Effect of Multiple Exposure to Perfluorinated Chemicals on Thyroid Function among Adults in the US: The National Health and Nutrition Examination Survey 2007-2008 and 2011-2012

Abstract

Background and Objectives: Perfluoroalkyl substances (PFASs) are known to disrupt the thyroid hormone system. However, no study has assessed the association between multiple exposure to PFASs and the thyroid hormone system. This study aimed to identify the singular effects of each PFAS and the effects of multiple exposure to PFASs on the thyroid hormone profile in a representative sample of the US population. Materials and Methods: We used data from the US National Health and Nutrition Examination Survey (NHANES) 2007-2008 and 2011-2012. To assess the effect of simultaneous exposure to multiple PFASs on thyroid function, principal component (PC) analysis with varimax rotation was performed. Multivariate linear regression analysis was conducted to identify the effect of each PFAS and PC on thyroid function. Results: In this study, perfluorooctanoate (PFOA) was associated with a decrease in total T4 and Free T4 levels. Perfluorooctane sulfonate (PFOS) was associated with a decrease in total T4 level and perfluorononanoate (PFNA) and perfluorodecanoate (PFDeA) were associated with decreases in TSH levels. In PC analysis, two PCs were identified. PC1 included PFOA, PFOS, perfluorohexane sulfonate (PFHxS), PFNA and 2-(N-methyl-perfluorooctane sulfonamido) acetic acid with high loading. PC2 included PFNA, PFDeA, and perfluoroundecanoate (PFUA). In the multivariate linear regression analysis, PC1 showed negative correlations with total T4 and Free T4 levels, whereas PC2 showed a negative correlation with TSH level. Conclusion: We found that singular and multiple exposure to PFASs was associated with a disruption in thyroid hormone system.