Document 93rBbzJaXYryk3m3qp9Knw5ML

Polychlorinated Biphenyls Another Long-Life Widespread Chemical in the Environment David B. Peakall and Jeffrey L. Lincer The recent finding that pelagic birds dying on the coasts of Great Britian had polychlorinated biphenyls (PCBs) in their livers in concentrations of several hondred parts per million (Bourne and Mead, 1969) shows that these compounds are present in the ecosystem in large amounts. Thus, it seems worthwhile to summarize and evaluate our current knowledge of these compounds. Structural and Physical Properties The picture is complicated by the fact that we are not dealing with a single com pound. The basic structure of PCBs is shown in Figure I. Any of the positions marked with an x can be substituted by chlorine. Widmark (1968) has calculated that of the 210 possible combinations 102 are probable. His criteria for these lim itations are those compounds containing five to eight chlorine atoms per molecule and the number of chlorine atoms per ring differing by not more than one. The commercially available Aroclors (Monsanto Company Trademark) are des ignated by numbersTMohsahto Technical Bulletins). The first two digits represent the molecular type: 12 - chlorinated bi phenyls: 25 and 44 blends of chlorinated biphenyls and chlorinated lerphenyls (75% biphenyl and 60% biphenyl, re spectively): 54 chlorinated lerphenyls. The last two digits give the weight per cent of chlorine. Thus, Aroclor 1242 is a chlorinated biphenyl containing 42% chlo rine. The biphenyls commercially avail able from Monsanto range from 21% to 68% chlorine. Mass speclrographic studies of Aroclor 1260 (Koeman et ai., 1969a) show the presence of 11 isomers: five con taining six chlorine atoms, five containing seven chlorine atoms, and one containing eight. Begley et al. (1970), studying Aroclor 1254, found 18 compounds: one con taining three chlorine atoms, four contain ing four chlorines, four containing five chlorines, five containing six chlorines, and four containing seven chlorines. Thus, rst MNn tt cwwwty u Un ImenUr UtwMwy. CwmI UUnN. tiUm. N.V. the number of compounds present is. for tunately. much smaller than is theoretical ly possible. PCBs are chemically inert, are not hy drolyzed by water, and resist alkalies, acids, and corrosive chemicals. They have low volatility, their boiling points ranging from 278 C for A roclor 1221 to 415 C for Aroclor 1268 (Penning, 1930). All are stable to prolonged heating at 150 C, and the lower Aroclors can be distilled al atmospheric pressure without appreciable decomposition. PCBs are described as in soluble in water and very soluble in hydro carbon solvents, although no exact figures appear to be available. Nothing is known about the biological decomposition of PCBs, but it is likely that they are more stable than DDT and Us metabolites since they lack the ethane component between the aromatic rings, which is the site of action of most of the transformations of DDT. Thus, PCBs have the necessary physical and chemical characteristics for persistence and accumulation up the food chain. Use of PCBs Polychlorinated biphenyls were first de scribed in the literature in 1881 (Schmidt and Shultz. 1681), and the successful com mercial production was achieved by the Swann Company in 1930. In (hat year the physical characteristics and commerical possibilities of these materials was de scribed by Penning (1930). PCBs are now manufactured by Monsanto in the United States (Trade name Aroclor), Prodelte in France (Phenochlor), and Bayer in Ger many (Colphen). Other manufacturers are located in Japan and the Soviet Union. No figures of the amount of these mate rials produced annually are available, but to judge from the uses listed in Table I they may be very large. The uses listed in the table are only suggested applications taken from Technical Bulletin 306 of the Monsanto Chemical Company, and again there is no information on the extent to which these recommendations are acted upon by the manufacturers of plastics and resins. The use of highly chlorinated Aroclors for extending the kill-life of formulations containing chlordane. aldrin, and dicldrin are mentioned under miscellaneous appli cations of Aroclors. This possibility has been considered in a number of papers. Sullivan and Hornstein (1953). Hornstein and Sullivan (1953), and Tsao el al. (19)3) found that the chlorinated terphenyi Aro clor 5460 increased the residual persis tence of lindane. Tsao et al. (1953) consid ered that there was some indication that chlorinated polyphenyl may have a syner gistic effect with lindane. Duda (1957) O0- Ol-Q- tuawnuncN or channc (a) HONS 097403 O- -IO tfCOMNxfnoN o-cj -e m "GO" ~ OMNkOaOOf'rtlrtl Fig. I. Bask stmetare at PCBs (A) sad psaiWi Hscltaw at PCBstB). 956 BioScienct Vol. 20 No. 17 /' sprayed dm saplings wttlt a lindane ArocU>r MM) mixture (1:4) and (hen tested the residual effect on the leaves lo infes tation with elm leaf beetle [GaieruceUa xanthomeioena). Me found that leaves treated with lindane plus Arocior were protected longer und that the insecticidal effect wus more rapid thurt with lindane alone. Peaks corresponding to Arocior 5460 huve not been detected in the envi ronment. However, under conditions of temperuture and flow-rute commonly used for gus chromatographic analysis these compounds would not be detected (Reyn olds, 1970). Nearly 25 yeurs ago it was noted that, Arocior 1242 was one of 175 compounds out of 6000 tested that was effective aguinat mosquito (Atgyps) larvae (Deonier el al.. 1946). Lichtenstein el al. (1969) tested the effect of adding a variety of biphenyls and tcrphenyls to DDT and di eldrin with respect lo their toxicity to house and fruit flies. It was round that PC8s had very low toxicity lo house flics when given ulone but PCBs increased the toxicity of dieldrin and DDT, especially the latter. The effectiveness of these com pounds decreased as the chlorinated level increased. For example, Arocior I2H in creased the mortality of fruit flies from 39% to 93%. whereas Arocior 1268 in creased it lo only 77%. Analytical Methods I) Identification. Since various com pounds with electron-capturing properties have been tentatively identified in atmo spheric samples in the past (Abbott et al., 1966), and some pesticides are capable of hybridizing in the soil to form a new com pound (Burtha, 1969), it is important that the presence of PCBs in field samples be proven beyond doubt. Identification by means of a combination of high resolution gas chromatography and mass spectrom etry has been carried out by three inde pendent laboratories in Sweden (Widmurk. 1967), Holland (Koeman et al., 1969a), and the United Stales (Bagley et al., 1970). Widmark's report states that all peaks were identified by mass spectrom etry (although no data were given), but Koeman and co-workers gave full experi mental details, and Bagley et al. (1970) demonstrated that most chemicals in the eagle samples examined were components of Arocior 1254. Thus, despite a recent statement by the Monsanto Chemical Company (in Riscbrough, 1970) that the case for labeling the peuks in question as PCBs was not proven, there is enough evidence to convince an unbaised scienti fic jury. Separation. The chemical techniques preliminary lo quantitation of residues in samples containing both PCBs and chlo rinated hydrocarbon pesticides fall into two groups those necessitating the de struction or alteration of one or more of the compounds, and those which do not. Included in the first group is nitration. Treatment with u 1:1 mixture of sulfuric acid nitric acid at 0 C for 5 min destroys or alters aldrin, p.p'-DDE, p.p'-DDD (TDE), p.p'-DDT, and dieldrin such thul they can no longer be detected ut the original position on the chromatogram. This procedure leaves unaffected PCB, lindane, and BHC (Jensen und Widmurk, 1967). A more rigorous nitration with a 1:1 mixture of sulfuric acid-fuming nitric acid for IS min at room temperature re moves, in addition to DDT and its related products aldrin, hcptuchlor, Kelthane, Perthane, Tedion, Tclodrin, and Trithion while lindane, hcptuchlor epoxide, toxuphene, and Strobane are not removed (Erro et ul., 1967). Kisebrough et al. (1969) reported that this nitration also removed the chromatographic peaks of PCBs. Rey nolds (1969) reported that his attempts to nilrutc samples were not fully successful in that there appeared to be loss of some of the more volatile PCBs while peaks with longer retention times appeared. Armour and Burke (1969) reported that complex chromatograms resulted after nitration which could ntot be related to the unreacted DDT-PCB mixture, and nitra tion'was not pursued as a practical means of separating DDT and PCB for further tests. Saponification with alcoholic NaOII or KOH will dehyrodrochlortnale Perthane, Toxaphcnc. DDD. and DDT to their re spective olefins (Archer und Crosby. 1966: Klein and Watts, 1964). Riscbrough ct ul. (1969) reported that PCB peuks arc not removed or displaced but gave no data. The second, and in some instances more desirable, group of anulyticul tech niques allows the special separation of many chlorinated hydrocarbon pesticides from PCBs. Reynolds (1969, 1970) re ported on an activated Florisil column technique which separated heptachlor. aldrin, DDE, und PCB with the first elu tion (60 ml n-hexune) from lindune: hep tachlor epoxide, DDD. and DDT with the second elution (40 ml 50% ethyl ether in hexane). Armour und Burke (1970) devel oped a method utilizing a silicic acidCelile column eluting aldrin and PCB with the first fraction (250 mi petroleum ether), and lindane, heptachlor. hvptuchior epoxide, dieldrin. endrin. p.p'DDE, o.p'-DDT, p.p'-DDT. and p.p'DDD with the second fraction (200 ml acetuniirile hexane methylene chloride 1:19:80). Koeman et al. (1969a). using an activated Florisil column, eluted the upo lar compounds including DDE and PCB with hexane, and (hen dieldrin and endrm with 10% diethyl ether in hexane. Muihern (1968) reported on a method which utilized silica gel-coated thin-layer plate*. ' TUU J September I, 1970 HONS 097404 959 I und hcxanc/ethyl ether (98.2) solvent system. The plute* were developed, sprayed with a silver nitrate solution, und ' exposed to IJV light. The plates were then divided into live horizontal sections. Dieidrin. endrin, v-BHC, heptachlor epoxide. p.p'-DDD, p.p'-DDT. o.p'DDT, and p.p'-DDE (in that order) were found in the first four fractions, while most or the interfering compounds found in wildlife samples were found in the fifth zone. Bagley et al. (1970) used this meth od but mentioned that zones three and tout contained practically all unknown components as well as p.p'-DDT (zone three) and p.p'-DDE (zone four). Armour and Burke (1969) used preconted (alu minum oxide) sheets and n-heptane and 2% acetone/n-heptane for solvent sys tems. PCBs (Aroclors 1254 and 1260) and DDE were nol separated, but p.p'-DDT and p.p'-DDD were completely sep arated from PCB by both solvent systems. Another possible means of separating in terfering substances is to use a series of differing polarity columns in the gas chro matograph at the time of determination. This is less lime consuming and muy be useful when operating conditions cun be selected such that PCB peaks are absent in the region where sought pesticides emerge (Simmons and Tatton, 1967). 3) Quantitation. Koeman et al. (t969a) semiquantiialivdy measured the residues in Japanese quail fed phenochlor DP6 by using one of the peaks in a phenochlor DP6 mixture as a standard. Risebrough (1969) quantitated relative levels of PCBs by assuming that euch PCB compound produced the sume peak height with the electron capture detector as the sume amount by weight of p,p'-DDE. After summing the heights of the individual peaks, the total was multiplied by a factor derived from measurements of standard solution* with electron cupture und microcoulomctric detectors. Jensen el al. (1969) reported PCB amounts as the sum of all PCB components and based the estimate on a combination of mass spectrometry and microcoulometric and electron cap ture detection. Even with this elaborate approach, these investigators suggest that the method is still rough and may be cor rect only within a factor of 2. Anderson et al. (1969) devised a method for obtaining a crude estimate of PCB residues as Arodor 1254 from chromatograms where sep aration had not been attempted. On an empirical basis, il was found that Aroclor 1254 could be quantitated by considering peak 10 as p.p'-DDT and multiplying that value by 10. Since this peak had originally been quantitated as p,p'-DDT, and in fact many of the original samples con tained little or no p.p'DDT. it was pos sible to estimate relative PCB values. Anderson und his co-workcrs also saponi fied samples to remove interfering p.p'DDT and p.p'-TDli and then quantitated PCBs as Aroclor 1254 by relating sample peuks 9 und 10 to the corresponding peuks of an Aroclor 1254 standard. Reynolds (1970) employed a method similar to Koeman et al. (1969a) but based his quan titation on an average of two or more peaks. In addition, his results were re ported as Aroclor 1254 or 1260 depending on the overall pattern of the chroma tographic peak profile. It is clear that we are still relatively unsophisticated in our PCB quantitation methodology and will continue to estimate only relative amounts of PCBs in field samples until we synthe size the individual PCB components com monly found in the ecosystem and are able to speak in terms of these individual peaks as we do for most pesticide residues. However, it has been kindly pointed out (Risebrough, pers. comm.) that, with ref erence to biological significance, the cor rect order of magnitude and accuruje rela tive amounts of PCB give the essential information. This is because biological effects, such as enzyme induction, are re lated to degree of chlorination, and the existing methods give some indication of this activity. Therefore, that information would be lost if stress were placed only upon quantitating individual peaks. 4) Magnitude of Error. Ever since PCB peaks were recognized for what (hey are, residue chemists and other researchers interested in pesticide residues have asked what magnitude of error is likely to result from ignoring the presence of PCBs. Only recently have studies either directly or indirectly resulted in an esti mate of this error. Anderson ct al. (1969) quantitated p.p'-DDU, p,p`-l)l)l), and p.p'-DDT in five egg sumples before und after saponification. There was no appre ciable change in the p.p'-DDE. but ap parent p.p'-DDD was reduced by ap proximately 58% and p.p'-DDT by 90%. Reynolds (1970) looked at a large number of samples before and after his PCB* Florisil separation and found that the actual p.p'-DDD residue (relative to the apparent residue) represented from 0 to 7% in California gull (Lams occidentals) fat, 0% in cormorant (Phalacrocorax auritus) eggs, 80% in 10 pooled mallard {Anas piaiyrhynchos) duck eggs, and from 0 to 104% in great blue heron {Ardea cinerea) eggs. Respective values for p.p'-DDT were 0 to 53%, 13 to 41%, 100%, and 18 to 102%. Actual residue levels ol heptachlor epoxide generally represented a majority of the apparent values. Before and after values for p.p'-DDI: and dieldrin were not significantly different. Obviously, the magnitude of error may vary depending on the trophic lev| sampled und certainly with the area from which a sample ts col lected (Risebrough et al.. 1968, Jensen et al., 1969). Since the publishing of ade quate separation techniques, there is no reason why there should be any error in pesticide quantitation contributed by PCBs Toxicology Despite some recent studies, the toxi cology of PCBs remains rather poorly known as compared to that of the chlo rinated hydrocarbon pesticides. For ex ample, no definite work has been done to establish LD50 values for the various formulations of PCBs. 1) Acute, single dose experiments. Tucker and Crabtree (1970) found that a single dose of 100 mg/kg Aroclor 1254 (stomach tubed in oil) was fatal to two out of three ruts, while 500 mg/kg was not fuiul to three rats. Aroclor 1268 killed one rut out of three at 500 mg/kg. 1000 mg/ kg, 2000 mg/kg. and 4000 mg/kg. Smyth (1931) found that a 4 g/kg (degree of chlo rination not stated) was nontoxic to guinea pigs and rabbits, but this appears to be due to the fact that material which was given as a paste passed through the intes tine unabsorbed. Tucker and Crabtree (1970) found that Aroclor 1242. 1254. 1260, and 1268 at a dose of 2000 mg/kg was not fatal to mallard ducks (four groups of three birds each). 2) Acute, feeding experiments. Mon santo Bulletin 306 states that 100 ppm diet hud no effect on rats, although no details of the studies were given. The ex periments of Bennett et al. (1938) in which 0.05 g/rut of 65% chlorine biphenyl was given oruliy every other day led to 50% mortality. If one assumes j body weight of 200 g, then the alternate day dose is roughly 250 mg/kg. which can be com pared to oral LD50 for DDT of 113 mg/kg (Frear, 1968). Miller (1944) found that two oral doses of 69 mg of 42% chlorine biphenyl a week apart were fatal to guinea pigs. At an estimuied body weight of 400 g. this gives a dose of 170 mg/kg Tucker and Crabtree (1970) fed rats diets contain ing 10 and 1000 ppm Aroclor 1254. One rat out of six on the low dose died: this mortality was considered to be due to other causes. Four out of four of the high group died within 53 days and the cal culated intake was 1330-1520 mg/kg. The 960 BioScienc* Vol. 20 No. 17 MQNS 097405 food intake of the 1000 ppm proup v.-s:; only 79% of Ihe control group. Pressl et ol. (1970) have examined the toxicity of Aroclor 1254 to Bengalese finches (Lpnchuni striata). This is a diffi cult species for which to calculate the dietury intake. Due to their dependence upon unshdled food, it is only possible to present the PCB-ludcn food for a few hours a day (Jefferies, 1967). Loss by evaporation and loss by spilluge must be allowed for. and increase of weight by def ecation must he kept to u minimum. Thus, ihe calculated dietary intake is sub ject to more error than is usually the case? Presst et al. (1970) also measured the con centration of PCBs in the liver; they found that the range was large (i.e., 70 697 ppm in birds that died compared to 3-634 ppm in those that survived). These authors conclude that Aroclor 1254 has only 1/13 the toxicity of DDT, although the different shape of the mortality curves--sleep with DDT, gradual with PCB-- makes comparison difficult. Jef feries and Walker (1966) found good cor relation between calculated dietary intake and liver concentrations for pp'-DDT in the Bengalese finch. However, other workers (Dale et al., 1963; Stickel et al., 1966: Stickel and Stickel, 1969) have con sidered that levU in the brain are a more reliable ihdex of toxic levels than those in the liver or whole carcass. De Vos and Koeman (1970) fed Phenodor DP6, Clophen A60, and Aroclor 1260 to chickens at a dosage of 400 ppm. Mor tality was complete (20/20) for those birds on Phenodor in 12-58 days and in 13-29 days tor Clophen. The mortality for Aro clor was only 3/20 for a 60-day period. This differential effect is unexplained and is surprising in view of the fact that all three formulations contain 60% chlorine. These workers measured the residue lev els in the liver, and, for some birds, in the brain, for chickens dying during the ex periment. Although there was consider able variation, most of the brain levels were between 210 and 420 ppm, which can be compared to 50-80 ppm for DDT (Stickel et al., 1966). On the basis of this work, PCB is 1/4-1/5 as toxic as DDT. Little difference was noted between the three different PCB formulations, al though the numbers of determinations involved was rather small. If this finding is borne out by subsequent work, it would suggest that differential absorption from the gut or differential penetration of the blood brain barrier is involved. The liver values were more variable. There was a considerable number in (he 200-400 ppm range, but there were several values in excess of 2000 ppm This finding is in agreement with the findings of Dale, Stickel, and co-workers thul the bruin levels are the best indication of acute toxic levels. McCune et al. (1962) found no mor tality with chickens fed 100 or 200 ppm Aroclor 1242 in their diet tor a 4-weck period. On diets of 400 ppm and 800 ppm, the mortalities over a 4.week period were, respectively, 50% und 90%. During the first 3 weeks, the mortality figures were 10% and 50%, respectively. Flick et al. (1965), using the same material at 400 ppm in the diet, had three birds out of 24 die In a 3-week period. Koeman et al. (1969a) found that a diet containing 2000 ppm Phenodor DP6 caused complete mortality with Japanese quail (5/5) in 5 13 days and rats (8/8) in I >56 days. Schoeitgcr (unpublished) found that the 96-hr TLm for Aroclor 1221 using cut throat trout was 1.2 mg/I and for Aroclor . 1260 was 60.9 mg/I. In general, they found that the toxicity of Aroclors was inversely proportional to their percentage chlorination and directly proportional to their solubilities. These figures suggest that PCBs are two to three orders of mag nitude lets toxic to fish than DDT. Work by Lichtenstein et al. (1969) on house and fruit flies found that PCBs were 40-300 times less toxic than DDT, the toxicity decreasing as the chlorine content in creases. Thus, it appears that the lower vertebrates and invertebrates are much less susceptible than mammals to direct toxicity from PCBs. 3) Sublethai effects. As with the chlo rinated hydrocarbon pesticides, Ihe most important effects are long-range sublethai effects. The pathologic changes in various organs are summarized in Table 2. The table shows some interesting differences between mammals and birds. The most striking finds in mammals are alterations to the liver, whereas fluid in Ihe peri cardial sac, kidney damage, and reduced spleen was found in birds. McLaughlin et al. (1963) found that 25 mg Aroclor 1242 injected into the yolk sac of chicken eggs caused complete mor tality. whereas 10 mg caused 95% failure and tcratogenelic effects were noted among the young that hatched (beuk deformity, edema, and growth retardant). Induction of hepatic hydroxyluling en zymes has been demonstrated in the pi geon (Riscbrough et al., 1968), rut (Street et al., 1969), and American kestrel (Folco sporvtriut) (Lincer and Peukall, 1970). Strdet and co-workers studied the effects of a diet of 50 ppm and 100 ppm on sleep ing lime induced by standard dose of hcxobarbitul, in vitro rates of aniline hydroxylation and dcmcthylation of p-niiroanisolc, and the rate of excretion of' dieldrin. These workers studied 10 com pounds ranging in chlorine content from 21% to 68% and found that all the effects increased with increasing chlorine conleni. For example. 50 ppm of Aroclor 1221 reduced hexobarhilal sleeping lime by 11%, whereas for Aroclor 1248 and 1268 the figures were, respectively, 35% and 48%. Thus, the sublethai effects have direct correlation with chlorine content, while the lethal effects appear to be in versely correlated (Tucker and Crabtree, in press). Lincer and Peakall (1970) noted an increase of the in vitro rale of metabo lism of estradiol in kestrels fed 0.5 and 5 ppm Aroclor 1254 in their diet and also demonstrated increased levels of cytoplas mic RNA with the higher dietary level using a cytophotometric technique. Tucker (unpublished) found that a sin gle oral dose of 500 mg/kg Aroclor I2S4 caused regular egg laying of Japanese quail {Cotumix cotumix) to turn first to scattered egg production and then to stop completely for a week. The scattered eggs had shells 9% thinner than normal, but thickness returned to control values when regular laying was resumed. Mallard's^ ducks dosed with 1000 mg/kg of Aroclor laid one or no eggs before stopping for I2 weeks. The few eggs laid after the sin gle large dose of Aroclor had shells 18% thinner, and again eggshell thickness was normal after resumption of regular laying. The period before egg laying has been noted to be increased in the ring dove (Peakall, unpublished). It is possible that the mechanism involved is increased rate of metabolism of circulating estradiol in the liver (Peakall, 1970). Anderson et al. (1969) had suggestive evidence that PCBs affected eggshell thickness, al though to a less extent than DDE. Pre liminary results with ring doves support this conclusion (Peakall, unpublished). Levels ol PCBs Found in Nature Roburn (1965), comparing total chlorine (by concentration cell techniques) with results calculated from gas chromatog raphy. found that some unknown chlorine compounds were present in several tissue sumples und eggs of wild birds in Great Britain. The first identification of these materials was by Jensen and it is stated (Anonymous, 1966) that residues in leath ers collected in Sweden go hack to 1944. PCB residues have been reported in wild life from Canada (Holden and Manden. 1967; Anderson et al.. 1969; Reynolds. September I. 1970 *'1 MONS 097406 TABLE 2. PatbnWgie dM*|ii tnriucari by PCI* Iummm Mri U* KMner Nrinarridni anri PmHmmm Othar ObsarvaMa Cbangan Aatarawap ' mhwilfcn uiiMimn BiWwNg Wt MAH Small IM 4r*gl*t* IlHMfb Mh. didit I* wAiWl CMMIgl (>***). I*eti MKfttit Wifi I* t*W nMi. IimUMi wmd Np wlpweilbp tbwgn* Afmnaii. iglaw. anri panciana ilawari na aainwarthy tbwgn. MM--11044) muMrlH AM CaM* iwaltaa. Marina pmMat praannt bibm Aari aMW law Ayi. Bannaw m at. ItMg) II mg rial* tot *!* mm KM Mlfri 03% wdgM taeraaael, larga awnbar *1 kyaNaa (pMdaa la cr'tptim. tmel AW Wring aiparHwnt. v" II.IB.aiNpga In Apt far It e*r in-met Amtonl Art latraaia in md|M, *H*M latiaaalag will 1mmating clWrin* iwtwt. Aradar IISIIM, 1242 12%. I2f414%. 1211-14% MHpga. Suwid.|lapNMl IN ppm In A* IMppainfM 411 toto BBBppainriMt (MW 1|4 CS-Mm N* tflaat Bapflaet Edargari aari WM Bamagari IMS4Mpga bMlHl pda 142%. And-) HAM Nt abaagaa aatari Ytripw 4mm (MUCLAimM -rr Nangel Bright MrriraparkarAaai NprimptricarAa* Myrimparitardwa. lyrirapartl--mm. trinpi. Priwwi M IN ppn, aitaaWn bamntrtiaga. mi wrinpamaat M 401 ppm. Ineraaiari Dairi in piritlfdnt aaa at 0i Palaaata at mmimi. antprgaawri al aril--al mi mat ida-- a) law twetaI'triaat, Al Irigbpr tawan(tiam pda him iriitri pantraat, ariranaia bamarrtwda. WaigM wai 32.4% *1 Me wnigM f*r cantmir anri 13.1% fit IfctM riylng Inn PCB paimMp. SligM wdgbl latrwBW * Ipw tbtwari iigdO fapariearriid nan. McCm w. nett) PNnb-aMtMM PtnaflM d. Uapmad 4MppfcA (MOppp nan an CWm Cwtrdtlnbr a--rppfr Irtmpri1 Mi 2). Una w*lgM (ntraarnri fna 2.H g/iei|t*4.}t g/tta pUiwpri. 31. FMIr 4*gw- Tebdar Aliuriw. Iwpi, I anri tl Am at* aw-ri. 3. Hyrimpatipgrrihw aa--wa wM) aaapfc. 1 anri 2. bn wW> aaapri. 3- wad with rihtllan nl rari pdp anri ttiepAp *t nriritn pdp (awnpri. 1 anri 2). tplaw riattwaari lip* 1144 g/tBI | Ip 0.IN g/IMg itwpri. 1). Vat anri NnwwadMnMt tMtMH HI II *4i*W HMkHM MI 1970). Germany (Fiuczynski and Wend* lund. 1968; Kocman et nl., 1967), Great Britain. {Holmes ct al.. 1967; Press! and Jefferies. 1969: Proud et al., 1970: Holden and Msrttden. 1967), Netherlands (Koemun et al., 1967; 1969), Sweden (Anony mous, 1966: Jensen et al., 1969), and the United Slates (Anderson et al., 1969: Risebrough et al., 1968: Risebrough, 1969).. Blologkal Magnification No detailed studies, such as those for DDD at Clear Lake (Hunt and Bisehoff, I960) and DDT and its metabolites in Lake Michigan (Hickey et al., 1966), have yet been made for PCBs. The most detailed studies currently available are those of Jensen at al. (1969). The figures (mean, range of values, and sample size) given in the table below are taken from their paper. PCS* (ppm In MimctaMt lm> Bailie SMefcMm Arrinpriaio Maud 4.)<I.W.*> (40) 3.20,4-7 0) (()) Herring M(0.)J)) (IS) J.I0M.J) (4) Seal J4(IM4> < J) KMIS-MI ( )) GMMI4gg* 230(140MON *) -- Wbiin-taftariEaglt PactnrdmMia -- l4.0pO(MM7.DOO|( 4) Srtin -- *10(440.1300) | )| Egg* -- 340(230.100) ( 3) Hemn -- *400 ( l) The levels in three species of fish in Clear Lake in 1968 were 0.03-0.005 ppm (wet weight) compared to 0.09K ppm in the breast muscle of a western grebe (Risebrough et al.. 1969). Anderson et al. (1969) found that in most fish extracts the levels of PCBs were less than 0.1 ppm. whereat the levels in the eggs of cormorants (Photacrocorax auritut) were 5-9 ppm. Press!, Jefferies, and Moore (unpublished) found that the livers of fish-eating birds in the British Isles ranged up to a maximum of 900 ppm (wet weight), bird feeders up to 70 ppm. mammal eaters to 50 ppm, and insectivores to I ppm. Unfortunate!), no average values or prey items were in cluded. The physical properties of PCB and the available residue dulu dear!) indicate that these materials are capable of bio logical magnification up the food chain. 962 HONS 097407 BioSciencc Vol. 20 No. 17 tun* ot mvr f. itn Kixcbrouph ct al. (I96K) and Risebrough (1970) have examined the rulio of local DDT, i.e., DDT and its metabolites to PCB. Me has found (hat the ratio DDT/ PCD was 1-2 in San Francisco Bay and 5 10 for seabirds in the Pacific: in the Gulf of California, a region relatively remote from contamination, the ratio was 9-10. Vermeer (quoted in Reynolds. 1970) in western Canudu found a DDE/PCB ratio of 7 for Californio gull tissues and 13 for great blue heron eggs. In the Bullic the ratio was 1*2 (Jensen el a!., 1969), al though ulong the west coast of Sweden the ratio wus us low os 0.15. In grebes in the British Isles the ratio wus 0.4-0.8 (Press! and Jefferies, 1969). For seu-bird eggs, Presst et al. (unpublished) found ratios of 0.06 to 0.5. The overall impression is (hat the amount of PCB in tissues tends to paral lel that of DDE, at least in local ecosys tems, and the DDE/PCB rulio is lowest near industrial areas suggesting that PCB is not carried quite so readily to remote areas. Nevertheless, the variation of the ratio is small enough to suggest that the routes of dispersal are similar. Since the evidence points to aerial fallout as the route of dispersal of the chlorinated hy drocarbon pesticides (Risebrough et al., 1968; Frost, 1969), it is likely that this is also the main route for PCBs. The path ways by which PCBs escape into the eco system are poorly known, although the possibilities have been recently discussed at some length (Risebrough. 1970; Rey nolds, 1970). Since a large number of plastics and resins may contain PCBs (Table I), the most likely route is combus tion of these materials. This supposition remains to be tested. The possibility that PCBs could be derived from DDT should also be considered. The possibility that this conversion occurs in tissue is most unlikely for two reasons. First, it has never been detected despite the detailed work on the metabolism of DDT. Second, the only mechanism likely to give rise to a biphenyl is via free radicals and this is unlikely to occur in tissue. However, in the atmosphere under the influence of UV light, such a breakdown is more prob able. A possible reaction is shown in Figure I. Tautomeric shift could lead to a variety of isomers of dichlorophenyl, but it is difficult to envision the formation of more highly chlorinated biphenyls by this route. Since PCBs extracted from biological material match well with higher Aroclors (i.e., 1254), it seems unlikely that PCBs found in nature could be derived from other materials. September I, 1970 Kiuniftcanre nf Current Levels In view of the similarity of PCBs to DDT and its metabolites, the addition of PCB residues to the environment is rough-* ly equivalent to an increase of DDE resi dues. However, since a synergistic effect of PCBs on DDT has been demonstrated in insects (Tsuo et al., 1953). this pos sibility should not be overlooked in higher organisms. The enzyme induction effects of PCBs have been well documented, and carbonic anhydrase inhibition is likely. The effect of PCBs on photosynthesis is u critical experiment that has not been done. Wurstcr's (1968) experiments with phytoplankton should be repeated with PCBs. The most critical area for research on PCBs is to discover the major source(s) of escape into the environment. Legislative control of a material escaping as a side effect of its use may have a different set of problems than the control of pesticides which are broadcast as a function of their normal use. The evidence suggests that it is important to find the leak and stop it. Acknowledgments We are grateful to Dr. Koeman (Uni versity of Utrecht), Drs. Presst and Jef feries (Nature Conservancy, Great Britian). Dr. Reynolds (Ontario Research Foundation), Dr. Street (Utah State Uni versity), and Dr. Tucker (U.S. Fish and Wildlife Service) for advance copies of important material. Some of the work presented here was carried out under NIH Grant ES00306, Dr. T. J. Cade, Principal Investigator. The review was written while one of us (D.B.P.) was an Established Investigator, American Heart Association. 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Science. 159: 1474-1475. : ) // MICROBIAL CULTURES COMMIT ISCS USTINGI GUARANTEED PURITY 1 OVER 200 SPECIES AVAILAM.E I MOST ORDERS FILLED WITHIN 46 HOURS NOTICE BACTERIA and FUNGI sa.oocultures--------- per culture ($2.50 par culture for ordots of 6 or moro eultures) BACTERIOPHAGE----------S4 .00 per 5 ml fiI torad broth suspensions BACTERIOPHAGE CULTURE SETS---------- Available at spdeM prices COMPLIMENTARY CULTURES Ono complimentary culture (bacterial or fungal) will bo included for voch six cultures ordered. Compliments may bo selected If so dostrod. free CATALOGUE OF CULTURES Available Upon Request (>X1SQUI ISL1 MICROBIOLOGICAL ASSOCIATES g---------------------- O P.O.SOX 1007-PRESQUE ISIS, PENNSYLVANIA T650S T.Uphan* I14-633-6J7] 964 BioScicncc Vol 20 No. 17 HONS 097409