Teflon tape is used to wrap the threads of a pipe to seal two pipes together. Credit: Linda Coan O'Kresik / BDN

Homeowners, water district operators and plumbers frequently wrap water pipes with plumber’s tape, which fills the spaces between interlocking pipe threads to seal the pipes and prevent leaks.

But the tape is made with a likely carcinogen called perfluorooctanoic acid, more commonly called PFOA, which is a type of “forever chemical” that has contaminated community water supplies and private wells across Maine and the country.

It’s not known whether the tape is contributing in a major way to the contamination, but some water district operators in Maine are beginning to grow suspicious of it, given their many miles of pipes to maintain and the common use of the tape. The tape is commonly referred to as Teflon tape, though chemical company Chemours said it has not authorized any plumber’s tape to be sold with the trademark name.

“All the systems have it. They were put together with it. Most of your shutoffs have Teflon in them. There are possibilities everywhere,” said Kevin Noyes, the public works director for Patten, which found 6.66 parts per trillion of PFAS, including PFOA, in one of its wells serving the town.

PFAS, or per- and polyfluoroalkyl substances, are a group of thousands of human-made chemicals commonly used in household and industrial products that have been linked to serious illnesses, including kidney cancer. 

Maine limits the amount of PFAS in drinking water to 20 parts per trillion. But the federal government issued a far lower, temporary recommendation for some specific chemicals in June. The U.S. Environmental Protection Agency says people’s exposure to PFOA, in particular through drinking water, should not exceed 0.004 parts per trillion over the course of their lifetime to avoid potential health problems.

The tape has not been tested to determine if it might leach into drinking water at either of these levels, however.

Frequently asked questions about pfas, answered

Maine requires materials that contact drinking water to be certified by NSF, an organization that determines if products comply with specific safety standards. NSF requires that certified plumber’s tape, which is also called PTFE tape, be tested annually, and it inspects facilities that manufacture the tape each year.

“Because PTFE materials are manufactured using perfluorooctanoic acid (PFOA) as a process aid … testing of PTFE materials requires analysis for PFOA,” said Kathryn Foster, senior operations manager for commercial water at NSF.

But when the tape is tested — to determine the quantity of contaminants that seep out when it’s exposed to water — NSF certification requires that the results not exceed an older and less stringent contamination threshold set in 2016 by the EPA: 70 parts PFAS per trillion parts water.

That’s 17,500 times the current, interim recommended level set this summer.

NSF does not require that the results meet the far lower benchmark because the EPA’s latest advisory level is temporary, Foster said. The EPA is expected to soon announce more permanent regulations that the NSF would adopt into its review of product safety, she said.

While the tape is applied to pipe fittings, rather than on the inside of the pipe where water flows, it is possible for the tape to tear and enter the system. 

“It should never be in any direct contact. That’s up to proper installation,” said Tyler Robinson of Mainely Plumbing and Heating in Gorham.

However, “I’m sure there are places where it’s in direct contact. My question is at what level it’s considered an issue,” said Robinson, who is also president of the Maine Plumbing-Heating-Cooling Contractors Association. 

It appears there is no settled answer to his question.

But Jean MacRae, an associate professor of civil and environmental engineering at the University of Maine, has a hunch that it’s unlikely a major source of contamination, especially given all the other potential sources of PFAS now in the environment. The toxic chemicals have been found in rainwater across the world, in addition to household dust. 

“It’s possible” the tape is contributing to contamination in drinking water, MacRae said, “but I would think it’s surely not going to be just that.” 

what we know so far

Some water districts discovering PFAS at levels that fall between the federal recommendation of nearly zero and the state requirement have been left feeling stuck, unsure how to pinpoint a source of contamination and how to address it.

The Newport Water District, for instance, found 2.23 parts per trillion of PFOA in its purified water. But it did not find the compound in its source of water, Nokomis Pond. That led Superintendent AJ Newhall to question whether the district itself was inadvertently contributing to the contamination. He plans to test again.

But he wonders about the effect of the tape, which he estimated he has used thousands of times.

“I’m interested in alternatives. I want everyone to have safe water to drink. That’s a human rights thing. At the same time, we have to look at it in a reasonable fashion,” Newhall said. 

That’s because there doesn’t appear to be a good available replacement for the tape.

“I think it’s not safe, but we don’t have another option at this point,” said Lisa Goodwin Robbins, an architect at Kalin Associates in Massachusetts who specializes in incorporating healthier materials into building design and technology. “We need to seal our pipes with something.”

Silicone-based thread-seal tapes are available but less common, according to the Green Science Policy Institute, which examined how to eliminate PFAS from building materials.

Goodwin Robbins is particularly concerned about the hazard the tape might pose to plumbers or others handling it frequently.

“Every plumbing fitting has Teflon tape on it. You would have it on your hands all day long,” said Goodwin Robbins, who is also chair of the Silent Spring Institute, which researches links between chemicals in everyday environments and health. 

The Maine Center for Disease Control and Prevention’s Drinking Water Program acknowledges that Teflon sealants, tapes or tubing might contaminate water. It warns water systems not to test for PFAS at locations with pumps or tubing that contain Teflon, to avoid getting a cross-contaminated sample. 

Massachusetts also notes the potential for contamination but does not prohibit the use of the tape in drinking water facilities. 

Massachusetts “has not heard a convincing argument that this type of application of Teflon tape is contributing significant amounts of PFAS,” reads a 2021 state summary of a Q&A session it held with public water systems. “This is not to say that we won’t identify this practice as a contributing PFAS source. The outstanding question is the scale of any potential contribution.”

Avatar photo

Erin Rhoda

Erin Rhoda is the editor of Maine Focus, a team that conducts journalism investigations and projects at the Bangor Daily News. She also writes for the newspaper, often centering her work on domestic and...