Complex contaminant exposure in cetaceans: A comparative E‐Screen analysis of bottlenose dolphin blubber and mixtures of four persistent organic pollutants

Abstract

Cetaceans are federally protected species that are prone to accumulate complex mixtures of persistent organic pollutants (POPs), which individually may exert estrogenic or antiestrogenic effects. In the present study it was assessed whether contaminant mixtures harbored by cetaceans are estrogenic or antiestrogenic using a comparative approach. Interactions of antiestrogenic and estrogenic compounds were first investigated with the E-Screen assay using a mixture of four POPs (dichlorodiphenyldichloroethylene [4,4'-DDE], trans-nonachlor, and polychlorinated biphenyls [PCBs] 138 180) prevalent in cetacean blubber. Estrogenic/antiestrogenic activity was determined for the individual compounds and their binary, tertiary, and quaternary combinations. Significantly different responses were observed for the various POP mixtures, including enhanced estrogenic and antiestrogenic effects and antagonistic interactions. These results were then compared to the concentrations and estrogenic/antiestrogenic activity of contaminant mixtures isolated directly from the blubber of 15 bottlenose dolphins (Tursiops truncatus) collected from five U.S. Atlantic and Gulf of Mexico locations. The lowest observed effect concentrations (LOECs) determined for 4,4'-DDE (20 µmol/L), PCB 138 (20 µmol/L), PCB 180 (21 µmol/L), and trans-nonachlor (3 µmol/L) in the E-Screen were greater than estimated dolphin blood concentrations. Although estimated blood concentrations were below the LOECs, significant estrogenic activity was detected in diluted dolphin blubber from Cape May, NJ and Bermuda. Positive correlations between blubber estrogenicity and select POP concentrations (ΣDDTs, ΣPBDEs, ΣHCB, Σestrogenic PCBs, Σestrogenic POPs) were also observed. Collectively, these results suggest that select bottlenose dolphin populations may be exposed to contaminants that act in concert to exert estrogenic effects at biologically relevant concentrations. These observations do not necessarily provide direct evidence of endocrine disruption; however, they may indicate an environmental source of xenoestrogenic exposure warranting future research.

Comparison of in vitro cytotoxicity, estrogenicity and anti‐estrogenicity of triclosan, perfluorooctane sulfonate and perfluorooctanoic acid

“…() and Yordy et al . (); briefly, MCF‐7 BOS cells (passages 71–93) reached ~80% confluence prior to experimentation. Cells were washed with experimental media (DMEM without phenol red, 5% CD‐FBS and 1% PSA), trypsinized and seeded into the inner 40 wells of 96‐well plates to a volume of 200 µl (10 4 cells per well) and allowed to attach for 24 h. The outer peripheral wells were not used in the experiment.…”

“…Antiestrogenicity is assessed with this assay by inducing the maximal proliferation of MCF-7 BOS cells with E 2 and measuring the reduction in proliferation that occurs as a result of co-exposure with the test compound. This method was previously described by Soto et al (1995) and Yordy et al (2010); briefly, MCF-7 BOS cells (passages 71-93) reached~80% confluence prior to experimentation. Cells were washed with experimental media (DMEM without phenol red, 5% CD-FBS and 1% PSA), trypsinized and seeded into the inner 40 wells of 96-well plates to a volume of 200 ml (10 4 cells per well) and allowed to attach for 24 h. The outer peripheral wells were not used in the experiment.…”

A broad cocktail of environmental pollutants found in eggs of three seabird species from remote colonies in Norway

“…In recent years, cocktail mixtures of chemicals and environmental pollutants have received growing attention. Evidence has shown that exposure to single compounds that do not induce an adverse effect can have negative synergistic and additive effects in organisms when exposure occurs as part of a mixture [2][3][4][5][6].…”

Toxicology of Marine Mammals: New Developments and Opportunities

“…Apart from these studies, an additional step forward in in vitro studies has been the development of biosensor systems, which use engineered cells (i.e. bioassays) to be applied to marine mammals and concepts like 'effect-driven approach' (EDA), 'adverse outcome pathway' (AOP) and 'toxicity pathway' (Yordy et al 2010;Burgess et al 2013;Jin et al 2013Jin et al , 2015Simon et al 2013). These developments allow to screen marine mammal tissue samples with respect to specific endpoints and, depending on the study design, can be used as an initial step to explore the influence of contaminant mixtures.…”