PCB's and their environmental effects

Population recovery of peregrine falcons in central Norway in the 4 decades since the DDT-ban

The breeding population of peregrine falcons (Falco peregrinus) in Norway was almost exterminated by the early 1970's. Long-term monitoring of breeding pairs has been conducted since 1976 up to present. Peregrine falcons were first established at breeding sites in coastal habitats, where they remained at stable low numbers until the early 1990's. Starting around 2000, numbers began to increase steadily, and current numbers have now reached historical population levels from the pre-DDT era. We documented a range expansion with increasing numbers of peregrines nesting in the fjords and inland valleys. We found that once a territory was colonized, the probability that a territory remained occupied was high (S > 0.958). During early stages of population recovery, the transitional probabilities of becoming or remaining a breeding territory were high (ψ_N-B > 0.40, ψ_B-B > 0.65) but declined over time, especially in coastal habitats. Moreover, the productivity per nest has also decreased over time at sites in coastal habitats in the former stronghold of the population. The levels of environmental pollutants in eggs of the peregrines have dropped sharply over the last few decades, and contaminant levels now seem to be below critical levels. Eggshells were relatively thin throughout the 1970s, 1980s, and 1990s, but have increased to almost normal levels during the last 2 decades. Reductions in levels of organochlorine pollutants, especially DDT, appear to have been the main factor in explaining the population recovery. The territory dynamics are consistent with density-dependence and the low breeding success of the coastal-breeding peregrines is believed to be caused by declining numbers of colonial seabirds and other prey species.

Organochlorines in egg samples from Norwegian birds of prey: congener-, isomer- and enantiomer specific considerations

The content of chlorinated persistent organic pollutants was determined in a total of 44 egg samples from 8 different raptor species collected throughout Norway in the period 1991-1997. The content of 8 chlorinated bornanes, 9 chlorinated pesticides, and 15 polychlorinated biphenyl congeners (PCB) were determined. The highest average concentrations for PCB were found for eggs from White-tailed Sea Eagle and Peregrine Falcon (average sum PCB concentration: 8.9 and 9.1 microg/g wet weight (w.w.), respectively). Merlin and Sparrowhawk eggs were the highest contaminated with chlorinated pesticides (average sum pesticide concentration: 3.0 and 4.3 microg/g w.w.). For the first time, the content of chlorobornanes was determined in Norwegian birds of prey eggs. However, only minor contamination compared to PCBs and conventional chlorinated pesticides was found. The highest sum concentration was determined for White-tailed Sea Eagle eggs (0.09 microg/g w.w.). No chlorobornane contamination was found in Osprey and Merlin eggs. No spatial and regional specific trends or pattern distribution were found for organochlorine contamination in the egg samples analysed. In order to gain information about enantiomer specific bioaccumulation and biotransformation capacity of the organism, enantioselective analyses was performed for the chiral contaminants trans-chlordane, oxy-chlordane and the chlorobornane B9-1679 (Parlar #50). Indications for species-dependent deviation from the racemic distribution (enantiomeric ratio = 1) were found. Peregrine Falcon and Merlin eggs were characterised with an extremely high enantiomeric excess of the (-)-trans-chlordane (enantiomeric ratio (ER) <0.01). For Golden Eagle, Goshawk and Sparrowhawk eggs, the ERs were between 0.1 and 0.22 demonstrating also here that the (-)-trans-chlordane was the most abundant enantiomer. For the distribution of oxy-chlordane and B9-1679 enantiomers no species-dependent differences were found. For all species the ER values between 0.3 and 0.8 were determined. Thus, also for oxy-chlordane and B9-1679, the (-)-enantiomers are the most dominating stereoisomers in the birds of prey eggs analysed.

Effects of the antiestrogenic environmental pollutant 3,3',4,4', 5-pentachlorobiphenyl (PCB #126) in rat bone and uterus: diverging effects in ovariectomized and intact animals

The purpose of this study was to compare effects on rat bone and uterus of estrogen depletion and exposure to the coplanar PCB-congener 3,3',4,4',5-pentachlorobiphenyl (PCB #126) which exhibits anti-estrogenic properties. Half of the rats were ovariectomized (n = 20) and the other half were sham-operated. Ten of the ovariectomized rats and ten of the sham operated were exposed to PCB #126 (ip injections) for 3 months (total dose: 384 microgram/kg body wt). The remaining control rats were injected with corn oil (vehicle). The rats were killed and the tibiae and uteri were dissected. The left tibia was used for measurements of weight, length, and bone mineral density and the right for histomorphometrical analysis. The uteri were analyzed with respect to estrogen receptor content. PCB #126 exposure did not affect bone mineral density or trabecular bone volume of tibia in sham-operated rats. In ovariectomized rats PCB #126 exposure resulted in a decreased length and an increased bone mineral density of tibia. An obvious PCB #126 induced increase in osteoid surface was observed in sham-operated rats. The cortical thickness and the organic content of the tibia were also increased in these rats. In estrogen deprived tissue like the uteri of ovariectomized rats, PCB #126 showed weak estrogen agonistic activity. The observed effects of PCB #126 on bone and uterine tissues differed between ovariectomized and sham-operated rats.

Organochlorine contaminants in eggs of Common Terns from the Canadian Great Lakes, 1981

To determine if contaminant levels in Common Terns had changed over the last decade, we collected and analyzed eggs from four nesting colonies on the three lower Great Lakes during 1981. DDE and PCBs were detected in every egg from the four colonies. Dieldrin, mirex and trans-nonachlor were detected in more than 45% of the eggs. Seven other organochlorine contaminants (DDD, DDT, hexachlorobenzene, oxychlordane, cis-chlordane, cis-nonachlor and toxaphene) were detected in less than 25% of the eggs. Eggs from the Lake Ontario colony were generally the most heavily contaminated. Comparisons of DDE and PCB data with earlier studies of Common Terns indicated that contaminant levels in eggs from the four sampled colonies, or nearby sites, have decreased by up to 80-90% from 1969-1973 to 1981. Interspecies comparisons showed that Common Tern eggs have lower organochlorine residue levels than eggs of Caspian Terns or Herring Gulls. Dietary variation and migratory status are possible explanations for the differences in residue levels among species. Eggshell thickness, log-PCBs, and log-DDE were not significantly intercorrelated. Elevated contaminant levels in the early 1970s might be at least partly responsible for the decline of the Great Lakes Common Tern population over the past decade. Stabilization of population numbers during the early 1980s suggests that organochlorine pollution levels have been reduced to a point where they are no longer an important factor in the population dynamics of this species on the Great Lakes.

PCB problems in the future: foresight from current knowledge

The present paper overviews the forthcoming PCB problems from current knowledge of their use, environmental contamination and toxicology. From a global point of view, PCB levels in the environmental media and biota are unlikely to decline in the near future due to the greater quantities of PCBs still in use than the quantity that has already escaped into the open environment. Considering all the information on the occurrence, distribution and behaviour of PCBs in the ecosystems, the marine mammals are probably the most vulnerable and possible target organisms in forthcoming long-term PCB toxicity. The recent isomer-specific analyses suggest that the intrinsic toxicity of PCBs principally resulted from the coplanar PCB congeners which may impose a greater toxic threat than chlorinated dioxins and furans to humans and wildlife. The measures necessary to reduce further discharge of PCBs into the environment should be set in motion immediately, otherwise there may be a subsequent deleterious biological impact.

Metabolism of 4-chlorobiphenyl by guinea pig adrenocortical and hepatic microsomes

Studies were carried out to determine if 4-chlorobiphenyl (4-CB) was a substrate for adrenal monooxygenases and to compare its interactions with adrenal and hepatic microsomal enzymes. Addition of 4-CB to guinea pig adrenal microsomes produced a typical type I spectral change, indicative of binding to cytochrome(s) P-450 and similar to that seen in hepatic microsomal preparations. The activities of several adrenal and hepatic microsomal monooxygenases were decreased by 4-CB in vitro. High pressure liquid chromatographic analyses revealed that both adrenal and hepatic microsomes, in the presence of NADPH, converted 4-CB to a major metabolite which eluted with a retention time identical to that of 4-chloro-4'-biphenylol (4'-OH-4-CB). The identity of 4'-OH-4-CB was confirmed by mass spectrometry. The maximal rate of 4-CB metabolism was greater in adrenal, compared with liver microsomes, but 4-CB had a higher affinity for hepatic than for adrenal enzymes. The rate of adrenal 4-CB metabolism was four to five times greater in microsomes derived from the inner cortical zone (zona reticularis) than those from the outer zones (zona fasciculata and zona glomerulosa). Hepatic microsomes also converted 4-CB to a minor metabolite whose production was blocked by epoxide hydrolase inhibitors, suggesting it might be a diol. 4-CB metabolism was not demonstrable in adrenal mitochondrial preparations. The results indicate that chlorinated biphenyls can serve as substrates for adrenal microsomal monooxygenases, suggesting that local activation may contribute to their adrenocortical toxicity.

Distribution and elimination of a polychlorinated biphenyl after acute dietary exposure in yellow perch and rainbow trout

Distribution and elimination of a single polychlorinated biphenyl isomer (2,5,2',5'-tetrachloro[14C]biphenyl, 4-CB) were compared in a nonfatty fish (yellow perch) and a fatty fish (rainbow trout). Adult fish were exposed acutely to 4-CB (0.8 microgram/fish) by the oral or intraperitoneal route and were killed at designated times thereafter for one month. Whole body elimination of 4-CB was similar in both species with 20 to 30% of the radioactive 4-CB being eliminated in the first 3 to 4 days after treatment, but very little thereafter. Also, the same extent of elimination was seen when the compound was given orally or intraperitoneally. Tissue distribution of 4-CB residues was different in the two species. Perch relied on viscera and carcass as main 4-CB distribution sites and skeletal muscle, skin and scales as minor sites. In rainbow trout, on the other hand, skeletal muscle and carcass were major distribution sites, whereas viscera and skin were minor sites. This species difference in 4-CB distribution was not due to a difference in sexual maturity of the perch and trout, because a build-up of eggs or sperm was not present in the peritoneal cavity of either species.

Effect of polychlorinated biphenyls on drug metabolism in Japanese quail and its progeny

PCB (DP5, 1 and 5 mg/female/day, orally for 40 days) induce microsomal hepatic enzymes (cytochrome P-450, aniline hydroxylase, aldrin epoxidase, p-nitroanisole demethylase, p-nitrophenol: UDPGA-transferase) in adult female Japanese quail. Toxicity of dinitro-o-cresol (DNOC) is reduced in treated animals. High hepatic activity occurs in young quails issued from treated females, but closely related to residue levels, normal enzyme activities are reestablished within 1 month.

The composition and distribution of PCB in arctic fox (Alopex lagopus) caught near Longyearbyen on Svalbard

Samples from 44 arctic foxes (Alopex lagopus), caught near Longyearbyen on Svalbard, were analyzed with respect to their content of PCB. Gas chromatographic-mass spectrometric investigations revealed that 7 PCB components constituted the main part of the total PCB present. These components were quantified individually. A moderate degree of PCB contamination was recorded. Calculated on a fat weight basis, the total concentrations of PCB in fat tissue and liver were about equal, but the relative amounts of most of the PCB components present were different in the 2 tissues. The total amount of PCB in brain, calculated on a fat weight basis, was significantly less than the corresponding concentrations in liver, kidney, muscle, and fat tissue. The special distribution trend observed in this study is related to the structure of the PCB components present and the arctic nature of the sampling area.

An environmental chemical, polychlorinated biphenyl, increases the protein synthesizing activity of liver and kidney pH 5 supernatant fractions

Homogenates of liver and of kidney cortex were obtained from control rats and from rats treated with the polychlorinated biphenyls (PCBs), Aroclor 1254, and were separated into ribosomes and into the postmicrosomal supernatant fraction. The latter fraction from liver and kidney was used to prepare the pH 5 supernatant fraction, containing elongation factors 1 and 2 (EF 1 and EF 2) for protein biosynthesis. These fractions were incubated with KCl-washed ribosomes obtained from control rat liver. The incorporation of [14C] phenylalanyl-tRNA into peptide was increased with the liver and kidney preparations derived from the treated rats. The elongation factor 1-dependent binding of [14C] phenylalanyl-tRNA to ribosomes was also markedly increased both with the liver and kidney preparations obtained from the rats that had received PCBs.