Jim Stahlnecker, a biologist with the Maine Department of Environmental Protection, stands inside the department’s boat barn in Augusta on March 17. Stahlnecker has been testing for PFAS chemicals in mussels and clams since 2013 and has recently expanded the sampling to include lobsters and inshore fish species. Gregory Rec/Staff Photographer

New research suggests that the amount of toxic “forever chemicals” in some of Maine’s freshwater fish and shellfish might make them hazardous for consumption.

Most of the discussion in Maine around per-and polyfluoroalkyl substances, or PFAS, has centered on farms, but the chemicals’ presence in the state’s freshwater fish has been known for at least a decade.

The Maine Center for Disease Control and Prevention is weighing whether to impose stricter standards and issue consumption advisories for PFAS in freshwater fish to better reflect the latest science. But the state CDC doesn’t directly regulate seafood products, and the U.S. Food and Drug Administration has yet to offer any guidance on safe levels of PFAS in shellfish or other seafood.

Any state consumption advisories likely would be along the same lines as those already in place for mercury levels in freshwater species in Maine lakes, ponds, rivers and streams. The warnings wouldn’t apply to seafood caught in the ocean or found in grocery stores.

PFAS are a class of over 4,000 manmade chemicals that have been used since the 1950s in industrial and household products such as waterproofing or anti-stick coatings and in firefighting foam. Exposure to PFAS can increase the risk of kidney and testicular cancer, lead to high blood pressure or pre-eclampsia in pregnant women, cause changes in liver enzyme levels, and decrease how well children respond to vaccinations.

The Maine CDC sets thresholds, or “action levels,” over which it would consider issuing a consumption advisory for recreationally caught freshwater fish. Over the years, it has adjusted the action level for perfluorooctane sulfonate, or PFOS, the most commonly found and studied of these compounds, which now stands at 34 parts per billion.


But State Toxicologist Andy Smith said he and his team are working to adjust the action level for PFOS to “about 10 times less than it is now” based on new toxicology data from the federal Agency for Toxic Substances and Disease Registry, setting the PFOS toxicity value at 2 nanograms per kilogram per day.

Dropping the action level to 3 or 4 ppb would bring many of the samples the Maine Department of Environmental Protection has collected over the hazard threshold. For more than half of the sites and species sampled in 2019 and 2020, the department found average concentrations of more than 4 ppb, according to a dataset provided by DEP Aquatic Toxicologist Tom Danielson.

Due to the presence of mercury, Maine CDC already has a fish consumption advisory in place. Pregnant women and children are advised not to eat any freshwater fish from Maine inland waters, and all others should limit their consumption to two meals per month, or one meal per week for brook trout or landlocked salmon. Certain polluted waterbodies have greater restrictions. Smith said that when considering whether to issue a PFAS-related advisory, Maine CDC would evaluate whether more restrictive advisories are needed compared with those currently in effect.

The presence of forever chemicals in Maine fish started to become known about 10 years ago, when the U.S. Environmental Protection Agency sampled fish from five rivers in Maine as part of a national survey of urban waterways across the country and found smallmouth bass with elevated concentrations of PFOS in the Androscoggin River in Lisbon and the Kennebec River in Waterville.

Scientists in DEP’s Surface Water Ambient Toxics, or SWAT, monitoring program began sampling in streams around the former Loring Air Force Base, a site used for firefighter training activities, after the chemicals were found during federal cleanup efforts there. They found  brook trout in the area with PFOS concentrations as high as 1,080 ppb, and all but one was over the Maine CDC’s action level at the time of 42 ppb. That prompted the team to collect more samples. They looked in areas with potential sources such as wastewater treatment plants, industrial areas or downstream of farms where PFAS-contaminated sludge may have been spread.

Since 2014, they have found elevated PFOS concentrations in fish at various locations downstream of industrial sources and wastewater treatment plants on the Mousam, Presumpscot, Androscoggin and Kennebec rivers, and in Estes Lake. They also found fish with slightly elevated concentrations of the chemical in Halfmoon Stream below a farm in Thorndike.



While his counterparts on the freshwater team were finding forever chemicals in freshwater fish, Jim Stahlnecker, a biologist with the DEP’s Bureau of Water Quality, started wondering if they might be in shellfish, too. He had been testing blue mussels for other toxins such as heavy metals, dioxins and PCBs for the marine section of the SWAT monitoring program. In 2013, his team started testing some mussels and clams for PFAS.

It found the water- and oil-repellant paper coating ingredient known as perfluorooctane sulfonamide, or PFOSA, in mussels at East End Beach in Portland. The team didn’t detect any of the 12 other compounds it tested for, nor did it detect anything in mussels at Sears Island in Searsport or in softshell clams from the Presumpscot River or the Piscataqua River.

But at the time, the testing method used to measure PFAS in shellfish samples couldn’t detect concentrations lower than single-digit parts per billion, depending on the compound. Some consumables such as drinking water are regulated based on parts per trillion of PFAS.

In 2014, Stahlnecker and his team looked for blue mussels in Harpswell Cove, near the former Brunswick Naval Air Station, another base where firefighting foam was used extensively. The mussels weren’t located as close to the station as they would have liked, but they sampled some partway down the cove. Concentrations of PFOSA ranging from 0.68 to 0.80 ppb were detected in the samples. Later, they sampled  softshell clams closer to the station did but not detect any PFAS chemicals.

Then, in 2020, Brunswick Citizens for a Safe Environment had more testing done, this time on the marsh species known as ribbed mussels from the mouth of Mere Creek, close to where the clams were sampled. They found PFOS at concentrations of up to 0.98 parts per billion with diminishing concentrations from north to south in the cove, and none in the control samples.


David Page, a retired Bowdoin College professor of chemistry and biochemistry who authored a report on the study, said it was designed to answer a simple question: Were the chemicals associated with activities at the Brunswick Naval Air Station migrating offsite and affecting biological communities in Harpswell cove?

“The answer was unequivocal,” Page said. “Part of the reason we asked the question was the Navy was reluctant to say there were any PFAS outside of base boundaries. Now it’s clear that that’s not true.”

The study prompted the Navy to include mussel sampling in this year’s monitoring plans for the now-redeveloped former Naval Air Station, he said.

The fact that different organisms in the same area may or may not collect different chemicals is one of the complications to the state’s sampling methods. While the DEP has been sampling fish muscle tissue and the portions of shellfish that humans eat, for the purpose of providing data from a human health perspective, that may not be capturing the whole picture.


Dianne Kopec, a research fellow at the University of Maine’s Sen. George J.  Mitchell Center for Sustainability Solutions, has spent her career looking into the way another contaminant, mercury, moves through aquatic food webs, such as from fish to harbor seals. She is working now with a team to study how PFAS moves between soil, groundwater and surface water, and is hoping to expand her work to study the movement of the chemicals from organism to organism. And the chemicals are moving to wildlife – an advisory was issued on deer meat in the Fairfield area last fall when five deer were found with PFOS concentrations of 37 to 44 ppb.


Research shows that various PFAS chemicals not only behave differently from mercury but also differently from each other, Kopec said. For one thing, rather than collecting in fish muscle, some of the compounds appear to be collecting in other parts of the body such as the liver or eggs, which affects other animal predators more than humans.

“Predators eat the whole fish, not just the muscle tissue,” she said.

Another difference from mercury is that the concentration of PFAS doesn’t appear to increase with the age and size of the fish, which Kopec speculates might be because in females, it may be transferred to the eggs. PFOS appears to accumulate higher up the food chain more than other compounds do, but she said that may be because other chemicals transform into it. PFOS is a legacy chemical that has largely been phased out, but newer replacement chemicals such as PFOSA are known to break down into the more persistent PFOS.

As scientists try to understand the movement of forever chemicals in the environment and between organisms, states are continuing to work toward understanding the risk to people through consumption.

In New Hampshire, the state Department of Environmental Services is partnering with scientists at Dartmouth College to study potential exposure through recreational shellfish harvesting near the former Pease Air Force Base, another firefighter training site. Megan Romano, an environmental epidemiologist, and Celia Chen, an aquatic ecologist, are including a survey of residents to get a sense of seafood consumption patterns. Their preliminary research indicates that average to frequent consumers of shellfish could be exceeding the minimum risk level for certain PFAS compounds as defined by the federal toxic substances registry.

“The project Dr. Chen and I are working on is really rooted in this idea that seafood are a potentially underappreciated source of exposure to PFAS,” Romano said.



Back in Maine, Stahlnecker and his team have expanded their sampling for the chemicals in blue mussels. Now, testing has improved and can detect concentrations down to about 0.2 ppb for some compounds. The breadth of detectable compounds has also increased to 33.

In 2019 and 2020, the team sampled mussels from 24 sites near potential sources and picked up low levels of about 10 different compounds, again the most common being PFOSA. It was showing up at the detection limit here and there along the coast, but was as high as 3.4 ppb in the western Casco Bay-Portland area, the lower Kennebec River, and one site in the lower Penobscot River.

For the rest of the detected compounds, the results were hit or miss, Stahlnecker said, with one compound detected at one site, another compound detected at another site, and often they were right at the minimum detection limit.

“The take-home is, we know there’s PFAS,” he said. “It’s all over the place, at very, very low levels.”

They only found PFOS, the compound seen most in freshwater fish, in one spot: at the heavily industrialized estuary of the Fore River in Portland, an area that is permanently closed to shellfish harvesting because of its proximity to wastewater treatment plants. It was the first time DEP detected the compound in shellfish in five years of sampling. The highest concentration found there was around 0.45 ppb.


“But it is hard to know what to compare that to,” Stahlnecker said. Maine CDC’s current fish tissue action level of 34 ppb does not offer direct guidance on seafood.

“We’re talking about shellfish, not finfish, marine waters not fresh, and the big thing is the consumption,” he said. “If you live on a pond or at a camp and you’re catching bass in front of your house, you might eat one of those every two weeks in the summer, so … that factors into how frequently you can take this in. If you take it in more often, the dose you can take in each time has to be lower, so it is not really applicable.”

State toxicologist Smith said the Maine CDC can, at the request of the Department of Marine Resources, develop action levels for marine species, but it hasn’t done so for PFAS in marine fish or shellfish.

As regulators gather more information, DEP scientists are continuing their testing efforts. This year, Stahlnecker is partnering with the marine resources department to expand sampling for the chemicals to include other marine species such as lobster, pollock, striped bass and bluefish.

“We’re generating this data (which can be used by others to develop advisories), but we don’t issue advisories or tell people what to do,” he said. “We’re trying to figure out what’s out there.”

Romano, who has spent much of her time studying exposure to mixtures, and she believes that when it comes to setting consumption guidelines for PFAS chemicals, they must be taken in combination.

“There are more than 4,000 to 5,000 of these PFAS,” she said. “More than 1,000 are commonly used in industrial applications, so we’re likely to be exposed to them in our daily lives. We simply can’t go one by one to regulate them.”

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