Gilmer County in North Georgia recorded the state's highest smog day on Thursday.

The violation of the federal ground-level ozone standard is under review by the state Environmental Protection Division.

Gilmer County, about 70 miles north of Atlanta, is near Fort Mountain State Park and includes a swath of the Chattahoochee National Forest. Ellijay is the county seat.

Susan Zimmer-Dauphinee, manager of the EPD monitoring program, said the violation was due to pollution blowing into Gilmer from elsewhere.

Metro Atlanta came close to failing the new, stiffer federal standard Thursday, the first day of smog season, but has yet to violate the standard this year.

On April 17, Augusta, Macon, Athens and the north Georgia town of Dawsonville violated the standard.

The U.S. Environmental Protection Agency changed the standard in March, making it tougher to meet. The new limit is 75 parts per billion of ozone, measured over an eight-hour period. The old standard was 84 parts per billion over eight hours.

Even with the easier standard, Atlanta failed about 30 days over the five-month season in each of the last two years. Ozone triggers asthma attacks and long term exposure limits lung function even in healthy people.

Nationwide, 345 counties, including 20 counties in metro Atlanta, are expected to fail the new standard. Metro Atlanta will have at least five years to meet it. Failure to make progress could result in the loss of federal road-building funds.