Officials Debate Whether Fort Peck’s Fish Are Too Polluted

Montanans who regularly eat fish harvested from some of the state’s most popular angling destinations may want to reconsider their diet. State agencies are directing people to limit their consumption of certain fish species found in the state’s rivers and reservoirs contaminated with PFAS, a class of chemicals linked to cancers and other serious health risks.

On April 23, a trio of state agencies updated the Montana Sport Fish Consumption Guidelines with new advisories that take into account concentrations of per- and polyfluoroalkyl substances, or PFAS, which have been dubbed “forever chemicals” due to their persistence in the environment.

According to those guidelines, women and children should avoid eating large walleye and northern pike from Fort Peck Reservoir, as well as brown trout from the section of Prickly Pear Creek downstream of the now-shuttered ASARCO lead smelter in East Helena. On a handful of other rivers and reservoirs, such as the East Gallatin River, Nelson Reservoir and Yellowstone River, the guidelines advise limiting consumption of other fish species ranging from channel catfish to mountain whitefish and smallmouth bass.

Current PFAS Advisories

The state released an advisory in April 2026, directing people to limit their consumption of certain game fish in all or parts of the following waterways: East Gallatin Fort Peck Reservoir Lake Helena Missouri River Nelson Reservoir Prickly Pear Creek Yellowstone River The Montana Department of Environmental Quality did not make any of that immediately clear in its press release. Instead, it wrote that PFAS are considered “emerging contaminants of concern,” and highlighted PFAS-associated health risks alongside the dietary advantages of eating fish. “While it is important to be aware that eating fish caught in Montana may expose individuals to low levels of PFAS in some waterbodies, eating a moderate amount of a variety of fish can provide significant health benefits for many people,” the agency wrote.

The calculations that underpin the state’s recommendations have come under scrutiny following a years-long investigation by Montana PBS. According to a 30-minute documentary reported and produced by the station’s Anna Rau, Gov. Greg Gianforte intercepted the monitoring report, delaying updates to the consumption advisory designed to help Montanans understand where game fish are safe to eat, where they should be consumed sparingly, and where they’re too contaminant-laden to eat at all. According to Rau’s reporting, DEQ and other state agencies prepared to implement a more stringent standard for fish consumption only to change course when faced with the number of “do not consume” advisories the stricter standard would have generated for popular fishing destinations like Fort Peck Reservoir, the lower Yellowstone River and the middle section of the Missouri River. Just hours before the documentary’s broadcast on April 23, the state released complicated guidance that left Montanans wondering if their local waters are too contaminated with forever chemicals to eat their catch.

The documentary has anglers like Russ Earl, a Havre resident, concerned. Earl doesn’t plan to eat what he catches when he fishes Fort Peck Reservoir and upstream stretches of the Missouri for catfish, bass, sturgeon, walleye and salmon later this year.

“What bothers me the most is the apparent possible delay and semi cover-up of the original report,” he wrote in a message to MTFP. “Unfortunately, I think this is the tip of the iceberg and more and more studies will find more and more PFAS through our food chain.”

Earl is not alone in trying to make sense of the state’s response to its own data. To better understand how the Montana Interagency Fish Consumption Advisory Group reached its guidance — and the diet shift that frequent fish consumers should contemplate — Montana Free Press spoke with PFAS experts and state and local regulators. This is what we found. The PFAS-Fish Connection

PFAS are a class of chemicals that manufacturing companies have long prized for their lubricant properties and their ability to resist grease and stains. There are so many of them — up to 14,000 by some counts — that federal agencies have struggled to regulate the chemicals. PFAS are frequently present in nonstick cookware, water- resistant outdoor apparel, personal-care products, food and beverage packaging, pesticides, the biosolids produced by wastewater treatment plants, and a variety of industrial applications, including firefighting foam.

PFAS received the “forever chemicals” moniker because they don’t break down the way other chemicals do. They’re also highly mobile and widespread. According to DEQ, PFAS have been detected in the blood of people and animals around the world.

That’s a problem because PFAS pose serious health threats. According to Julia Varshavsky, an environmental health professor at Northeastern University and member of the PFAS Project Lab, a growing body of research has demonstrated the link between PFAS exposure and low birth weights, preterm births, high cholesterol and diminished immune response. PFAS exposure is also associated with testicular and kidney cancer.

Researchers pay attention to the accumulation of PFAS in fish — freshwater fish in particular — because fish living in PFAS-contaminated waters are what’s called a bioaccumulator.

“When they get into an animal’s body they distribute to the fat tissue, and then because that gets concentrated and stuck in the fat tissue, the next higher-up animal on the food chain that eats the smaller one will further and further concentrate that PFAS,” Varshavsky said, pointing to fatty, predatory freshwater fish as particularly worrisome bioaccumulators.

Varshavsky added that the most important PFAS exposure pathways, based on what we currently know, are water and diet. When it comes to fish, she said there are no overarching federal regulations the way there are with PFAS in drinking water, for example.

Instead, states have developed their own standards that attempt to weigh the PFAS ingestion risks against the health benefits of eating fish, which are a source of lean protein, healthy fats, and essential vitamins and minerals. The result is a patchwork of recommendations. Some states, such as New Jersey and Michigan, have opted for stricter frameworks, some have adopted looser regulations, and some haven’t produced any guidance at all. Montana falls somewhere in the middle. Montana’s Forever Chemical Guidance In Montana, the conversation surrounding PFAS accumulation in fish dates back to 2020 when the state adopted the Montana PFAS Action Plan. That document was designed to reduce or eliminate human health and environmental risks posed by PFAS. It directed the state to identify sources and exposure pathways, to sample fish in PFAS-polluted water bodies and to develop fish consumption advisories.

The bulk of Montana’s monitoring occurred in 2023, when DEQ partnered with Fish, Wildlife and Parks and the Department of Public Health and Human Services to collect samples of common game fish at 14 sites located along nine waterbodies where PFAS is a known concern.

Lab results found at least one type of PFAS was present in 78 percent of the samples submitted. Of the 40 PFAS the lab tested for, the type that appeared most frequently was perfluorooctanesulfonic acid, or PFOS, a chemical commonly found in firefighting foams used at airports and military bases. Thirty-nine of the 50 fish samples sent to the lab for analysis contained PFOS.

After the concentrations came back, state employees working on the report debated how to interpret the results in order to develop updated fish consumption guidance. Materials submitted to PBS in a public records request reviewed by MTFP show that DEQ contemplated using two different calculations to translate fish-tissue concentrations into the fish-consumption advisories, which are designed to “help ensure that the fish you catch can be a safe part of your diet.”

One standard, based on guidance provided to DEQ by the U.S. Environmental Protection Agency in 2024, would have led to sweeping fish-consumption advisories. According to a June 2024 email from DEQ’s toxicologist and included in the PBS FOIA request, the EPA’s formula would have resulted in a different conclusion.

Proposed Guidance

Had the state used a stricter standard in its fish consumption calculations, far greater protective guidance would be in place. People would have been advised to avoid eating certain game fish, rather than limiting their consumption, in parts or all of the following waterways due to PFAS contamination: East Gallatin River Fort Peck Reservoir Lake Helena Missouri River Nelson Reservoir Prickly Pear Creek Yellowstone River “We find that the PFOS concentrations found in sampled fish end up corresponding to an ‘avoid all consumption’ advisory in all water bodies where PFAS is detected, including some very popular fishing destinations,” DEQ toxicologist Dawn Nelson wrote in the email.

Records show that had the state used the EPA’s standard for safe levels of PFOS — one of the most prevalent forever chemicals — popular game fish like walleye, brown trout, rainbows and smallmouth bass would have been subjected to an “avoid” advisory in certain waterways.

Instead of using that standard, the state decided to use a looser standard recommended by a different federal agency, the Agency for Toxic Substances and Disease Registry. That standard didn’t result in any broad “do not consume” advisories.

DEQ defended the use of the looser standard in an email to MTFP, writing that 20 states have used it “or something very similar to it.” Spokesperson Madison Mc-Geffers added that the federal government has found that PFOS levels in fish tissue are trending lower across the U.S.

Asked to respond to allegations that his office interfered with the release of the PFAS fish tissue report, a spokesperson from Gianforte’s office focused on the April 2026 report. “The governor was not involved in the decision as the timing of the release of the report was related to the fact that members of Interagency Fish Consumption Advisory Group reached consensus on using the health guidance value from Agency for Toxic Substances and Disease Registry in late 2025,” the spokesperson wrote.

Rau, with Montana PBS, argues that Gianforte is “splitting hairs” in his response by focusing on the report that came out last month — not the draft report that preceded it. As evidence to support her position, she points to a Feb. 14, 2025, email in which a DEQ employee directs her colleagues not to reach out to stakeholders about the release of the draft report because “the governor’s office may not want us to release the draft report.”

Varshavsky, the PFAS researcher, said Montana is not unique in wrestling with the political implications of PFAS regulation, particularly in the face of burgeoning data-center development. The semiconductors that are integral to data center operations — and the coolant to keep them from overheating via “closed loop” cooling systems — are common sources of PFAS, according to Varshavsky.

“It shouldn’t be polarizing to say that we need policies that protect public health, but unfortunately it kind of is,” she said. “It’s not necessarily that it’s a [political issue] for regular people, but it has become a political issue in these decision-making contexts where you have industries lobbying lawmakers.”

For her part, Rau said the state’s abrupt course change paired with the concentrations present in Missouri River and Fort Peck Reservoir fish, have crystallized her own views on the issue.

“I wouldn’t in a million years feed my kid a fish out of Fort Peck right now,” she told MTFP. “I just wouldn’t, for safety’s sake.”