Interpreting PFOA and PFOS Measurements at Tiny Fractions
Nanograms per litre (ng/L) and parts per trillion (ppt) describe extremely low levels
Government sampling reports PFOA and PFOS concentrations in Clarkstown's public water system between about 4 and 14 ng/L, or parts per trillion. These values represent fractions of micrograms per litre, indicating detection of very small quantities. Four decimal places in micrograms per litre (µg/L) correspond to parts per trillion, reflecting advanced analytical techniques. Understanding this scale helps put PFAS findings in context for treatment decisions.
Federal Maximum Contaminant Levels (MCLs) for PFOA and PFOS inform regulation
For 2024, the US EPA has set MCLs at 4.0 ng/L for PFOA and PFOS. Clarkstown's Veolia Water NY system reported 35 detections above the reporting level for PFOA with a highest measured value of 14 ng/L and 5 for PFOS with a highest of 6.8 ng/L. These are occurrence survey results, indicating presence but not violations or unsafe conditions by themselves.
Routes for PFAS to Surface Water and Distribution Systems in Rockland
Surface water sources can accumulate PFAS from multiple regional inputs
Veolia's supply for Clarkstown originates from surface water. PFAS enter surface water through atmospheric deposition, runoff from urban and industrial areas, and legacy contamination. Known contributors in the region include fire-fighting foams, industrial activities, and landfill leachate. These pathways explain why low-level PFAS are found consistently in monitoring.
PFAS persistence leads to long-term presence in water bodies
The nature of per- and polyfluoroalkyl substances, or 'forever chemicals,' means they resist degradation. Once in surface water, PFAS remain and accumulate over time, which is reflected in repeated detections by public utility monitoring efforts.
Differences Between Public System Records and Private Well Testing
Public water system data reflects aggregate and treated water conditions
The EPA's Unregulated Contaminant Monitoring Rule (UCMR5) samples source and treated water at various points for the entire Veolia system serving Clarkstown. This provides a broad regional picture but does not specify PFAS levels at any individual home tap.
Private well water requires specific testing to determine individual exposure
Well owners should conduct their own PFAS testing because local groundwater conditions, well depth, and construction affect contamination levels. Public system results cannot substitute for household-level data.
Influence of Plumbing Materials and Age on Household Water Quality
Fixture materials may interact with fluorinated compounds distinctly from source water
While source water contains PFAS, the plumbing network can influence final tap water quality. Older pipes, solder, or components may introduce other contaminants but do not affect PFAS concentrations directly. Understanding this helps isolate source contamination from household plumbing effects.
Residence age and plumbing maintenance are factors in overall water quality assessment
Because plumbing conditions vary, households should consider comprehensive water testing beyond PFAS to address any other water quality concerns.
How Sampling Methodology Impacts PFAS Results Expectations
Surface source sampling differs from groundwater or private well sampling
Veolia samples surface water reservoirs and treated water at multiple points, producing data relevant to public supply. By contrast, sampling private well water at various depths may reveal different PFAS levels depending on local contamination and aquifer characteristics.
Sampling depth and method matter for accurate PFAS assessment
Because PFAS distribution in groundwater can vary with depth and flow, well owners should specify sample depth and protocol when testing to obtain meaningful results.
Next Step: Testing Your Home’s Water for PFAS Levels
To clarify your household’s specific exposure, order a certified PFAS test for your tap water. A reliable laboratory analysis will measure concentrations of PFOA, PFOS, and other related fluorinated compounds. If results indicate the need for treatment, the C-Series PFAS Forever Chemicals Filter ships ready to configure and is designed specifically to reduce these contaminants at home.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2025-12-09. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for Veolia Water NY (NY4303673), NY: 729 results across 10 listed contaminants, 91 detections above the reporting level; 40 results above a 2024 federal MCL