Organic environmental contaminants in bottlenose dolphins
Jennifer Yordy, PhD student, Medical University of South Carolina,and John Kucklick, PhD, National Institute of Standards and Technology

Organohalogen compounds, such as polychlorinated biphenyls (PCBs) and chlorinated pesticides were manufactured by man to provide materials such as electrical transformers, flame retardants and insecticides. These compounds were released into the environment before their toxicities and environmental consequences were fully understood. Although currently banned from production, these compounds which were synthesized for their stability, have proven remarkably persistent and have been shown to accumulate to potentially toxic levels within the lipid rich blubber layers of marine mammals. While compounds such as PCBs have been banned, other compounds with similar toxicological and bioaccumulation properties are still in active use. Probably the most important of these “new” pollutants are the brominated flame retardants which include another group of organohalogen compounds, the polybrominated diphenyl ethers or PBDEs. To assess the concentrations, patterns and toxic potential of organohalogen contaminants found within the Sarasota Bay bottlenose dolphin population, over 195 blubber, blood and milk samples were collected for contaminant analysis during live capture and release programs since June 2000. To date, 81 organohalogen compounds have been detected in Sarasota bottlenose dolphin blubber, with PCBs (0.5- 52 ppm) and 4’4’-DDE (0.1-24 ppm), a toxic metabolite of the pesticide 4,4’-DDT, being the predominant contaminants detected. Although at lower concentrations, PBDEs were also detected at significant levels (.01-9.7 ppm).

Organohalogen contaminants are primarily absorbed through the diet and may be accumulated, excreted, offloaded through milk or transformed by the body to form potentially toxic metabolites. These processes result in a complex mixture of contaminants with toxicities that may differ significantly from those known for single compounds. Understanding of the different patterns and distribution of contaminants between body compartments such as blubber, blood, milk and tissue is important to understanding the link between contaminant burden and adverse health effects. The collection of biological samples from the Sarasota Bay bottlenose dolphin population spanning various years and seasons will allow for an in-depth examination of contaminant distribution between body compartments. In addition, tissues collected from stranded dolphins will be used to determine contaminant distribution throughout the body and help identify target organ exposure.

Many of the organohalogen compounds detected in Sarasota dolphins have been proven to interact and disrupt endocrine functions in cellular and animal models. However, there is little evidence of endocrine disruption in free-ranging marine mammals despite the extremely high levels of organohalogens found within their tissues. Many of the known contaminant interactions with the endocrine system do not result in physiological changes that could be easily measured in free-ranging dolphins. Consequently, we plan to use validated human and mouse cellular functional assays to assess whether the biologically relevant contaminant mixtures found in bottlenose blubber, blood and milk disrupt development and reproductive physiology. By determining the concentrations, patterns and distribution of contaminants throughout the bottlenose dolphin body we can accurately assess whether Sarasota Bay dolphins are at risk for the adverse health effects and endocrine disruption associated with organohalogen exposure. Funding has been provided by NOAA Fisheries and the National Institute of Standards and Technology.