PFOS Detected in Pepe‘ekeo Water System, Kula‘imano Well A, Within EPA Acceptable Standards

PFOS Detected in Pepe‘ekeo Water System, Kula‘imano Well A, Within EPA
Acceptable Standards
HILO, HAWAI‘I – The Department of Water Supply (DWS), County of Hawai‘i, detected low
levels of Perfluorooctanesulfonic acid (PFOS) for the first time in Kula‘imano Well A (makai)
during voluntary drinking water well testing across the island. PFOS is part of the group of
perfluoroalkyl and polyfluoroalkyl substances (PFAS). DWS reported the findings to the Hawai‘i
Department of Health (DOH) in accordance with Hawai’i State Law.
The testing results ranged from 2.6 to 3.0 nanograms per liter (ng/L). These results are within the
acceptable limits of the safe drinking water standards set by the Environmental Protection Agency
(EPA). The EPA’s Maximum Contaminant Level (MCL) for PFOS is 4.0 ng/L.
Site & Sampling Point Analyte Date Result Unit EPA Test
Method
KULA‘IMANO WELL A WELL HEAD,
WL002 PFOS 8/18/25 3.0 ng/L* 533
KULA‘IMANO WELL A WELL HEAD,
WL002 PFOS 8/18/25 2.6 ng/L* 537.1
KULA‘IMANO WELL A CHL WELL OUT.,
TP002 PFOS 9/16/25 2.6 ng/L* 533
KULA‘IMANO WELL A WELL HEAD,
WL002 PFOS 9/23/25 2.7 ng/L* 533
Table 1: August and September 2025 Kula‘imano Well Sampling Results.
*One ng/L equals one part per trillion.
Kula‘imano Well A is one of two groundwater sources in the Pepe‘ekeo Water System. The
primary groundwater source is Kula‘imano Well B (mauka), currently under repairs.
PFAS are concerning for their persistence in the environment and links to adverse health outcomes
in humans and animals, especially at high concentrations or with long-term exposure. PFOS is one
of thousands of human-made compounds that have been commonly used in non-stick, non-stain,
and water-resistant industrial and household products since the 1940s. In 2002, the primary US
manufacturer of PFOS voluntarily phased out production of this chemical compound.
“Our customers’ safety is our top priority,” said Keith Okamoto, DWS Manager-Chief Engineer.
“Although the new federal compliance regulations do not take effect for a couple of years, we did
not want to wait to act. We are proactively sampling active drinking water sources across the island,
over 60 locations, by the end of the year.”
Okamoto added, “The drinking water DWS provides meet all federal and state drinking water
standards – it is safe to use and drink. While I am proud of our proactivity and openness on the issue
of PFAS, it’s important to know most peoples’ exposure comes from everyday products – nonstick
food packaging, stain-resistant fabrics and upholstery, and cosmetics, to name a few.”
In addition to sampling its wells, DWS will be testing the use of granular activated carbon for PFAS
treatment implementation. The tests are scheduled to begin in early 2026.
For more information about PFAS, visit the Hawai‘i Department of Health’s webpage:
https://health.hawaii.gov/heer/environmental-health/highlighted-projects/pfas or EPA’s website at
https://www.epa.gov/pfas.