Estimation of Serum PFOA Concentrations from Drinking and Non–Drinking Water Exposures
By Alexander R. Bogdan, Sarah Fossen Johnson, and Helen Goeden
EHP
June 16, 2023
DOI: 10.1289/EHP12405
Concern has increased over potential human health effects from per- and polyfluoroalkyl substances (PFAS) exposure as more toxicity and exposure data about PFAS have become available. In 2022, the National Academies of Sciences, Engineering, and Medicine (NASEM)1 issued clinical care guidance for patients based on serum levels—the best exposure metric—for the sum of seven PFAS included in the “National Report on Human Exposure to Environmental Chemicals” published by the U.S. Centers for Disease Control and Prevention (U.S. CDC).2 The serum guidelines are a) less than 2 nanograms per milliliter<2 ng/mL<2 ng/mL, adverse health effects are not expected; b) 2 to 20 nanograms per milliliter2–20 ng/mL2–20 ng/mL, potential adverse effects, especially in sensitive populations; and c) greater than 20 nanograms per milliliter>20 ng/mL>20 ng/mL, increased risk for adverse effects. Infants and young children have been identified as especially sensitive to PFAS exposure.3 The most recent data (2017–2018) from the National Health and Nutrition Examination Survey (NHANES) reported serum levels in a representative sample of Americans 12 y of age and older for five of the seven PFAS identified by NASEM. The sum of median and 95th percentile serum levels for the five PFAS were 7.37 and 23.87 nanograms per milliliter23.87 ng/mL23.87 ng/mL,4 respectively.
The NASEM report also highlighted that multiple exposure routes exist for PFAS and how exposures might be reduced. When contaminated, drinking water can be a significant source of exposure; however, sources such as diet and consumer products predominate in communities where drinking water is not contaminated.4 In the early 2000s, some drinking water sources in Twin Cities East Metro area in Minnesota were found to be contaminated with PFAS.5 Drinking water treatment was initiated in 2006, and water samples taken after installation of treatment systems generally had PFOA concentrations below the limit of detection.
In 2008, adult longtime East Metro residents’ mean serum perfluorooctanoic acid (PFOA) level was approximately 15 nanograms per milliliter∼15 ng/mL∼15 ng/mL; by 2014, the mean had fallen by almost two-thirds.5 Significant serum decreases for two other bioaccumulative PFAS—perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHxS)—were also observed in East Metro residents during this time frame. Adults who moved to the East Metro area after installation of water treatment had serum levels of PFOA, PFHxS, and PFOS similar to those of the corresponding NHANES population. No relationship between duration of residence and serum PFAS was observed for new residents, supporting our hypothesis that the serum levels measured in new residents after the addition of water treatment are predominantly the result of ongoing non–drinking water exposures.5 This study also showed the efficacy of water treatment at reducing serum PFAS levels toward the national median in communities with contaminated drinking water.
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