UC Irvine

Background: Perfluorooctanoic acid (PFOA) is a perfluoroalkyl acid found in > 99% of Americans. Its health effects are unknown. Prior estimates of serum half-life range from 2.3 to 3.8 years. Objectives: We assessed the impact of years of residence and years since residing in the study area on serum PFOA concentration in a sample of current and former residents who were exposed to PFOA emissions from an industrial facility in six water districts in West Virginia and Ohio. Methods: Serum samples and questionnaires, including residential history, were collected in 2005-2006. We modeled log serum PFOA (nanograms per milliliter) for current residents as a function of years of residence in a water district, adjusted for a variety of factors. We modeled the half-life in former residents who lived in two water districts with high exposure levels using a two-segment log-linear spline. Results: We modeled serum PFOA concentration in 17,516 current residents as a function of years of residence (R(2) = 0.68). Years of residence was significantly associated with PFOA concentration (1% increase in serum PFOA/year of residence), with significant heterogeneity by water district. Half-life was estimated in two water districts comprising a total of 1,573 individuals. For the participants included in our analyses, we found that years since residing in a water district was significantly associated with serum PFOA, which yielded half-lives of 2.9 and 8.5 years for water districts with higher and lower exposure levels, respectively. Conclusion: Years of residence in an exposed water district is positively associated with observed serum PFOA in 2005-2006. Differences in serum clearance rate between low-and high-exposure water districts suggest a possible concentration-dependent or time-dependent clearance process or inadequate adjustment for background exposures.