Date of Award

5-11-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Public Health

First Advisor

Ike Okosun

Second Advisor

Christina H. Fuller

Third Advisor

Dora Il'yasova

Abstract

Polyfluorochemicals (PFCs) are industrial compounds that tend to bioaccumulate in humans and may be associated with impaired renal and liver function. Differences in background exposure to PFCs in the general population exist worldwide, which suggest that populations with lower exposure concentrations, such as foreign-born U.S. residents, may have lower risk for adverse health effects associated with PFCs. Using data from the 2007-2012 waves of US National Health and Nutritional Examination Survey (NHANES) this study investigated differences in serum concentrations of perfluorooctanoic acid, (PFOA), perfluoroctane sulfonic acid (PFOS), perfluorohexane sufonic acid (PFHxS) and perfluorononanoic acid (PFNA) among native-born and foreign-born U.S. residents; and examined the association between these chemicals and estimated glomerular filtration rate (eGFR), Alanine aminotransferase (ALT), γ-glutamylytransferase (GGT) and total bilirubin among foreign-born U.S. residents, and on stratifying by length of residence (LOR). Additionally, the association between joint exposures to multiple PFCs and renal and liver function was examined.

The results showed that least square geometric mean concentrations of PFOA and PFHxS were higher, and least square mean of eGFR was lower among native-born when compared to foreign-born residents. As LOR increased, mean and median concentrations of PFOS and PFHxS significantly increased, and mean eGFR decreased. LogPFOA, logPFHxS, and logPFNA concentrations were significantly associated with increased odds of having low eGFR. The associations remained significant among individuals who had been resident for 10-19 years, and 20+ years. Differences in the mean and median concentrations of ALT, GGT, and Total bilirubin between foreign-born and native-born residents, and by LOR were inconclusive. Similarly, significant associations between the selected PFCs and liver function indicators were not conclusive. Increasing quartiles of a combined PFOS/PFHxS exposure variable was associated with increased odds of low eGFR, and elevated total bilirubin.

Findings from this study suggest that differences in exposure to PFCs exist among native-and foreign-born U.S. residents. Also, increasing serum concentrations of some PFCs with increasing LOR may be associated with increased risk for decreased renal function. Longitudinal studies among new U.S. residents can help determine whether exposure to low background concentrations of the selected PFCs may be associated with any negative health effects over time. There are currently no studies on the combined effect of exposure to multiple PFCs. The findings of this study can serve as the basis for future studies on the association between combined exposures and adverse health outcomes.

Available for download on Saturday, May 02, 2020

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