If your lab report shows PFOA or PFOS near or above federal MCLs
Laboratory water tests occasionally show detections of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), two fluorinated compounds now regulated by federal Maximum Contaminant Levels (MCLs) established in 2024. In the Fairfax County Water Authority system, sampling found PFOA up to 0.0074 micrograms per liter (µg/L) and PFOS up to 0.0057 µg/L, which are equivalent to 7.4 and 5.7 parts per trillion (ppt), respectively. The federal MCL for each is 4.0 ng/L (4 ppt). These figures reflect measured concentrations within the system's surface water source, not specifically in individual household taps. The detection above the MCL in this record is a measurement from the public water system’s monitoring and does not indicate a violation or unsafe water by itself. A laboratory test of your own water is required to determine your household's specific PFAS levels.
If your test includes other PFAS compounds without federal MCLs
The EPA monitoring data for Fairfax County also listed detections of other PFAS substances without current federal MCLs. These include PFBS, PFHxA, PFPeA, PFBA, and PFHpA, where varying numbers of samples exceeded their method reporting levels, but none have established federal regulatory limits as of 2024. This absence of a regulatory threshold does not imply these compounds are safe or unsafe. Instead, these values provide a reference for presence in the water system, which can be a starting point for further analysis. To fully understand their presence in your household water, detailed laboratory testing focused on these compounds is recommended.
If you want to understand mixture levels of newer PFAS compounds
Scientific assessment often considers the overall exposure to multiple PFAS compounds together, sometimes expressed as a hazard index. This index estimates combined concentrations relative to health-based benchmarks but does not directly translate to individual health outcomes without professional interpretation. For Fairfax County’s water system, only PFOA and PFOS currently have federal health-based MCLs. Other detected fluorinated compounds contribute to total exposure but lack established toxicity benchmarks. The presence of these compounds should be considered in context and with professional advice, ideally after testing your own water to understand specific mixture levels.
If you want to know how different water treatment methods reduce PFAS
PFAS compounds vary in chemical structure and behavior, affecting how treatment options remove them. Granular activated carbon beds are proven to adsorb many PFAS compounds, effective especially for longer-chain substances like PFOA and PFOS. Ion-exchange resins operate by exchanging ions on their surface with PFAS anions, often targeting shorter-chain compounds and requiring different regeneration techniques. Understanding these differences helps in selecting water treatment solutions. The Autotrol PFAS Forever Chemicals Filter uses documented technology combining these approaches to reduce PFAS compounds effectively and ships ready to configure for residential water systems.
If you wonder how sampling frequency and size affect data reliability
The Fairfax County Water Authority’s EPA UCMR5 monitoring includes 24 sample results for each PFAS compound collected between March 2024 and February 2025. While 24 samples provide insight into system-wide conditions, individual well or household water can vary. A small number of samples may not capture all temporal or spatial changes in PFAS concentrations. Therefore, these data should be seen as an indicator of system characteristics rather than a precise reflection of any single home’s water quality.
If you consider how source and well depth influence PFAS presence
The water supply for Fairfax County originates from surface water sources, which may have different PFAS profiles compared to groundwater wells. Depth and type of water source can alter PFAS detection because these substances behave differently in environmental reservoirs. Shallow wells may show higher or more variable PFAS due to proximity to contamination sources, while deeper sources might show lower concentrations. This illustrates why testing your specific water source is critical to understanding your exposure.
In summary, the public water system record for Fairfax County presents a detailed view of PFAS occurrence based on multiple samples from a large surface water supply serving over 1.1 million people. This data is sourced from EPA’s Unregulated Contaminant Monitoring Rule 5 (UCMR5) program, which measures PFAS presence but is not a compliance test. For more information, please consult the EPA’s SDWIS database for Fairfax County Water Authority records.
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
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