SALT LAKE CITY (AP) — Federal regulators have announced plans to cut mercury emissions from Nevada gold mines, which have long been suspected of polluting Utah and Idaho waters.

The U.S. Environmental Protection Agency's proposal announced Friday would reduce mercury emissions from gold ore processing and production facilities to 1,390 pounds a year, a 73 percent reduction from 2007 levels.

Most of the nation's 20 such plants are in Nevada, the richest gold mining state in the nation. The facilities are the sixth largest source of mercury air emissions in the country, according to EPA.

After being released into the atmosphere from the plants, mercury transforms into toxic methylmercury in the environment and builds up in the food chain.

The emissions have been suspected of making some fish and waterfowl in Utah and Idaho so polluted with methylmercury they are unsafe to eat. Children and women of child-bearing age are most at risk.

"Taking mercury out of the air makes our communities safer for everyone," said Gina McCarthy, assistant administrator for air and radiation at EPA. "Our proposal will further progress that has already been made to limit mercury emissions from this industry."

The EPA estimates the capital cost of controls at $6.2 million initially and $3.8 million a year.

Calls to Barrick Gold Corp. officials in Salt Lake City and Toronto were not immediately returned Saturday.

Some facilities in Nevada already are making significant progress toward the proposed reductions under the state's program, according to EPA.

The state of Nevada began requesting voluntary reductions in 2001 and adopted mandatory controls a few years later at the 15 gold facilities in the state. Emissions have declined from about 11.5 tons in 1999 to 2.5 tons in 2007.

Justin Hayes of the Idaho Conservation League hailed the EPA's move, saying the rules appear stringent and likely to force lower emissions. Hayes' group had threatened to sue the EPA over the issue.

"Utah and Idaho are downwind from these high-mercury sources in Nevada," he said. "This is an important first step toward assuring that Utah children and Idaho children can once again safely eat locally caught fish."

Earthjustice, which also threatened to sue over the gold-plant emissions, said EPA needs to do more such as reducing the plants' cyanide releases.

"That said, (Friday's) action marks an important first step by the federal government to bring these highly dangerous and highly profitable polluters under control," said Earthjustice attorney James Pew.

Nevada ranks fourth in the world in gold production behind South Africa, Australia and China.

EPA will accept public comment on the proposed rule for 30 days.