ORGANOCHLORINES IN POLAR BEARS (URSUS MARITIMUS). AT SVALBARD. Aksel Bernhoft, a Oystein Wiig b & Janneche Utne Skaare ac. aNational ...
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Environmental Pollution, Vol. 95, No. 2, pp. 159-175, 1997 © 1997 Elsevier Science Ltd All fights reserved. Printed in Great Britain 0269-7491/97 $17.00+0.00
ELSEVIER
O R G A N O C H L O R I N E S IN POLAR BEARS AT SVALBARD
(URSUS MARITIMUS)
Aksel Bernhoft, a Oystein Wiig b & Janneche Utne Skaare ac aNational Veterinary Institute, PO Box 8156 Dep., N-0033 Oslo, Norway bNorwegian Polar Institute, PO Box 5027 Majorstua, N-0301 Oslo, Norway~Zoological Museum, University of Oslo, Sars gt. 1, N-0562 Oslo, Norway CNorwegian College of Veterinary Medicine, PO Box 8146 Dep., N-0033 Oslo, Norway
(Received 18 May 1996; accepted 1 October 1996)
compounds, and industrial chemicals like polychlorinated biphenyls (PCBs), have been released to the global environment the last 3-4 decades. Long-range transport, via air in particular, takes these persistent and lipophilic compounds to the Arctic (Bowes & Jonkel, 1975; Clausen & Berg, 1976; Muir et al., 1988; Muir et al., 1992; Oehme, 1991; Barrie et al., 1992; Hargrave et al., 1992; Zhu & Norstrom, 1993; Norstrom & Muir, 1994). In arctic areas, particularly in the Western Hemisphere, considerable levels of PCBs and chlordanes have been found in polar bears (Norstrom et al., 1988; Norstrom et al., 1996; Norheim et al., 1992), the top predator of the Arctic marine food chain. These organochlorines are known to generate adverse effects after chronic administration to laboratory mammals. Both the pesticides and the PCBs may produce a range of effects including neuro, reproductional and immuno toxicities (Hayes, 1982a,b; Safe, 1984; Tilson et al., 1990; Ahlborg et al., 1992; Peterson et al., 1993; Ecobichon, 1996). Norheim et al. (1992) found PCB levels in polar bears at Svalbard close to those connected with reproductional disorders in Baltic seals (Helle et al., 1976; Bergman & Olsson, 1985; Olsson et al., 1992). Polar bears mate in the spring (Wiig et al., 1992). Fertilised eggs do not implant before SeptemberOctober, about the same time that the pregnant female enters the den (Ramsay & Stifling, 1988). According to Sandell (1990), species with delayed implantation appear especially susceptible to deleterious reproductive effects from organochlorine pollution. Polar bears have delayed implantation and Derocher (1991) suggested that organochlorine-induced effects on reproduction may be one factor in the decline in reproductive performance of the Western Hudson Bay polar bears. Cubs are born around Christmas and the female emerges from the den usually with two cubs in March-April. She has then fasted for about six months. Polar bear milk has a high fat content (Arnould & Ramsay, 1994) and lactation seems to occur more or less until weaning at about 2 ½ years (Oehme et al., 1995). The objectives of this study were to provide comprehensive baseline data on important OC contaminants in polar bears at Svalbard and to assess the possible
Abstract
A comprehensive survey on organochlorine (OC) contaminants in polar bears at Svalbard has been undertaken. Subcutaneous tissue, blood and milk have been sampled from anesthetized free-ranging bears of both sexes and different ages in the period from 1990 to 1994. A number of sexually mature females have been fitted with satellite transmitters which make it possible to follow their reproductive behaviour pattern. We report on contamination levels and pattern of PCB congeners, chlordanes, DDTcompounds, HCB and HCH-isomers in the various tissues. The relation of age, sex and reproductive status to OC contamination has been described, and the capacity of polar bears in metabolising OCs has been discussed from the isomer/metabolite composition of residues. Finally, the possible association between OC contamination and reproduction success has been assessed. The PCB levels present in polar bears at Svalbard are extremely high. Especially high levels of higher chlorinated PCBs are found, and they accumulate with age, particularly in males. With females, considerable amounts of OCs are transferred to the offspring via milk. However, more efficient OC transfer between subcutaneous depot lipid and circulatory lipids than from the circulatory system to milk is found particularly for the most lipophilic compounds. The OC pattern in suckling yearlings reflects the low transfer of the highest chlorinated PCBs into maternal milk. The levels of most other OCs, however, are higher in depot lipid of yearlings than in that of their mothers. The polar bears have high capacity to metabolise several OCs. This may protect them against toxic action of the contaminants. No relation between OC levels in females and their ability to get pregnant is found in this preliminary investigation on OC effects on the polar bears at Svalbard. © 1997 Elsevier Science Ltd. All rights reserved
INTRODUCTION
Large quantities of organochlorines (OCs) including pesticides like chlordanes, dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB) and toxaphene related 159
A. Bernhoft et al.
160
influence of age, sex and reproductive status on the levels of these lipohilic compounds, particularly the toxicokinetic influence of elimination and exposure of OCs with milk. In addition, the possible association between OC levels and reproduction success was investigated.
MATERIALS AND METHODS Field studies
Sampling was done during March and April each year during 1990 to 1994 on land-fast ice, except in 1992 when l0 bears were captured on land during August. Most captures took place in the southern and southeastern parts of Svalbard, with a few bears captured in the northern parts of the archipelago. Bears were anesthetized by using remote intramuscular injection of Zoletil® (tiletamine + zolazepam) from a helicopter (Wiig, 1995). Anesthetized bears were measured and their physical condition assessed. A vestigal tooth was extracted for age determination by cementum annuli (Grue & Jensen, 1979). Each bear was assigned a unique number which was tattooed inside the upper lip and also applied to a plastic tag in the ear. Tissue samples were collected from a total of l l5 individual polar bears of both sexes and different ages. Most bears were sampled once, but 8 bears were recaptured and resampled the following year(s): 6 bears resampled once, 1 bear resampled twice, and 1 bear resampled three times. Thus the total number of samplings was 126 (Table 1). Samples of subcutaneous tissue (ca 0.5 g) were collected from the lateral thigh, blood samples (10-50 ml) from a femural vein and milk samples (10030 ml) were collected by manual milking of the mammae. Milk samples were from females with cubs of the year, except two samples from females with yearlings. Blood samples were placed in heparinized tubes, centrifuged and separated into plasma and cells. Samples were stored in polypropylene containers (-20°C) until analysed. Sample sizes for this study varied due to logistics and use in other projects (see Norstrom et al., 1996). Most adult females were equipped with satellite transmitters (Telonics Inc., Mesa, Arizona, USA) as described by Fancy et al. (1988), Harris et al. (1990), and Wiig (1995). The transmitters were programmed to send information during six hour intervals every six Table I. The total numbers of captures of polar bears during 1990-94 at Svalbard and types and numbers of collected samples for organochlorine analyses. Six bears were sampled two years, one bear was sampled three years and one bear was sampled four years
Bears Subcutaneous Blood B l o o d captured t i s s u e plasma cells 1990 1991 1992 1993 1994 Total
19 14 33 34 26 126
0 0 31 33 25 89
5 9 19 30 19 82
19 14 29 32 22 116
Milk 0 0 6 5 3 14
days for about two years. Information on the location of the transmitter as well as sensor data on internal transmitter temperature and short- and long-term bear activity were recorded. Reproductive rates can be estimated from satellite data. Female polar bears normally have a three year reproductive cycle and mate during spring (Ramsay & Stirling, 1988). The cubs are born the next winter and follow their mother for about two and a half years, when the mother is supposed to come in oestrus again. Females with 2-year-olds or without young in spring are available for mating. Females were tagged in spring (or summer) and classified as 'available for mating' or not. Only pregnant females are denning. Data recorded from the satellite transmitter make it possible to register if females are denning or not the preceding winter. Analyses of organochiorines
Samples of subcutaneous tissue (ca 0.5 g), milk (ca 2 g), plasma (ca 8 g) and blood cells (ca 8 g) were weighed and added internal standard TCN (samples from 1990° 1993) or PCB-112 (samples from 1994). The samples were extracted twice with cyclohexane and acetone using an ultrasonic homogenizer followed by cleanup with sulfuric acid as described by Brevik (1978), slightly modified by Bernhoft and Skaare (1994). For determination of extractable lipids, blood cell extracts were carefully evaporated to dryness. The extracts of subcutaneous tissue, plasma and milk were evaporated to ca 1 ml, then diluted with cyclohexane to fixed volumes (10 ml for subcutis and milk extracts, 5 ml for plasma extracts). Then aliquots (4 ml from subcutis and milk extracts, 2 ml from plasma extracts) were evaporated to dryness for determination of extractable lipid. The samples were automatically injected (Fisons autosampier AS 800) on a Carlo Erba, HRGC 5300 Mega Series (Carlo Erba Instrumentation, Milano, Italy) gas chromatograph, equipped with a split/splitless injector (1 /zl, 1:30) and an electron capture Nickel-63 detector. Hydrogen was used as carrier gas on a SPB-5 60 m capillary column with 0.25 mm i.d. and 0.25/zm film thickness (Supelco Inc., Bellefonte, PA, USA). Makeup gas was 5% methane/95% argon. Chromatographic data were calculated using the software Maxima 820 Chromatography Workstation (Millipore Waters, Milford, MA, USA). The following OCs were determined: chlordane related compounds: heptachlor, oxychlordane, trans-chlordane, cis-chlordane, trans-nonachlor, and cis-nonachlor; DDT-compounds: p,p-DDE, o,p-DDD, p,p-DDD, o,pDDT, and p,p-DDT; HCB; HCH-isomers: at-, 13-,and 7HCH; 22 PCB congeners (UIPAC nos, Ballschmiter & Zell, 1980): 28, 52, 66, 74, 99, 101, 110, 105, 118, 128, 138, 141,149, 153, 156, 157, 170, 180, 187, 194, 206 and 209. The standard curves used for quantification were made by fitting a straight line through two concentrations of the standards and the origin. Quantifications were carried out within the linear range of the detector. Percent recovery was calculated for each sample series of 24 samples by adding a known amount of a standard
Organochlorines in polar bears mixture to two samples of clean material. The recoveries of added s t a n d a r d a m o u n t were for PCBs and D D T s 80-110%, for chlordanes (including oxychlordane) 80100%, for H C B and H C H s 70-95%. Reproduceability was continuously tested by analysing a control sample (seal blubber) in each sample series. Detection limits for individual OCs were found between 0.5 and 5 ng g - l in subcutaneous lipid and milk lipid, between 2 and 18 ng g - ~ in plasma lipid and between 10 and 110 ng g - 1 in blood cell lipid. The l a b o r a t o r y has participated in several intercalibration tests. G o o d analytical quality for determination o f p , p - D D E , I3-HCH, total PCBs and the m a j o r PCBcongeners in h u m a n milk was confirmed by successful
161
participation in interlaboratory tests organized by The W o r l d Health Organisation/United N a t i o n s Environmental P r o g r a m m e ( W H O / U N E P ) in 1982 and 1992. Participation in the four steps o f the International Council for Exploration o f the Sea/International Oceanographic C o m m i s s i o n / O s l o - P a r i s C o m m i s s i o n ( I C E S / I O C / O S P A R C O M ) test on PCBs in marine material, placed the l a b o r a t o r y in good and acceptable groups c o m p a r e d to the other participating laboratories. Data analyses
The statistical calculations o f data were m a d e using J M P statistical software (SAS Institute Inc., Cary, N C , USA).
Table 2. Organochlorine concentrations in subcutaneous lipid (ng g - i ) of polar bears at Svalbard grouped according to age and sex. Group a: young 1-2 years, group b: subadults 3-6 years, group c: adult females 7-15 years, group d: adult males 7-15 years and group e: old males 16-22 years. Medians (means) and ranges are presented
N % extractable lipid Chlordanes DDE HCB HCHs PCB-99 2,4,5,2',4'-pentaCB PCB-105 2,3,4,Y,4'-pentaCB PCB-118 2,4,5,Y,4'-pentaCB PCB-128 2,3,4,2',Y,4t-hexaCB PCB-138 2,3,4,2',4',5'-hexaCB PCB-153 2,4,5,2',4',5'-hexaCB PCB-156 2,3,4,5,Y,4'-hexaCB PCB-157 2,3,4,3',4~,Y-hexaCB PCB-170 2,3,4,5,2~,3t,4'-heptaCB PCB-180 2,3,4,5,2',4',5'-heptaCB PCB-187 2,3,5,6,2',4',5'-heptaCB PCB-194 2,3,4,5,2',3',4',5'-octaCB PCB-206 2,3,4,5,6,2',Y,4',5'-nonaCB PCB-209 2,3,4,5,6,2',3P,4',5',6'-decaCB Sum PCBs
(a) Young
(b) Subadults
(c) Adult females
(d) Adult males
(e) Old males
8 54(51) 32-69 3210 (3380) a.e 912-6000 519 (567) 287-1120 157 (200) 75-496
25 45(45) 20-68 3340 (3440) a.e 858-8310 274 (305 < 2-859 126 (191) 64-522 212 (197) < 4-473 1080 (1190) 416-2740 23 (23) < 3-76 30 (39) < 3-109 15 (30) < 2-125 1040 (1140) 388 2750 6300 (7080) 1860-14 800 191 (189) 62-478 214 (198) 59-505 1700 (1820) 552-4430 3460 (3720) 921-8410 15 (21) < 1-97 788 (828) 198-2940 98 (100) a < 4-343 31 (35) < 5-160 14400 (16400) 5250-36 700
23 49(50) 10-82 2710 (3150) a,e 364-7550 227 (372) < 2-1820 130 (192) 49-461 172 (163) < 4-358 1040 (1200) 454-2410 27 (31) < 3-101 76 (76) < 3-282 19 (43) < 2-202 1240 (1330) 464-2750 4450 (5930) 1280-15 100 152 (166) < 3-400 111 (t25) < 4-237 1110 (1490) 552-3550 2480 (3470) 611-8750 27 (29) < 1-82 743 (1030) a 253-4580 141 (173) ~ 29 763 68 (114) ~.b < 5 510 13000 (15 700) 4790-41 500
20 40(40) 10-70 1030 (1250) 184-2970
9 51(41) 15-59 407 (613) 199-1870 202 (342) 89-1050 134 (238) 34-947 260 (318) 133-644 671 (706) 346-1650 33 (47) < 3-110 99 (108) < 3-261 32 (45) < 2-127 884 (922) 358-2170 4710 (4680) 1600-8040 173 (193) 72-347 230 (254) 81-418 2380 (2560) 797-3740 3780 (4220) 1160-6870 18 (25) < 1-91 3040 (2360) ~,b,c 746-3410 228 (289) ~'b 68-499 135 (187) ~.b 32-390 15400 (16600) 5540-27 700
258 (233)
109-365 1480 (1270) 379-1890 30 (33) < 3-110 57 (49) < 3-108 46 (44) < 2-115 1420 (1250) 553-2010 5060 (5020) 1590-8330 138 (132) < 3-244 133 (133) < 4-252 1140 (1110) 471-1670 2010 (1980) 943-3440 19 (14) < 1-28 323 (373) 255-568 27 (31) < 4-69 7 (11) < 5-29 11200 (11 400) 4810-18 300
~Significantly higher than corresponding concentrations of group a (p < 0.05). a'bSignificantly higher than corresponding concentrations of groups a and b (p < 0.05). a'b'cSignificantly higher than corresponding concentrations of groups a, b and c (p < 0.05). a'cSignificantly higher than corresponding concentrations of groups a and c (p < 0.05). bSignificantly higher than corresponding concentrations of group b (p < 0.05). b'cSignificantly higher than corresponding concentrations of groups b and c (p < 0.05). a'eSignificantly higher than corresponding concentrations of groups d and e (p < 0.05).
255 (340)
58-1490 192 (215) 62-480 335 (385) b," 212-1150 I100 (1300) 248-4 100 45 (40) < 3-71 90 (98) b < 3-194 55 (63) b < 2-176 1460 (1620) 306-4670 9060 (10800) 1570-27 900 231 (271) ~ 83-892 252 (320) ~,c 108-1160 2670 (3830) ".h," 879-11 800 5380 (7530) ~,C 914-22 600 26 (31) < 1-76 1160 (1900) ~.b 379-5740 158 (236) ~,h
49-827 75 (121) a,h < 5-400 21700 (28 100)~.' 6960-80 300
A. Bernhoft et al.
162
Because of lack of normality in the OC dataset, tested by Shapiro-Wilk W test, the data were log transformed to achieve normal distributions. For observations below detection levels, half of the detection levels were used. In order to explore the correlations between the OCs in a multivariate space we have applied principal component analysis (PCA). The OC concentrations in subcutaneous lipid of all sampled individual polar bears were both normalized and standardized to unit variance. The variables are presented as vectors in the system of the principal components (PCs) that explain most of the variable variance. By plotting the variables in two dimensions the correlating variables will appear as vectors with similar direction and length. Comparisons of the OC levels between groups were made using T u k e y - K r a m e r statistical method for comparing all pairs of groups. The OC levels are mainly presented as median concentrations with ranges. The medians are optimal averages of distributions with positive skewness and observations below detection levels (Altman, 1991). To explore the relations of the concentrations of OCs in different matrices Pearson product-moment correlations were used. Statistical significant level was set at p < 0.05. To demonstrate how the OCs vary with age for each sex we used smoothing spline (Eubank, 1988). This is a partial least square method, basically descriptive, to visualize in detail the relation between two variables. A coefficient ~, which determines the stiffness of the line was found optimal at ~,=100. In Figs 1-3 where smoothing spline were used, untransformed values are presented to show the real OC levels on y-axes. Statistical differences of OC levels between age and sex groups were tested elsewhere (Table 2). For comparison of the OC levels in different matrices sampled from the same individuals, median values at
log-scales were presented. The log-scales show the absolute median levels and also illustrate the relative relation between median levels in the matrices for individual OCs. Median OC levels in mothers and their offspring are presented similarly. For individual bears sampled two or more years, only the results from the last samplings are included in Tables 2-7, and in all figures, to reduce the influence of sampling dependency. The results from the resampled individuals are presented separately in Table 5. All the OC levels are given on the basis of extractable lipids.
RESULTS Types and levels of O C s in subcutaneous lipid
The following OCs were present consistently at levels above quantification levels: chlordanes (sum of oxy-, cis-, and trans-chlordane, and trans-nonachlor), DDE, HCB, HCHs (sum of ~- and [3-HCH) and PCBs (14 individual congeners with 5-10 chloro substituents (Table 2). PCBs and chlordanes predominated. The median concentration of sum PCBs in subcutaneous tissue of 85 individual polar bears was 15.5/zg g-1 lipid. PCB nos. 153 and 180 constituted about 62% of sum PCBs. The corresponding median concentration of chlordanes was 2.3 #g g-l lipid. Oxychlordane constituted about 72% of sum chlordanes. The oxychlordane levels may be conservative estimates due to the possibilities of losses in partitioning. The median concentrations of DDE, HCB and HCHs were 272, 146 and 240 ng g-I lipid, respectively. ~-HCH constituted about 81% of sum HCHs. The chlordane related compounds cis-nonachlor and heptachlor, the D D T compounds p,pand o,p-DDT, and p,p- and o,p-DDD, the 7-isomer of
Table 3. Correlation coefficients (r) of organochlorine concentrations (log ng g-i fipid) between subcutaneous tissue (subeutis) and plasma, plasma and milk, subeutis and milk, blood cells and plasma and between blood cells and subeutis in polar bears at Svaibard. For statistical significant correlations (p < 0.05), the coefficients are given in bold
Subcutis-Plasma N Chlordanes DDE HCB HCHs PCB-99 PCB-105 PCB- 118 PCB- 128 PCB- 138 PCB- 153 PCB- 156 PCB-157 PCB- 170 PCB- 180
PCB- 187 PCB-194 PCB-206 PCB-209 Sum PCBs
64 0.66 0.28 0.88 0.37 0.73 0.12 0.17 0.27 0.77 0.73 0.74 0.50 0.79
0.58 0.05 0.81 0.71 0.50 0.71
c.n.c. = correlation not calculated.
Plasma-Milk 9 0.47 -0.20 0.91 0.26 0.90 0.51 0.10 0.87 0.71 0.38 0.70 -0.31 0.29 0.12
0.56 -0.01 -0.01 c.n.c, 0.35
Subcutis-Milk
Bl.cells - Plasma
Bl.cells - Subcutis
12 0.91 0.36 0.91 0.91 0.89 0.39 0.67 0.65 0.89 0.93 0.91 0.91
79 0.66 0.42 0.66 0.55 0.57 c.n.c, c.n.c, c.n.c, 0.69 0.66 c.n.c, c.n.c,
76 0.77 0.58 0.71 0.55 0.71 c.n.c. c.n.c. c.n.c. 0.66 0.78 c.n.c.
0.80 0.86
0.69 0.49
0.66 0.51 0.27 c.n.c, 0.92
c.n.c, 0.70 c.n.c, c.n.c, 0.59
c.n.c. 0.73
0.70 c.n.c. 0.77 c.n.c. c.n.c. 0.73
Organochlorines in polar bears Table 4. Organochlorine concentrations in blood cells (ng g-I lipid) of adult female polar bears at Svalbard grouped according. to offspring status. The ages (years) are also listed. Medians and ranges are presented
HCH, and the PCBs no. 28 (tri chlorinated) nos. 52, 66 and 74 (tetra chlorinated) nos. 101 and 110 (penta chlorinated), and nos. 141 and 149 (hexa chlorinated) were all below the detection limits of the analytical method in almost all samples.
Adult females
N Age % extr. lipid Chlordanes DDE HCB HCHs PCBs
with cubs of the year
with yearlings
with 2-year-olds or without young
11 9 7-14 0.20 0.13-0.41 2500 722-4800 48 15 years old) males are presented in Table 2. The highest chlordane levels were found in young and subadult bears and were significantly higher than in adult and old males. The highest level of sum PCBs was found in adult males and was significantly higher than in young and adult female bears. Nine of 14 individual PCBs showed significantly higher levels in adult males than in one or more of the other groups. Also the highest level of HCHs was found in adult males and was significantly higher than in subadults and female adults. For D D E and HCB no statistically significant differences were found between the age/sex groups. In young and subadult bears, no sex differences in OC levels, except for significantly higher chlordane level in subadult females than in subadult males, were found. Change in subcutaneous lipid levels of OCs with age and sex is visualized by help of smoothing splines with partial least square lines, in Fig. 2. No change in HCB levels with age and sex is observed. The chlordanes show lower levels in males than in females above young age, a decrease with age in males, and a highest level in females at 5-6 years. D D E levels tend to decrease from young to subadult age. Higher levels o f HCHs and sum PCBs in males than in females are observed. In males, HCHs increase with age until about 12 years, while in females no change with age is evident. Sum PCB levels seem to increase with age until about 7 and 14 years in females and males, respectively, and thereafter a decline in levels can be seen.
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The levels of individual PCBs are similarly visualized in Fig. 3. All congeners except nos. 99 and 138 tend to increase with age in younger males. The increase is more prominent with increased chlorination. The levels of all PCB congeners, except PCBs 105 and 118, tend to reach a plateau or decline in old males. In females, the individual PCBs tend to follow the corresponding levels in males until adulthood. Then from 7-11 years of age a deviation from the corresponding male level, especially
for the hexa and hepta chlorinated congeners, nos. 153, 156, 157, 170 and 180, can be seen. Tissue distribution and transfer to offspring
Median per cent extractable lipids of blood cells, plasma, milk and subcutaneous tissue were 0.20, 1.1, 25 and 46, respectively. Correlation coefficients found between OC concentrations in different types of matrices are shown in
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---'-
0
-
T
5
-'
I
10 Age
'
:
I
15
'
I
20
Fig. 3. (Continued.)
Table 3. The correlation of OCs in subcutaneous and plasma lipids were significant for most OC compounds. The OCs in plasma lipids and milk lipid were less correlated. Significant correlations were found for most OCs in subcutaneous and milk lipids; however the highest chlorinated PCBs did not correlate significantly. The concentrations of detectable OCs in blood cell lipids correlated significantly with the corresponding OCs in both subcutaneous and plasma lipids. The subcutaneous and plasma lipids contained similar levels of chlordanes, HCB and HCHs. The PCB and DDE levels were significantly higher in subcutaneous lipid than in lipids of plasma. A comparison of median concentrations of chlordanes, DDE, HCB, HCHs and individual PCBs between subcutaneous and plasma lipids is shown on a log-scale in Fig. 4(A). The median concentrations of individual PCBs and DDE were about 2 and 4 times higher, respectively, in subcutaneous than in plasma lipids. For the individual PCBs, parallel paths of the median concentrations in subcutaneous and plasma lipids were found, illustrating similar ratio of individual PCBs between subcutaneous
and plasma lipids. Blood cell lipids contained about 50% higher levels of chlordanes, HCB and HCHs than plasma lipids. The levels of individual PCBs and DDE were similar in lipids of blood cells and plasma. In lactating bears, similar levels of chlordanes, HCB and HCHs were found in lipids of milk, subcutaneous tissue and plasma. The levels of DDE, penta and hexa chlorinated PCBs in milk lipid were similar to the corresponding levels in plasma lipids. However, for hepta to deca chlorinated PCBs, gradually decreasing relative levels with increased chlorination were found in milk compared to corresponding levels in subcutaneous tissue and plasma. The comparison of the median OC concentrations in subcutaneous and milk lipids is presented in Fig. 4(B). The median (and range) OC concentrations (ng g-l) in milk lipid from N = 12 bears were as follows: chordanes: 2070 (551-5210), DDE: 62 (
