Grantee Research Project Results
Final Report: PFAS UNITED: Poly - and Perfluoroalkyl Substances - U.S.National Investigation of Transport & Exposure from Drinking Water and Diet
EPA Grant Number: R839482Title: PFAS UNITED: Poly - and Perfluoroalkyl Substances - U.S.National Investigation of Transport & Exposure from Drinking Water and Diet
Investigators: Higgins, Christopher , Illangasekare, Tissa , Adgate, John L. , Stapleton, Heather , Knappe, Detlef , Hoppin, Jane , Carignan, Courtney
Institution: Colorado School of Mines , Duke University , Michigan State University , University of Colorado at Denver , North Carolina State University
EPA Project Officer: Packard, Benjamin H
Project Period: May 1, 2019 through April 30, 2022 (Extended to March 31, 2024)
Project Amount: $1,964,375
RFA: National Priorities: Per- and Polyfluoroalkyl Substances (2018) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Climate Change , Water , Water Quality
Objective:
The goal of this study was to develop a comprehensive set of data related to the fate, transport, and bioaccumulation of poly- and perfluoroalkyl substances (PFASs) and resultant human exposure. This study addressed three aims: 1) filling critical data gaps for the environmental transport of overlooked PFASs; 2) evaluating the uptake of PFASs into local foods through contaminated soil and water; and, 3) assessing the relative role of drinking water, diet and the indoor environment in determining exposure for communities impacted by differing sources of PFASs.
Summary/Accomplishments (Outputs/Outcomes):
Efforts during the final reporting period largely focused on finalizing manuscripts and analyzing data related to the final research question listed above. In prior years, the Colorado and North Carolina investigators assessed the effectiveness of three source apportionment methods (UNMIX, positive matrix factorization [PMF], and principal component analysis - multiple linear regression [PCA-MLR]) for identifying contributors to human serum PFAS concentrations in two highly exposed populations in CO and NC, where drinking water was contaminated from multiple sources, including a Space Force military base (CO) and a fluorochemical manufacturing plant (NC). The UNMIX and PMF models extracted three to four potential PFAS exposure sources in the CO and NC cohorts while PCA-MLR classified two in each cohort.
In our final year, we focused on applying these tools and assessing exposures in our Michigan Cohort. In Michigan, we enrolled 129 participants from 91 homes in a small community where elevated PFOA and PFOS (670 ng/L and 740 ng/L, respectively) was discovered in 2018 in the municipal water supply. From 2020-2021, we administered an exposure questionnaire, collected samples of blood, personal wristbands, tap water, indoor air and dust, produce and soil from home gardens, eggs from home flocks, and locally caught venison. Samples were analyzed for >34 PFASs using HPLC-MS/MS. Serum concentrations ranged up to 180 and 149 ng/mL for PFOA and PFOS, respectively, with geometric means of 24 and 19 µg/L among those who drank the municipal water. Serum concentrations were 14 and 4.5-fold higher compared to participants who drank lower concentrations in private wells (<66 ng/L PFOA and <24 ng/L PFOS) adjusting for age, sex, education and BMI. We identified PFAS ‘source’ mixtures in serum using principal component analysis-multiple linear regression (PCA-MLR) and positive matrix factorization (PMF). Both models identified PFOS, PFOA, PFHxS and PFHpS as the predominant mixture, which is consistent with predominant PFASs in the contaminated drinking water. The relative contribution from drinking water was 66% for the full cohort and increased to 81% when restricted to those participants who drank the municipal water.
Samples from home gardens, chicken eggs, and venison were collected from the homes of 28 participants (17 homes on municipal water and 11 with private wells). We additionally collected foods produced from farms within 15 miles of the study area (Site) as well as >15 miles from a known PFAS-impacted site (Background). Samples were analyzed for 48 different target PFASs using improved methods for unbiased extraction of PFASs in food matrices, and non-targeted suspect screening via liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) was performed on a subset of soil samples. We identified elevated PFOS in home and locally produced chicken eggs (3-6 ng/g) compared to background (< method detection limit) as well as in venison captured closest to a PFAS-impacted Site (>14 ng/g); with exposure estimates (1-8 ng/kg-bw/d) exceeding EPA’s non-cancer reference dose (0.1 ng/kg-bw/d). Consumption of local eggs and venison were significantly associated with serum PFASs.
Produce from home gardens contained up to 1.2 ng/g ƩPFASs, with PFBA being predominant. PFAS concentrations in produce were positively associated with concentrations in current tap water (p<0.05). Local produce contained up to 3.7 ng/g ƩPFASs with varying mixture profiles. Concentrations from the Site produce were often higher than Background; with the highest concentrations in squash, spinach and green beans. Exposure estimates ranged up to 3.5 ng/kg-bw/d and exceeded reference doses for PFNA, PFDA, PFHxS and PFOS in some samples. This investigation highlights the need for targeted intervention strategies to mitigate risks from dietary sources in affected communities.
Within this study population, 87 participants that provided blood samples also wore and returned a silicone wristband. Statistically significant differences were observed in wristband PFAS concentrations when stratified by age (age was categorized into 3 tertiles) or sex. Female participants who used mascara had a higher median level of 6:2 diPAP on their wristband compared to female participants who did not use mascara. This was also observed for the use of foundation. Individuals who spent a greater amount of time in their house per day (on average more than 17 hours per day) had higher wristbands concentrations of MeFOSE and EtFOSE compared to individuals who spent less than or equal to 17 hours inside their home per day. This indicates that the indoor home environment is a source of exposure to MeFOSE and EtFOSE, and a strong correlation was observed between MeFOSE on the silicone wristbands and N-MeFOSAA in the blood serum. Efforts to assess whether these levels of exposure are greater in this PFAS-impacted community as compared to “background” U.S. levels are the subject of ongoing work.
Residential indoor air and dust was also collected from 32 homes. Statistically significant differences were observed in air and dust concentrations of PFASs when stratified by the type of flooring of the room in which samples were collected. In particular, strong correlations were observed between MeFOSE levels in the air and N-MeFOSAA levels in blood serum, as well as MeFOSE levels in the air and MeFOSE levels in the silicone wristbands. Collectively, these data indicate that serum N-MeFOSAA levels seem to be influenced by indoor sources (such as indoor air). The silicone wristbands are able to capture this indoor exposure to MeFOSE which can biotransform into N-MeFOSAA. This is important because N-MeFOSAA is frequently identified in blood.
All participants opted to receive their individual results as well as overall results from the study. Results were provided as both tables and figures along with relevant context and explanation. Participants were invited to reach out with any questions and to attend a virtual meeting for a walk-through of the report-back and Q&A with co-PI Carignan. We asked participants to complete a brief survey to provide feedback on the clarity, structure, and content of the report back. A total of 52 participants completed and returned the feedback survey. More than 70% agreed that the results were presented clearly, and the content was important and helpful to them. Participants were also given the opportunity to share what they liked and disliked about the report. Many found their personal blood results to be most useful, while some would have liked to see more guidance on home grown food and soil, store-bought foods, and health effects. There were mixed responses about the structure of the report, as a few found the amount of information overwhelming and the data challenging to interpret. Overall, participants found the report helpful and feedback will be incorporated in future communications.
Finally, in the rural NC area surrounding a fluorochemical manufacturing plant, 53 produce samples harvested between 2013 and 2019 were collected from five residential gardens. We performed targeted analysis of 43 PFASs, including 13 PFEAs in produce and water samples collected from these gardens. Summed PFAS concentrations ranged from 0.0026 to 37.7 ng/g fresh weight, and the PFAS signature was dominated by PFEAs associated with air emissions from the fluorochemical plant. Perfluoro-2-methoxypropanoic acid (PMPA) and perfluorodioxahexanoic acid (PFO2HxA) were detected in over 95% of samples, with concentrations reaching 26.4 and 9.6 ng/g fresh weight, respectively. Hexafluoropropylene oxide-dimer acid (HFPO-DA, commonly known as GenX) was detected in 72% of samples. Among all produce types, water-rich produce exhibited the greatest PFAS levels compared to starch-rich or oil-rich produce. With some exceptions, PFEA concentrations exhibited a declining trend from 2013 to 2019, which may be related to air pollution control measures installed during the sampling period. Finally, the water-equivalent daily limit and chronic-exposure daily limit for children (3-6 yr) and adults were calculated based on the measured GenX concentrations in the produce and the reference doses (RfDs) used to establish the water limits, as low as 17 g and 249 g of produce per day for children, respectively. This study revealed that consuming residential garden produce grown in PFAS-impacted communities can be an important exposure pathway.
Conclusions:
The work conducted as part of this study aimed to answer key questions on PFAS fate, transport, bioaccumulation, and resultant human exposure, with a particular focus on “overlooked” PFASs. We developed scientific data and knowledge to support the ability of decision makers to address several key questions related to PFAS exposure. These questions and a summary of the relevant findings, are included here:
- Once a point source of PFASs is identified, what data are needed to predict the extent of contamination and how quickly will PFASs migrate, particularly through soil to groundwater?
Relevant Findings: As part of Aim 1, our investigations into PFAS transport through soil revealed that many PFASs, including the overlooked PFASs, are retained at the air-water interface during vadose zone transport from soil to groundwater. This retention is consistent with parallel work conducted for other PFASs. Further, there appear to be significant kinetic limitations both with respect to solid-phase retention of PFASs as well as their retention at the air-water interface. Collectively, these data and findings suggest that models will need to account for both air-water partitioning and kinetic processes to be most useful in predicting plume spread and migration.
- Which and to what extent are PFASs taken up in locally grown/raised/caught food in communities impacted by PFAS drinking water contamination?
Relevant Findings: The series of laboratory and field-based studies conducted here under Aim 2 indicate that while some PFASs are taken up in some locally produced foods, this is very much dependent on the PFASs released, the extent of contamination, and the food types. Mechanistic studies on food-crop accumulation indicate that the discrimination between PFASs that is observed during the uptake of PFASs by plants from soil pore water largely is a result of internal processes within the plants after the PFASs have entered the transpiration stream. Collectively, these data and findings indicate that food-based exposure may be a relevant concern for some PFAS-impacted communities.
- Will treating impacted water be sufficient to reduce human exposure to PFASs to “background” exposure? That is, if the drinking water is treated but the contaminated water (or soil) continues to be used for crops, gardens, and livestock, will serum levels revert to U.S. background?
Relevant Findings: As part of Aim 3, we found evidence of multiple sources of PFAS exposure even in PFAS-impacted communities. Our detailed biomonitoring study of PFAS exposure indicates that local foods and products used in the indoor environment may be significant sources of exposure for some PFASs, even in communities where the drinking water was a major source of exposure.
Journal Articles on this Report : 9 Displayed | Download in RIS Format
Other project views: | All 20 publications | 11 publications in selected types | All 11 journal articles |
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Brown JB, Conder JM, Arblaster JA, Higgins CP. Assessing human health risks from per-and polyfluoroalkyl substance (PFAS)-impacted vegetable consumption: a tiered modeling approach. Environmental Science & Technology. 2020 Nov 17;54(23):15202-14. |
R839482 (Final) |
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Herkert NJ, Kassotis CD, Zhang S, Han Y, Pulikkal VF, Sun M, Ferguson PL, Stapleton HM. Characterization of per-and polyfluorinated alkyl substances present in commercial anti-fog products and their in vitro adipogenic activity. Environmental Science & TechnologyM 2022;56(2):1162-73. |
R839482 (2021) R839482 (Final) |
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Meng P, DeStefano NJ, Knappe DR. Extraction and Matrix Cleanup Method for Analyzing Novel Per-and Polyfluoroalkyl Ether Acids and Other Per-and Polyfluoroalkyl Substances in Fruits and Vegetables. Journal of Agricultural and Food Chemistry 2022;70(16):4792-804. |
R839482 (2021) R839482 (Final) |
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Stults JF, Choi YJ, Rockwell C, Schaefer CE, Nguyen DD, Knappe DR, Illangasekare TH, Higgins CP. Predicting concentration-and ionic-strength-dependent air–water interfacial partitioning parameters of PFASs using quantitative structure–property relationships (QSPRs). Environmental Science & Technology 2023;57(13):5203-5215. |
R839482 (2022) R839482 (Final) |
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Carignan CC, Bauer RA, Patterson A, Phomsopha T, Redman E, Stapleton HM, Higgins CP. Self-collection blood test for PFASs:comparing volumetric microsamplers with a traditional serum approach. Environmental Science & Technology 2023; 57(21):7950-7957. |
R839482 (2022) R839482 (Final) |
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Wallis DJ, Barton KE, Knappe DR, Kotlarz N, McDonough CA, Higgins CP, Hoppin JA, Adgate JL. Source apportionment of serum PFASs in two highly exposed communities. Science of The Total Environment 2023;855:158842. |
R839482 (2022) R839482 (Final) |
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Schwichtenberg T, Bogdan D, Carignan CC, Reardon P, Rewerts J, Wanzek T, Field JA. PFAS and dissolved organic carbon enrichment in surface water foams on a Northern U.S. freshwater lake. Environmental Science & Technology 2020, 54 (22)14455-14464. |
R839482 (Final) |
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Zhang C, McElroy AC, Liberatore HK, Alexander NL, Knappe DR. Stability of Per-and Polyfluoroalkyl Substances in Solvents Relevant to Environmental and Toxicological Analysis. Environmental Science & Technology. 2021 Nov 4. |
R839482 (2021) R839482 (Final) |
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Stults J, Illangesekare T, Higgins C. The Mass Transfer Index (MTI):A semi-empirical approach for quantifying transport of solutes in variably saturated porous media. Journal of Contaminant Hydrology 2021:103842. |
R839482 (Final) |
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Supplemental Keywords:
media, groundwater, chemicals, hydrologyRelevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.
Project Research Results
- 2022 Progress Report
- 2021 Progress Report
- 2020 Progress Report
- 2019 Progress Report
- Original Abstract
11 journal articles for this project