| This dissertation has investigated different aspects of the occurrence of two groups of common persistent organic pollutants, organochlorine pesticides and brominated flame retardants, in the US.Atmospheric chiral signatures of organochlorine pesticides and some of their metabolites (chlordane, heptachlor, DDT, DDD, heptachlor epoxide) were determined in samples collected in Indiana, Arkansas, and Louisiana to gain information about their source and transport history. The enantiomeric fractions were generally different from racemic but they remain only a qualitative tool, indicating the extent that these pesticides have been degraded by biological processes as opposed to abiotic chemical processes.Using high volume air samplers, atmospheric concentrations of polybrominated diphenyl ethers (PBDEs) flame retardants were measured in air and precipitation samples collected at remote and urban sites to investigate their occurrences, sources, and temporal trends. Concentrations were determined using gas chromatographic mass spectrometry (GC-MS). The atmospheric concentrations of BDE-47 and 99 are generally decreasing rapidly with half-lives of &sim2 years, but the concentrations of BDE-209 are not decreasing at any of the five sites. The calculated atmospheric loadings to Lakes Superior, Michigan, and Erie suggest that PBDEs can undergo long range transport, that Chicago is a preferential source of BDE-47 to Lake Michigan and that Cleveland is a preferential source of BDE-209 to Lake Erie.PBDEs were determined also in cat serum and cat food to determine if any link existed between the increase in cases of hyperthyroidism and the increase in the usage of these flame retardants. No direct relationship was found between hyperthyroidism and PBDEs. Nevertheless, total PBDEs levels in cats were 20-100 fold greater than median levels in US adults, suggesting that pet cats may serve as sentinels to better assess human exposure and adverse health outcomes related to low-level but chronic PBDE exposure. |
