Estimation of Serum PFOA Concentrations from Drinking and Non-Drinking Water Exposures.

Abstract

Vol. 131, No. 6 Research LetterOpen AccessEstimation of Serum PFOA Concentrations from Drinking and Non–Drinking Water Exposures Alexander R. Bogdan, Sarah Fossen Johnson, and Helen Goeden Alexander R. Bogdan Address correspondence to Alexander R. Bogdan, P.O. Box 64975, St. Paul, MN 55164-0975 USA. Email: E-mail Address: [email protected] https://orcid.org/0000-0003-3513-0027 Minnesota Department of Health, St. Paul, Minnesota, USA Search for more papers by this author , Sarah Fossen Johnson Minnesota Department of Health, St. Paul, Minnesota, USA Search for more papers by this author , and Helen Goeden Minnesota Department of Health, St. Paul, Minnesota, USA Search for more papers by this author Published:16 June 2023CID: 067701https://doi.org/10.1289/EHP12405AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit IntroductionConcern 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, adverse health effects are not expected; b) 2 to 20 nanograms per milliliter2–20 ng/mL, potential adverse effects, especially in sensitive populations; and c) greater than 20 nanograms per milliliter>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/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; 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.In this analysis, we demonstrate a method for using chemical-specific toxicokinetic (TK) values to estimate the contribution of drinking water to serum PFOA levels, compare it to non–drinking water exposures, and discuss implications on public health policy.MethodsMean and 95th percentile lifetime water intake rates (WaterIntake) of 0.017 and 0.044 liter per kilogram per day0.044L/kg/d, respectively, from the U.S. Environmental Protection Agency (U.S. EPA)6 were used to estimate daily doses of PFOA from drinking water (perfluorooctanoic acid begin subscript daily water dose end subscriptPFOADailyWaterDose) with varying PFOA water concentrations (perfluorooctanoic acid begin subscript water concentration end subscriptPFOAWaterConc.;0.001 to 100 nanograms per liter0.001–100 ng/L) (Equation 1). PFOADailyWaterDose (ngkg×day)=[PFOAWaterConc.(ngL)×WaterIntake(Lkg×day)] [1] The daily drinking water PFOA doses were divided by the PFOA clearance rate (ClearanceRate) determined by California Environmental Protection Agency (0.28 milliliter per kilogram per day0.28mL/kg/d)7 to estimate serum PFOA levels resulting solely from drinking water exposure (perfluorooctanoic acid begin subscript serum from water end subscriptPFOASerumFromWater) (Equation 2).8PFOASerumFromWater(ngmL)=PFOADailyWaterDose (ngkg×day)÷ ClearanceRate (mLkg×day) [2] These calculations assume long-term exposure, attainment of steady state, and no large PFOA elimination events (e.g., childbirth, breastfeeding).8To estimate total serum PFOA levels (perfluorooctanoic acid begin subscript total serum end subscriptPFOATotalSerum), perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWater was added to the 2017–2018 NHANES median serum level (perfluorooctanoic acid begin subscript uppercase n h a n e s median serum end subscriptPFOANHANESMedianSerum; 1.47 nanograms per milliliter1.47 ng/mL). This scenario assumes negligible PFOA contribution from drinking water at the NHANES median serum PFOA level.PFOA is one of the most well-studied bioaccumulative PFAS chemicals and has well-characterized TK parameters. Although this analysis focuses on PFOA, it can be performed for any PFAS with the appropriate TK data.Results and DiscussionAt steady state, we calculated that serum PFOA increases by approximately 0.06 nanogram per milliliter∼0.06ng/mL (mean water intake) or approximately 0.16 nanogram per milliliter∼0.16ng/mL (95th percentile water intake) per ng/L PFOA in the drinking water (Table 1; Figure 1A). This calculated relationship is consistent with a recently published study that compared PFAS drinking water concentrations to serum levels at four contaminated sites in Sweden.9 Based on empirical data from these sites, serum PFOA increased by 0.05815 nanogram per milliliter0.05815 ng/mL per ng/L PFOA in the drinking water, identical to our calculated ratio using mean water intake.Table 1 Estimated contributions of PFOA from drinking water exposures to total serum PFOA levels.Water PFOA concentration (ng/L)Predicted serum PFOA level (ng/mL)Mean water intake (0.017 liter per kilogram per day0.017L/kg/d)95th percentile water intake (0.044 liter per kilogram per day0.044L/kg/d)perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWaterperfluorooctanoic acid begin subscript total serum end subscriptPFOATotalSerumContribution of water to totalperfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWaterperfluorooctanoic acid begin subscript total serum end subscriptPFOATotalSerumContribution of water to total001.470%01.470%0.0010.000061.470.004%0.000161.470.011%0.010.00061.470.04%0.00161.470.11%0.10.00611.480.41%0.0161.491.1%10.0611.534.0%0.161.639.7%30.181.6511%0.471.9424%4a0.241.7114%0.632.1030%50.301.7717%0.792.2635%100.612.0829%1.573.0452%20b1.212.6845%3.144.6168%402.433.9062%6.297.7681%1006.077.5481%15.7117.1891%Note: Predicted contributions to serum PFOA exclusively from drinking water (perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWater) were calculated by first establishing a daily PFOA dose by multiplying the water PFOA concentration by the mean and 95th percentile lifetime water intake rates from the U.S. EPA Exposures Factors Handbook. The daily PFOA dose was then divided by the PFOA clearance rate (0.28 milliliter per kilogram per day0.28mL/kg/d) from California Environmental Protection Agency to calculate perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWater. perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWater was added to the 2017–2018 NHANES median serum PFOA concentration (1.47 nanograms per milliliter1.47 ng/mL), representing non–drinking water PFOA exposures, to generate a total PFOA serum level (perfluorooctanoic acid begin subscript total serum end subscriptPFOATotalSerum) inclusive of both drinking water and non–drinking water PFOA exposures. The contribution percentage of PFOA-containing drinking water to total PFOA exposure at each water PFOA concentration was calculated by dividing perfluorooctanoic acid begin subscript serum form water end subscriptPFOASerumFromWater by perfluorooctanoic acid begin subscript total serum end subscriptPFOATotalSerum and multiplying by 100. U.S. EPA, U.S. Environmental Protection Agency; MCL, Maximum Contaminant Limit; NHANES, National Health and Nutrition Examination Survey; PFOA, perfluorooctanoic acid; UCMR3, Third Unregulated Contaminant Monitoring Rule; UCMR5, Fifth Unregulated Contaminant Monitoring Rule.aProposed MCL and UCMR5 Reporting Limit.bUCMR3 Reporting Limit.Figure 1. Predicted contributions of PFOA in drinking water on serum PFOA levels. (A) Predicted impact on serum PFOA levels exclusively from long-term consumption of drinking water with varying PFOA concentrations. Predicted serum PFOA levels were calculated for lifetime mean water intake (0.017 liter per kilogram per day0.017L/kg/d; blue circles and line) and lifetime 95th percentile intake (0.044 liter per kilogram per day0.044L/kg/d; orange squares and line) from the U.S. EPA Exposures Factors Handbook. Scenario assumes drinking water is the only source of PFOA exposure. (B) Predicted impact on total serum PFOA level from long-term consumption of PFAS-containing drinking water. Serum PFOA levels calculated in (A) were added to the 2017–2018 NHANES median serum level. Scenario assumes 2017–2018 NHANES median serum level is due to non–drinking water exposures. The red dotted line demarcates the NASEM border between no expected health effects (less than 2 nanograms per milliliter<2 ng/mL) and potential for health effects in sensitive populations (greater than or equal to 2 nanograms per milliliter≥2 ng/mL). All inputs and predicted levels are shown in Table 1. Note: NASEM, National Academies of Science, Engineering, and Mathematics; NHANES, National Health and Nutrition Examination Survey; PFAS, per- and polyfluoroalkyl substances; PFOA, perfluorooctanoic acid; U.S. EPA, U.S. Environmental Protection Agency.Assuming PFOA exposure occurred exclusively via drinking water, the NHANES median serum level (1.47 nanograms per milliliter1.47 ng/mL) would not be reached until the drinking water PFOA concentration was approximately 30 nanograms per liter∼30 ng/L (mean water intake) or approximately 10 nanograms per milliliter∼10 ng/mL (95th percentile water intake). In the U.S. EPA’s Unregulated Contaminant Monitoring Rule 3, only 2% of tested public water supplies had PFOA greater than 20 nanograms per liter>20 ng/L,10 suggesting drinking water is not the major contributor to the NHANES median.The contribution of drinking water exposures to total serum PFOA was also evaluated. At 1 nanogram per liter1 ng/L, drinking water is estimated to contribute approximately 4 percent∼4% (mean water intake) and approximately 10 percent∼10% (high-end water intake) of total serum PFOA. PFOA drinking water concentrations below 0.1 nanogram per liter0.1 ng/L were calculated to have a negligible contribution (less than or equal to 1 percent≤1%) to total serum PFOA at steady state (Table 1; Figure 1B).The U.S. EPA has proposed a Maximum Contaminant Level (MCL) for PFOA of 4 nanograms per liter4 ng/L,3 the lowest concentration that the U.S. EPA determined that PFOA can be reliably quantified. Drinking water containing PFOA at 4 nanograms per liter4 ng/L would contribute approximately 14 percent∼14% (mean intake) and approximately 30 percent∼30% (high-end intake) to the total serum PFOA level.Reducing PFOA exposures has broad public health impacts. This analysis indicates that, unless non–drinking water exposures are also addressed, treating drinking water to concentrations below 1 nanogram per liter1 ng/L PFOA would have limited impact on lowering current serum PFOA levels in the United States. PFAS-contaminated sites should be remediated and drinking water containing PFAS should be treated; however, to achieve meaningful reductions in serum PFAS, a comprehensive national approach must be undertaken to reduce PFAS exposures from all sources, including banning PFAS in food, consumer products, and other nonessential uses.AcknowledgmentsThe authors would like to acknowledge support by the Clean Water Fund, funded by the 2008 Minnesota Clean Water, Land and Legacy Amendment. The authors also want to thank staff at the Minnesota Department of Health and the Minnesota Pollution Control Agency for their helpful comments on this analysis and manuscript.