maternal fat to infant via erythyrocvies. In the AHH responsive mice (C3H/ milk.51'"* HeN and C57BL/6) the number of PFC produced The effects of various PCDDs, other than after prior administration of 1.2 pg kg" 'd " 1 for 7 2.3,7.8-TCDD have been studied for teratogenic days of 2,3.7,8-TCDD was significantly reduced. In potential in Wistar rats by Khera & Ruddick9* and non-responsive mice (DBA/2) a very much greater in Sprague Dawley rats by Schweiz tt at.*3 Isomers dose was required (30 pg kg" `d " f) in order to studied were 2-CDD. 2J-D C D D , 2.7-DCDD. elicit the same response. For 2.3.7.8.-TCDF. 1,2J.4-TC D D , OCDD and mixed isomen (unspec 180 pg kg"1 reduced humoral response in ified) of HxCDD. Of these PCDDs only the C578L/6 mice, but not in DBA/2 strain mice, again HxCDD was truly fetotoxic and teratogenic, with demonstrating a relationship with AHH respons effects found at the lowest dose used i.e. iveness. 0.1 pg k g -'d 1." Some effects were noted with the A study on 2,3.7.8-TCDF in Hartley guinea pigs other PCDDs, but these occurred at much higher indicated the effects are similar to those of 2.3.7.8- dosage levels. Khera & Ruddick* found 2.7- TCDD. although doses required were increased by DCDD to produce myocardial lesions in the fetus approximately tenfold.1:1 Alterations in immune at 1000 and 2000 pg kg"1d " 1 levels, although responses have been detected in the absence of Schwetz t t a/.63 found no such effects at overt signs of toxicity. 100 000 pg kg-1 dose: 1.2.3,4-TCDD produced A number of immunological effects have been 'n-signiiicanl increase in sfcelci.il abnormalities at studied in mice by Carfc il at,.' ' Groups ol 100 and 200 pg kg-1 dose, but not at higher dose C57BU6 mate mice received four weekly i.p. levels;** OCDD produced subcutaneous oedema at injections of 2.3.7,8-TCDD at doses of between 500 000 pg kg-1 dose.u Finally, negative results 0.001 pg kg-1 week"1 and lO O pgkg"1 w eek"1 were obtained when 1,2,3,4-TCDD and 2,7-DCDD and were studied I week after the fourth dose. The were tested in dominant leihal/fenility studies in results indicated the cellular content of the thymus Wistar rats.** Nagayama tt at.43 have shown cenain was lowered by 50% by doses of 1 pg kg"1 PCDFs can cross the placenta. The limited inform week"1 and doses of 25 pg kg"1 w eek"1 were ation available from 2.3,7,8-TCDF teratogenicity shown to reduce dramatically the ccllularity of the studies indicate it td be teratogenic in mice spleen and peripheral lymphocytes. The number of producing cleft palate and hydronephrosis. How plaque-forming cells in the spleen produced in ever, the dosing periods and observations were response to sheep erythrocytes (administered i.p.) limited in most studies and would not necessary or trinitrophenol conjugated Brucella abortus was have picked up all susceptible organs." '120-1- considerably decreased at 6 days after immuniz Hassoun tt of.'*1 demonstrated a strain difference ation in animals receiving 10 pg kg- ' w eek"1; in the mice tested in their study, this was thought to IgM, IgG and IgA responses were also alfected. be dependent upon the presence of the responsive Further investigatiohs indicated that depletion of T- Ah locus. hclper cells was nut the cause of the decreased immune competence. The production of cytotoxic mm unotosicology T-lymphocytes In response to the injection of One of the most consistent pathological changes 2 x 107 P-815 irradiated tumour cells (a source of following administration of 2,3.7,8-TCDD and the H-23 alloantigen) when measured 6 or 7 days related compounds, has been involuiion/a trophy of after immunization, was reduced in suspensions of the thymus, particularly the cortex, with an Spleen cells from animals receiving 6 .1 pg kg"1 associated depletion of lymphocytes. Doth humoral week"1 or higher doses. The generation of cyto and cell mediated immune effects have been toxic T-cells in vitro was reduced when cultures demonstrated following 2,3,7,8-TCDD (and were made from the peripheral lymph nodes of v jjL U N r u i u j i PCDDS ANO PCDFS: RISKS TO HUMANS ISS mice which had received 0.001 fig kg"1 week-1. TCDD (used as a positive control). This finding is The addition of 2.3,7,8-TCDD (25 ng) directly to of interest as 2,7-DCDD has very low or no binding control cultures produced no suppression, whereas affinity for the Ah receptor and may indicate some the mixing o f cultures from control and test animats aspect of PCDD/PCDF toxicity to be independent (0.1 jig kg-1 .week- ') produced _the response of the Ah receptor, although further work in this associated with th e ' lest culture. The level of area is required. The tam e study also reported a precursors to cytotoxic T-cells was not reduced negative effect on the immune system by OCDD in suggesting the response was due to an increase in one test system, although it was not studied as suppression, possibly via an activation ol T- comprehensively as 2.7-DCDD. suppressor cells. The immunosuppressive effects of pcntachloro- Subsequent work by the same group found that phcnol contaminants, including OCDD; the immunosuppressive effects of 2,3,7,8-TCDD 1.2.3.6.7.8- HxCDD; 1.2.3.4.6.7.8-lfpCDD and were dependent on the Ah gene,, not the H-2 1.2.3.4.6.7.8- HpCDF were studied in mice by locus.1-* By transplanting tymphomycloid cells Kcrkvleil el al.1*1 Mice (C57BL/6 strain) were from one strain of mouse into irradiated recipient given a single gavage dose of the compounds 2 days mice, the A h genotype of the recipient was found prior to i.p. inoculation with 2.5 x IO1 SRBC (T- to be dominant. It was suggested that this was due dependen! antigens). Mice were killed 5 days after to an Ah receptor present in the thymus; the inocculation. The IgM response or isolated splenic thymic receptor would be expected to have a lower cells was not reduced by OCDD at doses of up to dissociation constant (Kd) than the liver Ah 500 mg kg- *, however a 50% inhibitory dose receptor. (ID*i) of 7.1. 85 and 208 pg kg-1 was shown for The developing immune system in animals has 1.2.3.6.7.8- HxCDD: 1.2.3.4.6.7.8-HpCDD and been found to be particularly susceptible to the 1.2.3.4.6.7.8- HpCDF respectively. In a similar effects of 2.3.7.8-TCDD exposure. The effects can study. Vecchi el ai.123 reported 2.3,7,8-TCDD to be mediated either through in tero exposure or have an IDM of 0.65 pg kg-1, i postnatal exposure from mother's milk. Pre- and postnatal exposure to 2.3,7,8-TCDD in F W rats has been shown to produce prolonged reduction in certain immune functions: delayed hvpersensitivity Proposed mechanisms or toxicity of PCDDs and PCDFs and lymphnproli(eralive response.,s The doses Ah receptor and enzyme induction icvciviil by the mothers tu elicit a response in the The similarities between the effects produced in offspring were 5 pg kg-1 by gavage on days 0, 7 experimental systems by PCDDs, PCDFs and other and 14 after birth, with some groups receiving an halogenated hydrocarbons such as PCBs and PBBs additional prenatal dose on day 18 of gestation. (polybromlnated biphenyls] suggests the possibility Some indication of the exact dose received by the of a common mechanism. Such a mechanism was pups is required however before one can extra proposed by Poland Glover1'1 and was based polate these findings to man. A similar study .upon studies on 2,3.7,8*TCDD following the conducted in 5-week-old Swiss-Webster mice whose identification >of the *Ah-receptor*. The studies mothers had received 2,3,7,8-TCDD in the diet (1, involved the use of mice strains having a high 2.5 or 5 ppb) from 4 weeks before mating to 3 sensitivity for AHH induction (C57BL/6) a low weeks after birth (total dose approximately sensitivitity (DBA/2) or crosses having Inter 4 pg k g '1 for the I ppb group) has been re- mediate sensitivity. The sensitivity to AHH induc ported.11* The results were not entirely consistent tion was found to relate to levels or a so called ' h with those reported by Faith & Moore,11' as no receptor*. alterations were delected in delayed hypersensitiv The Ah (aromatic hydrocarbon) receptor is a ity, Iymphoprnlifetation or antibody response to soluble intracellular protein that binds specific sheep erythrocytes although a significant dose- halogenated aromatic compounds such as 2.3.7.8- related increase in monalUy due to S.typhimurium TCDD and certain polycyclic aromatic hydro endotoxin was demonstrated together with a reduc carbons such as 3-meihylcholanlhrene. A major tion in PFC at 2.5 and 5 ppb. function of the Ah-receptor is to regulate the Some studies have been reported on the effects induction of specific forms of cytochrome P-450, in of other PCDDs on the immune system, 2.7- animals exposed to aryl hydrocarbon hydroxylase DCDD has been shown to produce a number of (AHH) inducers. It has been demonstrated that the decreased immune responses, including a dose- binding affinities of compounds for the Ah-receptor related decrease in IgM-productng PFCs from correlate well with their toxicity and ability to splenic cells of young female B6C3FL mice.1111The induce A H H 13' and also -aminolevulinic acid effects of 2.7-DCDD were not as potent as 2.3.7.8- (ALA) synthetase.131 The induction of these IB6 S.A. SKENE el. enzvme activities is long lived and occurs following properties that arc similar to the properties of (h e a d minis!rat ion of very low levels of dioxins. receptors for steroid hormones and it appears (hat The activity of AHH in hepatic microsomes in he Ah-receptor and steroid receptors belong lo a female rat* was seen lo be significantly increased common family. Kesicr & Gustcwici137 reported following an oral administration of a that studies from several laboratories have shown 0.002 pg kg-1 d o of 2,3,7,8-TCDD. the Ah-receptor to be an oligomeric protein, Compounds capable of inducing both AHH and comparable lo steroid receptors in Stokes radius, ALA synthetase (e.g. PCDDs. PCBs. PCDFs and sedimentation coefficient, molecular weight and other halogenated aromatics) have two common frictional ratio, with an equilibrium dissociation properties: the first is halogen atoms occupying a constant for 2.3.7.S-TCDD within the range char minimum of three (or four for maximal activity) of acteristic of steroids. The Ah-receplor is more the lateral ring position (i.e, 2.3.7.8) and secondly, hydrophobic than steroid reccptnrs. however, it at least one ring position must be unsubstituted. interacts with polyanions (including DNA) in a Therefore the binding affinities of various PCDDs similar manner. It has been reported that the Ah- and related compounds for the Ah-receplor can in receplor. like receptors fur steroid hormones general be explained by the shape and electronic contain sulphvdryl groups which are essential Tor configuration of the molecule. However, the ligand binding function, although there exist subtle precise mechanism of PCDD interactions with the differences between the two receplor types in Ah-receptor has not yet been determined. response to a spectrum or sulphydryl-modifying The ligand-receptor complex is transported into agents.1*"' In spile of the number of similarities the nucleus, where it is thought to bind to DNA. between the two receplor types, the Ah-receplot is Evidence for this step has been provided by the apparently not identical to any known steroid analysis of radio-labelled 2.3.7.6-TCDD in prepara receplor.13 It has been soget Med that there is tions of cell nuclei.131 The interaction of the slight evidence that oestradio! levels may affect the complex with DNA is thought to rely on both action of 2.3.7.8-TCDD and its receptor at the electrostatic and configurational effects.13' The genomic level.11" However, Kcstcr & Gasiewicz1' 7 binding of the complex to DNA alters the rate of reported that oesrradio!, hydrocortisone, progester translation of a battery of genes coding for enzymes one, testosterone (and also the non-steroidal and oihet macromolecules, possibly via promotor oestrogen diethy1stilboestrol) did not enhance Ah- and inhibitor domains136 which are ultimately recovery or stability and furthermore TCDD bind responsible for the range nfbiolngk.il effects seen. ing was not inhibited by any iT these s'eroiiri, Die requirement lor a receptor to mediate the indicating that they do not compete with 'I(.D U fur action of PCDDs on DNA would explain the low- specific binding to the Ah-rcccptor. level of 2,3,7,8-TCDD binding to isolated DNA In a study by Gasiewicz & Bauman111 evidence compared to many known genotoxic carcinogens had been presented for the existence or at least and the lack of mutagenic potential in test systems. three forms of the Ah-receptor prepared from rat Several species (both vertebrate and invertebrate) hepatic cytosol in vitro and identified as: an including humans114 possess, a TCDD-binding unoccupied form, art occupied form showing some receptor, homologous to the Ah-receptor identified affinity toward DNA and an addilional occupied in the mouse and it has been suggested that this form that is less negatively charged and has greater protein haS been conserved during evolution to affinity for DNA. The transformation lo the latter perform a role in these species.157 It has also been was dependent upon the presence of 2.3.7,8-TCDD suggested that the Ah-receplor complex could have and the duration of the incubation and tempera once served in evolution as a hormone or growth ture. As assumed for the transformation of steroid (actor receplor for a variety of eciodermally- hormone receptors, this transformation may be due dcrived tissues.13* The Ah-receptor has been to exposure of positively charged groups on the isolated irom a number of organs11,1 and it is receptor molecule. The precise mechanism that conceivable that it exists in such tissues without a mediates the transformation or the Ah-receptor to natural ligand and is activated only when tissues are DNA binding species is unknown. However, the exposed to potent toxins such as 2.3,7.8-TCDD.,3<> finding that the fully transformed receptor can be There are both species and strain differences in the isolated from hepatic nuclei of rats pre-treated with response to 2.3,7.6-TCDD and it is possible that TCDD seem to indicate that the above process may not only concentrations of the receplor but also occur in vivo. variations in the binding affinities, translocation into (he nucleus and response of the affected genes could explain such differences. The Ah-receptor has many physicochemical There is therefore evidence to suggest that Ah- receptor binding is necessary for many aspects oi PCDD/PCDF toxicity and it is likely that a definite structure-activity relationship exists, 2.3.7.8-TCDD GENP 010383 -------------------- I'lULTk fliMU PCDFS: RISKS TO HUMANS J17 has a very high alfinily for the receptor and also has grcuicst toxic |xnency. The role of the Ah*rcceptr binding and receptor-mediated events in the tumour promoting activity of 2.3.7.8-TCDD has yet to be fully determined.1 - Other mechanisms Other mechanisms proposed to explain the multi farious effects of 2.3,7.8-TCDD include modifica tions in hormone levels, changes in metabolism due to enzyme induction and modifying the response of the epidermal growth factor receptor. Lipid peroxidation . Interactions Lipid peroxidation of membrane components, as Since `dioxins* bind to the Ah-receptor and are measured by levels of malonaldchyde and conju inducers of hepatic enzyme activity, il is possible gated dienes, has been reported to increase follow that they may modify the toxicity of other xeno- ing the administration of 2.3.7.8-TCDD to the bioitcs. Furthermore, the modification of `dioxin' ra t.'* '1" Other authors have disputed these find toxicity hy other components of an environmental ings as in another study there was found to be no mixture, is also possible. Studies on these imerac- increase in ethane exhalation (another marker for lions arc not extensive at present, hut those which lipid peroxidation) after administration of 2.3.7.8- have been published to date indicate that the TCDD.W combined effects may be additive/ An increase in the level of free-radicals formed synergisticT9ni'Nl`"1' 1 or antagonistie.w-,H The due to lipid peroxidation, has been suggested as a major (actors in determining any interactive effect mechanism for some or the non-specific effects of are the genetic make-up of the exposed animal and PCDDs.'*' Il has been suggested that a correlation the exact chemical nature of the mixture. exists between species susceptibility to TCDD- induced hepatic lipid peroxidation, AHH mdunbil- TCDD equivalents ily. inhibition of GSH-PX (selenium-dependent There is at present no reliable, rapid test for glutathione peroxidase), thymic atrophy and body assessing the biological activity of environmental eight loss.1" The administration of the anti samples likely to contain PCDDs and PCDFs. The oxidant butylated hydroxvanisole (BHA) or assessment of poiential risk is based on individual reduced glulhaihione to female Sprague-Da ley isomer analysis and refining these results to the rats which received 2.3,7,8-TCDD demonstrated a toxicity (where known) of the individual isomers.* decrease in the level of lipid peroxidation (as In order to simplify the risk assessment procedure malonaldehyde formation) and the BHA .treatment and to permit some form of regulatory control, the pr v*ed 'gaii-M the mortality produced by concept of 'TCDD equivalents' ha* been intro 2,3.7.8-TCDD.,JJ These results suggest that the duced. Ibis concept is derived Irom refilling ifiu levels of oxidizing molecules are increased by to.xicilies of groups of isomers to the toxicity of 2.3.7.S-TCDD administration, by either a primary 2,3,7,8-TCDD to produce a `toxic equivalence effect, e.g. due to direct inhibition of glutathione factor* with a summation procedure to give peroxidase or a secondary effect due to 2.3.7.8- 'TCDD equivalent' for the mixture. The major TCDD being transported into the nucleus and drawback of the TCDD equivalents concept is that inducing oxidizing enzyme synthesis. 1 is assumed all isomers In a defined group have (he same toxicity and that all interactions are Vitamin A Some of the effects of TCDD intoxication resemble those of vitamin A deficiency e.g. keratosis and immunosuppression and. it has been suggested that depletion of vitamin A stores in the liver produced by 2.3.7.8-TCDD administration may be respons ible for some of the signs of 2.3.7,8-TCDD toxicity.1'1*' An oral dose of 2.3.7.8-TCDD ( I 0pgkg~' ) has been found to modify the metabolism of vitamin A. when administered to Sprague Dawlcy rats.'1* The ad minisiration of vitamin A was shown to exiend the survival time of female Sprague Dawley rais when given 2.3.7.8T C D D .'" Whilst these studies demonstrated simply additive. Whilst TCDD equivalents are of use Tor screen ing mixtures, there are not enough data on the to.xicilies of many of the isomers to give a definite estimate of risk. Furthermore, where equivalence factors are derived, they are often based upon in vitro studies. The lack of reliable toxicity data is highlighled by the different equivalence factors given lo ihe same groups of isomers by different auihorhies.155 Although the concept cannot be used as a tool for accurately predicting human health effects, it is useful in assessing priorities in terms of potential risk to human health. vitamin A metabolism to be altered by 2.3.7.ETCDD. it is rot known whether this is a primary or Mortality and morbidity in humans secondary effect. There ha* been a considerable number of reports of IBS S.A. SKENE ol. 'non-experimentaI' human exposure to both of higher chlorinated phenols between 1940 and PCDDs and PCDFs. In virtually all' instances 1979. An attempt was made to provide estimates of however, exposures were to mixtures of PCDDs 2,3,7,8-TCDD exposure potential for each job. Up and/or PCDFs as well as to a range ol other to the end of 1979 death certificates were obtained chemicals sharing similar properties. Furthermore for a total of 298 men known to have died. For U has not been possible to ascertain accurately the cancer sites of particular interest (such as soft tissue uptake by individuals. Dose-response relationships tumours and non-Hodgkin's lymphoma) there were cannot therefore be established for any of the no significant increases in standard mortality ratios adverse effects observed. Commonly the design nor were dose-response relationships observed. and evolution of the reported studies detract from the conclusions drawn by the authors. Nonetheless A study o f workers synthesizing penochlorophenol the human epidemiological data need to be evalu (PCP) and sodium pcntacliloropltciwtr (Santobrile) ated carefully as animat data have demonstrated A group of workers at a plant synthesizing PCP and considerable variation in species sensitivity and Santobrile between 1950 and 1978 were reviewed in toxicokinetics. 1979, 1980 and J982.151 Exposures had been to Circumstances under which human exposures to PCP and intermediate lower chlorophenois, and a PCDDs and PCDFs have taken place fall into a number of PCDDs and PCDFs. The PCP contained number oi categories. Exposure to 2,3,7,8-TCDD hexa-, hepta- and ocia-homologues of PCDDs at is the prominent feature in most occupational levels of 5-15 ppm. 23-250 ppm and 1900 ppm. studies, and has been associated with: the synthesis respectively. No 2.3.7,8-TCDD was detected in the of trtchlorophenol and trichlorophenate; the syn PCP product at the then detection limit of thesis. compounding and use of irtchloiophcn- 10-15 ppb. The Santobrilc product contained hexa- oxyacetic arid herbicides and accidental releases to CDDs and OCDD. the environment in both types of industrial pro The results of the general health study among the cesses. Exposure to PCDFs has been studied in the workers were stated to show a non-significant follow-up of incidents involving PCBs: this includes elevation of serum triglycerides compared with the 'Yusho' incidents (associated with ingestion of controls. Those with chloracne had greater disturb rice oil contaminated with PCBs) and following ances than those exposed without chloracne. accidental fires involving electrical transformers The authors reported that exposure to PCP had containing PCBs. probably varied over the years, with higher expo Exposures associated with the synthesis of trich- sures in the earlier years and lower exiwsure Idiophcnol and trichlorophenate have resulted in latterly following considerable improvements in outbreaks of chloracne and malaise. Dugois ei a/.114 conditions. Because of the limitations in the design reported chloracne in workers at a French factory of the study, little can be said about the true synthesizing 2,4,5-trichlorophenol from tetrach- incidence or natural history of the observed effects. lorobenzene. Other complaints by the workforce However, it does support observations noted in included loss of weight, anorexia, weakness, head other studies of the association between1 dioxin* ache, digestive disturbances and conjunctivitis. exposure, chloracne and disturbance of lipid These observations were not necessarily related to metabolism. (he presence or severity of chloracne. The authors were unable to identify the agent or agents 77ie Philips Duphar accident responsible for the outbreak, although it is conceiv An explosion occurred in March 1963 at a plant able that PCDDs could at ieasl have been partly synthesizing sodium trichlorophenate from 1,2,4,5- responsible for some of the effects seen. tetrachlorobcnzene. causing widespread contamina D OW Chemical?mortality data tion of the containing building. A study was conducted to look at the effects of exposure during Investigations into mortality of trichlorphenol cleaning-up activities in 1963.IJS The results workers at DOW Chemicals have been reported by revealed normal liver function tests in the workers Cook u / . ' ' The first report1'5 referred to only exposed and a number of cases of chloracne. A a few workers and the most that could be follow-up report on morbidity was subsequently concluded from the results (apart from the develop published.IW However, details of the studies are ment of chloracne in exposed workers) was that the limited and to date no significant differences have TCDD coniaminant was unlikely to be a very been attributed to exposure. powerful human carcinogen. The second report1* involved a Tar more detailed analysis of the 77te Coalite episode Company data. A mortality study was carried out A number of studies have been reported following on a total of 2189 men involved in the manufacture an incident in 1968 at a UK plant (Coalite) CiiiNP 010384 ---- -- -------------- FCUUS AND PCDFS: RISKS TO HUWANS m synthesizing 2.4,5-trichlorophenol. As a result of malignancies* was above expectation, but indi unscheduled conditions a higher than nprmal yield vidually only stomach cancer, reached statistical of 2,3,7,8-TCDD occurred followed by an significance. The small size of the population and accidental release of reagents.160 Initially, a study the small numbers of deaths do not permit was conducted on 14 workers identified as having definitive conclusions to be reached from 'this been involved in the accident.1*0 Some slight study. The authors refer to reports of stomach complaints were reported plus a variety of cancer excess in other studies. abnormal biochemical and haematological results, which all returned to normal in 10 days. A follow* up of 79 workers who had suffered from chloiacne The exposure to trichlorophcnoxyacclic acid- up to the end of 1968*** found that the condition based herbicides and their `dioxin* contaminants persisted in a quarter. There were however, no has perhaps led to the most widely studied aspect acceptable biochemical indicators of toxicity, Of human health effects relating to dioxins. A brief before, during or after chloracne developed and account is provided of some of these studies, with off-spring of these workers were reported to be an indication of the effects noted in the populations normal and healthy. Unfortunately, in common studied. with a number of other reports, the lack of epidemiological expertise, and inadequate study 77te Danish pkenoxy herbicide industry experience design leave it open to a number of criticisms. In Denmark, the use of 2,4,5-T (2,4,5- Further ad hoc investigations on various subsets of trichlorophenoxyacetic arid), which contains these exposed workers have been reported by other 2.3.7,8-TCDD has always been limited, and it has authors. Jensen et at.,K reported chloracne in two not been marketed since 1960. Hie principal fillers, and also in a son of one and wire of another. production has been of D-type phenoxy herbicides No niher adverse effects were noted (liver function (based upon 2,4-dichlorophenol) and M-type and lipids were normal). Walker < Marlin1*1 (based upon 4-chIoro-ortho-cresol). While these independently conducted a study of eight men with herbicides contain PCDDs. they arc thought to be chloracne 10 years after cessation or exposure. Five of the less toxic variety and 2,3,7,6-TCDD is had raised serum triglyceride levels and gamma apparently not present.TM Lynge171 attempted to glutamyl transpeptidase (GG T) levels, and all had study all persons in Denmark involved in the reduced high density lipoproteins (HDL) and manufacture of phenoxy herbicides before 1982. increased total cholesterol. Martin16* compared However, of the four factories investigated, only exposed Coalite woike is with controls lor bio two had suitable data for analysis. The study was chemical effects, and found higher cholesterol and undertaken in the hope of evaluating the potential triglyceride levels in the exposed group together carcinogenic effects of the DM phenoxy herbicides. with higher D-glucaric arid/creatinine ratio. Finally, A number of analyses were conducted looking at Blank el a!. carried out a study of genotoxic employees from the two factories separately and effects 10 years after exposure, and found no also in combination. White the conclusions seem to statistically significant differences between exposed add support for an excess risk of soft tissue sarcoma and non-exposed groups. to be associated with phenoxy herbicide exposure, the authors were uncertain about the validity of 77ie BASF explosion their findings, since various biases may have In 1933 an explosive release took place at a BASF operated. plant fiom a vessel in a process synthesizing 2,4,5- TCP Irom 1.2,4,5-telrachlorobenzcne. Hoffmann166 A UK phenoxy herbicide study and Goldmann167 gave accounts of the incident and A mortality study was conducted by Coggan et Goldmann16* reviewed the conditions observed in al.m on 5754 people of a total workforce of 5784 the 42 chloracne-affected workers and described employed between 1947 and 1975, classified accord the natural history of their development. Subse ing to whether their exposure to phenoxy acids was quent to these reports. Theiss cl of.166 reported a 'high', `low* or `background', 2-MethyW-chIoro- mortality study of the total number of people phenoxyacelic arid (MCPA), considered not to involved in the incident (70 exposed initially and contain 2.3.7,8-TCDD was the principal product four for short periods during the next 2 years). In manufactured and contract sprayed by the company this population, 66 cases of chloracne and derma between 1947 and 1982. A range ol other com titis were recorded and overall the mortality for the pounds were manufactured, bought In and formu 'dioxin exposed' group was less than external lated including 2.4,5-T and other phenoxy adds, controls, but slightly higher than for the internal though on a smaller scale. Mortality statistics were controls. It was reported that mortality for 'alt compared with those expected for England and mm ill iStsitt*s i J9 S.A. SKENE tt ol. and the legions of Lombardy. An attempt was made to follow-up all children born in the contam inated zones. The study involved the complete examination of 2989 infants at birth and a periodic examination of physical and behavioural develop ments subsequently. No clear association was demonstrated b e n w . . > S E ? ssr- "4 2TS (0 S.A. SKENE ft ol. Wales and separately for aggregated niral areas for the period 1968-1976. The results did not suggest that these chemicals were powerful carcinogens. There were difficulties in defining an adequate control group, and the study was of insufficient power to identify low orders of carcinogenicity. The West Virginia 2,4,S-Tfactory experience In 1949 during the synthesis of 2,4,5-T, a reaction vessel overheated and the explosion which followed resulted in the contamination of the local environ ment. Foot workers exposed in 1949 in the clean up after the accident were examined. Subsequently an investigation was carried out on a larger number o f exposed plant workers. m j u A mixture o f signs and symptoms was reported including chloracne, hepatic enlargement, peripheral neuritis, delayed prothrombin time and elevated serum lipids. Of some 200 workers thought to have been exposed, 86% developed chloracne. There was said to be an increase in upper gastrointeslinal tract ulcers as well as a decrease in pulmonary function following exposure. There were no increased risks delected for cardiovascular, hepatic, renal or nervous system diseases and no adverse effects regarding reproduc tive function o r birth defects were recorded. Moses & Frioleau175 using a population of workers exposed following this incident, studied the incidence of skin lesions present up to 30 years after the onset o f disease. Of 37 workers found still to have chloracne, 21 were reported to have had the condition for 30 years, in a further study conducted in 1979 on both current and retired workers,,w a variety of non-specific symptoms were shown to be equally distributed among those with and without chloracne. The results demonstrated that acute effects of 2,3,7,8-TCDD were largely reversible with the exception perhaps of skin effects, changes in peripheral nerves and possibly changes in liver metabolism. No reproductive effects were detected. In addition to TCDD exposure, it was also reported that 50% had also been exposed to the known human carcinogen 4amino biphenyl. A Czechoslovakian herbicide factory study Between 1965 and 1968, 80 out of 400 production workers became ill in a Czech factory synthesizing trichlorophcnoxyacetic acid-based herbicides. The illness was attributed to the TCDD liberated in the process.'77 Although environmental levels were not measured at the time, TCDD was detected in the product and was detected several years later in the building and on painted surfaces. Of the 80 workers who had reported adverse effects, 55 were followed-up in hospital, where the natural history of development o f complaints were studied. Dis orders reported were immediate or delayed and included porphyria, lipid disturbance, hepatic diseases with plasma protein disturbances, abnormal glucose tolerance tests and central and peripheral nervous system disease. No cardiac, renal or blood diseases were reported. When workers were reinvestigated, some 15 years later, lipid metabolism effects and glucose tolerance abnormalities were still observable. The authors also reported severe general atherosclerosis assoc iated with some psychiatric disorders. A follotv-up studv o f workers synthesising 2,4.D and 2,4,5-T Poland cr of.11* followed-un 73 workers previously studied by Bleiberg et ai. at a factory, synthesiz ing 2,4,-D and 2,4.5-T, containing 2.3,7.8-TCDD. In (he original study. II workers had uroporphyrinuria, several had hirsutism, hyperpigmenta tion o r skin fragility, or all three. Two had vesicular eruptions on 'exposed* areas, two had hepatic dysfunction with liver biopsies showing UVR fluorescence. Three workers were considered to have fulfilled the criteria for the diagnosis of porphyria cutanea tarda (PCT). It was shown that neither chloracne nor PCT were related the to degree of exposure to 2.4-D and 2.4.5-T and furthermore 6 years later there were no cases of PCT. However, over this period the TCDD content o f the products would have been markedly reduced as would other porphyragcnic agents. The study demonstrated the prevalence of fiver dysfunction to be minimal. Personality disturbances seemed to be related to chloracne. However, no cardiovascular system, respiratory system, gastrointeslinal or central nervous system associated diseases could be linked with exposure, in conclusion, the results do seem to indicate a link with TCDD exposure and interference with liver porphyrin metabolism, although some authors180 have disputed ihis find ing, linking the raised porphyrin levels with hexachlorobenzene exposure. The Seveso accident This incident occurred at a 2.4.5-triehlorophenol manufacturing plant causing the release of about 2-3 kg of 2,3,7,8-TCDD, as well as TCP and other substances. The toxic cloud drifted downwind, settling over fields and houses in the vicinity. Three major zones were identified according to the level of TCDD soil contamination. A medical surveil lance programme was set up, but it was not designed asr a sensitive epidemiological study. Chloracne was first reported some 6 weeks after the accident, (he frequency of chloracne correlated to some degree with the ievel of TCDD soil contam ination. It was reported that'by the end of 1978 the ence <rf soft tissue s:,, COfna , . Jd forestry workers in 5u c& l < ai?.r,cu,`u' a Mfwucdnie$cohn^ftivrim- eind/Hbry-oliu.jtcr_ studies "H f,,l^,, cvcharV, Csomno^* PCDDS AND PCDFS: RISKS TO HUMANS cystitis and a unverified skin ft-.-I .1-*- fcuornthdeitriocna,senossteu dhyf5e'*e*Atrep.o. ,,rt.eI .d ' --------- O J t i i N r U I O j o j __________________ _ PCODS AND PCDFS: BISKS TO HUMANS 191 chloracne effect had disappeared. available data showed no single birth defect to be Biochemical effects were studied between 1976 unequivocally linked with 2.3.7,8-TCDD exposure. and 1981 in a group of 700 children, subdivided It should be noted that due lo the limited number according to zone o f residence. Parameters studied o f births in the high exposure zone, the likelihood included liver function tests, lipid metabolism and of delecting anything less than an enormous effect porphyrins. There appeared to be no significant was minimal. difference between groups when related to degree Spontaneous abortion incidence was reported to of exposure or incidence o f chloracne. In the study the health authorities before 1978, and after this of porphyria, although a few cases o f `hereditary' time the only available data were from hospital chronic hepatic prophyria (CHP) were reported, a records. The information gathered indicated no number of confounding causes were involved. In difference between polluted and unpolluted zones, the `non-hereditary' cases, porphyria was reported, although it was noted that a wide variation in rales but its clinical manifestation r- PCT, was lacking. within each zone occurred, possibly attributable lo Goldstein if of.1*1reported 2,3.7,8-TCDD to be the the small numbers involved. A further study was most potent porphyrogenic agent known. It inhibits reported by Remold et ef, m stating that there was uroporphyrinogen decarboxylase (UD). In chronic no increase in abortion rate in the 6 months after TCDD poisoning, this results in an increase in liver the incident. uro- and heptacarboxyporphyrins. It appears that a At the time o f the Seveso incident, a number of single dose does not produce porphyria, although it abortions were carried out. Chromosome analyses has been suggested that such an exposure will lead were performed on aborted tissues, as well as lo PCT if there is a predisposition in the form of an maternal peripheral blood.*"6 Although higher inherited UD defect. frequencies of chromosomal lesions were found in The long-term effects of TCDD in children, aged fetal tissues when compared to adult fibroblasts, 6-10 years at the time of the incident were they were comparable to those observed in investigated by Mocarelit et al.'K Children were amnio!ic fluid cells of 'normal pregnancies* at examined annually from 1976 to 1982. Various corresponding gestation periods. In 1979. aborted subsets were identified according to TCDD con tissues and specimens of maternal blood became tamination of soil at residence. A slight increase in available from control (unexposed) pregnancies. gamma-gfutamyltransferase (GGT) 'and alanine There appeared to be no statistically significant aminotransferase (ALT) was found in boys in the differences between maternal blood and placental `highest contamination zone* (where levels of up to cells between the 'exposed' and 'unexposed' 54 r>pb had been recorded). The results seemed to croups. However, a higher frequency of chromo indicate that males were more susceptible than somal abnormalities was noted in the `exposed* females to this effect. However, it was noted that fetal tissues, indicating the possibility of an effect even the most `exposed' children did not have linked to maternal exposure to 2,3,7,8-TCDD. alteration in cholesterol and triglycerides. Although to date there is no evidence for an Biochemical determinations o f liver function increase in birth defects in this population, it is still were carried out in 427 of the most heavily exposed not possible to draw definitive conclusions about a persons during the year following the incident. No lack of genetic consequence associated with the untoward effects were recorded in this population; chromosomal aberrations In the exposed popula paradoxically the `control' group chosen seemed lo tion. Remoiti rf al.,M reported on a study of exhibit a marginally greater abnormality than the placental tissues from a number of women who exposed group. were 8-12 weeks pregnant at the lime of (he Neurological effects in the exposed populations incident, and who had subsequently been exposed were folIowed-up.lM Peripheral neuropathy was to environmental levels of 2,3.7,8-TCDD. O f the found in 733 residents, who were evacuated 15-20 22 placentae studied, all showed normal histology, days after the accident from the most polluted area. but seven o f these showed unusual ukrastructural The observations made were the result of screening changes. The women were asymptomatic and only a proportion of the total number, at 9 months examination of the fetuses showed no abnormal and 21 months after the incident. The authors ities. Therefore the significance o f these findings identified some cases of mild polyneuropathy. remains to be determined. The lesions identified In view of the animal evidence for a teratogenic could have resulted from factors other than TCDD effect of 2,3,7,8-TCDD, a Seveso Birth Defects exposure. register was set up in 1977, This included all five Investigations into the incidence of stillbirths and and stillbirths in the various Seveso zones and in 11 neonatal deaths indicated that in general, the rates municipalities, covering data from hospitals, local were below those reported for Italy overall and health authorities and paediatric services.,M The were within the ranges for the province of Milan 191 S.A. SKENE at. and *lhe legions of Lombardy. An attempt was made to follow-up all children born in the contam inated tones. The study involved the complete examination of 2989 infants at birth and a periodic examination of physical and behavioural develop ments subsequently. No clear association was demonstrated between health problems and expo sure. but compliance rates were reported to be as low as 30-50%. Any biochemical abnormalities noted were always associated with chronic hepatitis B virus infection. Immunocompeience was studied in children with and without chloracne. in workers at the chemical factory and military personnel. No immunological impairment 'as detected. A further series of studies have been cited in which immune function in exposed children was investigated.1*1 The sub jects demonstrated higher litres or tola) haemolytic complement activity in serum, lymphocyte response to phytohaemagglutinin and pokeweed mitogen in the early part of the series of studies and a tendency toward higher values of peripheral blood lymphocytes. These chances did not correlate with any clinical disease. Finally, studies conducted on mortality of persons living around the area of Seveso at the time of the incident have to date failed to reveal any excess in overall mortality for particular causes such as cardiovascular disease, hypertension and liver disease. A report by the Seveso Cancer Registry indicated a higher I'ciA-tu-p of *ofi tissue sarcoma but no other cancers in exposed subjects, though causality is not yet demonstrable..1" The health experiences of civil and military personnel potentially exposed to phenoxyacid herbicides have been investigated in a number of studies. Conditions studied in these populations including soft tissue sarcoma, other malignant disease, non-malignant physical disease and psychological disease and the development of birth defects in the offspring of exposed persons, are discussed below. Agent Orange and the study o f defects in Vietnam Veterans Between 1962 and 1971 a range of herbicides/ defoliants was sprayed in Vietnam. The most widely used was 'Agent Orange', which was reported to be contaminated by up to 30 mg k g '1 2.3.7,8-TCDD, Among the 2.6 million Americans in Vietnam, only 1200 were crew involved in aerial spraying and 200 were civilians disposing of the surplus. It is reported that in addition to Agent Orange other herbicides based on Pidoram and insecticides based on Malaihion weie also used. thus making the task or determining exposure of these subjects to 2.3.7.8-TCDD very difficult. Greenwald et investigated the association of soft tissue sarcoma with service in Vietnam and herbicide exposure, using the New York Cancer Registry. No such association could be identified. Erickson er a/.119 used the Atlanta Congenital Defects Program in a case-control study to deter mine if children oi Vietnam Veterans had any excess risk of birth defects. Among the piohlems involved in the study was that of evaluating actual exposure to Agent Orange. No evidence could be found Tor an excess risk of birth defects. Donovan er at.,w reported on a study in Australian Vietnam Veterans, in which similar problems were encoun tered regarding assessment of actual exposure. Once more, no association between exposure and risk of malformations in the offspring were found. A study of the general health of the US Air Force herbicide sprayer Veterans was reported in which the results were compared with a control group not involved in spraying.191 The study revealed no increase in Ilie incidence of chloracne or soil tissue sarcoma. However, the exposed Veterans did show higher incidence of non melanoma skin cancer, minor birth defects in offspring, neonatal deaths, liver enlargement, por phyria cutanea tarda and psychological disorders. The methods used to establish measurement or exposure in this study are open to criticism on the crnunds of c-oir. nf niii.lasiifVmion and an alternative approach to the use ut the data has been proposed.19' A further study has been reported on US Air Force herbicide spraying personnel during 1962- 1971. with controls chosen as crew from cargo aircraft.191 The study now includes a planned follow-up to investigate mortality and morbidity until 2002. The results so far have not revealed any abnormal herbicide-associated mortality exper ience. However, it has disclosed a number of medical findings in the exposed group whose significance is of a minor or undetermined nature at present. The extended detailed follow-up will indicate their health significance. The investigators considered there to be insufficient evidence at present to support a cause and effect relationship between herbicide exposure and adverse health in the exposed group, and the data do seem reassur ing in so far as none of the reported symptoms are common to those of dioxin exposure. Studies to identify a link between the use of phenoxyacid herbicides and the development of soft tissue sarcoma and malignant lymphoma have been conducted in Sweden.1 197 New Zealand'71'9*~3',, and United Kingdom.17' Earlier reports of an association with an increased incid- PCDDS AND PCDFS: RISKS TO HUMANS 19] ence of soil tissue sarcoma in exposed agricultural cystitis and a further case study3** reported an and forestry workers in Scdenl'M,,w have not unverified skin condition, nose bleeds, headaches been confirmed by later studies. However, some and diarrhoea. Exposed horses, dogs, cals, birds studies have indicated an excess in risk of non- and mice were seriously affected and died. Animals Hodgkin's lymphoma in exposed workers. In all were more affected than humans; this could result ; cases the studies are unable to reveal a link from marked differences in species sensitivity | specifically with 2,3,7,8-TCDD, since the exposures and/or from differences in intake. are always confounded by the presence of the As part of the general Missouri study, levels of phenoxyacid herbicides. 2.3.7.8- TCDD were measured in adipose tissue taken from groups of exposed and non-exposed Missouri waste oil contamination - exposed subjects.3'" The cases were persons exposed to population studies 2.3.7.8- TCDD either at work, rcstdentially or In 1971. 29 kg of 2.3.7.8-TCDD-cbntaminated recrealionally. All persons in both groups had sludge was mixed with waste oils and used as a dust detectable levels of TCDD in their adipose tissues. suppressant over ten counties of Missouri.1"' By These results indicate the possibility of other 1983 some 241 residential, work and recreational background exposures. Of those subjects demon areas were suspected of basing become con strating adipose tissue levels greater than 100 ppt, taminated. five came from persons exposed during production A number or studies were reported on the of hexachlorophcne and one came from a man who populations thought to be at risk front the had been horse-riding in a contaminated arena. exposures. In a pilot epidemiological study. 130 Some 600 workers at a trucking terminal In people out or some 80(1 considered to be at risk Missouri were investigated in 1983 to evaluate the wcic examined for detailed physical, biochemical. potential health effects of exposure to TCDD- ' immunological and haemalological defects. The contaminated waste oil used as a dust suppres results demonstrated no abnormalities of porphyrin sant.3* A farmer worker who had become grossly metabolism. liver function or lipid metabolism. contaminated, subsequently (some 10 yean after There mas be a number of reasons why no specific the first exposure) developed porphyria cutanea effect was seen, possibly resulting from the limited tarda and later developed tumours in the right scope of the study. femur and pelvis. Angiosarcoma was diagnosed, Part of the pilot study involved the study of but the site of origin (bone o r soft tissue) was not '"n i'i'itsv"1 there were no statistically determined. The causa] association remains significant deferences between 'high* and Tow' uncertain. Thu study of o ilers it dm cm.lam exposure groups in terms of delayed hypersensi inated terminals is continuing and further studies tivity on skin test (indeed there are questions about are being carried out on workers exposed at several the technique) within (be 'high' exposure group chemical plants, but to date nothing significant has there was a small percentage of individuals with been reported. diminished T-helper to T-suppressor cell ratios, suggesting that 2,3,7.8-TCDD exposure may affect human cellular immunity. Further work would be Analytical chemists exposed to a TCDD standard required to confirm these findings. Results of this Oliver30" reported on the clinical progress of three pilot study have been published in greater detail scientists who had become exposed to 2,3,7,8- and the significance or the `findings further dis TCDD standards whilst developing analytical cussed.:<u methods for assessing the dioxin content in 2.4,5-T. A further stud)' on residents exposed whilst living The author considered that effects seen in the on a contaminated caravan site in Missouri was analysis resulted solely from exposure to 2.3.7.8- reported by Hoflman et al..x f None of the studies TCDD. since there had been no previous reports of on residential exposure provide any evidence to adverse effects in colleagues exposed to similar suggest any adverse elfects on liver function or lipid reagents In the absence of dioxin contamination. metabolism disturbance in relatively high risk After limited exposure on few occasions there were groups overall. varying latent periods before the onset of skin An outbreak of poisoning resulting from three effects and signs and symptoms of disease. The horse-riding arenas having been sprayed with the effects seen varied between the individuals, contaminated dust suppressant has been although liver function tests were normal in all reported. ^ Several incomplete case repons were three. On the whole signs and symptoms resolved provided of children and adults with varied symp after about a year following exposure and subse toms. including skin rashes. One child was reported quently follow-up was abandoned because of to have suffered nose bleeds and haemorrhagic negative findings (personal communication). ,? s S.A. SKENE et at. H used thoughtfully. cologist, At present L ,nVes,|gative l0*i- , M: 401-4. thlorioiiert H^L-i'.e? 'ac.'lIc,,D,,'ei'ol and 194 S.A. SKENE n at. Transformer oil: exposure o f maintenance workers and exposure after fires A study was conducted on transformer main tenance workers who had been exposed to the mixed polychlorinated biphenyl product Aroclor 12(0, and occasionally Arodocs 1255 and 1242.*' The chemical contaminants o r PCBs tend to be PCDFs rather than PCDDs. Examination of bulk oils have scvealed TCDF concentrations of 13116 ppb by weight. The results indicated that apart from statistically significant differences for adipose PCBs, 24-hour urinary 17-hydroxycorticosteroid excretion, serum PCB concentration and serum gamma G T , there were no significant biochemical differences found between currently exposed, past and non-exposed groups. Following an electrical transformer lire in an office building in Binghamton (USA), the building became widely contaminated with soot, containing PCBs (23-23 000 ppm) and PCDFs (1-1200 ppm). A ir sampling at the Ena) stages of decontamination showed maximum total PCDF and specifically 2,3,7,8-TCDF concentrations of 264 and 23 pgm . respectively. Low concentrations of PCDDs and polychlorinated biphenylenes were also detected.1" Two years after the incident, chemical analyses were conducted on liver and fat biopsies of subjects 'exposed* to the soot and the results were com pared to fat measurements from `non-exposed* persons.111 Although levels o f PCDDs and PCDFs were higher in the exposed subjects, they were also detected in non-exposed persons at a lower level, thus indicating a `background* body burden of these substances. The signs observed in one exposed subject included hypertension and raised serum cholesterol and triglycerides; whether the association was causal o r incidental is not estab lished, In addition this subject and two others studied had mild portal fibrosis. However in all cases, exposure to a range of compounds had been involved. Toxic rice oil (Yusho) outbreaks In 1963 in south-west Japan and in 1979 in Taiwan, two extensive groups were poisoned by rice bian oil contaminated with PCB heat exchange fluid. The poisoning resulted in thousands of people being affected by a wide range of signs and symptoms referrabte to most organ systems, and including swelling of the upper eyelids with discharge and acneiform eruptions with skin pigmentation.1" Babies born to both affected and non-affected females were found to have abnormal pigmentation of skin, eyelids, nails and gums as well as increased conjunctival discharge. The incident was originally thought to be due to PCBs. The PCBs however, were found to contain high levels of PCDFs and polychlorinated quaterphenyls and more recently, the presence of a further 'compound, 3,4,3\4'tetrachlorobiphenyl has also been delected.1" Levels of PCBs and PCDFs measured in blood, adipose tissue and liver of the two groups were determined1" -1*1 and a number of estimates of amounts of contaminants ingested were assessed.111 In general it was found that the clinical severity correlated more closely with total amount of oil consumed rather than amount of oil k g -'d -1; this is consistent with results from animal studies with 2.3,7,8-TCDD,*1 The health status of affected persons in Japan and Taiwan was reviewed some years later.11 Although a number of signs and symptoms had reduced considerably, some persisted in a substan tial proportion of those re-examined. By the end of 1932, 112 of the affected Japanese had died (of whom in only 31 cases was cause of death confirmed). The small numbers, variety of con ditions and the very mixed exposure did not permit any causal association to be established between death and PCDF exposure. A further analysis1" up to 1983 of 4S7 females and 552 males, of whom 28 females and 42 males had died, presumably (he same population reported by Masuda.1'concluded that there was no significant excess of liver cancer in males and mortality for ischaemic heart disease in females. Other authors1" reviewing 79 male and 41 female deaths in this population found a significant r.-.Liiil! n n c ci death excess only for males (33 observed versus 15.5 expected) accounted for largely by liver cancer (90:1.6 E) and lung cancer (80:2.5 E). A significant excess for heart disease was not found in females in this analysis. Background 'dioxin' exposure In man Monitoring of human tissues for the presence of PCDDs and PCDFs indicates that there ate 'back ground* sources of exposure to these com pounds.111 The primary source of exposure is largely theught to arise from environmental pollu tion from waste disposal, incineration and other combustion operations.1" PCDDs and PCDFs tend to concentrate mainly in lipid-rich tissues, i.e. adipose tissue and human milk-fat. and to a lesser extent in liver, muscle, kidney111 and blood.11J Most of these compounds remain in the body for some lime after exposure. Estimates of half-life values of PCDDs and PCDFs have been_ reported in the literature.101'111 The values seem to depend both on the chlorination number of the chemical as well as the specific isomer in question, Paiterson et at. K*? estimated the half-life of 2.3.7.8-TCDD in adipose tissue to be between 5-8 years, commenting that previous GENP 01U38 C A w o f o o r . ** m,, G H N F O IU ^ / ___________________________ _ PCDDS AND PCDFS: RISKS TO HUMANS 19S estimates of one year were not consistent with the determined that no significant human health hazard results they had obtained in their studies. Another existed, they are of considerable interest lo the Study conducted by Poiger & Sch latter14 indicated toxicologist. a half-life figure of approximately 5.5 years for The most extensively studied of the PCDDs and 2.3.7.8- TCDD in a single male volunteer, although PCDFs Is 2,3,7,8-TCDD. This isomer in certain a more recent presentation indicates the figure to species has been shown to be one of the most toxic be nearer 10 years.1" compounds known. The effects produced in Since samples of liver, kidney, muscle and animals are wide tanging and include thymic adipose tissue can normally only be taken during atrophy, immune system dysfunction, terato surgery or autopsy, the favoured approach for genicity. fetotoxicity and carcinogenicity. O f the more general monitoring studies has been the PCDDs and PCDFs so far studied it appeals that measurement of PCODs and PCOFs in human milk the toxic effects seen lend to vary quantitatively and blood. Hitherto the latter has only been o f use rather than qualitatively, with different species, when major exposures to these chemicals are strains and genders differing in their responses. expected, since the levels are generally very low in Whilst some insight has been achieved into some of such samples because of the limited fat content of the mechanisms o f action at the molecular level, blood. However more recently, blood lipid estima much remains to be determined. The involvement tions of 2.3.7,8-TCDD have been found to of the Ab-reeeptor and the necessity for chlorine correlate well with adipose tissue levels and lipo substitution at positions 2,3.7 and 8 is generally suction has replaced more conventional biopsy. accepted, however further investigation is required Jensen~: carried out a review of results obtained into other possible mechanisms of action. Until the from determinations of PCDDs. PCDFs and PCBs mechanisms of toxicity are clearly understood it in human milk, blood and adipose tissue. He will be difficult to extrapolate the results of animal concluded that the levels associated with 'back studies to man. ground' exposure to PCDDs and PCDFs may be The human data on `dioxins' are limited and 50-300 limes lower than levels associated with difficult to interpret. Human exposure studies have adverse effects from occupational or accidental virtually all been 'non-experimenur and on that exposure. Comparing the results from PCB ground alone present difficulty in interpretation. analyses, it was demonstrated that these occur at Too often the quality of investigation and the time levels of about 10 000 times higher than the sum of lag between exposure and investigation have levels of PCDDs and P C "'" uhnugh these adversely affected the outcome of the study. To substances arc i.cr than PCBs. varying degtees all exposures studied have been to Because these orcaiwm:. have similar mixtures of PCDDs or PCDFs as well as to other sites of concentration in tv . : oo;.. and because of compounds. In the epidemiological studies, it is the potential for toxicological interactions, Jensen rarely possible to distinguish the effects of the suggests it would be wrong to look at only one 'dioxins* from other associated compounds. Neither contaminant at a time. There is experimental has it been possible to distinguish between the evidence for antagonism between certain PCBs and relative human toxicity of different `dioxins' 2.3.7.8- TCDD in effects on enzyme induction (aryl present in mixtures. hydrocarbon hydroxylase, ethoxy rcsorufin O- Attempts to estimate the carcinogenic risk to deelhylase) and immunotoxicity (plaque-forming man from exposure to 2,3,7,8-TCDD have failed lo cell response) varying with the ratio of the two generate consistent results and are therefore agents**7 and, also, evidence for potentiation of unreliable. As 2,3,7.8-TCDD is considered a teratogenic effects with other PCBs (H CB).IIJ tumour promoter and non-genotoxic it is reason able to propose the use of safety factors to assess Discussion the 'acceptability' of a particular level`of exposure. Since PCDDs and PCDFs mostly occur as chemical PCDDs and PCDFs arc both ubiquitous and mixtures, many Regulatory Authorities have < persistent in the environment. They are generated adopted the use of the `TCDD Equivalents' by natural and man-made combustion processes as scheme. This approach relies on the simple welt as being present as unwanted by-products in a addition of toxicological potencies of individual range of commercially important compounds. They chemicals. There are obvious drawbacks to this have been found in body tissues of apparently approach as chemicals In mixtures may also act unaffected animals and humans and it appears that synergisiically or even antagonistically. However, their presence in both occurs largely as a result of until biological assays to predict the overall potency the ingestion of food. Even if at the prevailing of 'dioxin' containing mixtures are available the levels of environmental contamination it were `equivalents' approach seems to be the best option 1)4 S.A. SKENE tt al. if used thoughtfully. PCDDs and PCDFs there foie present a great challenge to both regulator and investigative toxi cologist. At present the ubiquitous nature of these chemicals in the environment, the lack of proven no-effect levels in animal studies and the paucity of data which can be related to man present a number of problems. In the future, with the elucidation or 20; 401-4. * Arsenault RD. Penlochlorophcnol and contained chlorinated dibenzodioxins in the environment. A study of environmental late, stability and significance when used in wood preservation, American Woodpreserver's Association 1976; 122-48. '* Cnunmett WB. Environmental chlorinated dioxins from combustion - the trace chemistries of fire hypothesis. In; Chlorinated Dioxins and Related the mechanisms by which these chemicals produce Compounds. Impact on the' Environment, cd. their multitude of effects, the task of establishing O. Hutzinger pp. 253-63. Pcrgamon Series on 'acceptable levels' in the environment will be made Environmental Science, no, 5, Oxford: Pergamon. easier. Furthermore, it may be possible to gain some insight into the mechanisms of certain natural disorders. " Ballschimiter K, Buchert H. Nicmczyk R. Mundcr A A Swerev M. Automobile exhausts versus municipalwine incineration as sources of the poiychtorodi- benzodioxins (PCDDs) and furans (PCDFs) in the We are grateful to the Department of Health for pemorion to publish. The contents of this article however, represent our views alone and in no way commit the Department. We also wish to acknowledge the generous help or our colleagues within the Department's Medical Toxicology and Environmental Health Division; Dr 5. Barlow, Mr 1. Carmichael, Dr R, Fielder. Miss F' Pollitl. Dr A. Wadge, Dr K. Woodward and all the staff in the Division's Information Unit. environment. Chemosphere 1986; 15: 901--15. 11 Marklund $, Rappe C. Tysklind M A Egcback K. Identification of polychlorinated dtbenzofurans and dioxins m exhausts from cars run on leaded gasoline. Chemosphere 1987; 16: 29-36. 11Esposito MP St Watkins DR.. Airborne dioxins: The problem in review. Presentation given at the 73rd Annual Meeting of the Air Pollution Control Associa tion. June 22-27. 1980. Monlicai. Quebec. 14Crummetl WB St Townsend Dl. The trace chemistries of fire hypothesis: tcvtew and update. Chemosphere 1981; 13: 777-88. '* Olie K. Vermeula PL A Hutzinger O. Chloro-p- References dioxins and chforodibcnzofuians are trace components of fly ash and flue gas of tome municipal incinerators 1 1ARC. Some fumigants, the herbicides 2.4-D and in the Netherlands. Chemosphere 1977; 8: 455-9. 2,4.5-T, chlorinated dibenzodioxins and miscellaneous ' Doyle BW, Drum DA A Laubci JD. The smouldering industrial chemicals. /ARC Monograph 1977; IS: question of hospital wastes. Pollution Engineering li-102. (July l?S5); 35-9. 1 Schiciber R. The clean up begins, Bulletin of Young AL. Lung-leim studies on the persistence and Environmental Contamination and Toxicology 1984; movement of TCDD in a natural ecosystem, fn: M: 726-34. Human and Environmental Risks of Chlorinated * Barnes DO. Assessing TCDD emissions from Dioxins and Related Compounds g eds RE Tucker, municipal waste combustors. Chemosphete 1981: tl; AL Young A AP Gray, pp. 173-90. Environmental MS-55. Science Research 26, 1983. 4 Stanley JS & Sack TM. Protocol for the antlytis of 11Oehme M. Mano S, Mikakcu A A Kirschmer P, 2.3,7,8-tetiaehIorodibenzo-p-dioxin by high resolution Quantitative method for the determination or remlo- gas chromatography/high resolution mass spectro gram amounts of polychlorinated dibenzop-dioxins metry. EPA 60014-86-004; January 1986. * Fishbein L. Analysis of aromatic amines, orgtno- and dibenzofurans in outdoor air. Chemosphere 1986; 15: 607-17. chlorine compounds and 'Dioxin' in biological " Rappe C. Nygren M. Lindstrom G A Ifansson M. samples. In Proceedings o fan International Workshop. Dioxins and dibenzofurans in biological samples or Environ Specimen Banking Monit Relat Banking, European origin. Chemosphere 1986; 15: 1635-9. 1984 w Fatxhetti S. Balisso A. Fichner C. Studies on the * Tong HY, Shore DL. Karasek FW, Helland P St absorption of TCDD by some plant species. Chcmo- Jcllum E. Identification of organic compounds sphere 1986; 15: 1387-8. obtained from incineration of municipal waste by 11 Crosby DG. Conquering the monster - the photo IIFLC fractionation and GC-MS. Journal of Chrom chemical destruction of chlorodioxins. American atography 1984: 285: 423-41. Chemical Society 1978: 173: I--12. ' Ryan 37, Lizotle R St Newsome Wit. Study of 11 Uberti A, Biocco D, Altergfini I A Bertoni G. Field* chlorinated diphenylctheis and chlorinated photodegradation of TCDD by ultraviolet radiations. 2-phenoayphenots as interfetenccs in the determina In: Dioxin; Toxicological and Chemical Aspects eds tion of chlorinated dibenzop-dioxins and chlorinated F Cattabeni el a/., vol. 1, J97S. dibenxofurans in biological samples. Journal of **Tschiriey FH. Dioxin. Scientific American 1986: 254: Chromatography 1984; 303: 351-60. 21-7. * BottomJey P. Chromatographic analysis of hazardous 34 Hutzinger O. Blumteh MJ. Berg M A Olie K. Sources impurities in pesticides. Analytical Proceedings 1983: and fate of PCDDs and PCDFs: An overview. ------- U J L V J O u PCDDS AND PCDFS: RISXS TO HUMANS JP7 Chemosphere 1935; 14; 381-400. hexachlorodrbemofuran on diethyl nitrosamine hepi- i9 Bumpus JA. Tien M, Wright D & Ausi 5D. Oxidation tocarcinogenesis in rata. Cancer Letters 1986; 33: of persistent environmental pollutants by while rot 333-9. fungus. Science 1985; 118: 1434-6. *' Moore JA, Harris MW 4 Afbro PW. Tissue distribu 11 Hutter R 4 Philippi M. Studies on microbial mela- tion of "C-ielrachlorodibenzo-p-dioxin in pregnant bolirm of TCDD under laboratory conditions. In: and neonatal rata. Toxicology and Applied Pharma Chlorinated Dioxins and Related Compounds. Impact cology 1976; 37: 146-7. on the Environment ed. O Hutiinger, pp. 87-93. 41 Nau H 4 Bass R. Transfer of 2,3,7,8-TCDD to mouse Pcrgacnon Series on Environmental Science no. 3. embryo and foetus. Toxicology 1981; 26: 299-308. Oxford: Pergamon, 1981, 41 Nagayama J. Tokudomc S, Kutaliunc M 4 Masuda 11 Malsumura F, Ouensen J 4 Tmshimuto O. Microbial Y. Transfer of PCDFi to the foetuses and offspring degradation of TCDD in a model ecosystem. In; of mice. Food and Cosmetics Toxicology 1980; IB: Human and Enviromental Risks of Chlorinated 133-8. Dioxins and Related Compounds eds RE Tucker, AL 44 Ramsey JC, Hefner JG. Karbouski RJ, Braun WH 4 Young & AP Gray, pp. 191-219, Environmental Gehring PJ. The in vivo biotransformation of 2.3.7.8- Science Research vot. 26. 1983. TCDD in the rat. Toxicology and Applied Pharma 24 EPA (US Environmental Protection Agency). Health cology 1983; 45: 180-4. assessment document for PCDDs. pans I and 2: 41 Olson JR 4 Bitner WE. Comparative metabolism and External Review Draft 1984; PB B4-220268. elimination of 2,3,7.8-TCDD. Toxicologist 1983; 3: " Gallo M. Cited in Pesticide and Toxic Chemical News 103-8. 1985; 13: 13. 44 Weber H- Poiger H 4 Schlatter C, Acute oral toxicity 10 Van den Berg M. deVroom E 4 Olie K. Bioavaili- of TCDD-metaboIitet in male guinea pigs. Toxicology bilHy of PCDDs and PCDFt on fly ash after semi- Letters 1982; H: 117-22. chronic oral ingestion by guinea pig and Syrian golden 42 Mason G 4 Safe S. Synthesis, biologic and toxic hamster. Chemosphere 1986; 15: 519-33. effects o the major 2J,7.8-telracUorodibenio-p- 11 Gasicwicz TA. Geiger LE, Rucci G 4 Neal RA. dioxln metabolites in the rat. Toxicology 1986; 41: Distribution, excretion and metabolism of 2,3,7,8- 153-9. TCDD in C37BL/6), DBA/2J and B6D2F,/J mice. 44 Tutp MTM 4 Hutiinger O, Rat metabolism of Drug Metabolism and Disposition 1983; 11: 397-403. polychlorinated dibertio-p-dioiini. Chemosphere 1978; 11 Gasicwicz TA Neal RA. 2,3,7.8-TCDD tissue 7: 761-8. - ------ - -- distribution, excretion and effects on clinical chemical 4* Williams DT, Cunningham HM 4 Blanchfield BJ. Dis parameten in guinea pigs. Toxicology and Applied tribution and excretion studies of oclichlorodibcitxo- Pharmacology 1979; 51; 329-39. p-dioxin in the rat Bulletin oj Environmental " Alien JR, Van Miller JP 4 Nn:' ' Tissue Contamination and Toxicology 1972: 7: 57-61. distribution, exerttk' and Li-A A f"C)- 20 iscrback Dlf, Erbium JF 4 Allen JR. Tissue TCDD in rats. Food and Ccirr:, .. . neology 1975; distribution and excretion of octachlorodibcnzo-p- 13: 30I-S. dioxin in the rat. Toxicology and Applied Pharma- 24 Van Miller IP, Matfar RJ 4 Alien JR. Tissue cofogy 1975; 32: 330-8. distribution and excretion of tritiated TCDD in non- 21 Birnbaum LS, Decad GM. Matlhcwa HB 4 human primates and rats. Food and Cosmetics Toxi McConnell EE, Falc of 2,3,7.8-TCDF in the monkey. cology 1976: 14: 31-4. Toxicology and Applied pharmacology 1981; 57; Apptelgren LE, Brandt l, Biuebo EB, Gillnet M 4 189-%. Gustafsson JA. Autoradiography of 2J.7.8- 22 Bowman RE, Schsnlz SL, Weeratinghe NCA, Gross teiiachloro (,4C) - dibertzo-p-dioxin: accumulation in ML 4 Banotti DA. Abstract from Dioxin `87 the nasal mucosa. Chemosphere 1983; 12: 343-8. Symposium, USA, 4-9 October 1987, 14 Gillncr M, Bilttbo EB & Brandt 1. Uptake and 92 Vinopal JH 4 Casida JE. Metabolie study of 2,3.7.8- specific binding of 2J.7,B-telraehIoiodibenzD-p-d(oxin TCDD in mammalian Ihrer microsomal systems snd In the olfactory mucosa of mice and rati. Cancer living mice. Archives of Environmental Contamination Research 1987; 47: 4150-9. and Toxicology 1973; I: 122-32. " Dccad GM, Birnbaum LS 4 Matthews HB. 2.3,7,8* 24 McConnell EE, Moore JA, Hiseman JK 4 Harris TCDF tissue dillribulion and excretion in guinea pigs. MW. The comparative toxicity of chlorinated dibcnio- Toxicology and Applied Pharmacology 1981; 57: p -dioxins in mice snd guinea pigs. Toxicology and 231-10. Applied Pharmacology 1978; 44: 335-56. M Birnbaum LS. Dccad GM 4 MaiIhews HB. Disposi 22 Nishiiumi M. Acute toxicity of polychlorinated diben- tion and excretion of 2,3.7,8-TCDF in the rat. xofurans fn CF-l mice. Toxicology and Applied Toxicology end Applied Pharmacology 1980; 55: Pharmacology 1978; 45: 209-12. 342-52. 94 Ptuss N. Poiger H. Hohbieh C, Suter C 4 Schlatter C, 24 Van den Berg M. Otic K 4 Hutiinger O. Uptake and Subchionic toxicity or 2.3.4.7,8-pentichlorodibcnzo- selective retention in rats or orally administered furan (PcCDF) in rats. Chemosphere 1988; 17; chlorinated dioxins and dibemofurans from fly ash and 1099-110. fly ash extract. Chemosphere 1983; 12: 537--44. 22 Hams MW, Moore JA, Vos JG 4 Gupta BN. * Nishiiumi M 4 Masuda Y. Enhancing effect of General biological effects of TCDD in laboratory 2.3,4.7.8pentach1orodibeniofuran and 1.2.3.4.7.B- animals. Environmental Health Perspectives 1973; S: III mm*mz c- i s\ / /O -' ; mm <L-:\ H i-': >.. :*/,; r'm :. V v;-V. f.: .. IM S,A. SKENE er at. Kociba RI, Keeler PA, Park CN A Gehring PJ. 2.3.7.8-TCDD: results ol a 13 week oral toxicity study In mb. Toxicology and Applied Pharmacology 1976; 38: J5W I. " NTP (National Toxicology Program). Bioassay or miiturc of 1-2.3.6,7,8-hcxachlorodibenzo-p-dioxin and U J . 7.B.9-tie*achlorodibenio-p-dio*m (gavage) for possible carcinogenicity, NTP-8Q-I2 1980: PB 81- 134844. Ml Puhvel SM. Sakamoto M. Erth DC & Reisner RM. Hairlets mice at model)' for chloiacne: study of culaneoui change) induced hv topical application of eitablithcd ehloracnegen).' Toiicology and Applied Pharmacology 1982: 64: 492-S03. 11 Knutson JC A Poland A. Kcratinisation ol mouse - letnoma cell line XB produced by 2J.7.B-TCDD; an in vim? model ol tonicity. Cell 1980: 33: 27-36. " Milttone LM A Lavigne JF. 2.3.7.8-TCDD induces hyperplasia in confluent culture) or human kerauno- cytet. Journal o f Investigative Dermatology 1984: II: 332-4. * Schweiz BA. Norri) JM. Spaitchu GL. tt al. Toii- cology of chlorinated dibenzo-p-dioxint. Environ mental Health Perspectives 1973: S: 87-99. M McNulty WP, Pometan)i I A Farrell T. Chronic toaicity of 2J.7.8-TCDF for Rhesus macaques. Food and Cormcrier Toiicology 1981; 19; 57-65. *' Oithl S, Morita M & Fukada H. Comparative toxicity of PCBs and dibenzoluran) in rats. Toxicology and Applied Pharmacology 1978; 43: 13-22. NIT (National Toxicology Program). Carcinogenesis bioassay of 2.3.7,8-tetrachlorodibenzo-p-dioxm (CAS No 1746-01-6) in Osbome-Mendel rats and B6C3F1 mice (gavage study). NTP/S0-31 1982: PB 82-163445. *' Koriba RJ. Keyes DG. Beyer JE tt cl. Result) of a 2 year chronic toaicity and oncogenicity study of 2J.7.BTCDD In rats. Toxicology end Appiitd Pharmacology 1978; 46: 279-303. " NCI (National Cancer Institute). Bioassay of 2.7dicMorodibenio-p-dioain (DCDD) for possible car cinogenicity. NCI Technical Report 1979a: No. 123. PB 290-570. ** NCI (National Cancer Institute). Brakuay of Dichloio-p-dtoxin Tor possible carcinogenicity. NCI Technical Report 1979: No. 122. PB 288-475. TMMcNulty WP. Fcloloairity of 2J.7.8-TCDD for Rhesus Macaques (Macaco mulatto). American Journal of Pnmatology 1984; 6: 41-7. " Allen 18, Barsolli DA, Van Miller JP. Abrahamson LI It Lalich JJ. Morphological changes in monkeys consuming a diet containing low levels of 2J.7.8TCDD. Food and Cosmetics Toxicology 1977; 15: 4P1-10. " Schama 5L, Banotti DA A Allen JR. Toxicological effects In non-human primates chronically exposed to 50 ppt 2,3,7.8-TCDD, Toxicology end Applied Pharmatology 1979; 48: A1B0. T> King ME, Shefncr AM A Bates RR. Caicinogenesii bioasray of chlorinated dibenzodioxins and related chemicals. Environmental Health Perspectives 1973: 5; 163-70. " Toth K. Somfai-Relle S, Sugar J A Bence J, Carcinogenicity testing of herbicides 2.4.5- trichlorophenoxyelhanol containing dioxin and pure dioxin in Swiss mice, Samre 1979: 178; 548-9. " Pitot HC. Goldsworthy T. Campbell HA A Poland A. Ouantilalive evaluation of the promotion by 2.3.7,8TCDD of hcpatocarcioogenesis from dielhylnitrosamine. Conetr Research 1980: 40: 3MA-20. ** Kouri RE. Rude TH. Jngtckar R. er at. 2.3,7,8-TCDD as cocarcinogen causing 3-melhylchoUinlhicne-iniiiaied Subcutaneous tumours in mice genetically 'rnnTcsponsive' at Ah locus. Cancer Research 1978: 38: 2777-83. " Nishizumi M A Mnsuda Y. Enhancing effect of 2.3.4.7.8- prniachloiodibcnznluran and 1.2.3.4.7.8hexachlorodibcnzofuran on dieihslnitrosamine hepalocarcinogenesis in rats. Cancer Letters 1986: 33: 333-9. 71 Digiovanni J. Viaje A. Betty DL. Slaga T i Juthau MR. Tumour initiating ability of 2.3.7.8TCDD and Arodor 1254 in the two stage system of mouse skin carcinogenesis. Bulletin of Environmental Contamina tion and Toxicology 1977; IS: 552-7. " Digiovanni J. Berry DL. Juchau MR & Slaga TJ. 2.3.7.8- TCDD; Potent anicarcinogenic activity in CD-I mice. Biochemical and Biophysical Research Communications 1979: 86: 577-84. M Wassom JS, Hull JE A Lopricno N. A review of the genetic loxtcology of chlorinated dibenrop-dioxins. Mutation Research 1978: 47: 141-60. " Giri AK. Mutagenic and genotoxic effects of 2.3.7.8tetrachlorodibenzo-p-dioxin. a review. Mutation Research 1986; 168: 241-8. " Shu HP. Paustenbach DJ A Murray FJ. A critical evaluation of the use of mutagenesis, catcinogenests and tumour promotion data in a cancer risk assess ment of 2.3,7,8-leirachTorodibcnzo-p-dioxin. Rtgulatory Toxicology end Pharmacology 1987; 7: 37-88. u McCann. Personal communications cited by Wassom et al. 1978 (No. 80). 11 Seiller JP. A survey of the mutagenicity of various pesticides. Experientia 1973; 19: 622-3. " Hussain S. Ehrenberg L. Lofrolh G A Gejuall T. Mutagenic effects of TCDD on bacterial systems. Ambio 1972: I: 32-3. " Geiger LE A Neal RA. Mutagenicity testing or 2.3.7.8- TCDD in histidine auxolrophs of Salmonella typhimurium. Toxicology and Applied Pharmacology . 1981; 59: 125-9. " Gilbert P, Sainl-Ruf G. Poncelet F A Mercier M. Genetic effects of chlorinated anilines and azoben zenes on Salmonella typhimurium. Archiva of Environmental Contamination and Toxicology 1980; 9: 533-41. " Bronzetti G, Zeiger E. Lee 1. Suzuki K A Mailing HV. Genetic effects of 2,3,7,8-TCDD in yeast, in vivo and in vitro. In: Chlorinated Dioxins and Related Compounds, Impact on the Environment, cd. O HuUingcr. Pergamon Series on Environmental Science no. 5. Oiford: Pergamon. J982. ** Rogers AM. Anderson ME & Back KC. Mutagenicity of 2,3.7.8-tetrachlotodibcnzo p-dmxin and petfluro-ndcunoic acid in L5I78Y mouse-lymphoma cells. Mutation Research 1982: 105: 445-9. GENP 010389 PCDDS AND PCDFS; RISKS TO HUMANS IW KnmJorosi A. Fedorcsak I. Solymosv F. Ehrenberg L A Ostctman-GolLat S. Inactivation of OBRNA by electrophiles. Mutation Research 197.1: 17: 149-61. *' Poland A A Glover E. An estimate of the maximum in vjYo covalent binding of 2.3.7.8-TCDD to rat liver protein, ribosomal RNA and DNA. Cancer Research 1979: 39: 3311-1. Allhut FR. Lawrence SD. Sattler GL, Longfellow DG & Pitot HC. Chemical quantification of unscheduled DNA synthesis in cultured hepatneytes as an assay tor the rapid screening or potential carcinogens. Cancer Research 1982: 41: .Mill). Lopricno N, Shrana L. Rusciano D. Lasclatfari D & Lari T. In m o cytogenetic studies on mice and rats exposed to I.J.7.H-TCDD. In: Chlorinated Dioxins and Related Compounds. Impact on the Environment, cd. O Hullinger. pp. 419-28. Pergamon Series on Environmental Science no. 3. Oxford: Pergamon Press. ^ Khcra KS A Ruddlck JA. PCDDs: Perinatal effects and the dominant lethal test in Winar rats. Advances in Chemistry Series 1973: 120; 70-84. *' Hay A. shby J. Styles JA & Elliott B. The mutagenic properties of 2J.7Jbletrachlorodlhenro-pdioxin. Ameriean Chemieal Society 1983; 186: 6 (abstract). " Aberncthy D J. Greenlee WF. Hubind JC it Boreiko Cf. 2.3.7.8-TCDD promotes the transformation of CJH/IOTVi cells. Carcinogenesis 1985: <: 651-3. " Zimmeiing S. Mason JM. Valencia R A Woodruff RL. Chemical mulageneiii testing in Drosophila. II. Results of 20 coded compounds tested for the National Toxicology Program. Environmental Mutagenesis 1985: 7; 87-100. ** Meyne J. Allison DC. Bose K, Jordan SW. Rldolpho PF A Smith J. Hcpatotoxlc doses of dioxin do not damage mouse bone-marrow chromosomes. Mutation Research 1985: 137: 63-9. ** Green S St Moreland FS. Cytogenetic evaluation of several dioxins in the rat. Toxicology end Applied Pharntaeoiog}' 1973: 33: 161 (abstract). Commoner B. Reliability of bacterial mutagenesis techniques to distinguish carcinogenic and noncarcinogenic chemicals. EPA 1976; 60QII - 76 - 022 PB 259-934. ,H1 Schocny R. Mutagenicity testing or chlorinated biphenyls and chlorinated dibenzofurans. Mutation Research 1982: 101: 45-56. Knutson JC St Poland A. 2J.7.B TCDD: failure to demonstrate toxicity in twenty three cultured celt types. Toxicology end Applied Pharmacology 1980: 54: 377-83. "1) Rice RH & Cline PR. Opposing effects or 2.3.7.8- TCDD and hydioconlsone on growth and dilfeienlla- tion of cultured malignant ketxtinocytei. Carrinogenesis 1984: S: 367-71. Nelson JO. Menzel RE. Kearney PC. Pllmmer JR. 2.3,7,8-TCDD: in vitro binding to rat liver mlerosomes. Bulletin of Environmental Contamination and Toiicologv 1977; 18; 9-13. "* Eaton DL A Klassen CD. Effects of 2.3.7.8-TCDD. keponc and polybiomlnaled biphenyls on transport systems in isolated rat hepalocyles. Toxicology and Applied Pharmacology 1979; 31: 137--14. Courtney KD A Moore JA. Teratogenicity studies with 2.J-5-Irichlotophcnoxyacclk add and 2.3.7.8TCDD. Toxicology end Applied Pharmacology 1971; 20: 396-M3. Courtney KD. Copeland MF & Robbins A. The effects or pcnlachtoroniirobeniene, hexachlorohenzene and related compounds on fetal development. 77>iiodnpy and Applied Pharmacology 1976: 33: 239-56. Smith FA. Schweiz BA and Nitwhtc KD. Terato genicity of 2J.7.K-TCDD in CF-l mice. Toxicology and Applied Pharmacology 1976: 38: 517-23. Ncubeil D A Dillman 1. Embrynltixic effects in mice treated with 2.15.-T and 2.3.7.8-TCDD. Xayttyn Sthmelderherg's Archives of Pharmacology 1972: 272: 243-64. "" Spatschu GL. Dunn FL A Rowe VK. Study of the teratogenicity of 2.3.7.8-TCDD in the rat. Food end Cosmetics Toxicology 1971; 9: 405- [I, 111 Giavlnl E. Prali M A Vismala C. RahhH teratology study with 2.3.7.8-TCDD. Eniiranmental Research 1932: 27; 74-8. 1 "'Giavlnl E. Prati M A Viimara C. Embryotoxic effects of 2.3.7.R-telrachtcimdihcnzo-p-dioxin administered to female rats before mating. Environmental Research 1983:31: 104-10. Murray FJ. Smith FA. Nitschke KD, Humlston CG A Kociba RJ. Three generation reproduction study of rats given 2.3.7.8-TCDD in the diet. Toxicology and Applied Pharmacology 1979; 50: 241-52.- - - "^Btrsotii DA. Abrahamson LJ A Allen JR. Hormonal Iterations in Female Rhesus monkeys fed a diet containing 2J.7.8-TCDD. Bulletin of Environmental Contamination and Toxicology 1979; 21: 463-9. "4 Mittler JC. Ertel NH. Peng RX. Yang CS A Kieman T. Changes in testosterone hydroxylase activity in the rat testis following administration of 2.3.7.8-TCDD. Annals o f she New York Academy of Science 1984; 438: 645-8. "* Silbergeld EK A Mattisott DR. Experimental and clinical studies on the reproductive toxicology of 2.3,7.8'lclrachlorodihenzo-p-dioxln. American Journal of Industrial Medicine 1987; II; 131-44 115 Birnbaum LS. Weber H. Harris MW. Lamb JC A McKinneyJD. Toxic Interaction or specific chlorinated biphenyls and 2.3.7.8-TCDD: Incieascd inddence of cleft palate En mice. Taxkotagy and Applied Pharma* cology 1985; 77: 292-302. "* Hassoun EM A Dcnkci L. TCDD cmbryotoxidly In the mouse may be enhanced by fbnaphthoflavonc, another ligand of the Ah receptor. Toxicology Letten 1982; 12; 191-8. Weber H. Harris MW. Hasemin JK A Birnbaum LS. Teratogenic potency of TCDD. TCDF and TCDDTCDF combination In C37BL/6N mice. Tbz/cofogy Letters 1985: 2(: 159-67. Schamz SL. Uughlln WK. Van Valkenberg HC A Bowman RE. Maternal care by Rhesus monkeys or Inlant monkeys exposed to cither lead or 23,7.8tetrachlorodihcn^o-p-dibxltl. Neuroioxicology 1986; 7: 637-50. 2tft S.A SKENE et al " " Bow man R E. Schantz SL. Gross ML 4 Ferguson S. **' Hannah RR. Lund J. Pncllingcr L. Gillner M 4 Abstract from Dioxin *87 Symposium. USA 4-9 Guslaftsnn JA Characterisation of the DNA binding October 1987. properties of the reccptot for 2.3.7.8- Hassoun E. DA rgy R. Denker L. Lundin LG 4 tclrachlorndihenzn /i dioxin European Journal o f Borwcll P. Teratogenicity of 2.3.7.8-TCDF in BXD Biochemistry 1986. IS6 237-12 recombinant inbred strains Toxicology tellers 1984; Jones PBC. Galeazzi DR. Fisher JM 4 Whitlock JP IS: 37-12. Control of cytochrome P,-450 gene expression by Havtoun E . D'Argy R A Denker L Teratogenicity of dioxin Science 1985. 227 1499-1502 2.3.7.8- TCDF in the mouse Journal o f Toxicology 1,7 Kester JE 4 Gasiewicz TA Characterisation of the in and Environmental Health 198-1; 14; 337-51. xtlro stability of the rat hepatic receptor for 2.3.7,8- Weber H. Lamb JC. Marnt MW A Moore JA Iclrjchlorndihcnzo/i dioxin (TCD D ) Arelinei o f Teratogenicity of 2.3.7.8-TCDF in mice Toxicology Biochemistry and Biophssies 1987. 252 6116-25 Letters 1984; 20 183-8 Pratt RM Dcncker l 4 Diewcrt ML 2.3.7.S TCDD- Vecchi A. Sironi M. Canrgrati M A. Recchia M 4 induced cleft palate in the mouse evidence fot G atallini S. Immunosuppressive effects of 2.3.7.8- alterations in palatal shell fusion Teraiogenesit Car TCDD in strains of mice with different susceptibility cinogenesis and Mutagenesis 1984 4 427-36 to induction of aryl hydrocarbon hydroxylase Toxi ,w Denison MS. Vella LM 4 Okey AB Structure and cology and Applied Pharmacology 1983. 8 434-41. (unction of the Ah receptor sulphydrvl groups 154 Luster M l. Faith RE 4 Lawson LD Effects of required for binding of 2.3.7.8-iettachloiodihenzo-p- 2.3.7.8- TCDF on the immune system in guinea pigs dioxin to cytosolic receptor from rodent livers Drug and Chemical Toxicology 1979; 2: 49-40 Archives o f Biochemistry and Biophysics 1987; 252 Clark D A . Gauldie I. Szewczuk MR 4 Sweeney G. 388-95 Enhanced supptessor cell activity a t a mechanism of Gallo MA. Hesse EJ MacDonald GJ 4 Umbreil TH immunosuppression by 2.3.7.8 TCDD Proceeding! o f Interactive effects of estradiol and 2.J.7.8- the Society for Experimental Biology and Medicine tetrachlorodibenzo p dioxin on hepatic cytochrome 1981; 148: 290-9. P450 and mouse uterus Toxicology l etters 1986. 32 IJ* Nagatkalli PS. Sweeney G D . Gauldie J 4 Clark DA. 123-32 Sensitivity to tupression of cytotoxic T-ctll generation 1,1 Gasiewicz TA 4 Bauman PA Heterogeneity of the by 2,3.7.8-TCDD is dependent on the Ah genotype of rat hepatic Ah teccptor and evidence for transfotma- the murine host. Toxicology and Applied Pharma lion in vitro and in vivo. Journal o f Biological cology 1984 ; 72: 169-76. Chemistry 1987; 262 2116-20 1,7 Faith RE 4 Moore JA . Impairment of thymus- Sloop TC 4 Lucier GW Dose-dependent elevation of dependent immune functions by exposure of the Ah receptor binding by TC DD in rat liver Toxicology developing immune system to 2.3.7.8-TCDD. Journal and Applied Pharmacology 1987; 88 329-37. o f Toxicology and Environmental Health 1977; 3 147 Stohs SJ. Hassan MO 4 Murray WJ Lipid peroxida 451-64. tion as a possible cause of TC DD toxicity Bio Thomas PT 4 Hindsill RD The effect of perinatal chemical and Biophysical Research Communications exposure to TCDD on the immune response of young 1983; III: 854-9 mice Drug and Chemical Toxicology 1979; 2: 77-98. 144 Hassan MQ. Stohs SJ A Murray WJ Effects of '** Kerkvtei! N l. Braunet JA 4 Matlock JP Humoral vitamins E and A on 2.3.7.8-TCDD induced lipid immunotoxieily of polychlorinated diphenyl ethers, peroxidation and other biochemical changei in the rat phenoxyphenols. dioxins and furant present at con Archives o f Environmental Contamination and Toxi taminants of technical grade penlachlorophenol. cology 1985; 14 437-42 Toxicology 1985; 34: 307-24. ,45 Robertson LW. Regel U. Filser JG 4 Oesch F llolsapple MP. McCay JA 4 Barnes DW Immuno Absence of lipid peroxidation as determined by ethane suppression without liver induction by subchronic exhalation in rats treated with 2.3.7.8-TCDD. espoturc to 2,7-dichlorodibenzo p-dioxin in adult Archives o f Toxicology 1985; 57: 13-16 female B6C3FI mice Toxicology and Applied Phar '** Thunberg T. Ahlborg UG 4 Johnsscm H Vitamin A macology 1986; 83 445-55. (retinol) status in the rat after a single oral dose of Poland A 4 Glover E. A model for the mechanism of 2.3.7.8- tetrachlorodihenzo p-dioxtn Archives o f Toxi action of 2.3.7.8-TCDD Estrogens in the Environ cology 1979. 42. 265-74 ment. ed. McClachan Netherlands: Elsevier. 1980 147 Hakansson H 4 Ahlborg UG The effect of 2.3.7.8- 111 Poland A. Greenlee WF 4 Kende AS Studies on the TCDD on the uptake, distribution and excretion of a mechanism of action of the chlorinated dibenzo-p- single dose of ( I I . 12 If) - rclinyl acetate and on the dioxins and related compounds New York Academy Vitamin A status in the rat Journal o f Nutrition 1985; o f Science 1979; 320: 214-30. 115: 759-71. 1,1 Shara MA 4 Stohs SI Biochemical and toxicological '** Rozman K Hexadecane increases the toxicity of effects of 2J.7.8-tettachlorodibenzo-p-dioxin (TCDD) 2.3.7.8- tetiachloiodibenzo-p.dioxin (TCD D) is brown congeners in female rats Archives o f Environmental adipose tissue the primary target in TCDD-induced Contamination and Toxicology 1987; 14: 599-605. wasting syndrome** Biochemical and Biophysical Kuchin KT 4 Woods JS 2.3.7.S TCDD induction of Research Communications 1984; (25 996-1004 AHM in hepatic microsomcs from female rats. ,4" Bannister R 4 Safe S Synergistic interactions of Toxicology and Applied Pharmacology 1978; 45: 297 2.3.7.8- TCDD and 2.2* 4 4*. 5.5'-hcxachlortihiphenyl (JfcINF U1U39U PCDDS AND PCDFS RISKS TO HUMANS 201 in C57BL/6J and DBA/2J mice. Role of the Ah Masseninloxikulion durch. 2.3.6.7 irlrachlorcxJibrn.ro- receptor Toxicology 1987; 44: 159--4*9 dioxin Der H auian: 1973; 24: 149-52. " " Ncuherl D. Zens P. Rothenwalner A A Merker NJ A Theiss AM . Frentzel-Beyme R A Link R. Mortality survey of the embryotoxie effects of TC D D in study of persons eiposcd to dtoxin in a irichloro mammalian species Environmental Health I'crspcc- phcnol process accident that occurred in the BASF I I I 1973; 5: 67-79. AG on November 17 1953. American Journal o f 1,1 Hassoun EA In vivo and in vitro interactions of Industrial Medicine 1982; 3: 179-89. TCDD and other ligands of the Ah receptor; effect on ' * Sorup P. In: Chlorophenols and Phcnoxy-herbicides. cmbrvonic and fetal tissues. Archives o f Toxicology Arhcjdslilsynet. Copenhagen 1982. (Cited by Lynge. 1987. 61 145-9. 1985 |N o 17 1)). ,v Bannister R A Safe S The effects of receptor 1.1 Lynge E A follow-up of cancer incidence among antagonists on the AHII induction activity of 2.3.7.8- workers in manufacture of phenoxt herbicides in TCDD in C57BL/6 and DBA/2 mice I.3.6.8 TCDF Denmark. British Journal o f Cancer 1985; 52: 259-7U Chrmosphere 1987. 16 1739--12. Coggan D . Pannell B. Winter PD. Acheson ED & USEPA (tin n ed States Environmental Protection Bonsai J Mortality of workers exposed to MCPA. Agency) Health assessment document for poly Scandinavian Journal o f MW4 and Environmental chlorinated diben/o p-dioxins EPA-6(Ky8-IU-0|4F. Health 1986; 12. 448-54. National Technical Information Service. Springfield Suskind RR A HcrUbcrg VS. Human health effects of 1985. VA PB86-1225461AS. 2.4.5- T and its toxic contaminants Journal o f the I,J Dugois P. Marechal J A Colomb L Acne chorique au American Medical Association 1984 : 251: 2372-80. 2.4.5-trichlotophenol Archivej Maladies Profes 1.1 Zack JA A Suskind RR The mortality experience of sionelles 1958. 19: 626-7. workers exposed to lelrachlorodibenzodioxin in a *'* C oot R R . Townsend JC. Ott MG A Silverstein LG. trichlorophenol process accident. Journal o f Occupa Mortality experience of employees exposed to 2.3.7.8 tional Medicine 1980; 22 11-14. tctrachlondibenzo-p-dioxin Journal o f Occupational Moses M A Prioleau PG. Cutaneous histologic Medicine 1980. 22: 530-2. *'* Cook RR. Bond G O . Olson R A . Ott MG A Gondck findings in chemical workers with and without Chiosacne with past exposure to 2.3.7.R lelrachlorodibenzo MR Evaluation of the mortality experience of p-dioxin Journal o f the American Academy o f workers exposed to the chlorinated dioxins Chemo- Dermatology 1985; 12: 497-506. sphere 1986: IS; 1769-76. " * Moses M. Lilts R. Crow KD. et a! Health status of Baxter RA Biochemical study of pentachlorophenol workers with past exposure to 2 .3.7.8 workers Annals o f Occupational hygiene 1984 ; 28; leirachlorodibenzo-p-dioxin in the manufacture of 429-38 2.4.5- ltichlorophenoxyacelic add: comparison of find IM Holmstedt B. Prolegomena to Seveso. Archives o f ings with and without chloracne. American Journal o f Toxicology 1980; 44; 211-30. Industrial Medicine 1984; 5: 161-82. Dalderup LM A Zcllenrath D Dioxin exposure: 20 1.1 Pazderova-Vejlupkova I . Nemcova M. Picknova J. year follow-up (teller). Lancet 1983; II: 1134-5. Jirasek L A Lukas E The development and prognosis May G Chloracne from the accidental production of of chronic intoxication by tetrachlorodibenzo-p-dioxin lelrachlorodibenzodioxin. British Journal o f Industrial Medicine 1973. 30 276-83. in men Archives o f Environmental Health 1981; 36: 5-11. May G Telrachlorodibenzodioxin: a survey of Poland A P. Smith D. Metier G A Possick P. A health subjects ten years after exposure British Journal o f study of workers in a 2.4-D and 2.4.5-T plant. Industrial Medicine 1982; 39: 128-35. Archives o f Environmental Health 22: 316-27. Jensen N E. Sneddon IB A Walket A E. Tetra- " * Bleiherg J. Wallen K. Brodkin R A A pplcbjum I. chlorobeniodioxin and chloracne. Transactions o f Industrially acquired porphyria Archiver o f Derma 5i John's Hospital Dermatology Society 1972; 58: tology 1964; 89 793-7. 172-7 Jones RE A Chelsky M. Further discussion concerning Walker AE A Marlin JV. Lipid profiles in dioxin- porphyria cutanea tarda and TCDD exposure. exposed workers. Lancet 1979; I: 446-7. Archives o f Environmental Health 1986; 4 |: 100-3. Martin JV Lipid abnormalities in workers exposed to Goldstein JA . Hickman P. Bergman H A Vos JO. dioxin British Journal o f Industrial Medicine 1984; 41: Hepatic porphyria induced by 2.3.7.8TC D D in the 254-6 mouse Research Communications in Chemical Path- Blank C E . Cooke P A Potter AM Investigations for olngv and Pharmacology 1973; 6: 919-28 gcnotoxic effects after exposure to crude 2.4.5- Mocarelli P. Marocrhi A. Brambilla P. er at. Clinical Irichlorophcnol British Journal o f Industrial Medicine laboratory manifestations of exposure to dioxin in 1983. 40 87-9 children: a six-year study of the effects of an Hoffman H Th Neute erfahrungen mil Hochtoxischen environmental disaster near Seveso. Italy. Journal o f Chlorkohlenwasscrstoffen. Archiver o f Experimental the American Medical Association 1986. 256: 2687-95. Pathology and Pharmacology 1957; 2J2: 228-30. Filippini G . Bordo B, Crenna P. Massetto N. Musicco Goldm ann PJ Schwerste akute chloracne durch M A Bocri R Relationship between dinical and Trichlotphenolzersetzunp Produkte. Arbeitsmedizin electrophysiological findings and indicators of heavy Sozial Medizin und Arhenshygeine 1972; 7 12-18. exposure to 2.3.7.8-lettachlorodibenzo-diotin. "* Goldm ann PJ. Schwerste akute chloracne eine Scandinavian Journal o f Work and Environmental I 101 S.A. SKENE cl at. Health 1981: 7: 237-62. i" plfa CM A Del Corno G. Pregnancy outcome in the Interview Endings concerning phenoxy acid exposure. Chetnotphcre 1983. 12: 365-71. Severo area after TCDD contamination. In: Preven '** Smith AH. Pearce Nl. Fisher DO. Giles ID. Teague tion of Physiol and Mental Congenital Defects. CA & Howard JK. Soil tissue sarcoma and exposure Pan D: Epidemiology. Early Detection and Therapy, to phenoxyhcrbicides and chlorophcnols in New and Environmental Faeton, ed. M. Mantis. Progress Zealand. Journal of the AWrumf Cancer Institute 1984. & in Clinical and Biological Research Series, voi. I6JB, 73: 1111-17. ; pp, 279-8}. New York: Alan R Lisi Ine.. 198J. *" Pearce NE. Smilh AH & Fisher DO. Malignant ** Remoti! G. DcVirgitii G. Bianco V A Candiani GB, lymphoma and multiple myeloma linked with agricul The mnipbnlogy of early irnphoblnU after dioxin tural occupations in a Ncu Zealand Cancer Registry poisoning In the Severa ate*, Placenta 1981:1: 33-62. based studs. American Journal of Epuh-mintogv 1983: Tcnchlni ML, Crimaudo C. Pacchetti G. Mottura A, III; 223-37. Agosti S & De Carli L. A comparative cytogenetic Pearce NE. Smilh AH, Howard JK. Sheppard RA. study on eases or induced abortions in TCDD- Giles HJ Sc Teague CA. Non-Hodgkin's lymphoma exposed and non-caposed women, Environmental and exposure lo phenoxy herbicides, chlorophcnols. Mutagenesis 1983: 5: 73-83. fencing work, and meal works employment: a case- 1.1 Puntoni R. Merlo F. Fini A. Meaeia L A Sant L. Soft control study. British Journal of Industrial Medicine tissue laeternai in Seveso. Lancet 1986; It: 323. t I9B6: 43; 75-83. "* Greenwald P. Kovasinay B. Collins DN A Therriaul ** Webb KB. The pilot Missouri health effect study. G. Sarcoma or soft tissues after Vietnam service. Bulletin of Environmental Contamination and Toxi Journal of the National Cancer Institute 1984; 73: cology 1984: 33: 662-72. 1107-9. :d> Knulsen AP. Roodmen ST. Slavin RG. er al. Missouri In Erkktson JD, Mulinare I. McClain FW, cl al. Dioxin Health Studies Progress Report: Characterisa Vrctium Veterans risk Tor fathering babies with birth tion ol Immune Parameters in Humans Potentially delects. Journal o f the American Medical Association exposed to Dioxin, Si Louis University Medical 1984: 232: 903-12. School. Missouri Department of Health, Centres for Iw Donovan 1W. Aden MA, Rose G A Battisiulta D. Disease Control. 1983. ' Case Control Sludy of Congenital Anomalies and w Stchr P. Sten G. Falk H. el al. A pilot epidemiological Vietnam Service (Birth Defects Study). Canbetsa: study of possible health effects associated with 2.3.7.8- Australian Government Publishing Service. 1983. teiracfalorodibenio-p-dioxin conlaminalions in 1.1 Lathrop GD. Wolfe WH, Albanese RA & Moyanhin Missouri, Archives of Environmental Health 1986: 41: ---- PMr An epidemiologic investigation of health effects 16-22. in Air Force personnel following exposure to herbi ** Hoffmin RE. Slebr-Grecn PA. Webb KB. er of. cides. Baseline morbidity study results. US Air Force Health effects of long-term exposure to 2.3.7.8- Report 1983. letrichlorodibcnio-p-dioxin. Journal of the American 1.1 Stellman SD & Stellman JM. Estimation of exposure * Medical Association 1986: 155: 2031-8.. to Agent Orange and other derollanti among *"* Kimbrough RD. Carter CD, Liddle JA, Oltne RE & American troops in Vietnam: a methodological Phillips PE. Epidemiology and pathology of a letra- approach, American Journal of Industrial Mrdicinr chtorodibcniodioxin poisoning episode. Arcitivts of 1986: 9: 305-21. Environmental Health 1977; 32: 77-86. Wolfe WH. Lathrop GD. Albanese RA A Moynahan ***Kimbrough RD, Falk H A Stehr P. Health implica PMrftJi epidemiologic investigation or health effects tions of 2.3.7.B-ietrachlorodibenaodioxin (TCDD) in Air Force personnel following exposure to herbi contamination of residential soil Journal o f Toxi cides and associated dioxins. Chrmospherr 1983: 14: cology and Environmental Health 1984; 14: 47-93. 707-16. m Patterson DG. Hoffman RE, Needham LL. er al. " Hardell L * Sanstrom A. Case-control study: oft- 2J.7,8-telrachloiodibeneo-p.dioxtn levels in adipose Iissue sarcomas and exposure to phenoxyaectic adds tissue of exposed and control persons in Missouri. An or chfotophcnols. British Journal o f Cancer 1979: 39: interim report. Journal of the American Medical 711-17. Association 1986: 256: 2683-6. lrl Hardell L. Eriksson M, Lenner P. Lundgren E. Hope W. Lischwe D. Russell W 4 Weis S. Porphyrii Malignant lymphoma and exposure to chemicals, cutanea tarda and sarcoma in a worker exposed to especially organic solventi, chlorophenots and 2,3.7,8-ieirachlorodibenrodioxin-Mssouri. Mortality phenoiy-arids. A case-control study. British Journal and Morbidity Weekly Returns 1984; 33: 113-14. o f Canter 1981; 43: 169-76. ^ Oliver RM, Toxic effects of 2.3.7.8-telrachlorodihenio- '"Eriksson M. Hardell L. Derg NO. Moller T & 1,4-dioxin in laboiatoty workers. British-Journal of Axclson O. Soil tissue titcoma and exposure to Industrial Medicine 1975: 32: 49-33. chemical substances: a case-reference study. British 1.0 Atbro PW. Crummeti WB. Dupoy AEJ, el at. Journal o f Industrial Medicine 1981; 38: 27-33. Methods for the quantitative determination of mul Wiktund K A Holm LE. Soli tissue sarcoma risk in tiple. specific polychlorinated dibenzo-p-dioxlns and Swedish agriculture and forestry workers. Journal of dibenzofuran isomers in human adipose tissue in the the National Cancer Institute 1986: 76: 229-34. parti-per-trillion range. An interlaboralory study. Smith AH. Fisher DO, Giles HI A Pearce NE. The Analytical Chemistry 1985: 57: 2717-23, New Zealand soft tissue sarcoma case-control study. 1.1 O'Keefe PW. Silkwonh JB. Gicrthy JF. et al. VENP 010391 PCDDS AND PCDFS: RISKS TO HUMANS 203 Chemical and biological investigation* of a Iruni with special reference to death from liver cancer. former acddenl ai Binghamton NY. Environmental gain to Seibunugaku 1985; lit : 11-16. Health renpfftiits 1985; 0: MI-9. Kirattune M, Nakamura Y. Ikcda M ft Hiiofuta T. 111 Scheeler A. Tiewan T. Schaffncr F. n of, Paiicnl fa) Analysis id deaths seen among patienti with Yusho: a biopsies for chemical analysis and liver biopsies for preliminary report. Chemotphere (in press). ultra-structural characteristics aller exposure to poly Schccter A. Ryan J1 ft Lizotte R. er af. Chlorinated chlorinated dioxins, furans and PCBs, Environmental dibenzodinxins ami dibenzofurans in human adipose Ittahh renprairtt 19S. 60: 241-54. tissue. Chemotphere 19S5: 14: 933-7. Katntsune M. Yoshimura T, Matsuraka J & 111 Jensen AA. Polychlorinated biphenyls (PCBs), poly Yumuguchi A. Epidemiological study on Yusho. a chlorinated dibcnio-p-dioxin (PCDDs) and poly poisoning caused by ingestion of rice oil contaminaled chlorinated dibenzofurans tPCDFtl in human milk, with a commercial brand of jmlychlurinatcd biphenyls. blood and adipose tissue. Scirner of the Total Environ- Enitrcinmemat Htalih Ttrspeaim 1972: I: 119-28. mtnt m l : M: 259-93. *MChen PH-S. Luo. M-L. Wong C-K ft Chen C J. Ryan JJ. Schccter A. Lizotte R, Sun Wing F ft Miller Polychlorinated biphenyls, dibenzofurans and qualcr- L. Tissue distribution of dioxins and furans from the phenvls in the toxic rice-bran oil and PCBs in the . general population. Chemotphere 1985; 14; 929-32. blood of patients with PCD poisoning in Taiwan. Rappe. C ft Nygren M. Chemical analysis of human ' American Journal of Industrial Mediant I98J: 5: samples: identifrcaticxi and quantification of poly 1.13--IS. chlorinated dioxins and dibenzofurans. Environmental :i' Bandicta S. FaneP K. Mason G. et al. Comparative Science Research 1981:3t; 305-14. loxicities ol the polychlorinated dibenzofuran (PCDF) Gorski T. Konopkn L ft Brodzli M. Persistence of and biphenyl (PCB) mixtures which penist in Yusho some polychlorinated dibcnzo-p-dioiinl and poly victims, Chtmotphert 1984; 13: 507-12. chlorinated dibenzofurans of pcntachloronhcnol in '** Kashimoto E. Miyata H. Kunita S, rr at. Role of human adipose (issue. Roezn Pzb lout- ' 297-301. polychlorinated dibenzofurans in Yusho (PCB) Poigcr H ft Schlatter C. Pharm tf TCDD poisoning. Archhri o f Environmental Health 1981:36: in man. Presented at the P npou'um. 321-6. Bavrcutb H -l 11 ' Hayabuchi H. Yoshimura T ft Kuratiune M. Con P r ' . ski T. Tuard I ft sumption of toxic oil by Yusho patienta and its relation j 2J.7Jt-tctrachlofodibcnio- to the clinical response and latent period. Food nr .i.i an(jg.>:.. effects on enzyme induction and' Cotmeiia Toxicology 1979; 17: 435-61. immunoioxtcity. Toxicology 1987; 46: 29-42. ll* Masuda Y. Health status of Japanese and Taiwanese Poiger H ft Schlatter C. Presentation at the Dioxin *88 after exposure to contaminated rice oil. Environmental Symposium, UMEA, Sweden. September 1988. Health Perspectives 1985: 60: 321-3. ]l* Amano M. Yalsuki K ft Umeda G. Cohort study on (Received 3 December 1983; accepted J9 December the causes of death in Yusho (PCB poisoning) patients i m >