Retrospective Exposure Estimation for Perfluorooctanoic Acid (PFOA) for Participants in the C8 Health Project

Abstract

O-30A6-2 Background/Aims: The primary source of PFOA in the environment of eastern Ohio and western West Virginia is believed to be the Washington Works facility. Percolation of deposited PFOA through the soil and pumping by industrial and municipal wells near the contaminated Ohio River is thought to explain elevated well water concentrations and human serum concentrations measured in recent years. Our objective is to estimate historical PFOA exposures and serum concentrations experienced by each of about 45,276 non-occupationally exposed participants in the C8 Health Project, based on their residential histories. Methods: We linked several environmental fate and transport models including AERMOD, PRZM3, BREZO, MODFLOW, and MT3D to simultaneously model PFOA air dispersion, transit through the unsaturated soil zone, surface water transport, and groundwater flow and transport. Annual PFOA exposure rates were estimated for each individual based on predicted calibrated water concentrations and predicted air concentrations, and default assumptions from the EPA Exposure Factors Handbook. Self-reported municipal water sources were verified using geocoded addresses and historical water distribution network maps for 6 municipal water districts. Individual exposure estimates were coupled with a one-compartment pharmacokinetic model to estimate annual serum PFOA concentrations. Results: Predicted water concentrations were within 2.3 times the observed mean water concentrations for all 6 municipal water districts. Predicted and observed median serum concentrations in 2005–2006 are 28.2 and 24.3 ppb, respectively (Spearman's rho = 0.66). Stratified by municipal water source at the time of the serum sample, Spearman rho ranges from 0.19 to 0.34. Conclusion: State-of-the-art fate and transport models provide the most defensible retrospective exposure estimates for epidemiologic studies when historical environmental measurements are lacking but source emissions rates are known. Our models predict recently observed municipal water PFOA concentrations and human serum PFOA concentrations surprisingly well, and will be used in a variety of epidemiologic studies being conducted in this region.