PFAS in Washington drinking water

Every Washington public water system that reported a PFAS detection during EPA UCMR 5 monitoring, how many sit above the 2024 federal limits, and the standard Washington applies. Concentrations are in nanograms per litre, the same unit as parts per trillion.

This is the United States view of the North American PFAS dataset. The complete dataset, including all 3,452 US systems and 97 Canadian sites, lives on the main PFAS contamination map.

Loading federal sample results

What Washington requires

Guidance value only

Agency

Washington State Dept. of Health

Citation

WAC 246-290-315, State Action Levels

Effective

2022-01-01

State Action Levels trigger monitoring and public notification rather than compliance action, so they are not enforceable MCLs. The State Board of Health voted in December 2025 to align them with the federal rule. Fairchild AFB at Airway Heights and Joint Base Lewis-McChord remain priority response areas.

Compound

Limit (ng/L)

Note

PFOA

State Action Level

PFOS

State Action Level

PFHxS

SAL

PFNA

SAL

PFBS

345

SAL

Citations

WA DOH, PFAS

US EPA PFAS National Primary Drinking Water Regulation (2024)

US EPA UCMR 5 occurrence data

Last reviewed 2026-08-13. Verify against the agency source before making a compliance or remediation decision.

Full Washington regulatory brief

All US state limits

Where the numbers on this page come from

Every count above is read straight from a published government file. Nothing is modelled, averaged, or estimated. The rules below are the exact rules used to produce the figures for Washington.

Dataset used for the system counts

Source

US EPA, Fifth Unregulated Contaminant Monitoring Rule (UCMR 5), public occurrence data

File

UCMR5_All.txt, the full public results file released by EPA

Extracted

2026-08-13

Units

Nanograms per litre, equivalent to parts per trillion. EPA publishes micrograms per litre and those values are multiplied by 1,000.

Coverage rules that decide what is counted for Washington

Who is in UCMR 5. All public water systems serving more than 3,300 people, plus a national sample of 800 smaller systems. Private wells and most small systems are not monitored, so they cannot appear here.

Which systems are listed. Only systems whose state field is WA and that reported at least one measured PFAS detection. Systems that monitored and found nothing are not shown, and their absence is not evidence of contamination.

Systems that cannot be placed. 87 systems nationally reported a detection but have no serviced ZIP code published by EPA, so they carry no location and are excluded from these counts. National totals on the map page include them.

Which value is used. The highest result a system reported for each compound across its sampling events. Results flagged by EPA as non-detects are excluded, as are the lithium results carried in the same file.

The above a limit count. A system is counted when its maximum result for a compound exceeds the 2024 federal Maximum Contaminant Level: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA, and HFPO-DA.

The Hazard Index count. Calculated with EPA's own mixture method for PFHxS, PFNA, HFPO-DA, and PFBS. A system is counted when the index is above 1.

What monitoring data is not. Exceeding a 2024 limit in this dataset is not a compliance violation. The federal limits carry a 2029 compliance date, which EPA proposed on 18 May 2026 to move to 2031 for PFOA and PFOS in a rule that is not final, and treatment may have been installed since the sample was taken.

If any figure on this page does not match its source file, tell Nelson and it will be corrected or removed.