A group of toxic chemicals found in firefighting foam has been detected in soil at Kahului Airport and in the groundwater below, according to the state Department of Transportation, with testing for the substances underway at other airports across the state.

The contaminated groundwater is not a source of drinking water nor a threat to nearby potable water sources, according to the state Department of Health.

Found in aqueous film-forming foam used by airport firefighters, the perfluoroalkyl and polyfluoroalkyl substances, dubbed PFAS, are linked to cancer and birth defects. They are known as “forever chemicals” because they don’t break down in the environment, inevitably accumulating in humans and other animals.

PFAS levels in Kahului Airport’s firefighting training pit were found to be 32 to 1,450 times greater than the state’s environmental action levels, which indicate a threshold below which no adverse effects are expected.

Groundwater affected by the PFAS contamination “has the potential to discharge into Kahului Bay” and is a “potential hazard to flora and fauna in the bay,” according to a remediation plan recently drafted by Environmental Science International Inc. and submitted to the Health Department.

The Transportation Department, which oversees state airports, is working in tandem with DOH to “address any issues that would arise out of the use of that foam,” said DOT spokesperson Shelly Kunishige.

With PFAS likely detectable “pretty much anywhere where the airport firefighters were using it for training,” Kunishige said DOT is testing training pit soil for PFAS at two pit sites at Hilo International Airport and individual sites at the Kahului and Lihue airports, Daniel K. Inouye International Airport in Honolulu and Ellison Onizuka International Airport at Keahole.

The sampling found PFAS levels above environmental action levels at the Honolulu airport, Kunishige said. “There’s no potential for direct exposure,” she said, because the site is fenced off in a secure area.

Concentrations of PFOS and PFOA, members of the PFAS chemical group, that are “near zero” can cause negative health effects, the Environmental Protection Agency announced in June. Evidence suggests that high exposure to PFOA and PFOS in drinking water can cause problems with cholesterol, immunity and thyroid gland function and decreased weight at birth, DOH said, and high-level, long-term exposure may lead to cancer. In lab animals, high exposure can cause developmental, reproductive, liver, kidney and immunological problems, the department said.

Six PFAS variants — PFPeA, PFHxS, PFHpA, PFHpS, PFOS and PFOSA — were found in groundwater below Kahului Airport at concentrations higher than DOH environmental action levels, according to the remediation plan. Five types — PFPeA, PFHxS, PFHpA, PFHpS and PFOS — were detected in recently installed monitoring wells closest to Kahului Bay.

The level of PFOS, perfluorooctanesulfonate, in the soil was measured at 0.8 parts per million, while the DOH environmental action level is 0.025 ppm, the department said. In the groundwater, PFOS was detected at 1,600 parts per billion, while its environmental action level for groundwater is 1.1 ppb.

State Sen. Gilbert Keith- Agaran, whose district includes Kahului, said he hopes for quick action and more information before the 2023 legislative session ends. “Because if we need to provide funding for them to actually implement, we’d like to have that addressed during the session,” he said.

“Because it’s not over an aquifer, that’s good. The biggest threat would probably be the county’s wastewater treatment plant,” which is close to the shoreline near the airport.

The proposed “interim direct exposure remedial action” comes in two phases: installing fencing and signage at the contaminated sites, completed last month, then removing the fencing and installing a geotextile fabric to prevent weeds from growing, adding 6 inches of asphalt and then building a bigger but still temporary fence.

The second phase is tentatively planned for March and, once complete, will remain “until a long-term remedial action is chosen and implemented,” which will likely take at least two years, the action plan said.