Perfluorooctanoic acid exposure and thyroid disease in community and worker cohorts.

Background: Perfluorooctanoic acid (PFOA) was released from a mid-Ohio River Valley chemical plant, exposing the surrounding community to PFOA for >50 years, primarily through drinking water. Toxicological studies and some previous human studies have suggested that PFOA can disrupt thyroid homeostasis. We examined the association between PFOA and thyroid disease among community members and plant workers.
Methods: Participants completed health surveys during 2008-2011. Yearly serum PFOA concentrations were estimated for each participant starting at birth or in 1952, whichever came later. We used Cox proportional hazard models, stratified by birth year, to assess adult thyroid disease hazard in relation to time-varying yearly or cumulative (sum of yearly estimates) estimated PFOA serum concentration, controlling for sex, race, education, smoking, and alcohol use.
Results: Of 32,254 participants, 3,633 reported functional thyroid disease (excluding neoplasms, congenital disease, nodules without functional changes, cysts, and unspecified type). Analyses were restricted to 2109 cases of functional thyroid disease with thyroid prescription medication use and validation through medical record review. In analyses starting at age 20 years or in 1952, thyroid disease hazard ratios across cumulative exposure quintiles were 1.00, 1.24, 1.27, 1.36, and 1.37 among women and 1.00, 1.12, 0.83, 1.01, and 1.05 among men (log-linear trend tests: P = 0.03 and P = 0.85, respectively); similar results were observed for yearly exposure. Associations were observed for hyperthyroidism and hypothyroidism among women. Some subanalyses also suggested an increased hazard of hypothyroidism among men.
Conclusions: Higher PFOA exposure was associated with incident functional thyroid disease in this large cohort with high exposure.