Characterizing Environmental Per- and Polyfluoroalkyl Substance (PFAS) Exposure and Effects in North Carolina Communities

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in a wide array of products and applications (e.g., nonstick cookware, waterproof and water-repellent textiles, firefighting foam). Following their decades of use, PFAS have garnered concern as “forever chemicals” due to their extreme persistence in the environment and in humans. PFAS have further elicited concern because they have been linked to adverse health effects in humans, and their huge number (over 12,000 different chemicals) and complex chemistry make them very challenging to analyze and study for exposure and toxicology. Two particular PFAS chemicals, perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), are drinking water contaminants that can be found in the blood of the vast majority of people. PFOA and PFOS are also linked to toxic effects like kidney and testicular cancer, increased blood cholesterol, and reproductive outcomes. These two chemicals are being phased out of use and federal drinking water standards are likely upcoming. However, the replacements for these two chemicals are much less well-characterized, and many of these newer, replacement PFAS chemicals can be found in the environment of North Carolina due (at least in part) to industrial pollution.

The overarching goal of this dissertation was to characterize the potential exposure and health effects of PFAS in North Carolina communities. The surface water and drinking water in some areas of North Carolina have been found to be contaminated with PFAS; however, there are additional routes of PFAS exposure beyond drinking water, such as ingestion of house dust or placental transfer during pregnancy. This dissertation explores various routes of PFAS exposure and better characterizes the specific PFAS analytes that can be found in North Carolina and the concentrations in which they are present. Additionally, this dissertation evaluates this exposure and potential associations with some adverse health outcomes in a few North Carolina communities.

In Chapter 2, the relationships between PFAS exposure during pregnancy and birth outcomes are explored. This chapter includes data on PFAS concentrations in placenta samples from 120 participants in Durham, North Carolina and evaluates the subsequent associations between placental PFAS exposure and birth outcomes (e.g., infant birth weight, gestational age). A total of 11 PFAS were measured in placental tissues collected in 2010-2011, and the compounds PFOS, PFOA, PFNA, and PFDA were detected in all placenta samples. A few placental PFAS were associated with birth outcomes. The most striking result was that placental PFOS was associated with changes in birth weight, but the direction of change depended on the sex of the infant. For male infants, placental PFOS was associated with lower birthweight, and in female infants, placental PFOS was associated with higher birthweight.

In Chapter 3, the exposure to PFAS through drinking water is evaluated in a community with known PFAS water contamination. This chapter includes data on PFAS concentrations in blood serum and drinking water samples from 49 participants in Pittsboro, North Carolina. The community receives its drinking water from the Haw River, a part of the Cape Fear River watershed. Blood and water samples were collected at two different timepoints to explore temporal variability in contamination. This community was found to have blood levels of PFAS about two to four times higher than the U.S. average. This chapter also includes results on the associations between PFAS blood level and clinical chemistry measurements, such as serum lipids, as indicators of health. Negative associations were found between serum PFOS and PFHxA with decreased electrolytes and decreased liver enzymes. Positive associations were found between serum PFOA and PFHxS with increased total cholesterol and increased non-HDL cholesterol.

In Chapter 4, the effects and toxicokinetics of PFAS in a pregnant rabbit model are evaluated. This chapter includes data from an animal study of 21 pregnant rabbits provided with drinking water that is representative of the PFAS exposure observed in Pittsboro, North Carolina. Rabbits were exposed to this environmentally-relevant mixture of ten different PFAS during and before pregnancy. After exposure, the wastes and tissues were evaluated to measure the PFAS concentration that accumulated. This provided information on where PFAS are distributed in the body after exposure. The liver of the pregnant rabbit was also evaluated to determine if there was an increase in lipids in the liver, or any changes in liver lipid metabolism. For this study, few differences were noted between treated animals and control animals, indicating that the environmentally-relevant dose had little effect on pregnant rabbits. However, due to the lack of PFAS accumulation in blood, tissue, or in wastes, it is likely that the dose of PFAS given through drinking water was too low.

In Chapter 5, the levels of PFAS in indoor house dust were evaluated. This chapter includes data on PFAS concentrations in indoor dust from 184 homes in Durham, North Carolina, as well as 49 fire stations across the U.S. and Canada. House dust and fire station dust PFAS concentrations were then evaluated for associations with characteristics of the building (e.g., square footage, amount of carpeting, age of building construction). Levels of precursor PFAS, such as fluorotelomer alcohols, were typically higher in dust than the perfluoroalkyl acids. This study, along with previous literature, shows that the legacy PFAS in dust has been decreasing, but the precursor PFAS has been increasing in U.S. house dust. Few associations were found between building characteristics and dust PFAS. However, one notable result was that higher 8:2 FTOH was found in dust from buildings with more carpeting, indicating that carpets may be an important source of exposure to fluorotelomer alcohols (possibly from stain-proofing treatment).

Collectively, this dissertation provides important information on the potential exposure and health effects of PFAS in North Carolina communities.