The gold "roasters" have been suspected of contaminating lakes, streams and wildlife with a dangerous form of the metal, so Nevada's move won support from downwinders in Utah and Idaho.

"This is a bold action they've taken," said Cheryl Heying, director of the Utah Department of Air Quality. "It shows they have teeth, and they can bare them."

Nevada had a voluntary program for years but implemented tougher, mandatory regulations last year. Now reports of mercury emissions are required and checked.

Two other companies have successfully cut their pollution under the new program, but roasters operated by Yukon-Nevada Gold Corp. at Jerritt Canyon, north of Elko, had been under investigation for more than a year. The Nevada Department of Environmental Protection directed the Jerrit Canyon plants Wednesday to shut down by March 17 until they can get the mercury out of emissions.

"These events demonstrate not only that the incentives we've built into the program are producing early emissions reductions, but also that the regulations contain strong enforcement provisions," said agency administrator Leo Drozdoff.

No clear link has been proven yet between Nevada's gold roasters and pollution in neighboring states. But it was only two weeks ago that the Utah Legislature approved $100,000 to buy a monitor to help track the microscopic mercury particles that many believe are drifting from Nevada.

In 2004, scientists discovered the highest levels of toxic methylmercury ever measured in a natural water body in the Great Salt Lake.

Methylmercury is the toxic form of mercury after it has been biologically transformed. It poses a public health risk, especially to children and unborn babies.

A neurotoxin, it builds up in the food chain and attacks the neurological system, causing retardation in the unborn and learning disabilities and behavioral problems in children. Humans are exposed most commonly by eating contaminated flesh, usually fish.

Utah has consumption warnings for several fish statewide and four duck species on the Great Salt Lake.

Idaho has similar warnings.

Canadian-based Yukon-Nevada Gold said the shutdown was planned and insisted its mercury controls simply aren't working right yet.

But Justin Hayes of the Idaho Conservation League said the company has been hiding the true volume of its mercury pollution. He called Nevada's shutdown order "a really big deal." He said: "This is the first step to solving this problem."

Lynn de Freitas, director of the Friends of the Great Salt Lake, applauded Nevada's action, too.

"What a responsible thing to do," she said.

fahys@sltrib.com