Document N2X77GZreVMz4aKLqbRjM07OQ

Scientific Communications Polychlorinated Biphenyls Storage, Distribution, Excretion, and Recovery: Liver Morphology After Prolonged Dietary Ingestion Virlyn W. Burse; Renate D. Kimbrough, MD; Ellen C. Villanueva, MS; Ralph W. Jennings; Ralph E. Linder; G. Wayne Sovocool, PhD Rat* were fed 100 ppm o! Aroclor 1242 (8.6 to 3.89 mg/kg/day) or 100 ppm Aro clor 1016 (6.9 to 3.5 mg/kg/day). Plasma, kidneys, urine, brain, liver, and adipose tissue were analyzed for polychlorinated biphenyl (PCB) residues at 0.5, one, two, four, six, eight, and ten months of expo sure. In additional groups fed the experi mental diet for six months, PCB tissue levels were determined two, four, five, and been restricted to closed systems. A new PCB, Aroclor 1016, which is a good dielectric and heat transfer fluid has been proposed. It contains a lower percentage of the higher PCBs and should prove to be less persistent in the environment. The higher PCBs appear to be more persistent, as evi denced by mass spectral residue anal six months after the exposure to PCBs ysis of environmental samples,4,5 was discontinued. PCBs were highest In It is the purpose of this paper to re adipose tissue where a steady state was approached In two and reached In 4 months. Utile PCB-derlved material was excreted In urine. After discontinuing PCB exposure, Aro clor 1016 was eliminated more rapidly from the organs than Aroclor 1242. Mea surable residue levels were still present after five (Aroclor 1016) and six (Aroclor 1242) months of recovery. Microscopic port results of feeding studies con ducted in rats with Aroclor 1016 and Aroclor 1242. Aroclor 1242 in its gen eral make-up is very similar to Aro clor 1016, it only lacks the higher PCBs (Papageorge, written commu nication, June 1973). The Aroclors dif fer in the percentages of fixed chlo rine, 43% 0.5% (1242) vs 41.3% examination ol the liver showed enlarged 0.5% (1016). Aroclor 1242 contains 9% liver cells with vacuolated cytoplasm and biphenyls with five or more chlorines Inclusions. and Aroclor 1016 contains 1% bi phenyls with five or more chlorines. The use and replaceability of poly chlorinated biphenyls (PCBs) has recently been reviewed.1 Because of MATERIALS AND METHOD their extensive UBe in the past and their slow biodegradability, PCBs are now widely distributed in the envi Aroclore 1242 and 1016 were of electrical gr- de, lot No. KB-05-415 and KB-06-756, res >ectively. The PCBs were fed in parallel ronment2^ Recently the use of these exj eriments to male Sherman Btrain rats, materials in the United States has 611) 73 days old. A total of 158 rats was dividi d into two groups of 27 and two groups of 52 rats each according to a table of ran SubmiLtod for publication May 10, 1974; ac cepted July 17. From the Environmental Protection Agency, Cham bloc Toxicology Laboratory, Chamblee, Ga (Mr. Burse, Dr. Kimbrough, Mb. Villanueva, Mr. Jennings, and Mr. Linder), and the NERC, EPA, Research Triangle Park, NC (Dr. Sovocool), Mr. Burse ig currently wilh the US Consumer Prod uct Safety Commission, Atlanta; Dr. Kimbrough li with the Center for Disease Control, Tox icology Branch, Atlanta; Ms. Villanueva is with the Coca-Cola Export Corporation, Atlanta; Mr. Jennings is wilh the Environmental Protection Agency, Region IV, Atlanta; and Mr. Linder is with the Pesticides and Toxic Substances Effects dom numbers. The rats were group caged and weighed weekly. Their food consump tion was measured, one week prior to each scheduled killing. The groups of 52 rats were fed the experimental diets that con tainer, 100 ppm of Aroclor 1016 or Aroclor 1242. "'he control rats were fed ground laborator- chow ad libitum. The PCBs were incorporated into the dietB by dissolving them in ether and pour ing this solution onto 100 gm of corn starch. The ether was evaporated and the laboratory, NERC, EPA, Research Triangle Park, NC. Reprint requests to the Toxicology Branch, Center for Disease Control, 1600 Clifton Rd, NE, Atlanta, GA 30333 (Dr. Kimbrough). PCB cornstarch mixture diluted with in creasing amounts of ground chow in an electric mixer. The following killing schedule was ob served (Table 1): one control and four rats fed Aroclor 1016 or 1242 were killed two weeks after onset of the experiment. Four additional rats of each experimental group were killed one and two months after onset of the experiment. The further killing of four experimental rats for each PCB mix ture as -veil as four controls that served for both experimental groups were made four, six, eight, and ten months after onset of the experiment. After six months feeding, the experimental diets were discontinued on 18 randomly selected rats for each PCB mixture. These rats were fed plain chow and four for each PCB mixture were killed together with four control rats at two, four, and five or Bix months (Table 2) of re covery. Twenty-four hours prior to each killing the rats were housed in individual metabolism cages and urine was collected. During the 24-hour pe -iod prior to death, none of the rats in the study was fed a for tified diet. Oxalated blojd was obtained by cardiac puncture from rats anesthetized with ether. The animals were killed by exsanguination and liver, fat, kidney, and brain tissues were collected. The liver was weighed and the tissues were frozen for chemical analysis. Liver tissue from the animals killed at four months and at sub sequent killings were also fixed in buffered 4% formaldehyde for microscopic examina tion, and stained with hematoxylin-eosin. Liver tissue at four months of exposure to Aroclor 1016 and at six months of exposure to Aroclor 1242 together with an equal number of controls for electron micro scopic examination was fixed in chilled, buffered 5% glutaraldehyde for two hours, poslfixed in 1% osmium tetraoxide, dehy drated through changes of alcohol and propylene oxide, and embedded in resin. Sections were cut with a glass knife, stained with lead citrate and uranyl ace tate, and examined with an electron micro scope. The analytical methods used for the de termination of PCB-derived materials have been described previously." Briefly, 100 to 200 mg of fat, brain, kidney, and liver or 1 to 2 ml of plasma were extracted with hexane. Brain was extracted with acetone, the solution evaporated to dryness Arch Environ Health/Vol 29, Dec 1974 iumm 'ramuHV nut DSW Polychlorinated Biphenyls/Burse el al 301 025630 muinwnh , ,n,.r--i.n aiann--ip> STLCOPCB4009585 lidWfc*.. -ok-L* 1i / 7 C a> u> c o Vaa)> 5 CC 4 Fig 1.--Chromatograms ot Aroclor 1242: 3,66 ng, an extract of urine: 4.5 mg, and adipose tissue: 0.027 mg from a male rat fed a diet containing 100 ppm Aroclor 1242 for eight months. Table 1.--Mean Concentration and Standard Error of PCB-Derived Materials In Tissues ot Four Rats Per Killing Fed 100 ppm Aroclor 1242 or 1016 Plasma Kidneys Urine' Brain Liver Adipose Tissue on Diet 0.5 1 2 4 8 10 Aro1242 0.081 *0.000 0.180 *0.030 0.310 *0.057 0.219 *0.028 0.528 0.150 0.240 0.052 0.172 *0.014 Aro 1016 0.182 0.017 0.175 0.028 0.331 0.010 0.372 0.040 0.3B4 0.024 0.394 0.014 0.334 0.040 Aro 1242 0.68 0.15 0.51 0.13 1.44 0.18 1.84 0.27 1.89 0.47 2.14 0,41 3.13 0.56 Aro 1016 0.63 0.08 1.58 0.11 2.74 0.19 4,76 0.24 3.21 0.48 2.07 0.06 1.84 0.38 Aro 1242 <0.02 <0.01 <0.02 0.030 0.02 0.02B 0.000 0,168 0.04 <0.01 Aro 1016 0.075 0.042 0.008 0.000 0.162 0.038 0.259 0.083 0.275 0.112 0.057 0.017 0.021 0.000 Are 1242 <0.25 <0.25 <0.25 0.56 0.08 1.69 0.25 1.63 0.24 2.05 0.08 Aro 1016 1.52 0.75 3.05 0.13 3.40 0.13 3.18 0.23 2.98 0.44 2.64 0.36 2.70 0.36 Aro 1242 Aro 1016 0.55 1.46 0.08 0.24 1.46 3.05 0.10 0.26 3.24 3.86 0.30 0.36 3.94 7.40 0.72 0.79 4.21 7.86 0.57 0.75 4.56 5.97 0.61 0.94 6.39 6.70 0.68 0.34 Aro 1242 35 2.4 85 10 92 1.5 115 11 110 13 143 6 133 15 Aro 1016 69 4 103 8 182 12 214 18 236 9 221 10 IBB 9 * Confirmed qualitatively by Coulson conductometry. Table 2,--Mean Concentration and Standard Error of PCB-Derlved Material In Tissues of Four Rats Two, Four, Five, or Six Months Alter They Had Been Fed 100 ppm Aroclor 1242 or 1016 for Six Months Months Recovery Plasma Aro 1242 0.438 0.091 0.149 0.000 0.122 0.026 Aro 1016 0.154 0.034 0.193 0.050 0.062 0.011 Kidneys Aro 1242 2.07 0.40 1.04 0.27 0.34 0.06 Aro 1016 1.08 0.27 1.82 0.44 0.44 0.14 Urine Aro 1242 0.02 0.01 <0.01 ... 0.004 0.000 Aro 1016 0.033 0.004 0.006 0.002 0.006 0.002 Brain Aro 1242 1.06 0.24 1.22 0.53 0.51 0.06 Aro 1016 1.40 0.07 1.35 0.21 0.30 0.06 Liver Aro 1242 4.32 0.72 3.46 1.04 0.97 0.35 Aro 1016 2.25 0.32 3.13 0.78 1.06 0.09 Adipose Tissue Aro 1242 60 3.7 44 9 24 5 Aro 1016 104 13 36 6 28 zt 1 ... * Experiment had to be prematurely terminated. 302 Arch Environ Health/Vol 29, Dec 1974 Polychlorinated Biphenyls/Burse et al OSW 025631 3' 2i 1( ( Fig 2, taininn LentiMi Expo-1 1!6 nm 2 nr- 6 mi; : 4 mu i 6m . 6 me- ' * Only and l! 10 to '. match ; volunn silica i hcxan. Sami' source in the : tation Arch L STLCOPCB4009586 , Fig 2.--Chromatograms of Aroclor 1016: 2,04 ng, extract of urine; 5.4 mg, and adipose tissue; 0.000 mg from a male rat fed a diet con- j tainlng 100 ppm Aroclor 1016 for eight months. . Table 3.-- Incidence of Microscopic Changes Observed In Livers of Rats Fed Aroclor 1242 or 1016 Enlarged Length of Hepatocyte* Exposure Aro 1242 Aro 1016 4 2/4 4/4 6 4/4 4/4 8 4/4 3/4 10 4/4 4/4 6 mo exp 2 mo rec 2/4 1/4 6 mo oxp 4 mo rec 3/3 3/3 6 mo exp* 6 mo rec 3/4 ... Vacuoleted Cytoplasm Aro 1242 .. 3/4 3/4 4/4 Aro 1016 1/4 1/4 1/4 3/4 1/4 1/3 1/3 Inclusions Aro 1242 Aro 1016 3/4 3/4 3/4 1/4 1/4 1/3 1/3 2/4 Brown Pigment Aro 1242 Aro 1016 2/4 ... 2/4 ... ... ... Foamy Cytoplasm Aro 1242 Aro 1016 2/4 ... Foci of Necrosis Hemorrhage Aro 1242 Aro 1016 ... 1/4 1/4 ... * Only rats fed Aroclor 1242 were examined microscopically. and the Bolule taken up in hexane. Urine, j 10 to 20 m), was extracted at approxi. malely pH 7 with hexane. Each sample in a I volume of 0.6 ml was eluted from a micro- 1 silica gel column using a 1:1 benzenehexane mixture. 1 Samples were analyzed with a tritium * Bource electron capture detector operated { in the direct current mode at 12 v. Quanti' tation of the standard and of the different kinds of samples was based in each in stance on total response in peak heights. However, as reported more fully below, there were qualitative differences in the peaks for the standard, the urine, the tis sues collected during dosing, and the tis sues collected after dosing was discontin ued. Under these circumstances exact quantitation is impossible, but the use of total response in peak heights is consid ered to offer the beat estimate of quantita tion. RESULTS The rats did not suffer from any overt clinical symptoms of poisoning. During the course of the experiment five rats that were fed Aroclor 1016 and one rat that was fed Aroclor 1242 Arch Environ Health/Vol 29, Dec 1974 I P ILUI...HM.II1WJ Polychlorinated Biphenyls/Burse et al 303 03 M 025632 STLCOPCB4009587 i- Mi . . \ i i i i I i i >i i i l * Fig 3.--Chromatograms ot adipose tissue: 0.011 mg from a rat ted a diet containing 100 ppm Aroclor 1242 for six months and six months ol a control diet; 0.016 mg from a rat ted a diet containing 100 ppm Aroclor 1016 for six months and a control diet for five months. (Relative retention times were computed relative to the most intense electron capturing peak present in Aroclor 1016 or 1242. All gas chromatographic columns were composed of 1.5% OV-17/1.95% QF-1 on 100/120 Gas Chrom Q.) ' died. The cause of death was not es tablished. No difference between the experimental and the control ratB was observed in the body weight gain and the food consumption. As the rats aged food consumption decreased relative to their body weight. The amount of Aroclor 1242 consumed by the rats ranged from 6.6 mg/kg body weigbt/day to 3.89 mg/kg body weight/day, and the amount of Aro clor 1016 consumed by the rats ranged from 6.9 mg/kg body weight/day to 3.6 mg/kg body weight/day. At autopsy the organs appeared grossly normal except for one rat fed Aroclor 1016 that had leukemia (a dis ease that occurs occasionally sponta neously in our colony). The liver weights of the experimental animals did not differ from those of the con trols. The concentrations of the PCB-de rived materials are given in Table 1. The observed levels in adipose tissue are also shown in Pig 1. The highest concentrations for both compounds were found in adipose tissue, ranging from 35 to 143 ppm for Aroclor 1242 and 69 to 236 ppm for Aroclor 1016. The levels for brain, liver, and kidney were lower. The concentrations in urine and plasma were always less than 1 ppm. In adipose tissue a steady state of storage of both compounds was approached in about two months and essentially achieved in four months. 304 Arch Environ Health/Vol 29, Dec 1974 DSW 025633 Gas chromatographic traces for all tissues were similar to those obtained from adipose tissue. The traces ob- tained from urine analysis had an en tirely different appearance. The dif ferent profiles obtained from adipose tissue, urine, and the PCB standards are illustrated in Fig 1 to 3. When the peaks in the PCB standards were compared with the peaks obtained from PCB-derived material stored in the adipose tissue, it was found that some of the early peaks were absent. the intensity of others was enhanced, and peaks also emerged that were observed only as "shoulders" in the standard. This observation suggests either preferential absorption from the gastrointestinal tract, or prefer- j i J . i j , ; j . I | , i Polychlorinated Biphenyls/Burse et al | STLCOPCB4009588 ential metabolism, distribution, and excretion in the rats or both. The urine samples show a very dif ferent pattern. This suggests that i certain isomers are excreted by the l kidneys, that the products excreted in the urine are polar metabolites, or that nonchlorinated moieties re sponded to the electron capture de tector. However, a positive response was obtained with a conductometric .detector (Coulson). Residue levels arising from Aroclor 1016 ingestion were generally found to be higher than for Aroclor 1242, Fig 4.--Residues resulting from a con tinuous diet of a 100 ppm concentration of Aroclor 1016 () or Aroclor 1242 () for a period of ten months. Residues following a continuous diet (or only six months and re covery for five months for Aroclor 1016 {) and tor six months for Aroclor 1242 (o). are Illustrated by the broken lines. Each point represents the mean and stan dard error (1) of four rats. Flg 5.--Liver of rat fed Aroclor 1016 for four months. Note dilated vesicles of smooth endoplasmic reticulum (SER). Some ol the mito chondria are degenerated and others show an increased number ot parallel arranged crlstae (lead citrate, uranyi acetate, x 35,000) I___ L 9 to the 016 or ot 1.6% for nil itaincd es ob an enhe difidipose ndards ion the i were itaincd >red in id that ibsent, lamvd, ere nbin 1 he ggests , from ;>rel'er- se et al Arch Environ Health/Vol 29, Dec 1974 DSW 025634 Polychlorinated Biphenyls/Burse et al 305 STLCOPCB4009589 with the exception of the residues ol>scrvcdJn the kidneys. However, this was not true for all organs at every killing. After a ten-month feeding period the concentration of both PCBs in the liver was about the same, while at four months almost twice as much Aroclor 1016 as Aroclor 1242 was found. The levels found in adi pose tissue indicate a very sharp rise during the first month for Aroclor 1242, while Aroclor 1016 also main tains a sharp rise through the second month. After two months of exposure no appreciable increase was observed in adipose tissue of rats exposed to ei ther Aroclor 1016 or 1242. Very little PCB-derived material was excreted in the urine, and the ex cretion was very erratic. When rats were fed Aroclor 1242 they only ex creted measurable amounts during four to eight months of exposure. Rats fed Aroclor 1016 excreted mea surable amounts at each urine collec tion. The variation in urinary excre tion of PCB-derived material has been observed previously in this labo ratory" and by other workers in the field.' The data resulting from the analy sis of tissues from rats that were fed the respective PCB-containing diets for six months and were then contin ued on plain chow for various inter vals up to six months are given in Table 2. The concentrations found in adipose tissue are also illustrated in Fig 4. Storage of material as detected by gas chromatography decreased more rapidly following discontinua tion of dosing in rats previously fed Aroclor 1016 than in those previously fed Aroclor 1242. Following a recov ery period of six months the residue levels in adipose tissue were 21.8% of those observed after a six-month ex posure period to Aroclor 1242. Follow ing a recovery period of five months the residue levels in adipose tissue of rats fed Aroclor 1016 were only 11.8% of the concentration found after six months of ingestion of this material. The gas chromatographic traces ob tained from the adipose tissue follow ing recovery from exposure to the PCB mixtures are shown in Fig 3. (Relative retention times were com puted relative to the most intense ' electron capturing peak present in Aroclor 1016 or 1242. All gas chro matographic columns were composed of 1.5% OV-17/1.95% QF-1 on 100/120 Gas Chrom Q.) If these results are compared with those obtained earlier from adipose tissue, a slight decrease in the number of peaks as well as a difference in the relative heights of the peaks is noticed. Composite urine and fat samples from rats fed Aroclor 1242 and 1016 continuously for varying time periods were analyzed by gas chromatogra phy-mass spectrometry. Spectra re sulting from the composite adipose tissue analysis showed primarily triand tetrachlorobiphenyls, for both PCB mixtures. Trace amounts of penta- and hexachlorobi phenyls were found in the Aroclor 1016 composites, while significant amounts of pentachlorobiphenyls and hexachlorobiphenyls were found in the oomposites obtained from rats that were fed Aroclor 1242. Spectra from urine composites of rats fed Aroclor 1016 revealed the presence of the same molecular ions observed in the adipose tissue compos ites, with the exception of hexachlorobiphenyl. Dichlorohydroxybiphenyls (DCHB) and trichlorohydroxybiphenyls (TCHB) were also observed. Dichlorohydroxybiphenyl was more abundant. Spectra from urine composites of rats fed Aroclor 1242 revealed the presence of the same molecular ions observed in adipose tissue, with the noted absence of hexachlorobiphenyl. In contrast to Aroclor 1016, hydroxylated chlorobiphenyls were not observed in any of the spectra result ing from Aroclor 1242 urine compos ite analysis. The incidence of the various micro scopic changes observed in the liver is given in Table 3. Light microscopic examination of the liver of rats fed the two PCBs showed enlarged hepatocytes predominantly in the center of the lobules. Occasional hepatocytes had coarsely vacuolated cytoplasm or contained inclusions within the cyto plasm. The cytoplasm of some of the hepatocytes was finely vacuolated and a brown pigment was noticed in the Kupffer cells and macrophages of some of the livers of the experimental rats fed Aroclor 1242 but not in rats fed Aroclor 1016. Vacuolation of the cytoplasm of the liver cells was more consistently ob served in the livers of rats fed Aroclor 1242. Generally not much difference was seen in the incidence of the vari ous changes between the two experi mental groups. All of the observed changes have to be considered as mild alterations that have been observed with a number of chlorinated cyclic chemicals. Four and six months after exposure to the PCBs was discontinued the hepatocytes were still larger than those of the controls, but only one out of three rats showed vacuolated cyto plasm or inclusions within the cyto plasm. Since the number of animals was small, these results have to be in terpreted with reservation; however, it appears that the morphological changes encountered following expo sure to Aroclor 1242 and 1016 are re versible and disappear gradually af ter dosing is stopped. Except for the hemorrhage and necrosis observed in one animal in each experimental group no evidence of serious liver damage was encountered. The livers of rats from the controls were normal when studied with the light microscope. Sections of four liv ers of rats fed Aroclor 1242 for six months and of four rats fed Aroclor 1016 for four months were also stud ied under the electron microscope, to gether with the same number of con trols. The livers of the control animals showed occasional lipid vacuoles but no abnormal changes. The livers of the experimental rats fed both PCB compounds showed an increase in smooth endoplasmic reticulum, an in crease in the number of lipid vacuoles, and atypical mitochondria. Stacking of membranes within the mito chondria was also observed (Fig 5). Except for one animal that showed lymphocytic leukemia, no other ab normal findings were made on gross inspection of the organs at autopsy. It must be emphasized, however, that the only organ examined microscopic ally was the liver, since it was this or gan that was primarily affected by Aroclor 1254 and Aroclor 1260 as pre 306 Arch Environ Health/Vol 29, Dec 1974 Polychlorinated Biphenyls/Burse et al viously tory.'" Levels found in level of 9 182 ppm month.-' ' containin crease th< sumpi ion both grou higher re Aroclor "li the gastr clor 1242. storage v; pounds. 1 Aroclor If attributal is known tion and Bubsuluti' tron '.apt compound electron 1 proport '.n An alien PCB fieri complex phenyls Whoth' factor- of dilferiM ,-e at simh; r ent not 1 ' the otho' for Ar'.'h that we: creased ;. exposure ued. From. Aroclor i d reached exposuti more rar 1016. Mass PCBs in pies wh: the corf ; terislie (3) obse: These w. Arch Envi DSW 025635 .............. ... I STLCOPCB4009590 Ml* i MM*** luomMMi d 1 i: i' (S r- j\ * a 0> l'l (M oN Hu ll vBix cl or udto onmls but of -CB in i li lies, ini' blo 5). wed nl>ros-; |,SV. hat pic , (/' >> pre viously reported from our labora_ tory.*1' COMMENT 1 Levels of PCB-derived components found in adipose tissue reached a level of 92 ppm (Aroclor 1242) and of 182 ppm (Aroclor 1016) after two months' exposure of rats to a diet containing 100 ppm, with little in- | crease thereafter. Although food con sumption of the rats was the same in both groups, rats on Aroclor 1016 had higher residues. It is possible that Aroclor 1016 is absorbed better from i the gastrointestinal tract than Aro clor 1242. Another possibility is that storage varies between the two com pounds. The higher residue levels of Aroclor 1016 vs Aroclor 1242 could be attributable to PCB quantitation. It is known that the degree of chlorinartipn and the position of the chlorine substitution contribute to the electron capturing properties of these (compounds. In some instances their electron capture responses are not proportional to their concentration.'"'" An alternative to quantitating the PCB derivatives in tissue could be complete chlorination of the bi phenyls to decachlorobiphenyl." Whether a combination of the various factors outlined contributed to the difference in the PCB concentration at similar exposure times is at pres ent not known, The concentrations in ! the other organs were often higher I for Aroclor 1016, and the residues ' that were built up in the tissues de creased faster for this compound once exposure to the PCBs was discontin ued. From previous experience with Aroclor 1254* equilibrium seems to be reached sooner, and elimination after exposure has been discontinued is more rapid with Aroclors 1242 and ' 1016. ' Mass spectral identification of ' PCBs in composite fat and urine sam| pies was based on: (1) the presence of the correct molecular ion, (2) charac (teristic chlorine isotopic clusters, and (3) observed fragmentation patterns. | These were all in agreement with previously published data. The presence of DCHB and TCHB in Aroclor 1016 urine composite is in keeping with published data on meta bolic products for these compounds.'5 However, one would generally not ex pect the method of extraction em ployed here (hexane at pH 7) to ex tract these metabolic products since they are generally found bound in the urine as glucosiduronides," and are detected following hydrolysis of the urine. It is feasible that small amounts of hydroxylated compounds could be found as free phenols and could then be chromatographed under selected conditions. As could be ex pected, the concentrations of the PCBs were much lower in the liver, kidneys, and brain than in adipose tissue, and even lower in plasma. Plasma concentration probably is not a very good indicator of the amount of PCBs stored in adipose tissue. The morphological changes ob served in the liver are similar to those observed with other chlorinated hy drocarbons.15 They were generally mild, particularly when compared with findings made earlier with Aroclor 1254 and 1260."1' Neither the pronounced lipid accumulation nor the adenofibrosis was observed in this study. However, some brown pigment was observed in the macrophages of the livers of some rats fed Aroclor 1242 but not Aroclor 1016. It was not determined whether the pigment rep resented ceroid or whether part of it was caused by an accumulation of hemosiderin and porphyrin in the liver. After feeding rats Aroclor 1242 and 1016 for six months, Goldstein et .al" found an increase in liver uro porphyrin for Aroclor 1242 at this die tary level but not Aroclor 1016 at the same dietary level. Unfortunately the number of rats was not large enough to determine if the occasional liver cell necrosis and hemorrhage that was seen was related to the exposure to Aroclor 1242. From this study it may be concluded that both Aroclor 1242 as well as Aroclor 1016 are less persistent in the rat and have also le3S of an effect on the liver than ei ther Aroclor 1254 or 1260. Aroclors 1242 and 1016 were supplied by Mon santo Chemical Company, Si. Louis, J. Cumcy, R. Moore, J. Coule, and J. M. Jack gave technical assistance. References 1. Broadhum MG: Use and replaceability of polychlorinated biphenyts. Environ Health Per- aped 2:81-102, 1972. 2. Koeman JH, Ten Noever De Brauw MC, et al: Chlorinated biphenyls in fish, mussels and birds from the river Rhine and the Netherlands coastal area. Nature 221:1126-1128, 1969. , 3. Risebrough RW, Kieche P, Peakall D8, et ai: Polychlorinated biphenyls in the global ecosystem. Nature 220:1098-1102, 1968. 4. Bagley GE, Rcichel WL, Cromartie E: Iden tification of polychlorinated biphenyls in two bald eagles by combined gas-liquid chromatogra phy-mass s|>ectrometry. J Assoc Off Anal Chem 63:251-261, 1970. 6. Zitko V, Hutzinger O, Choi PMK: Contami- nation of the Bay of Fundy-Gulf of Maine area with polychlorinated biphenyls, polychlorinated terphenyls, chlorinated dibenzodioxins, and di- benzofurans. Environ Health Perspectives 1:47 60, 1972. 6. Curley A, Burse VW, Grim ME, et al: Poly chlorinated biphenyls: Distribution and storage in body fluids and tissues of Sherman rats. Envi ron Res 4:481-495, 1971. 7. Plantonow NW, Liptrap RM, Geissinger HD: The distribution and excretion of poly chlorinated biphenyls (Aroclor 1254) and their effect on urinary gonadal steroid levels in the boar. Bull Environ Contam Toxicol 7:358-365, 1972. 8. Kimbrough RD, Linder RE, Burse VW, et al: Adenofibrosis in the rat liver. Arch Environ Health 27:390-395, 1973. 9. Kimbrough RD, Linder RE, Gaines TB: Morphological changes in livers of rats fed poly chlorinated biphenyls. Arch Environ Health 25:354-364,1972. 10. Zitko V, Hutzinger O, Safe S: Retention times and electron capture detector responses of some individual chlorobiphenyls. Bull Environ Contam Toxicol 6:160-163, 1971. 11. Rote JW, Murphy PG: A method for quan titation of polychlorinated biphenyl (PCB) iso mers. Bull Environ Contam Toxicol 6:377-384, 1971. 12. Berg OW, Siosady PL, Rees GA: Column chromatographic separation of poiychlorinatcd biphenyls from chlorinated hydrocarbon pesti cides, and their subsequent gas chromatographic ~ quantitation in terms of derivatives. Bull Envi ron Contam Toxicol 7:338-347, 1972. 13. Hutzinger O, Nash DM, Safe S: Poly chlorinated biphenyls: Metabolic .behavior of pure isomers in pigeons, rats, and brook trout. Science 178:312-314, 1972. 14. Block WD, Cornish HH: Metabolism of biphenyl and 4-chlorobiphenyl in the rabbit. J Biol Chem 234:3301-3302, 1959. 15. Kimbrough RD, Gaines TB, Linder RE: The ultraBtructure of livers of ruts fed DDT and dieldrin. Arch Environ Health 22:460-467, 1971. 16. Goldstein JA, Hickman P, Bergman H, et al: Induction of hepatic porphyria and drug me tabolism by two polychlorinated biphenyls (PCB) mixture containing 42% chlorine (Aroclor 1016 and 1242), abstract. Fed Proc 33:219, 1974. It aI Arch Environ Health/Vol 29, Dec 1974 OSk 025636 Polychlorinated Biphenyls/Burse et al 307 STLCOPCB4009591