"That haze obscures the scenery, especially out here in the West where a lot of people come to see the vistas," she said.
McKaughan said the hearing at the reservation was not intended to address anecdotal health complaints. Still, she said the EPA is interested in valid medical problems caused by pollution.
"We understand why they would prefer not to breathe this stuff. We totally get it," she said.
When coal is burned, carbon dioxide, sulfur dioxide, nitrogen oxides and mercury compounds are released into the air, according to the EPA. Research has shown those fine particles can be linked to serious health problems, including premature death.
But the Moapa Paiute tribe can only rely on general data to back up their claims. Despite their health concerns, the tribe has been unsuccessful in persuading local, state and federal health officials to investigate their complaints.
The lack of direct evidence has stroked accusations that the tribe's medical problems have been exaggerated by environmental activists who want to see the coal plant shuttered.
Clark County Commissioner Tom Collins, who represents Moapa, said the plant creates much needed jobs and tax dollars for the area.
"They are using those Indians as a vehicle to shut down the plant," Collins said of the environmental groups who want the facility closed. "As long as they are complying with the laws, (the plant) benefits the entire community."
The Reid Gardner facility provides enough electricity to power 335,000 Nevada households, according to NV Energy, the utility company that operates the plant. Under the EPA proposal, NV Energy would have five years to install nitrogen oxide burners, instead of more expensive selective catalytic emissions scrubbers that environmentalists claim do a better job of reducing emissions.
"We will continue our commitment to operate the Reid Gardner station in an environmentally responsible manner, in compliance with all federal and state laws, and in the best interests of its customers," spokesman Mark Severts said.
The Muddy River near the plant feeds into Lake Mead, the massive reservoir that serves Mexico, California, Nevada and Arizona.
"Second-rate pollution control is not good enough here," said Dan Galpern, a lawyer representing the tribe and the Sierra Club in Nevada.