PORTSMOUTH — The Environmental Protection Agency could be just weeks away from developing a lifetime health advisory for a toxin that closed the city-owned Haven well and has contaminated a growing number of water supplies in New Hampshire.

Jim Murphy, the team leader for community involvement and government relations for the EPA’s Boston office, said “we’re hoping it’s just a matter of weeks now” before his agency sets the permanent health advisory for PFOA.

The city of Portsmouth closed the Haven well in May 2014 after the Air Force found levels of perfluorooctane sulfonic acid 12.5 times higher than the EPA’s PHA.

The EPA classified PFOS and perfluorooctanoic acid, or PFOA, which was also found in Haven well but below health advisory levels, as “contaminants of emerging concern.” PFOS and PFOA are a class of chemicals known as perfluorochemicals. PFCs were also found in the city-owned Smith and Harrison wells at Pease International Tradeport but never above the PHA.

The EPA has not set an enforceable drinking water standard for PFOA under the federal Safe Drinking Water Act, the state Department of Environmental Services said in a recent press release about PFOA found in wells in Merrimack and Litchfield.

EPA’s Office of Water has, however, established a Provisional Health Advisory (PHA) of 400 parts per trillion for PFOA, but that level is only for short-term contact, it acknowledged.

DES is now providing bottled water for anyone whose wells test above 100 parts per trillion.

That action comes as both Gov. Maggie Hassan and U.S. Sen. Kelly Ayotte, R-N.H., have called on the EPA to expedite its effort to set a lower health advisory for PFOA because of the potentially dangerous and serious health effects from exposure to the contaminant.

Shawn Garvin, Region III EPA administrator, said the “EPA is in the process of developing an updated lifetime health advisory for PFOA based on the best available science.”

Garvin, in a letter to attorney Robert Bilott of Cincinnati, Ohio, who has represented thousands of people exposed to PFOA, said that once the lifetime health advisory is established, it will “supersede the agency’s provisional value for PFOA.”

He predicted the lifetime health advisory would be set “this spring.”

Bilott, in a letter to Tom Burak, commissioner of New Hampshire’s Department of Environmental Services, said the science panel was established after a class action lawsuit was filed because of PFOA exposure Ohio and West Virginia.

As part of the settlement of the case filed by about 70,000 people, the so-called “C-8 science panel” spent more than seven years and $30 million studying the effects of PFOA exposure, he said in the letter.

The panel determined human exposure to even low levels of PFOA caused “six serious diseases,” Bilott said, including kidney and testicular cancer, thyroid disease, hypertension and high cholesterol.

He chided the DES for saying health effects from PFCs are inconclusive, saying that claim is “inaccurate and ignores the vast wealth of published, peer reviewed and independent C-8 Science Panel Research.”

In the letter, Bilott also noted that EPA’s Science Advisory Board “recommended that PFOA be characterized as a ‘likely’ human carcinogen almost a decade ago.”

“Given the biopersistent nature of PFOA – meaning that even the tiniest, barely detectable amounts in drinking water will build up in the human body over time – and the finding of adverse health effects in laboratory studies at lower and lower dose levels, many scientists are questioning how a ‘safe’ level can ever be set for PFOA in drinking water,” Bilott said in the March 8 letter.

Sarah Vose, state toxicologist for Vermont, confirmed this week that her state set its PFOA drinking water guidelines at 20 parts per trillion, well below the 400 parts per trillion PHA set by the EPA.

Vermont’s level was set after looking at the draft health effects determined by the EPA in 2014, Vose said.

“You take a look at the toxicity value and you combine that with the exposure and that gives you the value,” she said this week.

She noted PFOA exposure is “particularly concerning” because “it has a very long half life in the body.”

She also pointed to the correlation of adverse health effects caused by PFOA exposure.

“When you combine that with the fact it’s in your body two to four years, those two things led us to the conclusion this should be mitigated,” Vose said.

The level of concern people exposed to PFOA should have should be based “on what level is found in their water and how long they’ve been drinking it,” Vose said.

Andrea Amico, the Portsmouth mother whose two children attend day care at the former Pease Air Force Base where PFCs led to the closure of the Haven well, said she applauds “the efforts of Sen. Ayotte and the governors of New York, Vermont and New Hampshire in their recent letters to the EPA advocating for an expeditious decision on lower standards for PFOA.”

“If the EPA continues to delay their decision on standards, I would like to see New Hampshire take a much more proactive and progressive stance and set their own standards for PFCs as seen in other states such as New York, New Jersey and Vermont,” Amico said.

She noted the former Pease Air Force Base, which is now a Superfund cleanup site is “not the only New Hampshire community facing PFC contamination in their drinking water.”

“The state owes it to the many communities dealing with PFCs in their drinking water to have standards that are protective of our health and should not delay setting a standard any longer,” Amico said.

Portsmouth’s Deputy Public Works Director Brian Goetz acknowledged that if the EPA lowered the PFOA standard, it could have wide-ranging implications on communities.

“You’ve got something now that’s in the news and there’s a lot of sites being tested,” Goetz said.

He noted the city is working to design a new carbon filter system to treat all three city-owned wells at Pease.

City officials are still searching for a site for another well, but he acknowledged the Air Force shifted its priorities to treat the tainted wells at Pease first.

“The city will get that volume of water through treatment of the Haven Well,” Goetz said.

The city still hopes to have test wells established for a new water source by the fall, noting “treatment isn’t going to happen right away.”