Polybrominated diphenyl ethers (PBDEs) are a class of additive flame retardants used since the 1960s in plastics, polyurethane foam, textiles, and electronic equipment to reduce the potential of ignition and to inhibit burning if the products do catch fire. Due to their widespread use and persistent nature, these chemicals are found throughout the environment, including in human blood, breast milk and other tissues. As a consequence, international regulatory authorities have placed restrictions on their use which has significantly reduced world-wide demand, including in Australia. The production and use of the commercial product pentaBDE and octaBDE are now banned in most countries although decaBDE is still permitted. However, there are stocks of all PBDEs from products in service and waste.
The main aim of this study was to determine concentrations of PBDEs in various environmental media near industrial point sources to investigate source-receptor relationships. Monitoring data on environmental levels of PBDEs was used to determine the extent of contamination near point sources and also the mechanisms of human exposure. Experimental evaluation of PBDE exposure matrices included samples of: air, soil, dust, and human blood serum.
A key regulatory response by many countries to concerns about PBDEs is atmospheric monitoring to establish background levels and monitor temporal changes. Knowledge of spatial variation on local scales, particularly of source regions assists in understanding their transport and fate processes. Using a network of air monitoring stations, this study investigated PBDE levels at sites in different land use categories (commercial, industrial, residential, semi-rural) within an urban subtropical airshed. Summed PBDE levels of all congeners quantified except BDE-209 were observed to decrease exponentially with distance from the central business district (CBD). Regardless of site characterization, levels 4 to 10 km away were half that at the CBD, and reached a baseline 30 km away. This trend paralleled population density.
A follow-up study focused on industrial PBDE emissions, in this case from a large automotive recycling and metal recycling facility in the same industrial region investigated previously. In this work both active and passive samplers were used to measure the magnitude of the recycling facility’s PBDE ‘footprint’ in the local area. The increased spatial resolution afforded by PAS provided data for the development of a model with which individual PBDE congener attenuation coefficients and the influence of prevailing winds on spatial distributions were investigated. The dominance of BDE-209 suggests relatively simple dust suppression measures may reduce emission rates from such recycling facilities.
Many people live and work near such industrial point sources and this study also evaluates whether PBDE releases from such sites results in a significant increase in exposure. Environmental media including: soil, indoor dust and blood of workers was collected near the automotive shredding facility where previous air monitoring data had indicated PBDE concentrations were elevated (~ a factor of 50 times higher than background measurements). Unlike air, indoor dust and soil profiles which were dominated by BDE-209, serum samples of workers at this site were dominated by congeners BDE-47, BDE-153, BDE-99, BDE-100 and BDE-183 and was similar to the profile previously reported in the general Australian population. The different PBDE profile in blood compared to exposure profiles may be explained by differences in metabolism or differential absorption. Results from this study indicated although the workplace had increased levels of contamination, exposure at this site contributed <25% of the calculated daily exposure dose (DED) of PBDEs with the majority via dietary intake and the home environment.
The results of this thesis provide new data on PBDE concentrations in environmental media near a large industrial point source. In this study near-source emissions were characterized by a more complex congener composition compared to background profiles. Importantly, no increase in exposure was observed for nearby workers and was attributed to the reduced bioavailability of BDE-209. However, emissions from industrial point sources to the environment are significant and likely to remain so for some time. Due to the persistence of PBDEs in the environment such sites will act as reservoirs from which these chemicals may leach into the external environment over time. Additional research is required in the identification and monitoring of other likely industrial point sources where PBDEs will accumulate, such as electronic waste (e-waste) recycling facilities and disposal sites.