A new American study concluded that coal mines in southeastern British Columbia province in the far west of Canada are polluting waters shared between Canada and the United States.

The United States Geological Survey (USGS) indicated that attempts to remove selenium from the wastewater of "Teck Resources" mining company have little impact on the quantity flowing south to the Elk River.

For her part, Meryl Storrb, the lead author of the study, acknowledged that "Teck Resources" wastewater treatment efforts are bearing fruit, but she says the company's facilities are less effective when they are most needed, especially when snowmelt leads to strong river flows.

Storrb said the total annual amount of selenium flowing into the Elk River and into Kootenay Lake has more than quadrupled since the measures began in 1985.

She also added that "Teck Resources" has quadrupled its wastewater treatment capacity since 2020 and plans to double it twice more by 2027.

A company spokesperson added that the rate of increase in the total amount of selenium in the Elk River has slowed.

These flows have been a point of contention between Canada and the United States since at least 2015, with Canada refusing to accept US demands for a joint investigation.

Selenium is also considered toxic to fish, and its quantities in the Elk River have for several years exceeded environmental guidelines.

The headquarters of "Teck Resources" is located in Vancouver, the largest city in British Columbia on the Pacific Ocean.