For many Montanans, rivers and lakes are more than scenic landscapes. They are a source of food, recreation and identity. Anglers travel across the country to cast a line, and communities rely on these waterways as part of everyday life. But growing evidence shows that PFAS, a class of so-called “forever chemicals,” are contaminating Montana’s waters and fish.
Recent state studies confirmed PFAS contamination in fish across major Montana waterways, including the Missouri River, Clark Fork River, East Gallatin River and Fort Peck Reservoir. Testing detected these chemicals in popular species such as trout, walleye and northern pike. Larger fish showed especially high concentrations because toxins build up as they move up the food chain.
In some cases, concentrations reportedly reached levels experts say are thousands of times higher than what is considered safe for human consumption. These findings show that PFAS contamination is not isolated. It is present in some of Montana’s most heavily used fisheries.
PFAS, or per- and polyfluoroalkyl substances, are synthetic chemicals used in products such as firefighting foam, nonstick cookware, waterproof fabrics and food packaging. They are called “forever chemicals” because they break down extremely slowly and can remain in water, soil, wildlife and the human body for decades.
Research has linked PFAS exposure to serious health concerns, including certain cancers, immune system suppression, developmental issues in children, and hormonal and reproductive problems. Because these chemicals accumulate over time, repeated exposure through fish consumption may create long-term health risks.
In response, Montana agencies issued updated fish consumption advisories in 2026 warning residents to limit or avoid eating fish from certain waters. Recommendations include limiting the number of fish meals consumed each month and imposing stricter guidelines for women and children. These advisories, however, are only recommendations.
One of the most troubling aspects of Montana’s PFAS issue is how long it took for the public to learn about it. A key state report identifying high PFAS levels in fish was completed in 2023 but was not publicly released until 2026. Reports suggest state officials were aware of the contamination long before the information became widely available.
Although the state has issued advisories, the public still is not receiving adequate warning, information, or a plan to address this. Researchers also acknowledge that only a small portion of Montana waterways have been tested, meaning contamination could be more widespread than currently known.
The contamination is documented, the health concerns are real, and the exposure is significant. Montana’s ecosystem depends on what we do next.
Morgan E. Tuss of Billings is an attorney with Silverman Law Office.