Alaska's active and abandoned mines released more than 450,000 pounds of mercury compounds in 2018 alone, according to federal Toxics Release Inventory data. That puts Alaska first in the nation for toxic releases from mining operations.

The Alaska Department of Environmental Conservation and federal agencies have documented widespread contamination from both operating mines and abandoned sites across the state. Five major active mines experienced hazardous spills in recent years, according to an Earthworks analysis of regulatory records. Those mines are Red Dog, Fort Knox, Pogo, Kensington, and Greens Creek.

Four of the five mines failed to control contaminated water, leading to violations of federal clean water standards. Four also operated out of compliance with federal air or water quality laws in recent reporting periods.

The abandoned Red Devil Mine on the Kuskokwim River presents ongoing risks to communities downstream. Mercury, arsenic, and antimony continue to leach from old tailings into sediments, groundwater, and the river itself, according to state environmental officials.

The Bureau of Land Management confirmed that contaminated material migrates from the site via Red Devil Creek into the Kuskokwim. The agency removed 2,000 cubic yards of contaminated soil and conducts annual water sampling to track pollution levels.

Communities near active and abandoned mines face direct impacts on subsistence lifestyles. Water near some sites cannot be used safely for drinking or fishing. That affects villages that depend on rivers for food and clean water.

The Red Dog Mine in Northwest Alaska produces zinc and lead. Fort Knox and Pogo extract gold near Fairbanks. Kensington operates a gold mine near Juneau. Greens Creek mines silver on Admiralty Island.

Spills at these operations have included cyanide, diesel fuel, and tailings, the waste material left after ore processing. The Earthworks report documented these incidents through federal and state regulatory filings.

Mining industry representatives say that reported releases under the Toxics Release Inventory include waste rock that may not pose biological risks. The EPA requires disclosure of certain materials even when they remain in managed storage.

Recent research from the University of California, Riverside found that warming temperatures in the Arctic increase metal leaching into rivers. Scientists observed streams turning orange as iron and other metals oxidize in the water, creating conditions toxic to fish.

The proposed Pebble Mine in Southwest Alaska would require management of billions of gallons of water annually if built, according to environmental impact analyses. The project would operate near Bristol Bay, home to the world's largest sockeye salmon runs.