The majority of exposure assessments for free-ranging cetaceans focus on contaminant concentrations measured in blubber, and there are few data for other tissues or the factors governing contaminant distribution between tissues. The goal of this study was to provide a detailed description of the distribution of persistent organic pollutants (POPs) within the bottlenose dolphin (Tursiops truncatus) body and assess the role of lipid dynamics in mediating contaminant distribution. Thirteen tissues (brain, blubber, heart, liver, lung, kidney, mammary gland, melon, skeletal muscle, spleen, thyroid, thymus, and testis/uterus) were sampled during necropsy from bottlenose dolphins (N=4) and analyzed for lipid content and 85 POPs, including polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers. Significant correlations between tissue POP concentrations and lipid suggest that distribution of POPs is generally related to tissue lipid content. However, blubber:tissue partition coefficients ranged widely from 0.753 to 6.25, suggesting that contaminant distribution is not entirely dependent on lipid. Tissue-specific and whole body contaminant burdens confirmed that, blubber, the primary site of metabolic lipid storage, is also the primary site for POP accumulation, contributing >90% to the whole body burdens. Observations also suggest that as lipid mobilizes from blubber, contaminants may redistribute, leading to elevated tissue concentrations. These results suggest that individuals with reduced blubber lipid may be at an increased risk for exposure-related health effects. However, data from this study provide evidence that that the melon, a metabolically inert lipid-rich structure, may serve as an alternate depot for POPs, thus preventing the bulk of blubber contaminants from being directly available to other tissues. This unique physiological adaptation should be taken into consideration when assessing contaminant-related health effects.
Citation: Environmental Toxicology and Chemistry
Pub Type: Journals
persistent organic pollutants, tissue distribution, body burden, bottlenose dolphin