Academic journal article Environmental Health Perspectives

Association between Serum Perfluorooctanoic Acid (PFOA) and Thyroid Disease in the U.S. National Health and Nutrition Examination Survey

Academic journal article Environmental Health Perspectives

Association between Serum Perfluorooctanoic Acid (PFOA) and Thyroid Disease in the U.S. National Health and Nutrition Examination Survey

Article excerpt

BACKGROUND: Perfluorooctanoic acid (PFOA, also known as C8) and perfluorooctane sulfonate (PFOS) are stable compounds with many industrial and consumer uses. Their persistence in the environment plus toxicity in animal models has raised concern over low-level chronic exposure effects on human health.

OBJECTIVES: We estimated associations between serum PFOA and PFOS concentrations and thyroid disease prevalence in representative samples of the U.S. general population.

METHODS: Analyses of PFOA/PFOS versus disease status in the National Health and Nutrition Examination Survey (NHANES) for 1999-2000, 2003-2004, and 2005-2006 included 3,974 adults with measured concentrations for perfluorinated chemicals. Regression models were adjusted for age, sex, race/ethnicity, education, smoking status, body mass index, and alcohol intake.

RESULTS: The NHANES-weighted prevalence of reporting any thyroid disease was 16.18% (n = 292) in women and 3.06% (n = 69) in men; prevalence of current thyroid disease with related medication was 9.89% (n = 163) in women and 1.88% (n = 46) in men. In fully adjusted logistic models, women with PFOA [greater than or equal to] 5.7 ng/mL [fourth (highest) population quartile] were more likely to report current treated thyroid disease [odds ratio (OR) = 2.24; 95% confidence interval (CI), 1.38--3.65; p = 0.002] compared with PFOA [less than or equal to] 4.0 ng/mL (quartiles 1 and 2); we found a near significant similar trend in men (OR = 2.12; 95% CI, 0.93-4.82; p = 0.073). For PFOS, in men we found a similar association for those with PFOS [greater than or equal to] 36.8 ng/mL (quartile 4) versus [less than or equal to]25.5 ng/mL (quartiles 1 and 2: OR for treated disease = 2.68; 95% CI, 1.03--6.98; p = 0.043); in women this association was not significant.

CONCLUSIONS: Higher concentrations of serum PFOA and PFOS are associated with current thyroid disease in the U.S. general adult population. More work is needed to establish the mechanisms involved and to exclude confounding and pharmacokinetic explanations.

KEY WORDS: C8, human population, PFOA, PFOS, thyroid disease. Environ Health Perspect 118:686-692 (2010). doi:10.1289/ehp.0901584 [Online 20 January 2010]

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The perfluoroalkyl acids (PFAAs) are a family of synthetic, highly stable perfluorinated compounds with a wide range of uses in industrial and consumer products, from stain- and water-resistant coatings for carpets and fabrics to fast-food contact materials, fire-resistant foams, paints, and hydraulic fluids (Organisation for Economic Co-operation and Development 2005). The carbon-fluoride bonds that characterize PFAAs and make them useful as surfactants are highly stable, and recent reports indicate the widespread persistence of certain PFAAs in the environment and in wildlife and human populations globally (Fromme et al. 2009; Giesy and Kannan 2001; Lau et al. 2007; Saito et al. 2004). Two of the PFAAs of most concern are the eight-carbon--chain perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA, also known as C8).

Most persistent organic pollutants are lipophilic and accumulate in fatty tissues, but PFOS and PFOA are both lipo- and hydrophobic, and after absorption will bind to proteins in serum rather than accumulating in lipids (Hundley et al. 2006; Jones et al. 2003). The renal clearance of PFOA and PFOS is negligible in humans, leading to reported half-lives in blood serum of 3.8 and 5.4 years for PFOA and PFOS, respectively (Olsen et al. 2007). Human biomonitoring of the general population in various countries has shown that, in addition to the near ubiquitous presence of PFOS and PFOA in blood, these may also be present in breast milk, liver, seminal fluid, and umbilical cord blood (Lau et al. 2007).

Extensive laboratory studies of the toxicology of PFOA and PFOS have reported enlargement of the liver, modulation of sex hormone homeostasis, developmental and immune system toxicity, hypolipidemia, and reduced body weight in rodent and nonhuman primate models [reviewed by Lau et al. …

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