The state Environmental Commission unanimously approved the regulations as a replacement for a voluntary program now in place at Nevada's largest gold mines.

Officials and environmentalists in Utah have watched the proceedisngs with interest. Gold mines in northeastern Nevada are suspected of being a main sources for mercury in Utah, where the Great Salt Lake has measured some of the highest mercury measurements ever recorded for surface water in the United States.

The state last year advised hunters not to eat two species of duck found on the lake because high levels of mercury in them could harm human health.

The Nevada rules require more monitoring, testing and reporting of emissions at industrial mines in the state.

''The program takes the control of mercury emissions from precious metals mining to a new level,'' said Leo Drozdoff, administrator of the Nevada Division of Environmental Protection.

But critics argue the regulations effectively rubber-stamp the status quo and provide little actual protection of public health and the environment. They wanted mandated reductions and/or limits on emissions.

''The companies are left to monitor themselves, and only report their emissions once a year,'' said Elyssa Rosen of the Reno-based Great Basin Mine Watch.

Or, as Crescent Valley rancher Lee Louden put it: ''They've got the fox guarding the henhouse.''

Conservation groups in Idaho and Utah blame Nevada gold mines for mercury in fish and ducks in certain bodies of water in their states.

''We're talking about the health of our children,'' Tim Wagner of the Sierra Club's Utah chapter said before Wednesday's hearing. ''We feel the situation is of a critical nature.''

Salt Lake City Mayor Rocky Anderson argued in a letter to the commission that the state of Nevada is more worried about the costs to the industry than the health of its residents.

''We have huge concerns,'' said Anderson, who called the proposed program "insufficient to ensure the quality of life for residents in surrounding states."

Anderson complained the Nevada program set no target for reductions of mercury emissions.

Dianne Nielson, executive director of the Utah Department of Environmental Quality, wrote the Nevada commission in support of the regulations, but also called for further reductions of pollutants.

Nielson wrote that "the commission should work expeditiously with the gold mining industry to continue to reduce toxic emissions."

She also called for installation of a continuous monitoring system when feasible.

Russ Fields, head of the Nevada Mining Association, was among those who testified in support of the regulations during Wednesday's hearing before the commission.

''The state of Nevada has taken a tremendous step here to reduce the mercury emissions and we're glad to support it,'' Fields told the Reno Gazette-Journal before the hearing.

An estimated 100 tons of mercury has been discharged into the environment from Nevada mines over the past 25 years, according to a 2005 U.S. Environmental Protection Agency report.

It typically is released into the atmosphere during roasting and other refining processes.

State and industry officials say the major mines deserve credit for dramatic reductions in mercury emissions after the voluntary program was formed.

Drozdoff said the ability to develop a new regulatory program ''of this magnitude and on such an aggressive schedule'' would not have been possible without cooperation from both the mining industry and environmentalists.

Nevada regulators maintain no link has been proved between Nevada gold mines and mercury levels downwind.