Document 6BgLEr5QvpL6ed3XbzGewg88R

and the environment . G. McConnell, D. M. Ferguson, and C. R. Pearson *. In recent years there has been concern about the potential toxic hazards of chlorinated organic compounds used as insecticides. It has come to be assumed that similar hazards arc presented by chlorinated hydrocarbons generally, many of which are manufactured and used in large quantities. The evidence reviewed in this article indicates that while a number of C, and C2 chlori nated aliphatic compounds arc widely distributed, they do not accumulate to the same extent as the chlorinated insecticides nor do they have their extreme persistence in the environment. In recent years concern has been shown over the domestic applications. Although industrial solvents 2re to environmental effects, on both wildlife and man himself, . a large extent recovered, the production of these solvents of the organo-chlorine insecticides (of which DDT is a represents the need to replace the handling losses incurred familiar example) and the polychlorinated biphenyls in their use. The quantities in column (a) therefore repre (PCB). This concern has extended to all `chlorinated sent the annual losses to the environment. This toss will hydrocarbons': consequently they have been included in arise from a multiplicity of sources, correlated with local 'the class of chemicals banned by the Oslo and Paris factors such as population density and industrial activitv. Conventions to regulate the discharge of waste into the The products in column (b) serve primarilv as chemi sea. We have made a study of the potential environ cal intermediates. The amount of them that enters the mental impact of those chlorinated aliphatic hydro environment is a very small fraction of the total produc carbons that are manufactured on a large scale. Several tion, and is limited to relatively few chemical manufac-. surveys relevant to such a study have been published turitig sites. At these sites smaller amounts of by-products recently, either as review articles or in government or will also be produced; these range from other chlorinated intergovernmental reports; a useful discussion has been C, hydrocarbons to chlorinated hydrocarbons of higher presented by G. T. Goodman [i]. The following factors molecular weight and tarry residues. These residues have must alt be considered, (a) What quantities are produced; in the past been dumped partly on land, but pariicularlv how, where, and in what form the materials are released at sea; A. Jernelov and co-workers [2] base described to the environment; (b) how they are distributed, and the effects of`EDC tar' dumped in the North Sea. The in what concentrations they occur in the atmosphere, in residues are now either incinerated under controlled fresh and marine waters, and in soil sediments; (c) at conditions, or returned where possible as raw material what levels they exhibit toxic effects to man or wildlife; . to modified production plants, in particular for manu (d) whether they accumulate in living organisms, and, facture of carbon tetrachloride. in particular, become concentrated up food chains; The products listed in Table t are characterized by (c) how stable they are in the environment, and whether high volatility and low solubility in water; some of their any of the products of degradation arc themselves likely physical properties are shown in Tabic 2. They enter the to have ill-effccts. environment primarily by evaporation to the atmosphere. Some chlorinated hydrocarbons will, however, be found Emission and distribution pathways . in aqueous effluents from factories handling them, and World production capacities for all the major chlorinated even in household sewage, and so will pass into municipal hydrocarbons are shown in Tahle i. Of the compounds drainage systems and rivers. During the determination of in column (a) the fluorochloromcthaucs arc extensively the partition coefficients shown in the last column of used as aerosol propellants; and are therefore almost Table 2, it was found that there is a rapid transfer of the completely lost to the atmosphere after use. The others chlorinated compound both from air to water, and from are employed principally as solvents in industrial or . water to air. Irrespective of whether the initial loss of chlorinated hydrocarbon is to the atmosphere or the 6. McConnell, M.4., BJc. - Wi born In England In tsts, Educoted st tbs Collegiate School, Liverpool, and the University o< OUord, where he graduated In chemistry in 1941, fn 1942 he Joined the Research Department pi. the then General Chemicals Division ol ICI (Since merged Into Mond Division). He has been Involved In S range Ol Industrial research problems, mainly in the field of organle chemicals end aince 1871 hat had a major interest In the environmental Impact ol the halo-organic compounds. 0. M. Ferguson, 8.Sc. Ph.D. Wat born in Scotland in 19*0. Ho graduated (in physiology) from Aberdeen Unlverelty In 196} and obtained hie doctorate from Edinburgh University in 1969. In 1966. he |olned ICI's Industrial Hygiene Research Laboratories (now Central Toxicology Laboratory) where he lias been concerned with the loslcotoglcel evaluation ol a wida range of industrial and agricultural chemicals. C. R. Pearson, M.A. Was born In England In 19:9. Read Natural Sciences af the Unlvereily of Cambridge, ipectallilng In biochomittry. He Joined ICI in t9S2, at the Brilham Laboratory in Devon. He hae been involved In e wide ranoe of atudlee associated with both assessment and prevention of water pollution. - hydrosphere, the transfer processes will lead to a wide distribution of these compounds, with aerial transport playing a major part. Such processes explain the occur rence of some chlorinated hvdrocarbon in rainfall and upland waters. OSW 033780 Table 1 Estimated world production capacities (1973) of major chlorinated hydrocarbons, in 10* tons1year (a) lb) Trichloroethylene 1010 Perchloroothlyene 1050 1,1,1-Trlchloroethane 480 Methylene chloride 400 Trichloronuoromelhone <85 Dlchldrodifluoromethano 570 Vinyl chloride 1,2-Dichloroethane Carbon tetrachloride Chloroform -Methyl chloride 10 500 19 500 1000 S<5 350 STLCOPCB4017742 Occurrence In (he environment Techniques for the isolation, identification, and measure tetrachloride arc widely distributed at the pg/kg level or lower. In addition some samples of sea water from ment of DDT and PCB have been extensively studied and Liverpool Bay, which receives large volumes of industrial described. Almost all depend on solvent extraction, and domestic effluents, contain traces {less than 1 pg/kg) careful clean-up by column chromatography, and of tctrncklorocthane, pcntachloroctlianc, penta- and measurement by gas-liquid chromatography (GLC) hcxachlorobutadicnc (HCBD), hcxachlorobenzcne, and using an electron capture detector. Where possible, y-benzenc hcxachloridc. identification is confirmed by a linked mass-spectrometer Samples of marine sediment from Liverpool Bay con MS . Although the same basic methods can be applied tained the same compounds as the overlying waters, but to the other industrially important chlorinated hydro there was no correlation between the chloro-organic carbons, their high volatility introduces considerable content of the sediment and that of the mid-depth water difficulties at the sampling, extraction, and GLC from the same point on the sampling grid. It appears that t separation stages. In addition, the response of the electron coarse gravels have little adsorptive capacity for these capture detector varies widely according to the number compounds, whereas sediments rich in organic detritus of chlorine atoms in the molecule, and this results in very have a much higher adsorptive capacity. Averaged over considerable differences in the sensitivity and accuracy all samples, the concentrations of chlorinated CJCt of determinations of different compounds. But these, compounds in the sediments were similar to those in the difficulties have been overcome. . water; hexachlorobutadiene with its higher molecular Initial observations of the occurrence of chlorinated weight does, however, show concentration factors up to hydrocarbons in the atmosphere have been made by a hundredfold. J. P. Riley [3], J. E. Lovelock [4], P. E. Wilkniss [5], and P. G. Simmonds [6]. Our own observations in the Occurrence In animal tissue atmosphere of north-western England, as well as a much Details of the distribution of chlorinated hydrocarbons fuller range of measurements in water, sediments, and in the tissues of marine plants and animals are being marine organisms are given elsewhere [7]. All the authors published [7]. The compounds found in sea water are agree that fluorochloromcthane, tri- and perchloro- also found in marine animals. Concentrations vary from eihylcnc, chloroform, and carbon tetrachloride are found 1 pg/kg or less in invertebrates, to 10 ug/kg in the flesh universally in the atmosphere at concentrations normally of fish, to a maximum of 50 pg/kg in the eggs of sea birds in the range between 1 and jo ng/1; we ourselves also and the blubber of seals. Special attention was paid to found i,i,[-trichloroethane at a similar concentration. the fatty tissues of sea birds and mammals, as these The distribution of fluorochloromethanes and of tri represent the highest trophic levels in which DDT and chloroethylene, perchloroethylene, and trichlorocthane, PCB arc found to accumulate. As man occupies a which are major solvents, is consistent with their usage. similar position at the head of a series of food chains, The concentrations of chloroform and carbon tetra analyses of a wide range of foods, of both animal and chloride, which are chemical intermediates with limited vegetable origin, have been made; the results are shown losses, is somewhat surprising, and led Lovelock to in Table 3. Finally, it has been possible to carry out suggest that they may arise naturally by reaction between some analyses of post-mortem human tissue; results are chlorine and methane in the atmosphere. presented in Table 4. During the early stages of these Analyses of rain-water, rivers, municipal water sup investigations it was not possible to distinguish analyti plies, and the sea [7] again show that tri- and per- cally between carbon tetrachloride and trichlorocthane, chloroethylcne, trichlorocthane, chloroform, and carbon but improved technique allowed this later. A summary of the results from this and the previous section is presented Table 2 Physical properties of some aliphatic chlorinated hydrocarbons in Table 5. From these results we draw two main conclusions: (a) The B.P. CC) Vapour pressure ' (mm Hg/20C) Solubility In water at 20C (parts/10` w/'w) Partition coefficient water/air at 20C (w/v per concentrations of DDT and PCB in fatty tissues are at least three orders of magnitude greater than those of the industrial solvents, (b) Chloro form and carbon tetrachloride are w/v) very widely distributed, and at un Methyl chloride -- 24-2 37S6 7250* 3-3 expectedly high concentrations. Methylene chloride Chloroform Carbon tetrachloride Ethylene dichlorlde 1,1,1-Trlchloroethane 401 61-3 768 83-6 74-1 362-4 150-5 90-0 63 9 96-0 13 200 (25*C) 8200 785 8800 480 8-1 86 1-1 26 4 071 Possible hazard to human health The ubiquitous distribution of the chlorinated hydrocarbons means that a population may breathe air, drink Vinyl chloride -13-9 - 2320 60 (10C) 0-02 (10C) water, and consume food containing Vinylldene chloride 31-9 Trichloroethylene 870 Perchloroethylene 121-2 Fluorotrlchloromethane 238 Difluordlchloromethane -29 8 Hexachlorobutadiene 215 496-5 57-9 14-0 6674 4306 0-15 400 1100 150 1100 280 (25V ~2 0-16 2-74 1-22 0-03 006 097 trace quantities of these materials. In many instances, the cooking of a foodstuff will reduce these levels still further. There is, moreover, evidence for the presence of these compounds in human tissue, again at extremely * Under 760 mm pressure of organochlorine compound low concentrations (Table 4). 4# DSW 0 3 3 7 8 1 STLCOPCB4017743 Tabic 5, which summarizes all the analytical data, demonstrates that there is no evidence for significant accumulation in human tissue or any of the materials under discussion. Rather, they indicate a general back ground, at the parts in to* level, which pervades the whole ecosphere--atmosphere, hydrosphere, and bio sphere. These results are in sharp contrast to those reported for DDT or PC-B, where accumulation in tissues of several orders of magnitude lias been observed [8]. , ' It is interesting to compare in Table 6 the threshold limit values (TLV) set by the American Conference of Governmental and Industrial Hygienists with the maxi mum atmospheric concentrations measured in our survey [7]. The threshold limit values define permissible atmo spheric concentrations applicable only to an 8-hour working day and a 5-day week. In the United Kingdom, maximum allowable ground level concentrations to which the public might continuously be exposed arc set in the range of 1/25111-1/40111 of the TLV. It can be seen that the environmental concentrations are less by some orders of magnitude. If we examine the possibility of poisoning by swallow ing, we find from tests on rats and mice [10-1O] that all five aliphatic compounds of Table 6 have low toxicides with J-.D50 values varying between 2 and iiv ke. Tire LD50 value is the dose that will kill 50 per cent of a group of experimental animals.) The corresponding LD50 value for DDT with rats was o 15-0-4 g kg. Clearly the presence of a few parts per 10* of these substances in food or water will not give rise to acute poisoning. The acceptable daily intakes (ADI) of substances in foodstuffs are set by bodies such as the FAO Working Party of Experts and the WHO Expert Group on Pesticide Residues. They are generally calculated by applying safety, factors (of 100-2000) to the maximum no-efiect levels observed in long-term feeding studies cn animals, taking into account the absorption, metabolism, and excretion of the substance. Absorption, metabolism, and excretion Published reports indicate that most of the chemicals are moderately to .veil absorbed from the gastrointestinal tract after oral administration [20, 2t, 22). Typically, a very large fraction of the administered dose is excreted unchanged in the expired air. It has been established Table 3 Chlorinated hydrocarbons In foodstuffs (Concentrations In pglkg) Foodstuff Dairy produce Fresh milk Cheshire cheese English butter Hans sggs Meal English beef (steak) English beef (fat) Pig's liver Olla and fats Margarine Olive oil (Spanish) Cod liver oil Vegetable cooking oil Castor oil Beverages Canned fruit drink Light ale Canned orange |uice Instant coffee Ta (packet) Wine (Yugoslav) fruit and vegetablas Potatoes (S. Wales) Potatoes (N. W. England) Apples Peart Tomatoes* Black grapes (Imported) t Fresh bread Chloroform Carbon tetrachloride 5 33 . 22 1-4 4 3 1 3 10 3 2 NA 2 0-4 8 2 18 NA 18 4 8 2 2 NO 2 02 5 14 05 7 8 8 18 16 0-7 NA 0-5 02 6 6 4 0-3 8 3 5 4 4-5 18-7 8 Trichloroethane Trichloroethylene Perchloroethylene Others 0-3 03 32 10 13 0-6 ND HCBD 0-08 HCB 1 ND HCBD 2 ND 3 16 0-9 ND 6 12 1-0 ND 4 22 5 TCE 0-5 PCE 0 4 87 PCE 0-8 10 8 7 ND 8 19 2 TCE 2 7 0-01 HCBD 0-2 HCB 0-7 6 ND 3 NA 52 PCE 0-8 0-7 ND HCBD 0 2 ND ND ND ' 43 ND 7 60 3 ND 002 ND NA 4 ND ND Nk 1 3 0-7 TCE 0-7 362 ND 242 ND 1-7 1-2 HCBD 0 8 HCB>0-1 TCE 1-0 2-9 ND HCBD 3-7 2 7 ,1 ND * Tomato plants were grown on a reclaimed lagoon at Runcorn Works of ICI. t HCBD Is still used In some countries as an insecticide for vineyards. ITCE, PCE Tetra-, pontachloroethane; HCBD *= Hexachlorobutadlene; HCB Hexachlorobenzene HA No Analysis; ND - Not Detected '. * DSW ' 033782 15 STLCOPCB4017744 Tibi# 4 Occurence of chlorinated hydrocarbons In human tIssue. Concentrations in pp/Ap (wet tissue) Age of Sex aubject 76 F 76 F 62 F 46 M 65 M 75 M 66 M 74 F Tissue Body let Kidney Liver Brain Body fat Kidney Liver Brain Body fat Uver Body fat Liver Body fat Uver Body fat Uver Body fat Body fat Chloroform Carbon tetrachlorlde+ trlchloro' ethane Trlehloroethylone Perchloro ethylene 19 2 5 4 5 5 1 2 67 8-7 67 M. 64 8-8 65 100 68 52 24 1 1 <1 4 3 4 2 1-6 35 2-1 . 3-5 110 3-5 13-6 5-1 1-6 52 32 <1 5 1 2 3 2 <1 1-4 3-2 6-4 3-5 34 5-2 14-1 5-8 4-6 4-9 6 <0-5 <0-5 <0-5 1 6 2 <5 0-4 1-2 , 0-8 0-7 21 3-4 29 2 4-3 05 4 HCBD _ _ . -- -- -- _ 08 12-1 1-8 5-7 1-8 11-8 0-8 13-7 1-2 4 Others . ._ ... -- _ -- TCE<05 y-BHC 24 y-BHC 7-5 y-BHC 22 that metabolism results in the formation of trichloro* acetic acid (From trichloroethylene and perchloroethylene), trichloroethanol (from trichloroethylene), chloroform (from carbon tetrachloride), and CO, (from carbon tetrachloride and chloroform) [20-23]. Some of the compounds have non-industrial uses and it is possible to compare permitted use concentrations with the maximum concentrations found in the survey described above. The relevant data arc summarized in Table 7. This table demonstrates that, with one exception, there are enormous differences between permitted-use concentrations of the chemicals, admittedly in some instances for discontinuous use, and the maximum levels found in food. The exception is carbon tetrachloride, where the suggested guidelines for grain residues are similar to the amount of this material in food; the grain Tabl# S Occurrence of chlorinated hydrocarbons In the environment. Typical concentrations (w/w) of the five major compounds (chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, trichloroethane) Air Rain water Surface water Potable water Sea watar Marine aedimenta Marine invertebrates Fish Waterblrds Marine mammals Fatty food* " Non-fatty fooda Human oroant - Human body fat Minimum Maximum 10- 10*" 10-" 10-" to-1* 10-" io- 10*' to-* id-* 10-* io- to-* io- 10-* 10-* 1D-* 10-* to-* 10-* 10-* to-4 >io-f >10-* 10-* 10-* 10-* 10-t 16 residues, however, do refer to regular daily intake. To put the remaining figures in perspective, some 500 kg of cheese would have to be consumed to give an intake of chloroform equivalent to one dose of the linctus described. Effect* on wildlife _ So far only a few results are available for the levels of the Cj/C, chlorinated hydrocarbons in land animals (other than marine and avian species) or plants. The indica tions are, however, that the levels in such species are not significantly different from the general background con centrations shown in Table 5. Hexachlorobcnzene (HCB) and hexachlorobutadiene (HCBD), of which we have found traces in fish and foodstuff samples, are used on a small scale as pesticides. J. G. Vos [24] showed that toxic effects occur only in birds fed high dose rates of HCB, namely 20 mg/1 over 3 months. At the end of the trials, the average HCB concentration found in the liver was 35 mg/1. Our own study of effects on marine organisms has been described [7]. Acute toxicity levels for marine fish, barnacle nauplii, and a unicellular alga are reproduced Table 8 . Threshold limit value compared with maximum observed concentrations (rngji) Trichloroethylene Perchloroethylene Trichloroethane Carbon tetrachloride Chloroform TLV . 0-50 0-67 1-90 ' 0-06 0-12 Max. observed concentration 0-00015 0-00009 0-00009* 0-00009* 0-00004 * Not differentiated by analysis, therefore, the concentration shown is the maximum value, assuming the GLC peak represents wholly trichloroethane or carbon tetrachloride. DSW 033783 STLCOPCB4017745 Table 7 Comparison of observed concentrations In food and permitted use concentrations Chemical Uses Trichloroethylene Perchloroethytene 1,1,1-Trlchloroethane Anaesthetic Extraction solvent Antihelminthic (veterinary and human medicine) ? Carbon tetrachloride Grain fumigant Chloroform Anaesthetic Flavouring agent US Food and Drug Administration (1973) Food Chemical News Guide t Martlndale 'The Extra Pharmacopoeia' 26th Ed. (1972) t FAO/WHO Expert Committees, WHO Pesticide Residues Series 1,1977 (1972) Permitted concentration s/dose 10-25 mg/kg decaffeinated coffee* . Max. concn. measured (ug/kg) 60 (packet coflee) 1-6-8.0 g/60 kg t (therapeutic dose) 13 (butter) 1 50 pg/kg (cooked cereal products): 15-30 mg/dose t (cough linctus) 20 (black grapes) SO (black grapes) 33 (cheese) in Tabic 8; comparison with Table 5 shows that they are It has been suggested that low concentrations of at least three orders of magnitude higher than those chlorinated solvents could, however, inhibit microbial found in sea water. There is no evidence that the bio degradation processes generally, especially in anaerobic accumulation up food chains, which is such a feature of environments. Particular concern has been expressed DDT and PCB, occurs to any significant extent with the over the effects on sewage treatment. Our observations commercial solvents. There is some indication that in show that concentrations in rats- sewage are noirnaliv fish, by-product `heavies' such as HCBD show some less than o-i ing/l; some of this is adsorbed on to primarv bioaccumulation intermediate between the two former sludge, while most is lost to the atmosphere during classes, but this docs not increase in birds and mammals biological oxidation, either by activated sludge or feeding on fish. trickling filters. Our initial experiments show that inhibition of aerobic Degradation In the environment oxidation docs not occur at concentrations below to mg 1; Biochemical degradation. As the major chlorinated hydro this concentration will not normally be found in any carbons are so widely distributed in the environment, sewage works. An extensive investigation of the effects they are exposed to a wide range of potential degradation on anaerobic digestion in sewage works, particularly by routes. Although there is evidence that they can be chloroform, is given in [25]. metabolized by mammalian tissues, we do not know how Physico-chemical degradation. There is evidence for the many other phyla have this ability. It is generally chemical breakdown of chlorinated hydrocarbons in accepted, however, that micro-organisms, whether water, but in general these reactions are very slow; we aerobic or anaerobic, do not have it. Microbiological estimate the chemical half-life or pcrchloroethylene in degradation, which is so important for the destruction of water to be about six years. Exceptions to this arise for many organic compounds, therefore probably docs not compounds which are easily dchydrochlorinatcd; the have any significant direct part to play in this case. reaction rate in such cases depends on the pH. An In mammals, the metabolic pathways of all the com important example of this is the dehydrochlorination of pounds discussed so far lead to chlorinated acetic acids, the solvent !,t,i-trichloroethane, which would have a either directly or via chlorethanols. Chlorinated acetic chemical half-life in sea water (pH 8. io:C) of about 9 acids have all been shown to be susceptible to further months. The decomposition product is vinylidene degradation by micro-organisms in sea water [7]. chloride, with (at environmental temperatures) only a minor amount of acetic acid arising Table 8 by hydrolysis. Rapid degradation in Acuta toxklty of chlorinated hydrocarbons to marine organisms 0Concentrations expressed as mgll) aqueous systems does, however, occur in the presence of metallic iron. At 90 h LC sa to 48 h LC sa to EC sa to Unicellular the present time the resulting degra dation products have not been iden Dab (flat-fish) Barnacle naupli! algae tified, but this faster rate in the pre Trichloroethylene Parchloroethylene Trlchloroethane Chloroform 16 5 33 28 20 , 6 3-5 10-5 76 S -- sence of metals could be important. The current implication of our work is that it is by tropospheric photo-oxidation that the environmen Carbon tetrachloride Hexachlorobutadlene ~50 0-45 --- -- 0-87 tal aliphatic organo-clilorine com pounds are principally destroyed. Ethylene Bichloride Propylene dichlotide 115 61 186 63 340 This will apply also to those com 50 pounds present in the hydrosphere. OSW 033784 17 STLCOPCB4017746 line; transfer reactions between hydrosphere and atmo sphere occur rapidly faG], Oxidation can easily be demon strated by introducing a few mg/1 of the organoclilorinc compound into a sealed quartz flask and exposing the latter out of doors. Monitoring the organic residue shows that the mean half-lives of the chlorine-substituted ethylenes lie in the range 6-12 weeks, and of the chlorinesubstituted methanes and ethanes in the range 10-33 weeks. These experiments are naturally influenced by diurnal and climatic variations of temperature and inci dent solar radiation, and the half-lives are reproducible only to within rb5 per cent. Nonetheless, they serve to show that the simpler aliphatic organochlorines do not have the high persistence associated with the chlorinated insecticides and PCB, nor on the other hand are they sufficiently reactive to give rise to photo-chemical smog, a view confirmed by the work of M. F. Brunellc el al. [27]. Similar experiments have been carried out exposing the flask to radiation from a xenon arc, suitably filtered to remot e radiation below 290 nm, taken as the lower limit of tropospheric solar radiation. Under these condi tions of constant radiation flux and temperature it has been found in a number of cases that the order of the reaction with respect to the halo-organic compounds is fractional, tending to zero at the higher (100 mg/1) initial conceritrations and to unity at the lower concen trations (o-l mg/1). At the much lower concentrations (ng.'l) found in the troposphere we can--at least to a first approximation--assume a first-order reaction with respect to the halo-organic compounds. The kinetic pattern observed does not appear to arise from heterogeneous reactions, since packing the reaction vessel with quartz wool has a negligible effect on half life, It can, however, be explained in terms of initial attack on the halo-organic compounds by some transient species present in the troposphere, possibly by active photolysis products of such species as nitrogen peroxide, ozone, or chlorine, known to be present in the tropo sphere at concentrations very similar to those of the halo-organic compounds. Deliberate addition of these inorganic species in the xenon arc experiments can accelerate the decay rate, even when the inorganic material is present in much less than stoichiometric equivalence. The implication is that, because of the excess of halo-organic compounds over trace inorganic species present in the outdoor flask experiments, the latter do not rcpicscnt a true microcosm of the troposphere. In that ease, the half-life ranges quoted above arc probably over-estimated. We have also identified the degradation products arising from xenon arc exposure. For the most part these are simple inorganic species (CO, C02, 11,0, HC1) already present in the atmosphere; in some cases (CCI,, CHjCClj) molecular chlorine can also be formed. Only tri- and pcrchloroethylenc yield relatively stable cltloroorganic intermediates, the di- and trichloroacetyl chlorides, with minor amounts of phosgene. The latter rapidly hydrolyses to COs and HCI, but the chloroacctyl chlorides will enter the hydrosphere as the di- and trichloroacetate anions, which have very long chemical half-lives at environmental temperatures. However, we have already noted the microbial breakdown in sea water of both these anions, complete oxidation occurring during a 20-day incubation period. It thus appears that not only are the simple chloroaliphatic compounds not particularly persistent, but their degradation products are simple species commonly found in the environment. Conclusion From evidence so far available we conclude that several chlorodcrivatives ofmethane, ethane, and ethylene are very widely distributed in the environment at a level of concen tration of the order of 1 part in io*. The particular com pounds are chloroform, carbon tetrachloride, trichloro ethylene, perchloroethylene, and trichloroethanc. The as sumption that the last three occur as a result of chemical manufacturing processes is tenable, but the occurrence of the first two may also be due to unidentified geochemical processes. All these compounds arc fairly rapidly degraded in the environment to carbon dioxide, water, and chlor ide ion, and there is no evidence for their significant bio accumulation, via the food chains, to higher trophic levels. Rafartncaa [1] Goodman, G. T. Proc. R. Sec. Lend., B, 185, 137, 1^74. [a] Jernelov, .V, Rosenberg, R. and Jensen, S. ffater Res., 6, : t8i, 1973. [3] Riley, J. P. and Murray, A. J. Mature, Lend., 142, 37, 1973. [4] Lovelock, J. E., Maggs, R. J. and Wade, R. J. Ibid,, 241, 194, 973[5] WI1knits, P. E. el al. Ibid., 245, 45, *973- [6} Siramonds, P. G., Kerrin, S. L., Lovelock, J'. E. and Shair, F. H. Almesph. Environment, 8, 309, 1974. {7] Pearson, C. R. and McConnell, G. Proc. R. Soc. Lend. B. (To be published.) [8] Kocman, J. H., National Swedish Environment Protection Board. PCB Conference n, 1973. - I9) Abbott, D. C., Collins, C. B. and Goulding, R. Br. Med. J., 353. '97alio] Smyth, H. F., Carpenter, C. P., Weil, C. S., Pozzani, U. C., Streigcl, J. A., and Nycum, J. S. List VII, Am. ind. Hyg. Au. J., 80, 470, 1969. (ll) Paribok, V. P. Farmakol. ToksikoL, 20, 78, 1937. (is) The Merck Index (1968), p. 1033. |lj) Barsoum, C. P. J. Pham. Lend., 7, a5. 934[14] Torkclson,T. R., Oyen, F., McCollister, D. D. and Rowe, V. K. Am. ind. Hyg. Ass. J., 19, 353, 1958. U [15] McCollister, D. D., Hollingsworth, R. L., Oyen, F. and Rowe, V. K. Archs ind. Hlth., 13, I, 1956. {16] Spector, W. S. In `Handbook of Toxicology', Vol. 1, p. 6o, W. B. Saunders and Co., 1956. [17] Smyth, H. F., Carpenter, C. P., Weil, C. S., Pozzani, U. C. and Striegel, J. A. List VI, Am. ind. Hyg. Ass.J., 23, 95, 1963. (18] MildftthevsUii, V. E., Tugarinova, V. N., Rakhmamia, N. L. and Yakovlova, G. P. Gig. Sanit., 31, 107, 1966. 119] Negherbon, W. O. In `Handbook of Toxicology', Vol. in, p, 87, W. B. Saunders and Co., 1959. [ao] Browning, E. `Toxicity and Metabolism of Industrial Solvent*', Elsevier and Co., Amsterdam, 1965. [31] Daniel, J. W. Biechem. Pharma., 12, 793, 1963. . [33] Paul, B. B. and Rubinstein, D. J. Pharmac. exp. Ther., 141, 1963. [33) Hake, C. L.. Waggoner, T. B., RoberUon, D. N. and Rowe, . V. K. Archs Environ. Hllh., 1, tot, i960. [34) Vo, J. C., Brecman, H. A. and Benschop, H. Meded. R\jks. Landbouwu-etcns., Gent., 33, 1263, 1968. (33) Swanwick, J. D. and Foulkes, M. Hater Pollut. Control, 70, 38, 1971. [a6] Maoknv, D. and WalkoIF, A. W. Env. Sci. Teehnol., 7, 611, 1973. [97) Brunette, M. F., Dickinson. J. E. and Hamming, W. J. `Effec tiveness of Organic Solvents in Photochemical Smog Formation'. Air Pollution Control District, Los Angeles, California, 1966. DSW 033785 i j I j i ' j I I ' STLCOPCB4017747