Polychlorinated Biphenyls In Blubber Research Articles

Historic changes of polychlorinated biphenyls (PCBs) in juvenile and adult cetaceans from the Pearl River estuary from 2003 to 2020

Polychlorinated biphenyls (PCBs), as a type of legacy persistent organic pollutants, pose significant health threats to wildlife. However, long-term residue changes and profiles of PCBs in cetaceans have not been extensively studied in the Pearl River Estuary (PRE), an important marine mammal area in China. Here, the body burdens, spatiotemporal trends, and health risks of 21 chlorobiphenyl congeners (∑21CBs) were analyzed in blubber samples collected from twelve cetacean species (n = 172) in the PRE from 2003 to 2020. Our results revealed medium levels of PCBs (316–96,233 ng g−1 lipid) compared to those reported for cetaceans elsewhere (70–370,000 ng g−1 lipid). Clear differences in PCB distribution patterns between inshore and offshore cetaceans and between odontocetes and mysticetes were also found. Both the coastal Indo-Pacific humpback dolphins (Sousa chinensis) and Indo-Pacific finless porpoises (Neophocaena phocaenoides) displayed similarly fine-scale spatial distribution patterns of PCBs, suggesting that the two cetaceans could serve as bioindicators of PCB pollution in the PRE. Additionally, both cetaceans exhibited decreasing trends in their blubber PCB concentrations over the past 20 years, likely reflecting the effective regulation of PCBs in the PRE Delta. Nevertheless, the relatively high and stable PCB-toxic equivalent (TEQ) levels detected in calf humpback dolphins during the sampling period suggested that the calves are still under the stresses of high PCB-related health risks. Our results highlight the need for more efforts to eliminate PCB contamination to prevent these cetaceans from continuous population decline and further extinction.

Levels of Polychlorinated Biphenyls Are Still Associated with Toxic Effects in Harbor Porpoises (Phocoena phocoena) Despite Having Fallen below Proposed Toxicity Thresholds.

Polychlorinated biphenyls (PCBs) are toxic, persistent, and lipophilic chemical compounds that accumulate to high levels in harbor porpoises (Phocoena phocoena) and other cetaceans. It is important to monitor PCBs in wildlife, particularly in highly exposed populations to understand if concentrations are declining and how levels relate to toxicological thresholds and indices of health like infectious disease mortality. Here we show, using generalized additive models and tissue samples of 814 U.K.-stranded harbor porpoises collected between 1990 and 2017, that mean blubber PCB concentrations have fallen below the proposed thresholds for toxic effects. However, we found they are still associated with increased rates of infectious disease mortality such that an increase in PCB blubber concentrations of 1 mg kg-1 lipid corresponds with a 5% increase in risk of infectious disease mortality. Moreover, rates of decline and levels varied geographically, and the overall rate of decline is slow in comparison to other pollutants. We believe this is evidence of long-term preservation in the population and continued environmental contamination from diffuse sources. Our findings have serious implications for the management of PCB contamination in the U.K. and reinforce the need to prevent PCBs entering the marine environment to ensure that levels continue to decline.

Effects of age, adipose percent, and reproduction on PCB concentrations and profiles in an extreme fasting North Pacific marine mammal.

Persistent organic pollutants, including polychlorinated biphenyls (PCBs), are widely distributed and detectable far from anthropogenic sources. Northern elephant seals (Mirounga angustirostris) biannually travel thousands of kilometers to forage in coastal and open-ocean regions of the northeast Pacific Ocean and then return to land where they fast while breeding and molting. Our study examined potential effects of age, adipose percent, and the difference between the breeding and molting fasts on PCB concentrations and congener profiles in blubber and serum of northern elephant seal females. Between 2005 and 2007, we sampled blubber and blood from 58 seals before and after a foraging trip, which were then analyzed for PCBs. Age did not significantly affect total PCB concentrations; however, the proportion of PCB congeners with different numbers of chlorine atoms was significantly affected by age, especially in the outer blubber. Younger adult females had a significantly greater proportion of low-chlorinated PCBs (tri-, tetra-, and penta-CBs) than older females, with the opposite trend observed for hepta-CBs, indicating that an age-associated process such as parity (birth) may significantly affect congener profiles. The percent of adipose tissue had a significant relationship with inner blubber PCB concentrations, with the highest mean concentrations observed at the end of the molting fast. These results highlight the importance of sampling across the entire blubber layer when assessing contaminant levels in phocid seals and taking into account the adipose stores and reproductive status of an animal when conducting contaminant research.

Vitamin A and E profiles as biomarkers of PCB exposure in beluga whales (Delphinapterus leucas) from the western Canadian Arctic

We evaluated the utility of vitamin A and E profiles as biomarkers of contaminant exposure in beluga whales (Delphinapterus leucas; n=66) harvested by the Inuvialuit in the Beaufort Sea. Blubber was an important repository for these vitamins, accounting for 76.8±2.6% of the total body store of vitamin A, and 98.5±0.4% of total vitamin E. While the free alcohol form of vitamin A (retinol) appeared highly regulated, the vitamin A esters were influenced by several biological factors including age, body condition and length. Vitamin E concentrations in liver and blubber were related to age, condition, length and feeding ecology, as described δ15N and δ13C. Despite the influence of these factors, collective results from univariate statistics, best fit multiple regressions, and principal component analysis (PCA) identified polychlorinated biphenyls (PCBs) as important determinants of vitamin concentrations and profiles in beluga tissues. Blubber PCB concentrations best explained variation of the first principal component in a PCA of hepatic vitamins (r2=0.13, p=0.014), and regression models found that vitamin A concentrations were negatively correlated with PCB levels in liver (esters: r2=0.19, p=0.001), but positively in plasma (retinol: r2=0.20, p=0.06) and blubber (retinol: r2=0.22, p=0.001, esters: r2=0.43, p<0.001). Our analyses provide a basis to propose an integrated toxicity reference value for disruption of vitamin A and E profiles in beluga of 1.6mg/kglw PCBs. This disruption of vitamin profiles by moderate levels of PCBs in an arctic cetacean highlights the global reach and impact of these legacy chemicals decades after their peak use.

Anaemia, hypothyroidism and immune suppression associated with polychlorinated biphenyl exposure in bottlenose dolphins ( Tursiops truncatus )

Polychlorinated biphenyls (PCBs), persistent chemicals widely used for industrial purposes, have been banned in most parts of the world for decades. Owing to their bioaccumulative nature, PCBs are still found in high concentrations in marine mammals, particularly those that occupy upper trophic positions. While PCB-related health effects have been well-documented in some mammals, studies among dolphins and whales are limited. We conducted health evaluations of bottlenose dolphins (Tursiops truncatus) near a site on the Georgia, United States coast heavily contaminated by Aroclor 1268, an uncommon PCB mixture primarily comprised of octa- through deca-chlorobiphenyl congeners. A high proportion (26%) of sampled dolphins suffered anaemia, a finding previously reported from primate laboratory studies using high doses of a more common PCB mixture, Aroclor 1254. In addition, the dolphins showed reduced thyroid hormone levels and total thyroxine, free thyroxine and triiodothyronine negatively correlated with PCB concentration measured in blubber (p = 0.039, < 0.001, 0.009, respectively). Similarly, T-lymphocyte proliferation and indices of innate immunity decreased with blubber PCB concentration, suggesting an increased susceptibility to infectious disease. Other persistent contaminants such as DDT which could potentially confound results were similar in the Georgia dolphins when compared with previously sampled reference sites, and therefore probably did not contribute to the observed correlations. Our results clearly demonstrate that dolphins are vulnerable to PCB-related toxic effects, at least partially mediated through the endocrine system. The severity of the effects suggests that the PCB mixture to which the Georgia dolphins were exposed has substantial toxic potential and further studies are warranted to elucidate mechanisms and potential impacts on other top-level predators, including humans, who regularly consume fish from the same marine waters.

Concentrations and accumulation features of PCDDs, PCDFs and dioxin-like PCBs in cetaceans from Korean coastal waters

Despite several studies that report accumulation of polychlorinated biphenyls (PCBs) and DDT in marine mammals worldwide, very few have examined polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like PCBs. In particular, no earlier studies have reported concentrations and accumulation profiles of persistent organic pollutants (POPs) in marine mammals from Korea. In this study, concentrations and accumulation features of PCDD/Fs and dioxin-like PCBs were measured in liver and blubber of minke whales and long-beaked common dolphins collected from Korean coastal waters. The concentrations of PCDFs and dioxin-like PCBs in blubber were 3–10 times higher than the concentrations measured in liver, but PCDDs were higher in liver than blubber. Total toxic equivalent (TEQ) concentrations in blubber of minke whales and common dolphins from Korean coastal waters were similar to, or higher than those reported for cetaceans and seals from other countries. Homologue and congener profiles of PCDD/Fs were different between livers and blubbers, while the profiles of dioxin-like PCBs were similar between the tissues. Concentrations of PCDD/Fs and dioxin-like PCBs in liver and blubber of dolphins were significantly higher than those measured in whales, due to differences in habitat and diet. The relative contribution of individual chemical groups to total TEQs was different between the two cetacean species, suggesting different exposures and metabolic activity. The TEQ levels in minke whales did not exceed the threshold level suggested for immunomodulation, while TEQs in all dolphin samples exceeded the suggested threshold level, implying potential adverse health effects from exposure to PCDD/Fs and PCBs.

Contaminant-associated disruption of vitamin A and its receptor (retinoic acid receptor α) in free-ranging harbour seals ( Phoca vitulina)

Polychlorinated biphenyls (PCBs) have been associated with a number of toxic effects in marine mammals such as endocrine disruption and immunotoxicity that, in turn, are widely thought to have contributed to population level impacts including reproductive failure and outbreaks of disease. In this study, the dietary hormone vitamin A and expression levels of one of its receptors, retinoic acid receptor α (RARα), were used as biomarkers of PCB-associated health effects in harbour seals. Harbour seal pups ( n = 24) were live-captured in coastal British Columbia, Canada, and Washington State, USA, and sampled for whole blood (to obtain peripheral blood mononuclear cells, PBMCs) and blood plasma, as well as biopsies of blubber and skin. Concentrations of circulatory vitamin A (retinol) in plasma and stored vitamin A in blubber were negatively associated with blubber PCB concentrations ( R = −0.518, p = 0.013 and R = −0.645, p = 0.009, respectively). However, vitamin A concentrations in skin, an important target tissue, remained constant, which likely reflects a compensatory transfer from blubber to maintain physiological functions. In addition, we characterized the harbour seal RARα, and investigated its expression levels as a potential biomarker in seals. RARα expression in blubber, but not on PBMCs, was elevated in more contaminated animals ( R = 0.580, p = 0.009). This may represent a direct contaminant-related effect, or, a compensation for the contaminant-related disruption of (circulatory and/or blubber) hormone levels. Since vitamin A is critical to developmental, reproductive and immunological health, our observations of a contaminant-related disruption of its physiology in free-ranging seals may portend population level consequences. Vitamin A concentrations and RARα expression levels can therefore represent relevant and sensitive biomarkers of PCB-associated toxic effects in toxicological studies of marine mammals.

The Risk of Infection from Polychlorinated Biphenyl Exposure in the Harbor Porpoise ( Phocoena phocoena ): A Case–Control Approach

The objective of this study was to determine whether the risk of mortality from infectious disease in harbor porpoise in U.K. waters increased with high exposure to polychlorinated biphenyls (PCBs), using a case–control study design. This is the first time that data from a long-term marine mammal strandings scheme have been used to estimate any increase in risk. The exposure odds ratio (OR) from a logistic regression model with infectious disease deaths as cases and physical trauma deaths as controls, after controlling for the effect of confounding factors, was 1.048 [95% confidence interval (CI), 1.02–1.07]. To further adjust for the difference in energetic status between cases and controls and account for the negative relationship between PCBs (sum of 25 chlorobiphenyl congeners) and blubber mass, we also “standardized” the blubber PCBs to an optimal blubber mass. This lowered the OR to 1.02 (95% CI, 1.00–1.03). Thus, for each 1 mg/kg increase in blubber PCBs, the average increase in risk of infectious disease mortality was 2%. A doubling of risk occurred at approximately 45 mg/kg lipid. In this study, we have endeavored to avoid selection bias by using controls that died of physical trauma as representative of the exposure prevalence in the population that gave rise to the cases. In addition, we controlled for the effect of variation in energetic status among the cases and controls. However, as with case–control studies in human and veterinary epidemiology, unforeseen misclassification errors may result in biased risk estimates in either direction.

Systemic Effects of Arctic Pollutants in Beluga Whales Indicated by CYP1A1 Expression

Cytochrome P450 1A1 (CYP1A1) is induced by exposure to polycyclic aromatic hydrocarbons (PAHs) and planar halogenated aromatic hydrocarbons (PHAHs) such as non-ortho polychlorinated biphenyls (PCBs). In this study, we examined CYP1A1 protein expression immunohistochemically in multiple organs of beluga whales from two locations in the Arctic and from the St. Lawrence estuary. These beluga populations have some of the lowest (Arctic sites) and highest (St. Lawrence estuary) concentrations of PCBs in blubber of all cetaceans. Samples from these populations might be expected to have different contaminant-induced responses, reflecting their different exposure histories. The pattern and extent of CYP1A1 staining in whales from all three locations were similar to those seen in animal models in which CYP1A has been highly induced, indicating a high-level expression in these whales. CYP1A1 induction has been related to toxic effects of PHAHs or PAHs in some species. In St. Lawrence beluga, the high level of CYP1A1 expression coupled with high levels of contaminants (including CYP1A1 substrates, e.g., PAH procarcinogens potentially activated by CYP1A1) indicates that CYP1A1 could be involved in the development of neoplastic lesions seen in the St. Lawrence beluga population. The systemic high-level expression of CYP1A1 in Arctic beluga suggests that effects of PAHs or PHAHs may be expected in Arctic populations, as well. The high-level expression of CYP1A1 in the Arctic beluga suggests that this species is highly sensitive to CYP1A1 induction by aryl hydrocarbon receptor agonists.

Congener-specific data on polychlorinated biphenyls in tissues of common porpoise from Puck Bay, Baltic Sea.

Individual congeners of polychlorinated biphenyls (PCBs), including the highly toxic non-ortho coplanar 3,3',4,4'-tetrachlorobiphenyl (IUPAC No. 77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC No. 126), and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC No. 169), and their mono- and di-ortho analogs, have been identified and quantified in the blubber, liver, and muscles of three female common porpoise Phocoena phocoena collected from the Puck Bay (inner Gulf of Gdańsk, Poland) in 1989-1990, to elucidate actual concentrations and toxic potential. The total 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent for 13 coplanar PCBs in blubber was 1,500 +/- 470 pg/g wet wt. 2,3',4,4',5-Pentachlorobiphenyl (IUPAC No. 118) was the most contributing individual and occupied between 57 and 67% in total toxic equivalent of coplanar PCBs in blubber, while 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC No. 153), 2,3,3',4,4'-pentachlorobiphenyl (IUPAC No. 105) and 2,2',3,4,4',5'-hexachlorobiphenyl (IUPAC No. 138) comprised between 9.5-14, 7.6-11.5, and 7.2-11.0%, respectively (totally 82-95%), and 2,3,3',4,4',5-hexachlorobiphenyl (IUPAC No. 156) was absent. A potentially most toxic non-ortho PCB members such as 3,3',4,4',5-pentachlorobiphenyl, 3,3',4,4',5,5'-hexachlorobiphenyl and 3,3',4,4'-tetrachlorobiphenyl were only minor contributors, altogether occupying between 1.0 and 14.5% in total TEQ of coplanar PCBs. Concentrations of total PCBs in lipids of the blubber ranged from 26 to 47 micrograms/g and were comparable or lower than reported earlier for common porpoises from the Baltic Sea, North Sea, and North Atlantic by other authors.

Levels of selected individual polychlorinated biphenyls in different tissues of harbour seals ( phoca vitulina) from the Southern coast of Norway

Concentrations of individual polychlorinated biphenyls (PCBs) were determined in blubber, liver, kidney and brain tissues of 10 male harbour seals ( Phoca vitulina) of different ages. The animals were found dead or dying on the southern coast of Norway in 1988 during the morbilli virus epizootic. Twenty-three PCB congeners were investigated in all tissues by capillary gas chromatography with electron capture detection and comparison with standards of the respective congeners (IUPAC numbers 28, 52, 74, 99, 101, 105, 110, 114, 118, 128, 138, 141, 149, 153, 156, 157, 170, 180, 183, 187, 194, 206 and 209). In addition, three toxic coplanar congeners (IUPAC numbers 77, 126 and 169) were investigated in the blubber samples. Total PCB (sum of the determined congeners) in kidney (12–60 nmol g −1), liver (12–90 nmol g −1) and blubber (10–79 nmol g −1) were similar on extractable lipid basis, while total PCB in brain lipid was about 1/10 (1·6–12 nmol g −1). The absolute concentrations of the individual congeners in brain lipid correlated poorly with the respective concentrations in each of the other tissues, while the individual congener concentrations in the lipid fractions of kidney, liver and blubber tended to correlate with each other. The relative concentrations of the sum of the most persistent congeners (PCB-99, −128, −138, −153, −170, −180, −187 and −194) correlated in all tissues, and an increase of the relative concentrations of these congeners, most distinct in blubber, with higher carcass weight, was shown. Also, total PCB in blubber correlated with carcass weight. When comparing the relative concentration patterns of individual congeners (per cent of total) in the four tissues, six congeners differed significantly between tissues, and the relative brain concentrations showed most deviation from the other tissues. The concentration of the coplanar PCBs was 1 : 1000–1 : 1000 of the total PCB concentration. The results demonstrate a lower accumulation together with a different concentration pattern in the brain as compared to other tissues.