Exposure, Bioaccumulation, Metabolism and Monitoring of Persistent Organic Pollutants in Terrestrial Wildlife

Abstract

Despite the reduction in the production and emissions of legacy organohalogenic compounds, such as polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), these persistent organic pollutants (POPs) are still amongst the most relevant found in wildlife tissues. With some exceptions, POPs are very lipophilic, and thus the movement of dietary lipids drives the movement, distribution and sequestering of these compounds in wildlife tissues. Other avenues of exposures, however, can also be important in special circumstances, such as inhalation and dermal exposures. Although these POPs are relatively resistant to metabolism, the rates of metabolism are generally the rate-limiting step for their elimination and contribute to substantial differences in body burdens amongst species. The capacity for metabolizing POPs is highest in mammals, on average slightly lower for birds but much lower for ectothermic vertebrates. Nonetheless, differences in metabolic ability for specific enzymes, such as cytochrome P450, in related taxonomic groups are sufficiently large to show differences in compound-specific accumulation. Due to the reduction in the production and emissions of legacy POPs, in general the body burdens in wildlife have declined worldwide. Despite that, concentrations of POPs are still elevated in many wildlife populations, particularly higher trophic level predators. The rates of elimination of POPs from body burdens of wildlife are much higher than the much slower rates of environmental degradation; hence, the changes in body burdens better reflect any changes in the bioavailability of POPs. Lastly, some of the advantages of using wildlife as monitors of POPs are discussed.