Decreased lymphocyte responses in free-ranging bottlenose dolphins (Tursiops truncatus) are associated with increased concentrations of PCBs and DDT in peripheral blood

Spatiotemporal Trends Spanning Three Decades Show Toxic Levels of Chemical Contaminants in Marine Mammals

Despite their ban and restriction under the 2001 Stockholm Convention, persistent organic pollutants (POPs) are still widespread and pervasive in the environment. Releases of these toxic and bioaccumulative chemicals are ongoing, and their contribution to population declines of marine mammals is of global concern. To safeguard their survival, it is of paramount importance to understand the effectiveness of mitigation measures. Using one of the world's largest marine mammals strandings data sets, we combine published and unpublished data to examine pollutant concentrations in 11 species that stranded along the coast of Great Britain to quantify spatiotemporal trends over three decades and identify species and regions where pollutants pose the greatest threat. We find that although levels of pollutants have decreased overall, there is significant spatial and taxonomic heterogeneity such that pollutants remain a threat to biodiversity in several species and regions. Of individuals sampled within the most recent five years (2014-2018), 48% of individuals exhibited a concentration known to exceed toxic thresholds. Notably, pollutant concentrations are highest in long-lived, apex odontocetes (e.g., killer whales (Orcinus orca), bottlenose dolphins (Tursiops truncatus), and white-beaked dolphins (Lagenorhynchus albirostris)) and were significantly higher in animals that stranded on more industrialized coastlines. At the present concentrations, POPs are likely to be significantly impacting marine mammal health. We conclude that more effective international elimination and mitigation strategies are urgently needed to address this critical issue for the global ocean health.

Modulation in Persistent Organic Pollutant Concentration and Profile by Prey Availability and Reproductive Status in Southern Resident Killer Whale Scat Samples

Persistent organic pollutants (POPs), specifically PCBs, PBDEs, and DDTs, in the marine environment are well documented, however accumulation and mobilization patterns at the top of the food-web are poorly understood. This study broadens the understanding of POPs in the endangered Southern Resident killer whale population by addressing modulation by prey availability and reproductive status, along with endocrine disrupting effects. A total of 140 killer whale scat samples collected from 54 unique whales across a 4 year sampling period (2010-2013) were analyzed for concentrations of POPs. Toxicant measures were linked to pod, age, and birth order in genotyped individuals, prey abundance using open-source test fishery data, and pregnancy status based on hormone indices from the same sample. Toxicant concentrations were highest and had the greatest potential for toxicity when prey abundance was the lowest. In addition, these toxicants were likely from endogenous lipid stores. Bioaccumulation of POPs increased with age, with the exception of presumed nulliparous females. The exceptional pattern may be explained by females experiencing unobserved neonatal loss. Transfer of POPs through mobilization of endogenous lipid stores during lactation was highest for first-borns with diminished transfer to subsequent calves. Contrary to expectation, POP concentrations did not demonstrate an associated disruption of thyroid hormone, although this association may have been masked by impacts of prey abundance on thyroid hormone concentrations. The noninvasive method for measuring POP concentrations in killer whales through scat employed in this study may improve toxicant monitoring in the marine environment and promote conservation efforts.

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.

Lobomycosis-like disease in wild bottlenose dolphins Tursiops truncatus of Laguna, southern Brazil: monitoring of a progressive case

Lobomycosis is a chronic dermal infection affecting humans and small cetaceans. In 1993, a study identified the presence of the etiologic agent of lobomycosis in a resident population of Tursiops truncatus (bottlenose dolphin) in Laguna, Brazil. Until now, no additional information relating to the persistence or prevalence of this pathogen in this population has been available. Numbering less than 60 animals, the residency of these dolphins in an impacted lagoon system has raised concerns about the health and viability of this small population. Using photo-identification data collected between September 2007 and September 2009, this study evaluated the occurrence of lobomycosis-like disease (LLD) throughout this population. Of 47 adult dolphins and 10 calves identified, 7 (12%) presented some form of epidermal lesion and 5 (9%) had evidence of LLD. The lesions were stable in all but 2 cases, in which a progressive development was recorded in a presumed adult female and her calf (referred to here as the LLD pair). During the first few months of observation, the lesion grew slowly and at a constant rate on the adult. However, in the fourteenth month, the growth rate increased rapidly and the first lesions appeared on the calf. Compared to the rest of the population, the LLD pair also presented a different spatial ranging pattern, suggesting a possible social or geographic factor. Current and previous records of LLD or lobomycosis indicate that the disease is endemic in this population. These findings highlight the importance of monitoring both the health of these cetaceans and the quality of their habitat.

Immunotoxicity of polychlorinated biphenyls (PCB) in free-ranging gray seal pups with special emphasis on dioxin-like congeners

Increased pinniped and dolphin mortality rates have led to speculations that persistent pollutants, in particular polychlorinated biphenyls (PCB), are immunomodulatory, making individuals susceptible to infections. The aim of the present study was to investigate effects that PCB may exert on peripheral blood mitogen-induced lymphocyte proliferation responses in free-ranging gray seal (Halichoerus grypus) pups from the polluted Baltic Sea and from the cleaner open waters of the Atlantic Ocean. T-cell mitogen (phytohemagglutinin [PHA] and concanavalin A [Con A]) and T-/B-cell mitogen (pokeweed mitogen [PWM]) responses were significantly lower in the more PCB-contaminated Baltic gray seal pups than in reference pups from the Atlantic. Best regression analysis revealed that dioxin-like mono-ortho PCB accounted for the immunosuppressive responses. In the Baltic seals, the immunosuppressive effects were limited to the more persistent dioxin-like mono-ortho PCB. In the Atlantic seals a positive correlation existed between PCB concentrations and mitogen-induced lymphocyte proliferation responses. Although direct cause-effect relationships are difficult to demonstrate in free-ranging animals, our results are consistent with the weight of evidence available that PCB, and dioxin-like PCB in particular, modulate lymphocyte function in free-ranging marine mammals. Thus, exposure to PCB most likely result in increased susceptibility to infections or reduced host resistance in pinnipeds.

Immune dysfunction in Atlantic bottlenose dolphins (Tursiops truncatus) with lobomycosis

Lobomycosis (Lacaziosis) occurs only in humans and dolphins under natural conditions. We evaluated the immune status of eight dolphins with lobomycosis and 40 healthy dolphins from the Indian River Lagoon (IRL), Florida. Lobomycosis cases had multiple abnormalities in their immunologic parameters when compared to healthy dolphins. The absolute number of circulating lymphocytes and serum albumin concentration were reduced (P<0.05) while the segmented neutrophils, alpha 1, total beta, total gamma and total globulins were increased (P<0.05). Although innate immunity was relatively intact and phagocytosis and natural killer cell activity were not affected, the plasma lysozyme concentrations were elevated in dolphins with lobomycosis (P<0.05). Adaptive immunity was depressed with statistically significant decreases found in the absolute numbers of CD4(+) helper T cells and CD19(+) and CD21(+) B cells. The ratios of CD2(+) T cells to CD4(+) cells and CD2(+) to CD21(+) cells were increased (P=0.05 and P<0.05, respectively) and the numbers of lymphocytes expressing MHC class II molecules was decreased in dolphins with lobomycosis (P<0.05). Lymphocyte proliferation was reduced in response to stimulation with lipopolysaccharide and concanavalin A (P<0.05). Antibody titers to Erysipelas rhusiopathiae, a common marine micro-organism, were decreased (P<0.05). In summary, dolphins with lobomycosis exhibit significant impairment in adaptive immunity.

Effects of organochlorines, individually and in mixtures, on B-cell proliferation in marine mammals and mice

Organochlorines (OC) are lipophilic and stable, and therefore accumulate in tissues of top predators, such as marine mammals. While the immunomodulatory effects of individual OC have been studied in lab animals, their effects in other species (such as marine mammals) and the possible interactions between chemicals in mixtures are not well understood. This study investigated the immunomodulatory effects of four polychlorinated biphenyls (PCB, IUPAC numbers 138, 153, 169, and 180), as well as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), individually and in mixtures, in marine mammals and mice. Mitogen-induced B lymphocyte proliferation was mostly modulated by non-coplanar PCBs, for which general mechanisms underlying toxicity are poorly understood. Simple additive effects of OC in mixtures were found only in mice, while both synergistic and antagonistic interactions between OC were found in marine mammals. The toxic equivalency (TEQ) approach, which is currently used to assess the dioxin-like toxicity of OC mixtures, failed to predict immunotoxicity in mice and marine mammals, likely due to the complexity of interactions between OC and effects via dioxin-independent pathways. The commonly used mouse model failed to predict the immunotoxicity due to OC in the marine mammals tested. In addition, clustering data suggested that phylogeny might not help predict the toxicity of OC. Lymphoproliferative response was modulated in most species tested suggesting the possibility of increased susceptibility to infectious diseases in these animals. These findings may be helpful in more accurately characterizing the immunotoxic potential of OC in different target species and help in more relevant risk assessment.

Blood concentrations of some persistent organohalogens in free-ranging spotted seals (Phoca largha) from Bristol Bay, Alaska

In recent years, the relatively high levels of organochlorine contaminants and increasing levels of brominated flame retardants found in tissues of marine mammals have raised concerns that exposure to these marine pollutants may compromise individual health. In this pilot study, levels of 11 polychlorinated biphenyls, 3 polybrominated diphenyl ethers, and the DDT metabolite p,p'-diphenyldichloroethylene were analyzed in whole blood of 7 free-ranging spotted seals (Phoca largha) from Bristol Bay, Alaska, sampled during 2000 and 2001. Blood concentrations of analytes were generally low (<1 ppb wet weight). Open-ocean foraging and feeding on a lower trophic level may contribute to the relatively lower levels of organohalogens found in this species as compared to the closely related harbor seal, Phoca vitulina, occurring in Bristol Bay.

Non-coplanar PCBs induce calcium mobilization in bottlenose dolphin and beluga whale, but not in mouse leukocytes

Polychlorinated biphenyls (PCBs) have been demonstrated to modulate marine mammal immune functions; however, the underlying mechanisms involved are poorly understood. Cytosolic calcium (Ca2+) is an important second messenger involved in numerous leukocyte functions. The direct effects of in vitro exposure to PCBs on Ca2+ mobilization were evaluated in leukocytes isolated from bottlenose dolphins, beluga whales, and B6C3F1 mice. Concentration- and time-response experiments with three non-coplanar PCBs (138, 153, 180), one coplanar PCB (169), and TCDD were tested. Exposure to the three non-coplanar PCBs significantly increased cytosolic Ca2+ in dolphin neutrophils, while PCB 180 significantly increased cytosolic Ca2+ in beluga neutrophils. Two non-coplanar PCBs (138 and 153) significantly increased Ca2+ in beluga monocytes, yet the response was delayed compared to that in neutrophils. Neither PCBs nor TCDD increased cytosolic Ca2+ in mouse neutrophils or monocytes. In experiments with Ca2+-free medium, only PCB 153 increased cytosolic Ca2+ in dolphin neutrophils, though the increase was less than that observed with Ca2+-supplemented medium, suggesting that extracellular Ca2+ was the predominant source for the rise in cytosolic Ca2+. Furthermore, in cells incubated with Ca2+-free medium, a significant increase in cytosolic Ca2+ was induced by thapsigargin following PCB exposure, indicating that intracellular Ca2+ was available, yet not mobilized by the PCBs, and further suggesting that PCBs mobilize extracellular Ca2+. These results demonstrate for the first time the direct effects of non-coplanar PCBs on Ca2+ mobilization in marine mammals, which may be involved in the modulation of phagocytosis previously observed in these species.

Contaminant loads and hematological correlates in the harbor seal (Phoca vitulina) of San Francisco Bay, California

An expanding body of research indicates that exposure to contaminants may impact marine mammal health, thus possibly contributing to population declines. The harbor seal population of the San Francisco Bay (SFB), California, has suffered habitat loss and degradation, including decades of environmental contamination. To explore the possibility of contaminant-induced health alterations in this population, blood levels of polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (DDE), and polybrominated diphenyl ethers (PBDEs) were quantified in free-ranging seals; relationships between contaminant exposure and several key hematological parameters were examined; and PCB levels in the present study were compared with levels determined in SFB seals a decade earlier. PCB residues in harbor seal blood decreased during the past decade, but remained at levels great enough that adverse reproductive and immunological effects might be expected. Main results included a positive association between leukocyte counts and PBDEs, PCBs, and DDE in seals, and an inverse relationship between red blood cell count and PBDEs. Although not necessarily pathologic, these responses may serve as sentinel indications of contaminant-induced alterations in harbor seals of SFB, which, in individuals with relatively high contaminant burdens, might include increased rates of infection and anemia.

PCBs and TCDD, alone and in mixtures, modulate marine mammal but not B6C3F1 mouse leukocyte phagocytosis

Increasing evidence has supported the general hypothesis that organochlorines (OC) can produce immunotoxic effects in marine mammals. One important innate defense mechanism is phagocytosis, the ability of cells to ingest extracellular macromolecules. The present study is aimed at characterizing the immunomodulatory potential of mixtures of OCs on phagocytosis compared to that of individual compounds in different species of marine mammals and mice, the traditional model to study mammalian immunotoxicity. The ability of peripheral blood neutrophils and monocytes to engulf fluorescent microspheres was evaluated using flow cytometry. The immunomodulatory effects of three non-coplanar polychlorinated biphenyl (PCB) congeners, 138, 153, 180, one coplanar PCB, 169, as well as 2,3,7,8-TCDD, and all possible mixtures (26) were tested upon in vitro exposure. All species were not equally sensitive to the adverse effects of OCs on either neutrophils or monocytes phagocytosis. With the exception of harbor seals, all mixtures that significantly modulated neutrophil or monocyte phagocytosis contained at least one non-coplanar PCB. Regression analysis revealed that the non-coplanar congeners, more than the coplanar congeners, explained the variability in phagocytosis. Dendrograms revealed that phylogeny could not predict immunotoxicity. The currently used toxic equivalency (TEQ) approach and the traditional mouse model both failed to predict experimentally induced immunomodulatory effects in marine mammals tested, leading us to question the reliability of both TEQs and mouse model in risk assessment of OC mixtures. Testing the relative sensitivity to immunomodulatory effects of contaminants and contaminant mixtures between different species of marine mammals may have important implications for risk assessment as well as conservation and management strategies.

Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part II: Possible effect of OCs on mitogen- and antigen-induced lymphocyte proliferation

Previous studies have reported alarmingly high levels of organochlorines (OCs), particularly polychlorinated biphenyls (PCBs), in free-ranging polar bears (Ursus maritimus). In this study plasma concentration of PCBs ranged from 14.8 to 200 ng/g wet weight. The aim of the study was to investigate associations between OCs and lymphocyte proliferation after in vitro stimulation with different mitogens and antigens. In 1998 and 1999, 26 and 30 free-ranging polar bears from Svalbard and Churchill, Canada, respectively, were recaptured 32-40 d following immunization with inactivated tetanus toxoid and hemocyanin from keyhole limpets (KLH) to sensitize lymphocytes. At recapture, blood was sampled for determination of plasma levels of PCBs and organochlorine pesticides (OCPs) and lymphocyte proliferation after in vitro stimulation with specific mitogens--phytohemagglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A), lipopolysaccharide (LPS), and purified protein derivative of Mycobacterium avium subsp. paratuberculosis (PPD)--and antigens: tetanus toxoid and KLH. The combinations of sum(PCBs) (sum of 12 individual PCB congeners), sum(OCPs) (sum of 6 OCPs), and their interactions contributed up to 15% of the variations in the lymphocyte responses. By using multiple regression analyses, followed by classical mathematic function analyses, thresholds for immunomodulation were estimated. Depending on the lymphocyte proliferation response studied, the estimated thresholds for significant immunomodulation were within the concentration ranges 32-89 ng/g wet weight (ww) and 7.8-14 ng/g ww for sum(PCBs) and sum(OCPs), respectively. Thus, this study demonstrated that OC exposure significantly influences specific lymphocyte proliferation responses and part of the cell-mediated immunity, which also is associated with impaired ability to produce antibodies (Lie et al., 2004).

Organohalogen contaminants in delphinoid cetaceans

This chapter reviews the global distribution, biotransformation, accumulation patterns, and mechanisms of action and the potential impacts of persistent organohalogen contaminants (PHCs) on physiological systems of cetaceans with emphasis on delphinoids. Methods used to study PHCs in stranded and free-living cetaceans are discussed, and concentrations of PHCs of stranded, hunted, by-catch, and free-ranging delphinoids are summarized. Overall, the highest concentrations of PHC contamination were found in delphinoids from industrialized areas of the Northern Hemisphere compared to the Southern Hemisphere. Nonetheless, PHCs are also found in marine mammal tissues from the Southern Hemisphere and in remote regions such as the Arctic, reflecting the global distribution and contamination of PHCs in the marine ecosystem.

Specific non-coplanar PCB-mediated modulation of bottlenose dolphin and beluga whale phagocytosis upon in vitro exposure

Contaminant-induced immunosuppression by organochlorines (OC), particularly polychlorinated biphenyls (PCBs), has been suspected as a cofactor in the deaths of thousands of marine mammals. One important innate defense mechanism is phagocytosis, the ability of cells to ingest extracellular macromolecules. The present study was aimed at characterizing the immunomodulatory potential of representative OCs on phagocytosis in bottlenose dolphins and beluga whales. The ability of peripheral blood leukocytes to engulf fluorescent microspheres was evaluated using flow cytometry. The immunomodulatory effects of three non-coplanar PCB congeners, 138, 153, and 180, one coplanar PCB, 169, and 2,3,7,8-TCDD and all possible mixtures (26) were tested upon in vitro exposure. In both species, all mixtures containing at least two non-coplanar PCBs significantly reduced both neutrophil and monocyte phagocytosis, with effects more marked in dolphins than in belugas. Coplanar OCs, on their own or when added to non-coplanar congeners, did not further modulate phagocytosis, suggesting an Ah receptor-independent mechanism. Concentration-response experiments with individual congeners further demonstrated a non-coplanar PCB-induced suppression of phagocytosis, while coplanar congeners produced no consistent effects. Our results suggest simple additive interactions of chemicals in a mixture. However, calculation of toxic equivalency (TEQs) failed to predict the experimentally induced immunomodulatory effects of OCs on dolphin and beluga phagocytosis, confirming the Ah receptor-independent nature of the effects on phagocytosis. Overall, our results suggest that non-AhR mechanisms may explain one facet of immunotoxicity (phagocytosis), something that is not captured using the TEQ approach. This is the first report demonstrating the immunomodulatory effects of OCs on dolphin and beluga phagocytosis, and the first overall demonstration of immunomodulatory effects on phagocytosis mediated specifically by non-coplanar PCBs.

Effects of perinatal exposure to low doses of PCB 153 and PCB 126 on lymphocyte proliferation and hematology in goat kids

Pregnant does (10 goats/group) were dosed orally with either PCB 153 or PCB 126 dissolved in corn oil or only corn oil (control group) from day 60 of gestation until delivery. Effects on in vitro mitogen-induced lymphocyte proliferation and blood cell counts in their goat kids exposed to low levels of PCB 153 and PCB 126 during gestation and lactation were assessed. The concentrations of PCB 153 and PCB 126 in adipose tissue in the goat kids 9 mo postpartum were 5800 ng/g (fat weight) and 0.49 ng/g (fat weight), respectively. Kids exposed to PCB 153 had a significantly higher number of white blood cells, neutrophils, and lymphocytes at 2 wk of age compared to controls. In the kids exposed to PCB 126 there was a significantly lower concentration of monocytes at 2, 4, and 8 wk of age. The mean lymphocyte response to phytohemagglutinin (PHA) and to concanavalin A (Con A) was significant lower in the PCB 153 compared to the control group at wk 2, 4, and 8 postnatally. The results of the present study support previous reports on immunotoxic effects of PCB exposure in animals. However, this is the first report to demonstrate immunotoxicity in animals by using low doses of PCB 153. The difference in results between PCB 126 and PCB 153 treatment groups may strengthen the hypothesis that PCBs mediate immunotoxic effects through both AhR-dependent and -independent mechanisms.

Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part I: Effect of OCs on the humoral immunity

This study was undertaken to assess if high levels of organochlorines (OCs) are associated with decreased ability to produce antibodies in free-ranging polar bears (Ursus maritimus) and thus affect the humoral immunity. In 1998 and 1999, 26 and 30 polar bears from Svalbard, Norway, and Churchill, Canada, respectively, were recaptured 32-40 d following immunization with inactivated influenza virus, reovirus, and herpes virus and tetanus toxoid. Blood was sampled at immunization and at recapture for determination of plasma levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), serum immunoglobulin G (IgG) concentrations, and specific antibodies against influenza virus, reovirus, and herpes virus, tetanus toxoid, and Mannheimia haemolytica. The OCs alone contributed with up to 7% to the variations in the immunological parameters. The combination of sigma PCBs (sum of 12 individual PCB congeners), sigma OCPs (sum of 6 OCPs), and biological factors accounted for 40-60% of the variation in the immunological parameters. Negative associations were found between sigma PCBs and serum immunoglobulin G (IgG) levels and between sigma PCBs and increased antibody titers against influenza virus and reovirus following immunization. In contrast, a positive association was registered between sigma PCBs and increased antibodies against tetanus toxoid. sigma OCPs also contributed significantly to the variations in the immunological responses. OCs did not have the same impact on the antibody production against M. haemolytica. The present study demonstrated that high OC levels may impair the polar bears ability to produce antibodies and thus may produce impaired resistance to infections.

Avian immunotoxicology

Methods for studying the avian immune system have matured during the past two decades, with laboratory studies predominating in earlier years and field studies being conducted only in the past decade. One application has been to determine the potential for environmental contaminants to produce immune suppression, while another research direction is looking at the evolutionary significance of a robust immune system, and the relationship between immune competence and fitness parameters. Laboratory studies of immunosuppression following exposure of birds to environmental contaminants have adapted conventional mammalian methods to the avian immune system, and both lines of research have developed field-deployable measures of immune function. This review describes the avian immune system with emphasis on how it differs from the better known mammalian system, reviews the literature on contaminant-induced immunosuppression, and discusses the work on evolutionary biology of avian immunocompetence. Evidence indicates that the field of avian immunology is technically robust, even for nontraditional species such as passerines, seabirds, raptors, and other free-ranging species. It is now possible to screen chemicals for immunotoxicological properties following the same tiered approach that has been established for mammals. Despite the increased capacity and interest in avian field studies, there has not yet been a reported study of measured immune suppression associated with an avian epizootic. It is more likely that the immune suppression in adult birds resulting from low-level chronic stress (e.g., crowding onto poor quality habitat, food reductions, or climate stress) and (or) environmental contaminants causes slow but consistent morbidity and mortality associated with multiple pathogens, rather than an acute epizootic with a single pathogen. Increased fitness costs associated with such stress may significantly alter genetic diversity and species survival over time.

Toxicological characteristics of endocrine-disrupting chemicals: developmental toxicity, carcinogenicity, and mutagenicity

It is generally accepted that endocrine-disrupting chemicals (EDCs) play a role in a variety of adverse health effects in an intact organism or its progeny as a consequence of changes in the endocrine system. Primary toxic effects of EDCs were reported to be related to infertility, reduction in sperm count, and teratogenicity, but other important toxic effects of EDCs such as carcinogenicity and mutagenicity have also been demonstrated. The aim of the present study was to systematically analyze the toxicological characteristics of EDCs in pesticides, industrial chemicals, and metals. A comprehensive literature survey on the 48 EDCs classified by the Centers for Disease Control and Prevention (CDC) was conducted using a number of databases which included Medline, Toxline, and Toxnet. The survey results revealed that toxicological characteristics of EDCs were shown to produce developmental toxicity (81%), carcinogenicity (79%, when positive in at least one animal species; 48%, when classified based on IARC evaluation), mutagenicity (79%), immunotoxicity (52%), and neurotoxicity (50%). Regarding the hormone-modulating effects of the 48 EDCs, estrogenic effects were the most predominant in pesticides, while effects on thyroid hormone were found for heavy metals. EDCs showing estrogen-modulating effects were closely related to carcinogenicity or mutagenicity with a high degree of sensitivity. Systematic information on the toxicological characteristics of the EDCs will be useful for future research directions on EDCs, the development of new screening methods, legal regulation, and for investigations of their mechanism of action.

Associations of dichlorodiphenyltrichloroethane (DDT) 4.4 and dichlorodiphenyldichloroethylene (DDE) 4.4 blood levels with plasma IL-4

DDT (dichlorodiphenyltrichloroethane) reportedly induces cancer in animals, mimics estrogen activity, induces antiandrogen effects, and impairs Natural Killer (NK) cells and T lymphocyte responses. In this study, the authors attempted to determine associations of DDT, dichlorodiphenyldichloroethylene (DDE), and dichlorodiphenyldichloroethane (DDD) blood levels with several immune parameters in patients occupationally exposed to insecticides. The study subjects were 49 patients who worked as farmers or farmhands in the former German Democratic Republic and who had been occupationally exposed to insecticides for at least 6 mo; 80% of them had been exposed for more than 20 yr. Blood levels of DDT, DDE, DDD, 2,3,4,5,6-pentachlorophenol (PCP), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and gamma-hexachlorocyclohexanes (HCHs) were determined, and blood lymphocyte subpopulations, in vitro responses to mitogens or pooled allogeneic stimulator cells, plasma neopterin, and cytokine and soluble cytokine receptor levels were studied. The majority of patients were contaminated with more than 1 chemical--most commonly DDE, PCBs, and HCB. Linear-regression analysis showed that interleukin-4 (IL-4) plasma levels were associated with plasma levels of DDT 4.4 (p = .0001) and DDE 4.4 (p = .001). The data in this study suggest that PCBs, PCP, HCB, HCHs, DDE, and DDD suppress TH1 cytokines, such as IL-2 and interferon-gamma (IFN-gamma), and induce TH2 cytokines, such as IL-4. The authors hypothesized that clinical symptoms, such as the frequent infections reported by many patients, could be a consequence of these immunological abnormalities.

Cord blood lymphocyte functions in newborns from a remote maritime population exposed to organochlorines and methylmercury

The consumption of fish and sea mammals can be an important source of exposure to organochlorine compounds (OCs) and heavy metals in populations relying on seafood for subsistence. Exposure to these substances, especially during the prenatal period, has been shown to induce immunotoxic effects in mammals. Immunological status was assessed in 48 newborns from a remote maritime population living on the Lower and Mid North Shore of the St. Lawrence River (subsistence fishing group) and 60 newborns from the coastal urban center of Sept-Iles (reference group). Women were recruited upon arrival at Sept-Iles regional hospital to give birth. Cord blood samples were collected for organochlorine and heavy metal analyses and to isolate lymphocytes for immunological assays (proportions and functional responses of the main cellular subsets T, B, and NK (natural killer) cells. Concentrations of polychlorinated biphenyls (PCBs) and mercury were respectively three- and twofold higher, significantly greater, in the subsistence fishing group than in the reference group. Compared to the reference group, the subsistence fishing group showed significant decreases in the proportion of the naive helper T-cell subset CD4+CD45RA, T-cell proliferation following an in vitro mitogenic stimulation, and plasma immunoglobulin M (IgM) level, while plasma IgC level was increased. NK cytolytic activities were similar in both groups. The proportion of CD4+CD45RA cells was inversely correlated to mercury and PCBs, while T-cell clonal expansion was negatively associated with PCBs and p,p'-DDE. Mercury was inversely correlated to plasma IgM. Data show that subtle functional alterations of the developing human immune system may result from in utero exposure to OCs and mercury. Epidemiological studies are needed to determine the relevance of these alterations in predicting detrimental health effects in the developing child.