Why Are PFOA and PFOS Measured in Nanograms per Litre with Four Decimal Places?
PFAS, or per- and polyfluoroalkyl substances, are often present in water at extremely low concentrations. Measurements use nanograms per litre (ng/L), equivalent to parts per trillion (ppt), because these compounds occur in traces far below milligrams or micrograms. Reporting values with four decimal places, such as 0.0066 µg/L (6.6 ng/L), reflects the precision needed to track ultra-low levels of these 'forever chemicals' that resist environmental breakdown.
Which PFAS Compounds Carry Federal MCLs for 2024, and Which Do Not?
In Kalispell's public water system record, the U.S. Environmental Protection Agency (EPA) classified PFOA and PFOS with federal maximum contaminant levels (MCLs) effective in 2024, set at 4.0 ng/L each. Other fluorinated compounds detected here, including PFHxS, PFNA, and HFPO-DA, currently lack federal MCLs despite monitoring under UCMR5. MCLs represent enforceable thresholds intended to guide water safety management, but compounds without MCLs remain under observation rather than regulated.
Which Household Fixtures and Appliances Are Most Affected by PFAS?
PFAS present in water can most directly impact fixtures that use or dispense water frequently, such as drinking fountains, kitchen faucets, refrigerators with water dispensers, and ice makers. These points of use deliver water consumed by residents and, therefore, are prioritized for filtration when concerns about PFAS arise. Water used for bathing or irrigation generally sees less direct exposure to PFAS concerns.
How Do PFAS Enter Groundwater and Water Distribution in Flathead County?
In Flathead County, groundwater serves as the source for Kalispell's public water system. PFAS can enter groundwater through various channels including historic use or disposal of firefighting foams, industrial activities, and the gradual leaching of these stable compounds into soil and water tables. Once introduced, their environmental persistence means they can travel with groundwater and enter municipal systems, although the levels detected here remain low.
How Does the UCMR5 Survey Differ from Previous Monitoring Efforts Like UCMR3?
The EPA’s Unregulated Contaminant Monitoring Rule (UCMR) evolves to track emerging concerns. UCMR5, conducted from 2023 to 2025 for Kalispell’s system, targets a wider group of fluorinated compounds and uses more sensitive detection limits than UCMR3. For example, UCMR5 measures compounds like PFBS and HFPO-DA not covered previously, and applies lower reporting levels, enabling detection of minute quantities that older surveys might have missed.
What Do 'Detected', 'Median', and 'Range' Mean in This PFAS Sampling Record?
'Detected' means the compound was measured at or above the instrument's reporting level, not that it exceeds safety limits. For example, one PFOS result was detected at 0.0066 µg/L (6.6 ng/L), below the 2024 MCL of 4.0 ng/L. The 'median' is the middle value of detections, helping summarize typical levels, while 'range' shows the span from lowest to highest detection. These terms help characterize the presence of PFAS without implying health risk or regulatory violation.
What Should You Not Conclude from Kalispell Area PFAS Data?
While the federal record shows some detections of PFAS compounds in Kalispell’s water system, it does not indicate any health-based violations for these substances. The presence of low-level detections is not an assessment of safety or risk for your individual household water; only a direct test of your plumbing’s water can establish that. Equipment failure affecting your household water quality may require addressing what your own water contains rather than relying solely on system-wide data.
For households facing equipment failure after PFAS concerns, the Pentair PFAS Forever Chemicals Filter ships ready to configure for residential use. This technology has documented capability to reduce PFAS levels, helping protect water at points of use within your home. Because each home’s water chemistry is unique, testing for PFAS at your taps before and after applying filtration is recommended to confirm performance and safety.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2023-07-18. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for KALISPELL PUBLIC WORKS (MT0000259), MT: 160 results across 10 listed contaminants, 3 detections above the reporting level; 1 results above a 2024 federal MCL