After more than a year of review and study, today the U.S. Environmental Protection Agency (EPA) released new nationwide maximum contaminant levels (MCLs) for per- and polyfluoroalkyl substances – commonly known as PFAS – in drinking water. An MCL is the highest level of contaminant allowed in drinking water.

PFAS are a large family of human-made chemicals used to make a wide variety of stain-resistant, water-resistant, and non-stick consumer products. In Washington, PFAS have also been used in certain types of firefighting foams used by the U.S. military, local fire departments, and airports. PFAS are sometimes called “forever chemicals” because they stay in the environment for a very long time. Some types of PFAS could harm human health if they build up to high enough levels in your body.

In 2021, the Washington State Board of Health adopted PFAS state action levels (SALs) that require Washington’s more than 2,430 Group A water systems, non-transient and non-community systems to test by law for PFAS in drinking water by December 2025. So far, 1,228 systems have been tested and 30 systems detected PFAS greater than the SALs.

Chemical 2021 WA State Action Levels (SALs)

PFOA     10 ppt

PFOS     15 ppt

PFNA     9 ppt

PFHxS    65 ppt

PFBS      345 ppt

The EPA’s new federal MCLs are mostly lower than Washington’s SALs. That means they are more stringent and protective to human health:

Chemical  2024 EPA Maximum Contaminant Levels (MCLs)

PFOA     4 ppt

PFOS      4 ppt

PFNA     10 ppt

PFHxS    10 ppt


HFPO-DA (GenX chemicals)*  10 ppt

Mixture of two or more: PFNA, PFHxS, HFPO-DA, and PFBS  Hazard Index of 1**

* GenX chemicals have not been found in Washington state.

** Hazard Index: The Hazard Index is a long-established approach EPA regularly uses to understand health risk from a chemical mixture (i.e., exposure to multiple chemicals). The Hazard Index is made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water to the health-based water concentration.

State SALs will continue to be in place until the Washington State Board of Health adopts the new federal MCLs, which can take up to two years.

“In the meantime, public water systems still have to finish sampling under our existing rule. We will still know where contamination has been found by 2025 for all of our public water systems” said Mike Means, Capacity Development and Policy Manager, Office of Drinking Water, DOH. “We will continue to work with those public water systems to address treatment, reduction of exposure, and work to leverage any state and federal funding we can.”

In anticipation of the EPA’s new regulation, DOH developed a PFAS Media Resource Page.

Topics covered in the interviews include:

  • What MCLs are and what they mean for Washington.
  • The science behind MCLs and why they are important for health.
  • If and when Washington will adopt the new MCLs.
  • What to do if you have PFAS in your water above the MCL.
  • Who to contact if you’re concerned about PFAS in your water.
  • How DOH is engaging communities and centering equity in PFAS work.