On April 30, President Trump issued a presidential authorization for the construction and maintenance of the Bridger Pipeline – a 645-mile crude oil transmission system designed to transport 1,047,000 barrels of tar sands oil across Montana. The cross-border permit was approved without completing any environmental analysis, despite tar sands oil being one of the most environmentally and health-related destructive fuels on the planet.
Tar sands are thick and heavy, almost like peanut butter or asphalt. To move through pipelines, they’re mixed with lighter petroleum chemicals to create diluted bitumen (known as “Dilbit”). These diluents may contain benzene, toluene, ethylbenzene, and xylene, compounds linked to blood disorders, nervous system effects, respiratory problems, and increased cancer risk. Unlike conventional oil, which often floats when it spills into waterways, Dilbit’s lighter chemicals evaporate, leaving heavier bitumen to sink into rivers and sediments.
This means that cleanup after spills is often more difficult, and contamination may move downstream during floods or high flows. Oil does not necessarily stay where it spills. Rivers move. Floodwaters rise. Contaminants travel. In fact, Bridger Pipeline, the company that will build and maintain the proposed Bridger Pipeline, already has a history of spills: the burst that dumped 50,000 gallons of Bakken crude into Montana’s Yellowstone River in 2015 and a 45,000-gallon diesel spill into Wyoming ranchland. After the burst in the Yellowstone River, around 6,000 residents were advised not to use tap water, and benzene concentrations reached 10–15 ppb, above levels considered a long-term concern. An oil sheen was observed over 59 miles downstream, an indication that communities far removed from the project may still feel the effects.
The current proposed pipeline would cross 16 “riverine features” listed as impaired under the Clean Water Act and intersect blue-ribbon fisheries, known for their ecological and recreational value. While the proposed expansion avoids major population centers, it would potentially pass through or near many rural communities, including Malta, Glasgow, Wolf Point, and Poplar near the Fort Peck Reservation, as well as other small towns in eastern Montana.
The rural, sometimes remote, location of the proposed pipeline changes the public health risk profile. Compared with urban centers, where more people could be affected, the same spill or contamination event can have more severe consequences when communities have fewer healthcare resources and, importantly, localized water sources. Exposure detection and response will be made more difficult by households’ reliance on private groundwater systems. A contamination event in an urban area could draw resources from multiple hospitals, specialists, and municipal water alternatives. In rural communities, it will place additional burdens on critical access hospitals already facing staffing shortages, long distances and the inherent delays to access advanced medical care, and uncertainty about exposures and water quality.
Groundwater provides around 94% of Montana’s rural domestic water supply. In many Montana counties, more than 40% of residents rely on private wells. This means contamination near pipeline routes could affect households outside municipal water systems. Emerging research also suggests that diluted bitumen may release toxic compounds such as benzene into soil at higher concentrations and with faster transport rates than comparable heavy crude oils. Unlike public water systems, private wells are not federally regulated under the Safe Drinking Water Act and often rely on individual homeowners for testing and monitoring.
The health risks extend beyond contaminated water. Volatile compounds from tar sands can evaporate into the air, creating inhalation hazards linked to headaches, respiratory symptoms, neurological effects, and increased cancer risk. When diluted bitumen spills, some of its most harmful compounds do not remain in soil or water — they become airborne. Tar sands are additionally among the most carbon-intensive fossil fuels because extraction is highly
energy-intensive, meaning their continued development only compounds growing health concerns associated with climate change: more intense wildfire seasons, heat-related illness, flooding, declining air quality, and expanding tick-borne disease ranges. The health consequences of tar sands do not stop at rupture sites; increasingly, they arrive through smoke-filled summers and climate stresses already reshaping life in Montana.
While contractors cite this project as an opportunity to provide jobs in the energy sector and increase fuel security, there needs to be a proper evaluation of the consequences this project could pose to Montana Tribes, residents, and the environment that Montanans love and depend on. Approving a project of this scale without environmental analysis does not erase risk; it simply shifts uncertainty onto communities, nearby and distant residents, and future generations expected to bear the costs, few of whom will gain any benefits from the pipeline.
Haley Yarborough, Robert Byron, MD, and Bob Merchant, MD, area representatives of Montana Health and Climate.