EPA to conduct PCB sampling in the Clark Fork, Bitterroot and Blackfoot rivers 

DENVER (August 20, 2026) – Today, U.S. Environmental Protection Agency (EPA) announced it will conduct a sampling project in the Clark Fork, Bitterroot and Blackfoot rivers to better understand the distribution of polychlorinated biphenyls (PCBs) across the watershed.  

These persistent chemicals were widely used in industrial applications until production was banned in 1979. They can cause a variety of health concerns in humans and do not easily break down in the environment. Over time, they can build up in plants and animals, having an increasing impact through the food chain. The Montana Department of Fish, Wildlife and Parks and the Confederated Salish and Kootenai Tribes have issued PCB-related fish consumption advisories for all waterways expected to be sampled in this project.  

“EPA is committed to strengthening the scientific foundation needed to better understand PCB contamination across these important Montana watersheds,” said Cyrus Western, EPA Region 8 regional administrator. “This project reflects our commitment to responsive science, meaningful community engagement and a clearer understanding of conditions in the Clark Fork, Bitterroot and Blackfoot rivers.” 

The sampling project is being led by EPA Region 8 scientists in the Laboratory Services and Applied Sciences Division, with support from EPA’s Office of Applied Science and Environmental Solutions. 

Tribes, state agencies, community advisory groups and organizations have consistently expressed interest in understanding PCB contamination in these rivers. EPA’s current effort responds to those concerns and will help fill important data gaps related to the current spatial distribution of PCBs. 

While past federal and state sampling has focused on fish tissue and human health exposure through consumption, this project will take a broader look at PCB distribution by analyzing sediment and aquatic insects and will extend 100 miles upstream of the confluence of the Clark Fork and Flathead Rivers.  This expanded scope will help provide a more complete picture of PCB levels in the Clark Fork, Bitterroot, and Blackfoot watersheds.  

Sampling is expected to occur from late August through early September 2026 with results expected in the summer of 2027. 

For more information about EPA’s work in the region, please visit https://www.epa.gov/aboutepa/epa-region-8-mountains-and-plains.