Chemical pollution and diseases of marine mammals

Man-made persistent pollutants (such as PCBs, pesticides and trace metals) reach aquatic organisms through the food chains. Pollutants are ingested and assimilated by smaller organisms, and their concentration in tissues increases from prey to predators. Being at the top of the food chains, marine mammals accumulate some of the highest environmental contaminant levels of all wildlife. They are good sentinel species for monitoring long-term environmental pollution. Exposure to contaminants may have large consequences, both on an individual and a population level. The prevalence and severity of diseases of aquatic wildlife has recently increased in many species. Scientists use new methods to understand how pollutants affect the immune system of marine mammals. Learning about contaminants may also contribute to our understanding of outbreaks of infectious diseases in marine mammals.