Many Fairfax County households notice subtle but persistent PFAS-related issues in their water, such as unusual taste or concerns about long-term accumulation. Even with existing water equipment, managing the full range of these fluorinated compounds can be challenging as new data emerges from recent federal monitoring.
Understanding the Hazard Index for PFAS Mixtures
PFAS, or per- and polyfluoroalkyl substances, are a group of fluorinated compounds sometimes called "forever chemicals" because of their persistence in the environment. In Fairfax County's public water system, multiple PFAS compounds have been detected, including PFOA, PFOS, PFBS, PFHxA, PFPeA, PFBA, and PFHpA, among others. The hazard index concept combines the potential effects of these substances in mixture form without implying a health risk. This index helps evaluate how different concentrations may interact rather than treating each compound in isolation.
Differences Between the UCMR5 and UCMR3 Monitoring Surveys
The 2023–2025 UCMR5 survey, which applies to Fairfax’s public water supply, captures a broader and more sensitive detection of PFAS compounds compared to the previous UCMR3 survey. UCMR5 includes additional fluorinated chemicals and lower detection levels for certain substances, enabling a more detailed picture of occurrence. Fairfax's monitoring results show several detections above the reporting level that were not necessarily captured or detectable under UCMR3 standards. This expanded scope aids in understanding the full spectrum of PFAS in the water system.
Federal MCLs for Fluorinated Compounds in 2024
The Environmental Protection Agency set federal maximum contaminant levels (MCLs) in 2024 for several PFAS compounds. In Fairfax's water system record, PFOA and PFOS have detected concentrations above their MCL of 4.0 nanograms per liter (ng/L), equivalent to parts per trillion (ppt), in some monitoring results. Other compounds like PFHxS, PFNA, and HFPO-DA remain below their respective MCLs of 10 ng/L or were not detected above reporting limits. It is important to note that a detection or concentration above the reporting level is not a violation or indication of unsafe water under current records.
A Worked Example: Interpreting Fairfax’s Median and Range of PFAS Detections
For example, PFOA was detected in three out of 24 samples with levels ranging up to 0.0074 micrograms per liter (μg/L), or 7.4 ng/L; its median detected level was 0.0061 μg/L (6.1 ng/L). PFOS was found in two samples with a highest detection of 0.0057 μg/L (5.7 ng/L) and a median of 0.0052 μg/L (5.2 ng/L). These numbers illustrate the variation in concentrations over the surveyed period and highlight the importance of understanding both median and highest detections when evaluating water quality rather than relying on a single figure.
Information to Record Before Considering Treatment Solutions
- Document your own water test results from a certified laboratory to understand your household-specific PFAS levels.
- Note if your current equipment filters all detected PFAS compounds effectively, especially those with new federal MCLs.
- Track any noticeable changes in water taste, odor, or appearance that may indicate shifts in contaminant levels.
- Identify which fluorinated compounds are most prevalent or concerning in your water supply based on the Fairfax County Water Authority’s monitoring data.
Having this information allows for informed decisions on upgrading or supplementing water treatment systems.
For households in Fairfax County, the Autotrol PFAS Forever Chemicals Filter offers a documented method to address a spectrum of fluorinated compounds, designed to be ready to configure for residential needs without complicating replacement or setup.
This overview reflects the Fairfax County Water Authority’s public water system record as reported in the EPA’s UCMR5 survey from March 2024 through February 2025. These data summarize system-wide measurements but do not provide details for individual home water quality. For more information, please consult the EPA’s official records on unregulated contaminant monitoring.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2025-02-13. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for FAIRFAX COUNTY WATER AUTHORITY (VA6059501), VA: 240 results across 10 listed contaminants, 36 detections above the reporting level; 5 results above a 2024 federal MCL