Brominated flame retardants in bottlenose dolphins in Sarasota Bay
By Jenn Yordy, PhD student, National Institute of Standards and Technology, Charleston, SC

Brian Balmer and Rhonda Swor measure pH levels in a fecal sample.

Brominated flame retardants (BFRs) are chemicals that are added to many industrial and consumer products to decrease their flammability and reduce the risk of fire. Fire incidence has dropped over the past 25 years partly as a result of government regulations and fire prevention policies which mandate the use of flame retardants in many automotive and household products in use today. Flame retardants save lives and also reduce the economic impact of fires. However, many BFRs are simply additives to products and are not chemically bound, enabling them to separate and leach from the product into the environment. Some BFRs are very persistent in the environment and are found in many types of samples, including house dust, human blood, and arctic wildlife. Recent studies also suggest BFRs may disrupt endocrine system function and nervous system development and that levels, especially in the US population, are increasing.

In an effort to assess the degree of BFR exposure and potential health effects in the Sarasota Bay bottlenose dolphin population, approximately 195 blubber, blood and milk samples were collected for contaminant analysis during live capture and release health assessments since June 2000. Dolphin tissue samples were analyzed for two different types of BFRs: polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs). Both contaminant types were detected in bottlenose dolphin blubber, with PBDE concentrations ranging between 40 and 1500 parts per billion (ppb). HBCDs were detected at much lower concentrations and were often below 10 ppb.

Elizabeth Berens reads blubber thickness ultrasonically as part of the dolphin health assessment project.

Previous research has demonstrated that the lipid-rich blubber layer of dolphins is an excellent storage site for lipophilic contaminants such as BFRs. Blubber can hold >90% of an animal's entire body burden of fat soluble contaminants making it a useful tissue in which to assess the long-term exposure of bottlenose dolphins to BFRs and other contaminants. However, it is not known whether the contaminant concentrations and mixtures stored in the blubber are representative of those found in more sensitive tissues, such as blood and other internal organs that may be targets for contaminant toxicity. To determine the availability of BFRs in blood, PBDE concentrations are being measured in paired blubber and plasma samples collected during live capture and release health assessments. Also, a collaborative project between the Sarasota Dolphin Research Program and the University of North Carolina Wilmington has allowed for the collection of tissues from bottlenose dolphins that will be used to determine BFR distribution throughout the body and help to identify target organ exposure. Preliminary data suggest that BFRs such as PBDEs are well distributed throughout the body. PBDE distribution appears to be dependent on tissue lipid content; therefore, the highest concentrations were detected in the blubber. However, PBDEs were detected within the blood of all animals analyzed to date and significant burdens of PBDEs were detected in internal tissues such as the brain, liver, spleen, thymus and thyroid gland. As these internal tissues may be targets for PBDE toxicity, these data may be used to further assess the risk of Sarasota Bay dolphins resulting from BFR exposure.

The collection of biological samples from the Sarasota Bay bottlenose dolphins will allow for an assessment of current BFR exposure in this population. In addition, to understand how diet may influence BFR exposure in Sarasota dolphins, the analysis of common prey species, including pinfish, pigfish, spot and mullet is currently underway. By determining BFR concentrations in prey species and distribution of these contaminants throughout the bottlenose dolphin body we can reliably assess whether Sarasota Bay dolphins are at risk for the adverse health effects and endocrine disruption associated with PBDE exposure.

Funding for this project is provided by the Sarasota Dolphin Research Program, National Marine Fisheries Service and the National Institute of Standards and Technology.