Understanding Nanograms per Litre and Four Decimal Place Reporting for PFOA and PFOS
Why use nanograms per litre (ng/L)?
PFAS concentrations in water are measured in nanograms per litre, equivalent to parts per trillion, reflecting extremely low levels. Reporting to four decimal places, like 0.0042 µg/L, shows precise detection just above minimal thresholds.
What does four decimal place precision mean?
Precision to four decimals helps identify the smallest detectable presence of compounds like PFOA and PFOS, though it does not indicate health risk or rule violations on its own.
Comparing UCMR5 with Earlier Monitoring Surveys
New compounds and detection levels
The current UCMR5 survey (2023-2025) samples a broader range of PFAS compounds at lower reporting thresholds compared to UCMR3, detecting previously unmonitored fluorinated substances.
Implications for local water data
This enhances understanding of Jefferson County's water quality but does not imply individual household water conditions or health violations.
Local PFAS Sources: Firefighting Foam, Textile Finishing, and Landfills
Common regional contributors
PFAS detected in this area likely originates from historical use of firefighting foam, manufacturing processes including textile finishing, and landfill leachate affecting surface water sources.
System source and impact
Walnut Grove Utilities sources water from surface supplies, where these inputs can contribute to measurable but varied PFAS levels.
Distinguishing Aesthetic Secondary Standards from Health-Based Limits
What secondary standards cover
Standards for taste, odor, or staining potential differ from health-based Maximum Contaminant Levels (MCLs). Exceeding aesthetic thresholds does not mean water is unsafe.
Applying standards to Jefferson County data
Chloride or total dissolved solids may affect water quality perception but are not health concerns at detected concentrations.
Which Fluorinated Compounds Now Have Federal MCLs in 2024?
Set limits for PFOA and PFOS
Federal MCLs for PFOA and PFOS are both 4.0 ng/L (4 parts per trillion). Jefferson County's Walnut Grove Utilities recorded some detections above this reporting level, a measurement indicator rather than a violation.
Other compounds without MCLs
PFHxS, PFNA, and newer substances have detections but currently carry no federal MCLs as of 2024, meaning no enforceable limits apply yet.
Summary
Government data for Walnut Grove Utilities shows several PFAS detections, with a few measuring slightly above new federal MCLs for PFOA and PFOS. However, these values reflect system-wide monitoring, not a specific household's water condition. Understanding this data helps residents decide if testing of their own water and additional filtration is appropriate.
For households concerned about PFAS, the C-Series PFAS Forever Chemicals Filter provides a documented technology designed to reduce these compounds effectively. It ships ready to configure, offering a tailored solution when individual water quality warrants treatment.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2025-10-21. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR5 monitoring (2023-2025) for WALNUT GROVE UTILITIES (WV3301942), WV: 180 results across 10 listed contaminants, 29 detections above the reporting level; 7 results above a 2024 federal MCL