TRURO — The wells at the Stone’s Throw condominium complex on Shore Road have edged past the state’s limit for contaminants known as PFAS — per- and polyfluoroalkyl substances — and solutions to the problem probably won’t be cheap.

The so-called forever chemicals are used in hundreds of products and remain in the environment for an unknown amount of time, according to the National Institute of Environmental Health Sciences. Researchers are concerned about their cumulative long-term health effects.

Stone’s Throw trustee Barbara Correa told the Truro Board of Health on Oct. 18 that the two wells serving the 28-unit complex initially tested above 10 parts per trillion for PFAS in March, which triggered a state requirement for monthly rather than quarterly testing.

Water testing has been done monthly since then at a cost of $1,000 each time — $12,000 annually.

The test results for July, August, and September averaged slightly more than the 20-parts-per-trillion (ppt) limit in the state’s regulations for public drinking water supplies, Correa said. She is discussing the situation with the Mass. Dept. of Environmental Protection (DEP) to see what the agency will require.

Edmund Coletta, DEP’s director of public affairs, said in an email that the test results were 15.2 ppt in July, 22 in August, and 23 in September. The average reading for the three tests was 20.1, which was rounded down to 20 — “equaling the standard but not exceeding” it, he said.

But the DEP has “strongly recommended” that the trustees notify condo residents, Coletta said.

“MassDEP has drafted a voluntary public education message, which will be provided to board members in hopes that they will share [it] with residents,” said Coletta. The state agency is working with the company that operates the water system at the complex “to determine the source of the PFAS contamination.”

Meanwhile, PFAS test results for October were again above the state standard at 21.7.

Massachusetts has one of the strictest limits in the country for PFAS in drinking water. The DEP’s limit of 20 ppt applies to the sum of sampling results for six different PFAS. They are perfluorohexane sulfonic acid (PFHxS), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA).

All municipal wells, along with water supplies that serve public venues like restaurants, hotels, and condominiums, must be tested.

The Mass. water standard is based on studies of PFAS compounds in laboratory animals as well as studies of exposed people, according to the state’s website. Exposure to sufficiently high levels may cause developmental effects on fetuses during pregnancy and in breast-fed infants. The state website also states there have been reports of effects on the thyroid, liver, kidneys, hormone levels, and immune system.

According to the state’s website, water that tests over the limit can still be safely used for bathing, since PFAS are not absorbed well through the skin. The water can also be used for washing dishes and even rinsing vegetables.

The ‘Forever Chemicals’

PFAS are a group of chemicals used since the 1940s in packaging materials, water- and stain-resistant and nonstick products, and foam used to extinguish fires. They are known as “forever chemicals” because they don’t break down easily and can be difficult to remove or mitigate.

If test results remain above 20 ppt, Correa told the board of health, bottled water would be supplied to condominium residents whose health is compromised while other solutions are worked on.

“Obviously, tying into public water is the best long-term plan for us,” Correa said. Some parts of Truro are on Provincetown’s municipal water line. Currently Provincetown has a water line on Shore Road about 500 feet from the Stone’s Throw property.

Provincetown Water Supt. Cody Salisbury confirmed he had a preliminary discussion with the condominium trustees regarding an extension of the water line. It would need a closer look to determine feasibility, Salisbury said, adding that the cost of the extension would have to be borne by the property owners.

Under the current agreement between Provincetown and Truro, the select boards in both towns would have to approve an extension of the water line.

The other option would be to install filters on the wells. Correa had a private company take a look at the well house. The building may have to be enlarged to house the filters, she said. Some piping would also need replacement.

Whether the solution is a water line extension or a filtration system, it will be costly. The cost of filtration alone is estimated at $50,000 to $60,000.

Correa told the board of health she has installed an individual reverse osmosis carbon filtration system under her sink as a temporary fix.

Board of health Chair Tracey Rose asked whether all unit owners could install those individual systems to address the problem. Correa said it would be up to the DEP as to whether the filtration systems could be installed individually under sinks or whether they must be on the wells. It would also affect testing.

“They do the testing at the well house, so they would have to pick certain houses to do the testing on,” she said.

Health Agent Emily Beebe called filtration at the individual units “a Band-Aid sort of solution.”

“It’s just at the point of use, not at the source, and the state is looking at the source,” Beebe said.

Rose felt it would still be worth installing such a system. “If I owned a unit, I would most definitely put in a short-term solution,” she said.

The board of health has continued the discussion to its Nov. 15 meeting, when both Beebe and Correa are expected to have more information.