ABSTRACT
This study uses an individual-based contaminant bioaccumulation model for marine mammals to explore factors controlling the transfer of PCBs from mother to calf via nursing in beluga from the St. Lawrence Estuary. Beluga blubber samples (n = 46), along with four matched milk samples from stranded animals over the 1986-1994 period were used for comparison with modelled results. Based on 68 POPs, including 48 PCBs and 20 other organochlorine compounds, milk:blubber ratios were 0.65 between log K OW 3-6.5, then decreased to 0.1 at log K OW 8. Model simulations based on this relationship indicated females were transferring PCBs that were relatively very hydrophobic and highly chlorinated less readily than their lower chlorinated counterparts, resulting in an enriched concentration of very hydrophobic congeners in nursing females relative to adult males. There was very good agreement between observed and modelled male:female PCB concentration ratios. Four females within our dataset (15 %) had male-like ΣPCB concentrations as well as male-like congener profiles, suggesting that these individuals may have had a reduced or limited nursing history.
Subject(s)
Beluga Whale/metabolism , Hydrocarbons, Chlorinated/metabolism , Milk/metabolism , Polychlorinated Biphenyls/metabolism , Water Pollutants, Chemical/metabolism , Animals , Canada , Female , LactationABSTRACT
An individually based (IB) model to predict PCB concentrations in the bottlenose dolphin population of Charleston, SC, USA, was developed with the aim to gain a better understanding of the bioaccumulation behavior and health risk of dietary PCBs across the population and their prey. PCB concentrations predicted in male and female bottlenose dolphin were in good agreement with observed tissue concentrations corroborating the reliability of the model performance and its utility in gaining a more complete view of risk. The modeled cumulative distribution of ΣPCB concentrations for the population with a breakdown into juvenile, adult male, and female subclasses ranged from 3600 to 144,400 ng/g lipid with 66% to >80% of the population exceeding the established threshold for adverse health effects of 17,000 ng/g lipid. The model estimated that a dietary PCB concentration not exceeding 5.1 ng/g wet wt would be required to reach a condition where 95% of the population would have tissue levels below the health effect threshold. The IB model for PCBs in bottlenose dolphins provides a novel approach to estimating the maximum acceptable dietary concentration for PCBs, a central and important factor to protect these apex predators. The model also enables effective prediction of concentrations in dolphins from fish contaminant surveys which are logistically easier and less costly to collect.
