State health officials said trace levels of contaminants have been detected in water samples collected at two Oahu drinking water sources, but remain safe to drink.

Dieldrin was found at the Pearl City Shaft, while Perfluoropentanoic acid, or PFPeA, was found at the Aina Koa Well I. Both drinking water sources are part of the Honolulu Board of Water Supply’s Honolulu-Windward-Pearl Harbor water system.

Health officials said drinking water from these sources remains safe, however, as the trace levels detected were far below health advisory limits.

Dieldrin — an organic chemical once used as a pesticide for controlling ground termites — is not regulated by the U.S. Environmental Protection Agency.

The detected levels in the Pearl City Shaft, according to officials, ranged from 0.0109 micrograms per liter to 0.0121 micrograms per liter, which is below the state’s health advisory of 0.2 micrograms per liter. The dieldrin may get into drinking by leaching into groundwater, officials said.

PFPeA is part of a group of chemical substances known as per- and polyfluoroalkyl substances, officials said, but are not regulated under any EPA advisories.

According to the nonprofit Environmental Working Group, PFPeA is a member of a group of perfluorinated chemicals used in many consumer products such as non-stick cookware and food packaging that can cause serious health effects. EWG says no national drinking water standard exists for PFPeA.

In April, the Hawaii Department of Health established a drinking water environmental action level for PFPeA of 0.80 micrograms per liter. The PFPeA level confirmed at the Aina Koa Well I ranged from 0.002 to 0.003 micrograms per liter.

“The trace levels of these chemicals are so small that they do not pose a public health threat, and the water from these wells is safe to drink,” said Kathleen Ho, deputy director for environmental health, in a news release. “The Department of Health will continue to work together with the Honolulu Board of Water Supply to ensure tests for these chemicals continue. Such testing is conducted to ensure that everyone’s water is safe and public health is not compromised.”

Officials said the BWS has been sampling their wells in advance of monitoring for perfluoroalkyl substances — expected to be an EPA requirement in 2023. To date, officials said, the Honolulu-Windward-Pearl Harbor water system continues to be in full compliance with all federal and state standards for drinking water.