Hazard Index for PFAS Mixtures Without Drawing Health Conclusions
Laboratory reports for water samples often show various per- and polyfluoroalkyl substances (PFAS), a family of persistent fluorinated compounds sometimes called "forever chemicals." When multiple PFAS compounds are detected, a hazard index estimates their combined presence relative to safety benchmarks. Though this index appears in some assessments, it is important to note it does not establish any immediate health risk or legal violation. Instead, it helps water professionals gauge relative levels for further consideration.
Which PFAS in Madison Carry a 2024 Federal Maximum Contaminant Level?
As of 2024, federal regulations set maximum contaminant levels (MCLs) for several individual PFAS compounds in public water systems. For Madison’s water supply, tested under the EPA’s Unregulated Contaminant Monitoring Rule 5 (UCMR5) from October 2023 through October 2024, these are the compounds with established MCLs:
- PFOA (4.0 ng/L or parts per trillion)
- PFOS (4.0 ng/L)
- PFHxS (10 ng/L)
- PFNA (10 ng/L)
- HFPO-DA (also called GenX) (10 ng/L)
Sampling results show no detections of PFOA, PFOS, PFNA, or HFPO-DA above their reporting levels. PFHxS was detected at low levels in 4 out of 40 samples, with the highest concentration well below the 10 ng/L MCL. Other tested PFAS compounds like PFBA showed some detections but currently do not have federal MCLs.
Comparing Madison’s PFAS Data with Neighboring Counties
Local water system records provide a snapshot of PFAS presence in the public supply but do not reflect conditions inside individual homes or wells. Comparing Madison’s data to adjacent counties requires reviewing those counties’ own federal or state sampling records. Differences in source water types, industrial activity, and treatment processes all influence PFAS levels. It is important not to assume one area’s data applies to another, nor to generalize from detections alone without considering detection thresholds and MCLs.
Key Information to Note Before Seeking Treatment Recommendations
Before discussing water treatment options for PFAS, Madison residents should have the following on hand:
- The latest PFAS test report or water quality statement from their local water utility
- Information on whether their home uses municipal water or a private well
- Any independent water test results specific to their residence, especially if using a private well
- Details on water usage patterns and treatment needs
This information helps identify if additional treatment is advisable and the best approaches for it.
Changes in Tap Water with the Pentair PFAS Forever Chemicals Filter
The Pentair PFAS Forever Chemicals Filter ships ready to configure for household use and is designed to reduce a wide range of PFAS compounds from water. When in operation at the tap, this system can lower fluorinated compound concentrations, including those detected at low levels in Madison’s system, often below federal MCLs. Users may note improvements in water taste and odor associated with PFAS removal, yet routine water testing remains essential to confirm treatment effectiveness.
Sources of PFAS in Madison’s Groundwater and Distribution System
Madison’s drinking water system draws on groundwater, which can acquire PFAS from historical and ongoing environmental sources such as industrial emissions, firefighting foam usage, landfills, and atmospheric deposition. These substances persist in the environment and enter water supplies primarily through infiltration and percolation into aquifers. The municipal water system treats and monitors these sources to maintain regulatory compliance.
Recommended Test to Clarify Your Household PFAS Level
The single most informative test for a Madison residence concerned about PFAS is a comprehensive laboratory analysis of their tap water specifically for the common PFAS compounds listed in the federal UCMR5 survey. This test reveals the actual concentrations present in that home’s water supply, confirming or clarifying any concerns raised by public water system data. With that knowledge, informed decisions about treatment options such as the Pentair PFAS Forever Chemicals Filter can be made confidently.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2024-10-08. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for MADISON WATER UTILITY (WI1130224), WI: 400 results across 10 listed contaminants, 6 detections above the reporting level; compared with the applicable federal MCL, none above