Credit: Newsday/Gustavo Pabon

Additional wells have to be tested in the Town of Islip near Long Island MacArthur Airport for a firefighter foam contaminant linked to several illnesses, officials said Friday.

The tests were ordered after samples from two private wells revealed amounts of the pollutant — perfluorooctane sulfonate, or PFOS — above the federal health advisory level of 70 parts per trillion, Suffolk health officials said in a statement.

Suffolk health officials did not immediately say how high a level of PFOS was detected in the wells or how many wells will be tested.

The contaminant, which can be especially harmful for unborn and breast-fed babies, has not been found in the public water supply.

In January, MacArthur Airport was listed as a possible Superfund site over concerns that firefighting foam used before 2000 might have fouled groundwater, state environmental officials said.

That announcement was made shortly after PFOS was found in a well in Bohemia, about 7,500 feet from the airport.

That well supplies the Suffolk County Water Authority. Its water was already being treated to remove PFOS.

The new tests will be conducted in the area bounded on the north by Peconic Street and the Long Island Rail Road; on the west by Louis Kossuth Avenue, Sycamore Avenue and Pond Road; on the east by Lincoln Avenue, Veterans Memorial Highway and San Souci Lakes; and on the south by the Great South Bay, Suffolk health officials said.

The tests — free for homeowners — will be done by a private laboratory hired by the state’s Department of Environmental Conservation, Suffolk’s statement said.

The DEC is also offering free bottled water to people who rely on private wells for drinking water in the testing sites, Suffolk health officials said.

PFOS, technically called perfluorinated compounds, do not break down easily in water.

Bathing and showering with water that contains them is not viewed as hazardous, officials said. But the compound can affect immune systems and cause thyroid problems, liver damage and certain cancers if people are exposed to them through water they drink or cook food in, according to the U.S. Environmental Protection Agency.

People can also be exposed through air, water or soil from industrial sources and from consumer products, Suffolk health officials said.

The EPA does not regulate the pollutant, which was also used in coatings that repel water, oil, stains and grease.

Two years ago, New York listed PFOS and a related compound known as PFOA as hazardous substances, which allows the state to regulate their use and go after polluters.

To sign up for well tests, homeowners should call Suffolk Health’s Office of Water Resources at 631-852-5810. People who do not know if their water comes from the Suffolk County Water Authority can call 631-698-9500.

Bottled water can be picked up at the Bohemia Recreation Center, 1 Ruzicka Way, between 7:30 a.m. and 2 p.m. daily.

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