EPA Data on Clarkstown's PFAS Levels in Public Water
The public water system serving Clarkstown in Rockland County is supplied by surface water and is managed by Veolia Water NY (System NY4303673), which serves approximately 270,000 people through 56,150 connections. Recent federal monitoring under the UCMR5 program from 2023 to 2025 reports multiple types of PFAS detected in this system. These include PFOA and PFOS, with several measurements above their reporting limits and below or near new federal maximum contaminant levels (MCLs) set for 2024. While detections are present, these are measurements and not violations or safety determinations for any individual home.
Why PFOA and PFOS Are Measured in Nanograms per Litre (ng/L) and Four Decimal Places Matter
PFAS compounds, including PFOA and PFOS, are quantified in extremely low concentrations expressed in nanograms per litre (ng/L), also known as parts per trillion (ppt). This unit indicates one nanogram, or one billionth of a gram, in one litre of water. The use of four decimal places in reporting levels reflects the precision necessary to detect these compounds at trace amounts that may be of regulatory and health interest. Even small numeric differences at this scale influence how results compare to federal guidelines. For Clarkstown, PFOA was detected up to 0.014 µg/L (14 ng/L) and PFOS up to 0.0068 µg/L (6.8 ng/L), with federal MCLs set at 4.0 ng/L for these substances starting in 2024.
What Changes for Large Households, Second Homes, or Seasonal Properties
Larger households or properties with intermittent use may face different considerations regarding PFAS exposure and treatment. Variations can arise in water consumption volume, storage patterns, and stagnation periods within plumbing. For seasonal homes, periods of inactivity may affect water quality by allowing compounds to concentrate or settle differently than in primary residences. Households with fluctuating usage should be particularly attentive to testing their own water to understand localized conditions rather than relying solely on public water system data, which represents broad averages and multiple sources.
The Hazard Index for Mixtures of Newer PFAS Compounds Explained Without a Health Claim
PFAS often occur as mixtures, including newer compounds beyond PFOA and PFOS such as PFHxS, PFNA, and others. Although some compounds are detected at low levels, assessments sometimes use hazard indices that combine exposure potentials without concluding specific health outcomes. In Clarkstown’s water system, several PFAS compounds have been detected, but at various concentrations below or above reporting levels. Such indices help regulators prioritize monitoring but do not constitute a direct health risk statement for the household.
Why Granular Carbon Beds and Ion-Exchange Resins Are Documented Differently for PFAS Treatment
Water treatment technologies to address PFAS differ in their mechanism and effectiveness. Granular activated carbon (GAC) beds adsorb PFAS compounds from water over time, beneficial for reducing long chain PFAS like PFOA and PFOS. Ion-exchange resins operate by chemically capturing charged PFAS molecules, sometimes offering higher efficiency for certain compounds including shorter chains. Documentation for each method varies based on testing performance and compound specificity. Understanding these differences helps users select suitable treatment equipment that ships ready to configure for household PFAS reduction.
Firefighting Foam, Textile Finishing, and Landfill Sources: Which Fits Clarkstown’s PFAS Record
Common environmental sources of PFAS include aqueous film-forming foams (AFFF), textile finishing, and landfills. In Clarkstown’s system, detections of PFOA and PFOS at low nanogram per litre levels reflect typical presence observed near urban and suburban surface-water supplies potentially influenced by such sources. The pattern of detections—several samples of PFOA elevated above reporting levels and fewer for PFOS—aligns with these known industrial and environmental inputs. This regional context helps frame potential origins of PFAS but does not assign source-specific contamination to any one household.
What Questions Commercial or Industrial Operators Add That a Household Does Not
While residential users focus on safety and nuisance factors, commercial and industrial operators must consider regulatory compliance, process compatibility, and discharge requirements regarding PFAS. They may require higher-frequency sampling, specialized testing for lesser-known PFAS compounds, and treatment systems tailored to specific industrial inputs. Households, in contrast, primarily seek confirmation of their own water quality and effective point-of-entry solutions to reduce PFAS exposure.
Recommended Next Step: Testing Your Household Water for PFOA and PFOS
To determine the presence and level of PFAS compounds in your specific household water supply, you should order a certified water test that includes PFOA, PFOS, and other priority PFAS compounds at detection levels aligned with federal standards. A result below the new federal MCLs of 4.0 ng/L (0.004 µg/L) for PFOA and PFOS would provide clarity on your home's water quality relative to these "forever chemicals." For mitigation, the Pentair PFAS Forever Chemicals Filter is documented to reduce a broad spectrum of PFAS effectively when configured for residential use.
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