PFAS

PFAS Information

Seattle's drinking water remains safe and protected from contaminants, including the group of man-made chemicals labeled PFAS (per- and polyfluoroalkyl substances).

PFAS are manufactured for a variety of industrial purposes. If detected in drinking water, PFAS have the potential to raise health concerns.

For more information about PFAS, including the health and safety risks associated with these compounds, visit the Environmental Protection Agency and Washington State Department of Health websites.

In 2023, SPU conducted four rounds of PFAS testing for the Cedar and Tolt supplies in compliance with state and federal regulations. Although PFAS had not been previously regulated and routine testing had not been required prior to 2023, Seattle Public Utilities (SPU) also conducted testing in 2015, 2018, and 2022.

Tolt and Cedar River Test Results

• In 2015, SPU tested its Tolt and Cedar River surface water sources for six types of PFAS. Test results in 2015 showed no detection of PFAS.
• In October 2018, SPU conducted additional tests on the Tolt and Cedar water supplies, this time using a more sensitive sampling method and testing for 14 types of PFAS. Test results again showed no detection of PFAS and Seattle's surface water supplies continue to be safe and protected from contaminants. A summary of the 2018 tests is shown in the table below.
• In compliance with recently established state and federal regulations for PFAS, in March of 2023, SPU began testing its Tolt and Cedar River surface water sources again. Those results are posted on this web page.

Seattle Wells Test Results

• In addition to the City's primary surface water sources (Tolt and Cedar River supplies), Seattle also has wells available for emergencies. The wells are not used very often, and they have not been used since 2015.
• As a precaution, SPU tested the wells for PFAS in October 2018. Two of the three wells had no detection of PFAS. Trace detections of several PFAS compounds were measured in the third well with a maximum concentration of 5 parts per trillion (see 2018 table). 
• The wells were tested again in August 2022. Two of the three wells had no detection of PFAS. Trace detections of several PFAS compounds were measured in the third well (Blvd Park) with a maximum concentration of 5 parts per trillion (see 2022 table). In all cases with the exception of the PFOA compound, the amount detected was far below health advisory levels established by the Washington State Department of Health (DOH) and the U.S. Environmental Protection Agency (EPA). ). In the case of the PFOA compound, the DOH advisory level is 10 parts per trillion and the EPA proposed MCL is 4 parts per trillion. The PFOA level in the Blvd Park well was 5.7 parts per trillion. The tests conducted in 2018 and 2022 on the wells were done without putting any well water into the drinking water system.

Results Summary 2023

Samples collected from the Cedar and Tolt treatment facilities finished waters in 2023 have not shown any detections for the 29 PFAS compounds in the analyses.  Samples were collected in June, July, October, and December 2023 as part of UCMR5 required monitoring.

Here is the list of PFAS compounds included in the UCMR5 analyses (for both Cedar and Tolt):

Results Summary August 2022

All results in ng/L.

EPA Methods 533 and 537.1 were used for analyses. All units are ng/L which equals parts per trillion (ppt). Field blanks did not have any detections.

Results Summary October 2018

All results in ug/L.

*Compound was also part of UCMR3. EPA Method 537 was used for all analyses. Method Reporting Limit was 0.002 ug/L for all analytes. Sample date for Cedar and Tolt was 10/08/2018. Sample date for the wells was 10/03/2018. Field blanks did not have any detections. ND = not detected.