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.

Although PFAS have not been previously regulated and routine testing has not been required, Seattle Public Utilities (SPU) conducted testing in 2015, 2018, and mostly recently in August of 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, SPU will test its Tolt and Cedar River surface water sources again starting in March of 2023. Those results will be 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). This amount is far below the health advisory level of 70 parts per trillion established by the U.S. Environmental Protection Agency (EPA) prior to 2022.
  • 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 level is 0.004 parts per trillion. The PFOA level in the Blvd Park well was 5.7 parts per trillion. The tests conducted in 2022 on the wells were done without putting any well water into the drinking water system.

Results Summary October 2018

All results in ug/L.

PFC Compound Name Acronym Cedar Tolt Riverton1 Riverton2 Blvd Park

N-ethyl Perfluorooctane sulfo namido acetic acid

NEtFOSAA

ND

ND

ND

ND

ND

N-methyl Perfluorooctane sulfo namido acetic acid

NMeFOSAA

ND

ND

ND

ND

ND

Perfluorobutane sulfonic*

PFBS

ND

ND

ND

ND

0.0018

Perfluorodecanoic acid

PFDA

ND

ND

ND

ND

ND

Perfluorododecanoic acid

PFDoA

ND

ND

ND

ND

ND

Perfluoroheptanoic acid

PFHpA

ND

ND

ND

ND

0.0029

Perfluorohexanesulfonic acid*

PFHxS

ND

ND

ND

ND

0.0022

Perfluorohexanoic acid*

PFHxA

ND

ND

ND

ND

0.0047

Perfluorononanoic*

PFNA

ND

ND

ND

ND

ND

Perfluorooctane sulfonic acid*

PFOS

ND

ND

ND

ND

ND

Perfluorooctanoic acid*

PFOA

ND

ND

ND

ND

0.0050

Perfluorotetradecanoic

PFTeDA

ND

ND

ND

ND

ND

Perfluorotridecanoic

PFTrDA

ND

ND

ND

ND

ND

Perfluoroundecanoic acid

PFUnA

ND

ND

ND

ND

ND

Sample Location

-

CLT-5

TPT-3

RHW1-R

RHW2-R

BPW-R

* 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.

Results Summary August 2022

Compound Name Acronym Lab Reporting Limit State Action Level EPA Health Advisory Level Riverton Well 1 Results Riverton Well 2 Results Blvd Park Well Results
Perfluorobutanoic acid 4.5 ND ND ND
Perfluoropentanoic acid 1.8 ND ND 3.9
Perfluorohexanoic acid PFHxA 1.8 ND ND 2.4
Perfluoroheptanoic acid PFHpA 1.8 ND ND 3.1
Perfluorooctanoic acid PFOA 1.8 10 0.004 ND ND 5.7
Perfluorononanoic acid PFNA 1.8 9 ND ND ND
Perfluorodecanoic acid PFDA 1.8 ND ND ND
Perfluoroundecanoic acid PFUnA 1.8 ND ND ND
Perfluorododecanoic acid PFDoA 1.8 ND ND ND
Perfluorobutanesulfonic acid PFBS 1.8 345 2000 ND ND 1.8
Perfluorohexanesulfonic acid PFHxS 1.8 65 ND ND 2.9
Perfluoroheptanesulfonic acid 1.8 ND ND ND
Perfluorooctanesulfonic acid PFOS 1.8 15 0.02 ND ND ND
Perfluoropentanesulfonic acid 1.8 ND ND ND
9-Chlorohexadecafluoro-3-oxanonane-1-sulfonic acid 1.8 ND ND ND
Perfluoro(2-propoxypropanoic) acid 1.8 ND ND ND
11-Chloroeicosafluoro-3-oxaundecane-1-sulfonic acid 1.8 ND ND ND
4:2 FTS 1.8 ND ND ND
1H,1H,2H,2H-perfluorooctanesulfonic acid (6:2) 12 ND ND ND
1H,1H,2H,2H-perfluorodecanesulfonic acid (8:2) 1.8 ND ND ND
PFECA B 1.8 ND ND ND
PFECA F 1.8 ND ND ND
PFECA A 1.8 ND ND ND
PES 1.8 ND ND ND
DONA 1.8 ND ND ND
Perfluorotetradecanoic acid PFTA 1.9 ND ND ND
Perfluorotridecanoic acid PFTrDA 1.9 ND ND ND
N-ethylperfluorooctanesulfonamidoacetic acid NEtFOSAA 1.9 ND ND ND
N-methylperfluorooctanesulfonamidoacetic acid NMeFOSAA 1.9 ND ND ND
Sample Location - RHW1-R RHW2-R BPW-R

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.