Final Report: Findings Across Ten Exposure Assessment (EA) Sites

This page summarizes the findings of analysis of data from all exposure assessment sites. Individual reports were published detailing the findings from each site. Additional information, including individual site reports, can be found on the site locations page.

The EAs were conducted in:

* We refer to the two pilot PFAS exposure assessments as “pilot EAs” and the remaining eight EAs as the “ATSDR-led EAs.” Although similar data were collected for all sites, the methods were slightly different. Only the blood data from the pilot EAs were combined with ATSDR-lead EAs in the analyses below.

Why did we select these sites?
Tri-folded paper with a location dot on it

When selecting EA sites, ATSDR considered the extent of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) contamination in drinking water supplies, the duration over which exposure may have occurred, and the number of potentially affected residents. These ten sites were identified with PFAS drinking water contamination from use of products such as aqueous film forming foam (AFFF). The two pilot EAs were implemented by state agencies under cooperative agreements with ATSDR, and the remaining eight were led by ATSDR.

Possibly as early as the 1970s, Air Force and Air National Guard bases used AFFF containing PFAS for firefighter training and to respond to fires. Over time, the PFAS from the AFFF entered the ground, moved to offsite locations, and affected drinking water supplies (municipal wells, private wells, or surface drinking water). At all EA sites, exposures were mitigated (reduced) through corrective actions. This included removing contaminated water sources, installing filtration and treatment systems, or providing alternative drinking water supplies. Final mitigation was achieved in each community between 2014 and 2019. Based on information available to ATSDR, all households in affected areas across the EAs now have a drinking water supply with PFAS concentrations that meet or are below current federal and state guidelines for PFAS in drinking water. ATSDR does not recommend that community members who get drinking water from any of the affected public water systems use alternative sources of water. For affected private wells, ATSDR recommends community members continue to use the alternative sources of water or filtration systems provided to them.

How were participants selected?

Each ATSDR-led EA site focused on a specific geographic area where known or expected PFAS exposure occurred. At some sites, households within these areas were randomly selected to participate. At other sites, all households were invited to participate so there were enough participants to provide meaningful results. The selection process allowed ATSDR to estimate exposure to PFAS for the entire community within the geographic area, even those who were not tested.

Across the 10 EA sites, we analyzed the blood samples of
Questionnaire on a clipboard
Blood samples were analyzed from 2,384 residents from 1,212 households.
Blood and urine sample vials
Not all participants completed the data collection activities.
Key Takeaways
  • Average age-adjusted perfluorohexane sulfonic acid (PFHxS) blood levels are higher than national levels in all EA communities.
  • Average age-adjusted PFOS and PFOA blood levels are higher than national levels in most EA communities.
  • Elevated blood levels may result from past drinking water contamination in those communities.
  • Some demographic and lifestyle characteristics are linked with higher PFAS blood levels.
  • All tap water samples collected during the ATSDR-led EAs were below EPA’s 2016 health advisory and state public health guidelines for PFAS in drinking water. Two tap water samples had concentrations of PFOS above ATSDR’s environmental media evaluation guide (EMEG) for PFOS in drinking water.

EMEGs represent estimated contaminant concentrations below which humans exposed during a specific timeframe (acute, intermediate, or chronic) are not expected to experience noncarcinogenic health effects. Drinking Water EMEGs are derived from the corresponding oral MRLs using conservative assumptions of intake rate and body weight.

What did we learn about PFAS levels in blood?

Since 1999, the National Health and Nutrition Examination Survey (NHANES) has measured PFAS levels in blood in the U.S. population. PFAS levels are shown to be age dependent and tend to increase with age in part due to longer periods of exposure. ATSDR adjusted blood levels of EA participants to the age distribution of the U.S. population during NHANES 2015-2016. Age-adjustment enabled more meaningful comparison to the national average.

Average age-adjusted blood levels of PFAS are higher than national levels in many but not all EA sites.
Average PFAS blood levels (age-adjusted) at PFAS exposure assessment sites compared to national averages+
Bar chart of PFHxS  age-adjusted blood levels for all 10 sites compared to NHANES with all 10 higher averages than NHANES.
Bar chart of PFOS age-adjusted blood levels for all 10 sites compared to NHANES with 9/10 higher averages than NHANES.
Bar chart of PFOA age-adjusted blood levels for all 10 sites compared to NHANES with 7/10 higher averages than NHANES.
Bar chart of PFNA age-adjusted blood levels for all 10 sites compared to NHANES with 5/10 higher averages than NHANES.
Bar chart of PFDA age-adjusted blood levels for all 10 sites compared to NHANES with 2/10 higher averages than NHANES.
Bar chart of PFuNA age-adjusted blood levels for all 10 sites compared to NHANES with 2/10 higher averages than NHANES.
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Page last reviewed: September 22, 2022