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" , -.c in the 1. lungs of . this et' "acleria) . The imi.. in the Imonary _ ' ni inhaii i.li-rtaken > i to dif- II as to i. '-naj con- - are in . S Deptrtu uvaiiablt ir.'il ury JA. H < raiflc b*. in i '>-rn Mtd th... . ily di*. A nn JnUrn , V: mimunm - J Ind Mtd X, n al. walls liy con* vlih. Ixxb /a* ilmonnry wR lual extract* nr* mechfr fly.. / Sound idi- in dgaiU. Stand J artlrlf'a and \ dnii age, in 'j/ Cl in Air *7.1. jp A2S- jK?n*c to irw irwi Hfallfl >f J.iFcrenl Mr'1 ir> -.-.parity i tin! their . )t> J }nd rictt 1 id'tioni UukI . Hr J n . t*t al: tYU]ution*l if du-M*. Br dot'nin. J Distribution and Metabolism of 2,4,5,2', 5'-Pentachlorobiphenyl Vttha Berlin, MD; John Gage, PhD, DSc; Stina Holm Single doses of 2,4,5,2',5'-pentichloroNphtnyl uniformly labeled with 'C have been administered Intravenouely and erelly to mice. Whole-body autoraClogrsms and eclntllletlon counting of Sieue aamplee have shown that moti redloictlvlty laavee the circulation for tha tnuss within ona hour. Peak concentra tions varied, being hlghait In brown fat, hlch after 24 hour* comprised tha majo< reservoir of the unchanged compound In the body. Radioactivity disappeared rather rapidly from most other tlseuai, al though tha longest retention occurred In bronchial epithelium and tome parte of the renal tubuloe. The excretion of radioactivity waa mslnly through tha blit, Into lecet, with a hell-time of tlx daya. There was little un changed compound In the faces, the ma jor metabolite wee a hydroxylated deriva tive, both (rat and conjugated. PCB mixtures' and of a commercial mixture labeled with tritium." The most reliable information on the fate of PCBs in an ecosystem iB obtained from the use of single com ponent PCBs labeled with a radio active isotope. Such investigations have been reported with dichlorobiphenyl,1 with tetrachlorobiphenyl,* and in the early stages of the pressent investigation with a pentachlorobiphenyl.' 2,4,5,2',5'-Pentachlorobiphenyl is a suitable compound for an investigation into the relation be tween structure and storage, metabo lism, excretion, and toxicity, as it is a major component of the commercial mixtures such as Arochior 1254,10 and it has been stated to be present in samples of human fat." METHODS 2,4,5,2',5'-Pentachloroblphenyl Earlier investigations into the re tention, metabolism, and excre A sample uniformly labeled with "C (30 tion of the various chlorinated bi millicuries/gm) in the 2',5'-dichtorophenyl phenyls (PCBs) were based on analysis ring was supplied In benzene solution (0.67 of tissues and excreta from animals dosed with one of the commercial PCB mixtures, or from animals or man that had absorbed those compo miilicurie/ml) and gave a single PCB peak by gas liquid chromatography (glc) at a re tention time of 6.2 minutes. The thin layer chromatogram (tic) R, value was 0.6 (see below). nent PCBs that are persistent in the environment. Such investigations have shown that PCBs containing four chlorine atoms or less, which form the major part of PCBs enter ing the environment, largely dis appear in the lower stages of food Preparation of the Dose The PCB was administered to CBA mice as a solution in dimethylBulfoxide (DMSO) or in an aqueous emulsion. For the DMSO solution, a measured volume of the PCB solution was evaporated to dryness and the chains, and that the retention of residue dissolved in sufficient DMSO to higher PCBs by mammals is influ enced by their extent of chlorina tion.'" These conclusions have been confirmed by the study of the fate of single components of the commercial give 10 microcuries in 0.05 ml. For the emulsion, a measured volume of the ben zene solution waa evaporated in a poly propylene tube and the residue dissolved in the lipid-phosphatide phase of a pharma ceutical emulsion (Intralipid) 20% (Vitrum AB [Stockholm]). This solution waa emulsi fied in 4 volumes of 2.5% aqueous glycerol Submitted for publication April 3, 1974; ao- etpled April 90. From the Department of Environmental Heilth, University of Lund, Sweden. Reprint requeiti to the Department of Envi ronmental Health, University of Lund, Box 2009, 9-220 02, Lund 2, Sweden (Dr. Berlin). by pumping it several times through a needle attached to a syringe, and this pri mary emulsion was then homogenized by placing the tube in an ultrasonic bath (Varian) maintained at 60 C. The droplet size of the emulsion so produced was about the same as that of Intralipid, most drop lets being less than 1pm diameter. Whole Body Autoradiography For the whole body autoradiograms, 10u curies of the DMSO soluliun or of the emulsion was injected into the tail vein, or 10 microcuries of the emulsion was admin istered orally by stomach tube. This dose of PCB corresponds to about 15 mg/kg body weight. Animals were killed 20 min utes, one, four, and 24 hours after an injec tion, and 1, 8, 16, and 32 days after an oral dose, and autoradiograms were prepared from whole body sections by the method of Ullberg." Exposure of the sections to the photographic emulsion was performed at -15 C, as earlier experiments had shown that a considerable diffusion of radio activity from faL occurred al room tem perature. The isotope "staircase" scale in Fig 1 and 2 was prepared by the method of Ber lin and Uliberg," using "C-labeled NA.CO, solutions varying by a factor 2. Determination ol Radioactivity in Tissues and Excreta Mice were dosed orally with 5 micro curies of PCB emulsion (about 7 mg/kg body weight), groups of three were killed 1, 4, 8,16, and 32 days after dosing, and the organs were removed for radioactivity measurements. Organs were also included from the mice dosed with 10 microcuries for the autoradiographic experiments. An other group of three mice, each receiving 5 microcuries was maintained in a melabce iism cage and the urine and feces collected separately. A sample of each tissue was weighed on filter paper, dried, and ignited in an oxy gen flask containing 1 M sodium hydroxide solution. The daily output of feces was dried and weighed, then ground in a mor tar and a weighed amount similarly ig nited in the oxygen flask. Diluted urine and the sodium hydroxide solutions were added to Instagel and the radioactivity measured with a scintillation counter (Packard Series 3000). Samples of fat were taken from seven of the mice, with survival times ranging be tween one hour and eight days; they were bulked together and analyzed for PCB by the method of Jensen et al *'tt r et al Arch Environ Heatth/Vot 30, March 1975 iw 2,4,5,2',5'-PamBchlorobiphenyl/8erlin et al 141 DSW 025983 STLCOPCB4009945 J Metabolism Four mice were dosed orally each with 6 mg of PCB containing 0.4 microcuric'CPCB. Feces were collected from the mice for seven days and dispersed in water. The suspension was fractionated by the scheme given below. Thin layer chromatograms were on silica gel F254 (Merck) plates, eluted with toluene containing 19o volume per volume (v/v) ethanol. Column chromalogrsphy was on 25 X 1 cm columns of Billca gel 60-200 mesh (Sigma Chemical Co, Type 1) or fiorisil 60-100 mesh activated at 110 C for five hours. Gas-liquid chromatograms were made (Varian 1400 instrument with an EC detector). A 6 footxy;. inch column was used, packed with 4% SF96 on Chromusorb W HP 80/100 (Varian). Column, in jector, and detector temperatures were 175, 200 and 192, C respectively. The car rier gas was N, at 30 ml/min. Mass Spectroscopy A mass spectrograph (LKB 9000) was used with direct inlet of the sample and the following conditions; acceleration volt age, 3,500 v; ion source temperature, 270 C; electron energy 70 electron volts; and in jection temperature, 50 to 60 C. RESULTS Whole Body Autoradiography The autoradiogram in Fig 1 shows that 20 minutes after an intravenous injection of the PCB emulsion, a great part of the radioactivity had al ready left the circulation and entered the tissues. With an intravenous in jection of the DMSO solution the pro portion in the circulation was rather less at this period, but one hour after administration there was no signifi cant difference between the distribu tion patterns produced by the two different physical states of the injec tions. At this time there was little ra dioactivity in the blood, and most was located in brown fat and the adrenalB, with rather less in the liver. Radio active material was visible in the gallbladder, and in the gastrointesti nal tract from the stomach to the transverse colon. At one day no radio activity could be seen in the blood (Fig 2), and fatty tissues throughout the body were well defined. The dis tribution pattern at one day after an oral dose of the PCB emulsion was very similar to that in Fig 2. At 8 and 16 days the autoradiographic pattern was dominated by the liver and fatty tissues, but at 32 days (Fig 3) the most clearly defined areas were the lungs, kidneys, and nasal sinuses. Respiratory Organs,-A preferential concentration of radioactivity in the respiratory organs, particularly in the nasal sinuses and bronchi was seen 20 minutes after injection, and this was maintained throughout the experimental period. At 32 days these tissues were more dearly defined than other organs (Fig 3). The uneven dis tribution pattern in the lungs, with radioactivity mainly in the bronchial epithelium, is seen clearly in Fig 4. Cardiovascular and Lymphatic Syv tems.-The radioactivity in the myo cardium was not significantly differ ent from that in the skeletal muscles, and there was no increased concen tration in the walls of the blood ves sels. There was no specific concentra tion apparent in the bone marrow or lymph nodes after one day, though this might have been masked by the high concentration in fat. At one day after injection there was a relatively high concentration in the spleen. Digestive System.--Radioactive ma terial appeared in the stomach mu cosa and contents 20 minutes aftci intravenous injection, and thereafic: rapidly spread through the whole of the gastrointestinal tract. A concen tration in the gallbladder was clearly visible four hours after intravenous injection (Fig 5). From one day onward, when the high radioactivity in the liver had diminished to some extent, this organ showed a marbled distribution pattern with the highest I | | i 'i I I ' i | j 1 1 > i Fig 1.--Autoradiogram from mouse 20 minutes after a 10 microcurie intravenous dose of PCB emulsion. Brain Brown Fat Spleen Kidney --------------------- " --------- *" V lfl Heart liver 142 Arch Environ Health/Vol 30, March 1975 If* 2.4.5,2',5'-Penlachforobipheny1/Berlin et a' DSM 025964 STLCOPCB4009946 * "spen.1 -'0 Visi i than it n disn , wiLh ' ,) ch ia! . :ir -1. ' Svs- il, myoly iifTcrm -.cles. m-en1 "I vos' utratn-'.vv or .ugh 1 V. the or" day In I ively een. ivo mau'h mil* .8 n Tver .roafter '111 'l' of cor' encloarly IVCI1UUS lay onivity ill me cxlarhlcd liglu'St Brain Liver Gallbladder Feces Fetus Flfl 2.-Autoradiogram from mouse one day after a 10 mlcrocurle Intravenous dose of PCB emulsion. Nasal Sinuses Lungs Kidney * cl al Heart Feces Fig 3.--Autoradiogram from mouse 32 days after a 10 mlcrocurle oral dose ot PCB emulsion. concentrations in the periportal areas (Fig 6). A relatively high concentra tion was seen in the salivary glands but not in the pancreas. Endocrine Glands.-The adrenals showed a marked radioactivity 20 minutes after injection (Fig 7), but this decreased rather rapidly and at 24-hours only a trace could be seen in the cortex (Fig 8). Urogenital Organs.--At the end of the experimental period the kidneys were more clearly defined than most other organs (Fig 9), due to a punc tate distribution pattern in the cortex that may have been associated with a special location in the tubular sys tem. Some radioactive material was visible in the bladder at all periods. The ovaries exhibited marked radio activity up to 24 hours after injection (Fig 10), but this had disappeared at 16 days. There was a slight pene tration into the fetus, with no clearly defined distribution pattern. The con centration in testes was low after one day. Skin and Ectodermal Glands.--A rel atively high concentration was ob served throughout the experimental period in the hair follicles, partic ularly in the region of the nose, and to a lesser extent in the lachrymal gland3. Central Nervous System.-The radio activity in brain decreased as the Arch Environ Health/Vol 30, March 1975 2,4,5,2',5'-Penlachlorobiphenyl/Berlin et al 143 DSW 025985 Gallbladder Lungs Fig 4 --Autoradiogram of mouse lung 16 days after a 10 mlcrocurle oral dose of PCB emulsion. Fig 5.--Autoradiogram of mouse liver four hours after a 10 mlcrocurle intra venous Injection of PCB emulsion. Fig 6.--Autoradiogram of mouse liver eight days after a 10 mlcrocurle oral dose of PCB emulsion. Adrenal Adrenal ! Fig 7 --Autoradiogram of mouse kidney wilh adrenal indicated by arrow, 20 min utes after a 10 microcurie Intravenous In jection of PCB emulsion. Fig 8.--Autoradiogram ol mouse adrenal one day after an intravenous injection ot 10 mlcrocurles ol PCB emulsion. Black areas indicate teces. Fig 9 --Autoradiogram of mouse kidney 32 days after a 10 microcurie oral dose of PCB emulsion. ; , I blood concentration decreased. With the shorter experimental periods, a tendency for a preferential retention .in white matter was observed. Radioactivity Measurements In Tlssuas and Excreta The radioactivity of pooled urine and feces from three mice, expressed as a percentage of the dose given, is shown in Table 1. The radioactivity in the organs at various periods after dosing is shown in Table 2. The re sults obtained from the mice used in the autoradiographic experiment are not strictly comparable to the rest, as the dose was twice as large and thus the obtained values have been halved for comparison with the rest of the material. In one pregnant female dosed intravenously with 6 micro curies 0.7 nanocuries/100 mg ap peared in the fetus after one day. Metabolism The feces from the four mice col lected during the seven-day period contained 0.65 microcuries, corre sponding to 41% of the dose adminis tered. Figure 11 shows the percent- age of this fecal radioactivity that was obtained in the various fractions. Fraction FI.-The hexane solution was evaporated to small volume and chromatographed on a silica gel col umn with toluene as the eluant. The radioactive fractions from the column were shown by tic to contain a major component with R.0.28, and a trace of a component with an R, approxi mately 0.56. The major component was extracted from the tic plate with acetone, and by glc it gave a peak with a retention time and shape iden tical with that of the crystalline me- 144 Arch Environ Health/Vol 30, March 1975 2,4,5,2',5,-Pentachlorobiphenyl/'Berlin el al DSW 025986 STLCOPCB4009948 ] 1 4 jse liver 'f al dose Ovary Fetus Fig 10 --Auloradlogram of ovary from pregnant mouse one day after an Intra venous ln|ection of 10 mlcrocurles of PCB emulsion. The (etuses are visible In the lower part of the figure. tabolite isolated from fraction F3. Fraction F2.-Attempts to isolate the components of this fraction from an oil that remained in the aqueous layer after hexane extraction were unsuccessful. Fraction F3.-This fraction con tained the hydrolysis products of con jugated metabolites in feces. There was much oily contamination and the fraction was further purified by chro matography on a florisil column, elut ing with hexaneiacetone (9:1 v/v). A further clean-up was effected by tic, and the single radioactive component was extracted with acetone and again subjected to tic. The metabolite had an Rt. 0.28; it was extracted from the plate with hexane and on evaporation the solution yielded a trace of solid residue with no oily contamination. By glc the solution showed a single component with a tailing peak at a retention time of 16.1 minutes, Table 1.--Excretion of Radioactivity In Urine end Feces Expressed as Percentages ol the Dose Administered (5 Mlcrocurles per Mouse). Day* Aftar Doting t 2 3 4 5 6-7 8 9-10 11 12 . 13 14 15 18 17-18 19 Totaft Feces 20 3 9.9 4.1 7.0 3.0 5.4 3.6 6.4 2.3 1.8 2.5 2.2 2.0 2.3 2.4 1.8 77.4 UHno 0.23 0.11 0.12 0.13 0.17 0.16 0.13 0.11 0.07 0.10 0.08 0.09 . 0.09 0.06 0.12 0.06 1.8 Total 20.53 10.01 4.22 7.13 3.77 5 56 3.73 6.51 2.37 1.90 2.58 2.29 2.09 2.36 2.52 1.66 79.2 Fig 11.--Fractionation ol feces. Figures In parentheses Indicate percentage of Initial radioactivity In feces. kid' i'v lose . l th;ii ion.'-. iitinn and 1 col . Tli.lumi, j oajor | ce of : i'OXI* ; nent with peak ilenme- ot al Fecal Suspension (0.65 Microcurie) Extracted With Hexane ( Hexane (14%) t Water FI Extracted With Ether 1 1 1 Ether (73%) Water 1 Extracted With 0.1 M NaOH L--_------ - | 0.1 M NaOH (48%) 1 Brought to 3 M HCI and Boiled for 3 hr: Extracted With Hexane | 1 Hexane (30%) t Chromatographed on Florisil Column; Eluted 1 F2 Ether (11.5%) I 1 Chromatographed on Silica Get Column Eluting Successively With Hexane, CCl^ and Toluene 1 1----------------- --------------------------- CC1 (4%) Toluene (5%) F5 4 F6 With Hexane-Acetone (9:1) i 1------------------------ -------------------- 1 Eluate (14%) Retained on F3 Column F4 Arch Environ Health/Vol 30, March 1975 2,4,5,2',5'-PBn1achloroblphenyl/Berlin et al 145 DSW 025987 STLCOPCB4009949 r U' Nahoc.imes/100 mg 1 utable to a loss of CHO. Fraction F4.--This fraction re Blood 10 mained on the florisil column and all attempts to remove it were unsuc 20 fat 10 0 20 lungs 10 0 20 Kidney 10 n 111111 cessful. Fraction F5.--The radioactive frac tions were evaporated to small bulk and subjected to tic. A single radio active component with R, 0.59 was obtained. 1 II a_________ to Fraction F6.-This small volume and was evaporated on tic showed a 20"j___ 4, , 1 4 B 16 32. radioactive component remaining at mm h, Days Fig 12--Mean tissue radioactivity (nanocunes/jpp mg) trom groups ot mice In Table 2. ' the origin. This was extracted with acetone and hydrolyzed by boiling for three hours with 3 M HC1. All of the radioactivity could then be extracted into hexane. The extract on glc Fig 13.--Log percent radioactivity re tained by mice alter 5 mtcrocurles ot PCB emulsion administered orally. Curve cal culated trom the results in Table 1. re lint rnp JV Vh Hifr cm' T ii. i rut Of l* l i--n Uir lh<' The metabolite was examined by mass spectroscopy and the spectrum showed the characteristic isotope cluster for Cl, at m/e (mass to charge ratio) 340 to 348, corresponding to a molecular formula C,,H,0 Cl,. There was a clearly defined Cl, cluster at 27p to 276, and another Cl, at 241, attrib showed a peak with a shape and re tention time identical with that of the metabolite from F3. Analysis of Fat All of the radioactivity in the col lected fat samples analyzed was ex tracted into hexane. By glc the ex tract gave a peak with a retention time identical with that of PCB, There was no such peak in an extract of fat from an untreated mouse and no evidence of any dechlorination of PCB. ' COMMENT The results show that the uptake of Table 2.--Distribution of Radioactivity In Tissues After a Single Dose of WC-PCB In Nanocurle/100 mg (Equivalent to 0.33 ppm PCB)* 1-t 1' U r 'i a- - 'u (Mil ifUl'l Ui-r v,i v nifi tU tl lime jin a TUftua Blood Bile Heart Lungs Uver Spleen Kidneys Adrenals Testes Ovaries Fat Skin Muscle Thymus Brain Sex 20 min M (8.0) F M (38) F M 12 F M 27 F M 51 F M 7.0 F M 19 F M F M 0.34 F M 4.3 F M F M 2.0 F M (44) F M 0.50 F 1 ht (3.5) (590) 9.9 15 33 9.8 (54) (7) 13 51 5.8 (23) 6.5 4 hr (3.6) 13 5.7 12 2.1 8.4 0.44 12 17 1.7 1.1 3.8 1 Dev 1.7, 1.8 0.58 (20) (60) 2.2. 2.4 0.47 0.88.9.2 2.8 6.5, 5.7 2.6 12.4.1 0.33 8.6. 3.4 2.1 (6.4), (69) 135) 1.0. 0.57 (4) 28. 25 4.t 12. 8.9 7.1 15, 9.0 5.4 5.3. 1.6 3.2 0.97. 0.41 (0.14) 4 Days 2.8 t.1 (8) (25). (21) 0,50 0 37.0.29 3.1 3.2. 2.1 2.8 IB. 3.2 1.2 0.40. 0.63 1.7 1.5. 2.6 (18) (8.2), (12) 0.92 (3.4). (7.7) 11 11. 21 9.6 8.1, 11 2.0 0.94. 2.7 0.71 4.5. 0.94 0.18 0.23. 0.31 8 Days 0.43. 0.27 0.41 (14) 0.41.0.44 0.45 1.9. 3.0 4.0 3.6. 1.1 ,1.7 0-75. 0.39 0.35 0.99, 1.31 1.40 (9), (1.5) (8.1) 0-55. 0.48 (6.6) 13. 12 22 4.1. (6.6) 10 1.5. 3.5 6.7 2.7, 2.0 34 0.21.0.14 0 19 IS Day* (0.18) 0.29.0.25 (7.6) (10). (5) 0.54. 0.41 0.22 5.2. 4. 9 0.78 1.3. 0.97 (0.19) 0.30, 0.22 0.50 0.10, 0.90 (3.9) (51). (6.3) 0.37 (13). (4 0) 8.2 14, 14 5.0 6.4, 6.8 2,7 2.6. 2.5 0.59 2.2. 1.5 0.11 0.21.0.13 32 Day* 0.16, 0 32 0.20 (3.2) (2) 0.18, 0.24 0,30 9.8, 6.7 6.3 0.47, 0.49 1.0 0.11. (0.28) (0.14) 0.86. 0 92 1.2 (2). (2.9) (5 0) 0.14, 0.19 5.2. 5.0 19 1.1, 1.5 4.9 0.54, 0 66 0.35 0.23. 0.37 1.1 (0.061, (0.08) 0.21 P* i< all A is s t IV!h" ns i I'.t ; i fr-:i nicm Ta l:t r Tb* tv- ci U l1' ].: I ('> f V;, i r Tii * Figures In parsntheaes are of low precision due to lower organ weights or low counts. ir l 146 Arch Environ HeaUh/Vol 30, March 1975 2.4,5,2',5'-Pentachlorot>lphenyl/0orlin et.al OSM 025988 l STLCOPCB4009950 ?CB by Ihe tissues from the circula tion after intravenous injection is rapid, and not much delayed if the PCB is administered in the lipid phase of an aqueous emulsion. This method of administration is free I from some of the disadvantages asso ciated with the use of organic liquids u solvents for intravenous injections. The tissue analyses in Table 2 are in general agreement with the con clusions drawn from the auto radiograms. During the first 20 min utes after intravenous injection most re of the radioactivity leaves the circula C* tion and is taken up mainly by liver, ra kidneys, and brown fat. Thereafter the radioactivity increases in the gen eral body fat, rising to a maximum 'n between 4 and 24 hours, at a time ;ic'. when the amount in other tissues is mil rapidly decreasing. Thus, it must be of assumed that the radioactivity is ini tially stored in the tissues and subse quently migrates to fat and is stored there. The results are too few to give of any clear indication of a sex differ ence, thought there is a suggestion that the radioactivity is retained longer in the fat of female mice. The mean values for all mice in each group are presented diagrammat ically in Fig 12. Analysis of fat has shown that PCB is stored mainly unchanged in the body, so it is likely that the early tis sue distribution is due to unchanged PCB. However, at the dose adminis tered, nearly all the PCB is excreted as a metabolite. Table 1 shows that radioactivity is lost fairly rapidly I from the body with a half-time of about aix days, and is excreted almost entirely in the feces. The results in Table 1 have been transformed in Fig 13 to show the rate of change of log residual radioactivity in the body. The graph shows a two-phase excre tion, Bn initial more rapid loss that is probably due to metabolism and ex cretion of PCB while it is concen trated in the liver, and a later linear portion that car. be attributed to a rei lease from fat. Extrapolation of the ! graph shows that a reduction of the | total body burden to 1% of its original I value would require about 65 days, j The presence of radioactive material f in bile 20 minutes after intravenous I al Arch Environ Health/Vol 30, March 1975 L injection indicates that this is the ma jor route of excretion of the metabo lite. Radioactivity in the stomach con tents after intravenous injection may be due to excretion through the stom ach wall or salivary glands, or to a re flux of duodenal contents. The adrenals initially have a high affinity for PCB, but like most other tissues their radioactivity decreases rapidly as the blood concentration falls. Kuratsume'1 has reported that the pattern of urinary 17-ketosteroid excretion in patients suffering from Yusho disease indicates adrenocorti cal hyperfunction, and it is possible that the changes in steroid metabo lism associated with PCB may in part be due to a direct action of PCB or its metabolites on the adrenals/ in addi tion to the induction of liver enzymes reported by several investigators. It is possible that the initial higher concentration of PCB in brown fat than in yellow fat is due to the greater vascularity of the former, leading to a more rapid attainment of an equilibrium with PCB in the blood. This would result in a slower rise in concentration in yellow fat but a more prolonged retention as PCB is lost from the body. The accumulation of radioactivity in the bronchial epi thelium leading to a late rise in Lhe lung concentration, and the sustained concentration in mucous membranes, may be due to a high affinity of these tissues for a metabolite produced in the lungs or elsewhere. Reid et al" have observed that metabolites of certain halogenated hydrocarbons are firmly bound to lung tissue. This investigation into the metabo lism of a PCB leads to the conclusion that earlier investigations into the fecal excretion of unlabeled PCBs are likely to have given incomplete reaults when only unchanged PCB was measured/ or when only the metabo lites in a hexane extract of feces were investigated.* Stalling and Mayer1' have shown that the pentachlorinated biphenyls are a major component of the PCB residues in fish, and are, therefore, likely to constitute an important part of the PCB intake in food. The rather low proportion of 2,4,5,2',5'-pentachlorobiphenyl in the PCB content of hu man fat suggests that man, like the mouse, is aide to metabolize and ex crete this PCB more rapidly than lower members of the food chain. The work was supported by the Swedish Envi ronmental Protection Board. Rolf Serwin. Department of Organic Chem istry, University of Lund, prepared and inter preted the mass spectrograms. References 1. Grant DL, Phillips WEJ, Villenueve DC: Metabolism of a polychlorinated biphenyl (Arochlor 1264) mixture in the rat. Hull Environ Contain Toxical 6:102-112, 1971. 2. Curley A, Burse VW, et al: Polychlorinated biphenyls: Distribution and storage in body fluids and tissues of Sherman rats. Environ Rea 4:481-495, 1971. 3. Koeman JH, ten Noever de Brauw MC, de Vos RH: Chlorinated biphenyls in fiah, mussels and birds from the river Rhine and the Nether lands coastal area. Mature 221:1126-1128, 1969. 4. Yoshimura H, Oshimura M: Studies on the tiuue distribution and elimination of several components of KC-400 (chlorobiphenyl*) in mice. Fukuoka Acta Med 62:5-11, 1971. 5. Hutzinger 0, et al: Polychlorinated bi phenyls: Metabolic behaviour of pure isomeres in pigeons, rats and brook trouts. Science 178:312 313, 1972. 6. Yoshimura H, et al: Studies on the tissue distribution and the urinary and fecal excretion of 'H-kanechlor (chlorobiphenyls) in rats. Fu kuoka Acta Med 62:12-19, 1971. 7. Moia P, et al: Verteilung und Metabolismus von 2,2'-Dichlorbiphenyl-MC in der hbheren Sumpfpflanze Veronica beecabunga. Chrmoephere 2.217-222, 1973. 8. Melv&s B, Brandt I: The Distribution and Metaboli'*m oflabelled Polychlorinated Biphenyla in Mice and Qvaila. National Swedish Environ mental Protection Board Publication 4E 1973, pp 87-100. 9. Berlin M, Gage JC, Holm S: The Metaboliam and Diatribution of 2^,5tt.S'-pen(aehlorobiphenyl in the Mouse. National Swedish Environmental Protection Board Publicition 4E 1973, pp 101 108. 10. Siaaona D, Welti D: Structural identi fication of polychlorinated biphenyls in com mercial mixtures by gas-liquid chromatography, nuclear magnetic resonance and mass spectrom etry. J Chromatogr 60:16-21, 1971. 1L Price HA, Welch RL: Occurrence of poly chlorinated biphenyls in humans. Environ Health Perepect 1:73-77, 1972. 12. Ullberg S: Studies on the distribution and fate of S"-lsbelted bentylpenicillin in the body. Acta Radiol[Suppl) (Stockh) p 118, 1954. 13. Berlin M, Ullberg S: Accumulation and re tention of mercury in the mouse. Arch Environ Health 6:589-601, 1963. 14. Jensen S, et al: DDT and PCB in Herring and Cod from the Baltic, Kattegat and Skagerak. Ambio Special Report, 1972, vol 1, pp 71-85. 15. Kuratsume M: An abstract of results of laboratory examinations of patients with Yusho and of animal experiments. Environ Health Frr. spect 1:129-136, 1972. 16. Reid WD, et a): Metabolism and binding of aromatic hydrocarbons in the lung. Am Rev Rtspir Die 107:539-551, 1973. 17. Stalling D, Mayer FL: Toxicilies of PCRs to fish and environmental residues. Environ Health Perspect 1:169-165, 1972. 2,4,5,2\5'-Pentachlorobiphenyl/8ernn al 147 DSW 025989 STLCOPCB4009951