Risk-based analysis of polychlorinated biphenyl toxicity in harbor seals.

Persistent organic pollutants (POPs) have been associated with adverse health effects in marine mammals. However, the complex mixtures to which free-ranging populations are exposed constrain the elucidation of cause-and-effect relationships between specific POPs and the observed health risks. In this study, we 1) assembled data from studies showing polychlorinated biphenyl (PCB)-associated effects on the health of free-ranging harbor seals in the northeastern Pacific Ocean, 2) carried out additional POP analyses on seal samples to broaden the available data on contaminant residues, and 3) derived estimates of individual POPs and their toxic risks. Taken together, these components were used to generate a new toxicity reference value (TRV) for the protection of marine mammal health. In this case study of seals in British Columbia, Canada, and Washington State, USA, PCBs were the single most abundant POP and were correlated with several adverse health effects. PCB exposures consistently exceeded regulatory toxicity thresholds for fish-eating wildlife. Nursing seal pups were at particular risk, reflecting their greatly increased dietary intake of PCBs and their sensitivity to developmental toxicity. Based on the collective evidence obtained, we propose TRVs (consisting of 5% tissue residue concentration and dose) of 1.3 mg/kg lipid weight tissue residue in blubber and 0.05 mg/kg lipid weight tolerable daily intake in prey. Insofar as the TRVs are lower than previously established TRVs and regulatory guidelines, our study highlights the current underestimation of risks associated with PCBs in high-trophic-level wildlife.

Effects of diesel on survival, growth, and gene expression in rainbow trout (Oncorhynchus mykiss) fry.

Diesel spills are all too frequent disturbances of freshwater ecosystems, largely as a result of the quantities transported and consumed. Assessing the risk that such events may pose to aquatic life remains a difficult process, because of the complexity of this hydrocarbon mixture and our limited knowledge of its toxicity. A diesel spike experiment with rainbow trout (Oncorhynchus mykiss) fry was carried out to fill this knowledge gap. Survival, growth, and gene expression changes were assessed and toxicity thresholds were determined. Whereas the biological end points were consistent in the determination of (sub)lethal doses, microarrays supplied additional information on the mechanism of toxicity (oxygen deprivation) and potential long-term effects (feminization, immune system alterations) of diesel exposure on salmonids. Hemoglobins, prostaglandins, cytochromes, and gluthathion-S-transferases were among the molecular biomarkers proposed for use in future risk assessments based on microarray results. By bridging traditional toxicity testing with recent microarray technologies, this study shows the potential of genomics tools in ecotoxicity studies as well as industrial applications, including risk assessment, in the near future.