A Hampton Bays Fire District parcel on Montauk Highway may be added to the state Superfund list after contamination from perfluorinated compounds was discovered nearby, most recently in May, and the local water district took two drinking water wells out of regular service, officials said.

It is the third firefighting or training site on Long Island in the past 14 months to come under state Department of Environmental Conservation scrutiny because of detections of perfluorooctanoic acid and/or perfluorooctanesulfonic acid, known respectively as PFOA and PFOS.

The compounds do not break down easily in water and exposure can affect the immune system and fetal health and development, and also can cause liver damage, cancer and thyroid problems, the U.S. Environmental Protection Agency has said.

Both in May and last year, the Hampton Bays Water District took wells offline after detections exceeded a federal health advisory level, Superintendent Robert King said. The district, which has 11 wells, serves more than 7,200 commercial and private water accounts.

“The detection was there and we took it immediately offline,” King said. “We’re hopefully going to be putting in a treatment.”

The compounds are not regulated in drinking water supplies, but the EPA has a health advisory level of 70 parts per trillion for combined PFOA and PFOS.

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If that level is hit, the federal agency said water suppliers should confirm the results and notify health officials and consumers. There are no requirements for wells to be closed, for supplies to be blended to lessen concentrations or for removal systems to be installed.

The DEC notified the fire department in July that it was listing the 2-acre property, where the firehouse is located, as a potential hazardous waste site.

At the time, the agency said the fire department could do its own investigation. When there was no response, officials said, the DEC sent another letter in late August saying the state would proceed with a probe.

“The intent is to find the source of the contamination,” said Martin Brand, DEC’s deputy commissioner of remediation and materials management.

The fire district’s attorney, Stanley Orzechowski of East Northport, said the department will cooperate but the data must be evaluated.

“If it’s something we have to deal with, we’ll deal with it,” said Kevin Kenny, chairman of the Hampton Bays Fire District. “We’d like to figure it out ourselves.”

The DEC decided to take a look at Hampton Bays after the water district wells saw detections and county monitoring wells installed near the water district also got hits. The fire department, in response to a DEC survey conducted statewide last year, said it had used or stored fire suppression foam.

“We hope it’s not a source,” Brand said of the fire district, “but obviously there is something out there that is contributing PFOS/PFOA to the local wells and we need to find out where it is coming from.”

In May, the DEC added the 28-acre Suffolk County fire academy in Yaphank — known as Firematics — to the Superfund list. And last September, Gabreski Air National Guard Base in Westhampton Beach also was added because of PFOS contamination, detected through a federal survey of water supplies nationwide.

The Suffolk County Water Authority and the county have worked to connect homes with private wells near the Yaphank and Westhampton sites to the public water supply.

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Activated carbon systems can remove the compounds from drinking water.

“If there’s a positive development with [perfluorinated compounds], it’s that our most common treatment method is effective in removing it,” said Jeff Szabo, the water authority’s chief executive officer.

The organic compounds, commonly used in firefighting foams, also were used to make water- and stain-resistant carpets, fabrics, furniture and other materials. Manufacturers voluntarily phased out production in the United States about 15 years ago, according to the EPA.

“Once they get into groundwater . . . these fluorinated chemicals don’t break down over time,” said Laurel Schaider, a research scientist with Silent Spring Institute, a nonprofit research organization in Newton, Massachusetts. “They will travel long distances with the water.”

Attention to the compounds increased in late 2015 when PFOA at 400 parts per trillion was detected in the public water supply of upstate Hoosick Falls and the EPA recommended that people not drink the water or use it for cooking.

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The DEC subsequently named Saint-Gobain Performance Plastics Corp. and Honeywell as responsible parties.

In early 2016, New York listed PFOA and PFOS as hazardous substances, allowing the state to regulate use and go after polluters. Later that year, the agency sent surveys to 2,500 entities statewide inquiring about the use, storage, handling, release or disposal of perfluorinated compounds used in fire suppression.

Nearly 300 surveys were sent to Long Island locations, including fire departments, airports, storage facilities, companies and military installations. Of those, 114 respondents said that the fire suppression foam had been used or stored in some manner.

Only two of those — the Hampton Bays Fire District and Firematics — were within one-half mile of public or private water wells, prompting state action.

“Public water supplies and private supplies are absolutely our highest priority,” Brand said. Of the other positive responses, he said, “Eventually we’ll address all of these in some way.”