Contaminant-related disruption of vitamin A dynamics in free-ranging harbor seal (Phoca vitulina) pups from British Columbia, Canada, and Washington State, USA

Marine mammals can bioaccumulate high concentrations of lipophilic environm ental contaminants, such as polychlorinated biphenyls (PCBs), polychlorinat ed dibenzo-para-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs), through the diet. Both laboratory and wildlife studies have shown that the se persistent chemicals can disrupt the regulation of vitamin A (retinol), a dietary hormone required for immune function, reproduction, growth, and d evelopment. To determine whether environmental contaminants affect the circ ulatory vitamin A dynamics of free-ranging harbor seals (Phoca vitulina), w e live-captured 61 pups from British Columbia, Canada, and Washington State , USA, and obtained blood and blubber biopsy samples. Harbor seal pups from Washington State were six times more contaminated with total PCBs than pup s from British Columbia and had significantly lower circulatory retinol lev els. However, when data were corrected for differences in nursing status an d analyzed as ungrouped sets of data, circulatory retinol levels were posit ively correlated with contaminant levels in the blubber of nonnursing pups. This increase in retinol may have resulted from a mobilization of liver vi tamin A stores into circulation following exposure to milk-derived contamin ants; this has been observed in laboratory animals exposed experimentally. The contaminant-related disruption of vitamin A dynamics observed in our st udy occurs at a time when vitamin A is required for growth and development.