Ozone alerts will be issued when the new standard is violated, she said. On Tuesday, however, ozone levels were listed as "good" at monitoring stations around the valley.

Nevertheless, Williams said, "We're liable to have (violations) because the standard has been lowered so much."

That means Clark County will likely be designated a non-attainment area for ozone in 2010. And, like hundreds of other areas across the nation, Nevada will have three years to submit plans to demonstrate Clark County's compliance in 20 years.

In March, EPA Administrator Stephen Johnson announced the eight-hour standard for smog-forming ozone would be tightened from 80 parts per billion to 75 parts per billion. His decision was spurred by a court decision from a 2003 lawsuit filed against the EPA by Earthjustice on behalf of the American Lung Association and conservation groups.

Failing to meet the standard could result in federal management of an implementation plan or loss of federal highway funding in noncompliant areas, but EPA officials have said the possibility of that happening is remote.

Ozone is a summertime pollutant that irritates the lungs and especially affects children and the elderly, and people who suffer from asthma and cardiovascular diseases.

To curb ozone, the two-month advisory suggests that local residents mow their lawns after sunset, tightly cap all solvents to prevent vapors from escaping into the air, and don't top off gasoline tanks when refilling vehicles at service stations.

In addition, the advisory recommends avoid using lighter fluid to start charcoal barbecue grills. "Use an electric starter or 'charcoal chimney'" instead, the advisory reads.

Williams said county officials might consider challenging any violations that they think are linked to out-of-state pollution that is transported to Nevada from sources in Southern California, for example.

Computer models have shown that ozone reaches Nevada from Los Angeles, Arizona and Mexico and on rare occasions from the southeastern United States.

Ozone pollution can drift into Nevada from wildfires in Southern California and other areas of the West.

Nevada Environmental Protection Division officials have written the EPA stating that Nevada's potential for growth and economic development could be seriously curtailed because of emissions that are not generated in Nevada.

Williams said if the standard hadn't been lowered and ozone levels remained as they were last year "we wouldn't be issuing the advisory."

Contact reporter Keith Rogers at krogers@reviewjournal.com or 702-383-0308.