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Charlotte heading to a clean-air milestone

By Bruce Henderson
bhenderson@charlotteobserver.com

Charlotte is on track to log its cleanest air on record.

Long bedeviled by ground-level ozone, an irritating gas that causes breathing problems, the metro Charlotte area has not exceeded the federal standard all summer. Ozone season doesn’t officially end until Oct. 31, but bad-air days are much less likely in September and October.

North Carolina as a whole has broken the ozone standard only once, and then barely, in Winston-Salem on May 15.

“So far we’re on a record-breaking pace,” said Tom Mather, spokesman for the N.C. Division of Air Quality. “We’ve had the fewest number of exceedances we’ve had since we started monitoring for ozone in the 1970s.”

A summer of cleaner air meant easier breathing for the thousands of people with asthma and other respiratory conditions. It will also help metro Charlotte meet federal air standards that threaten tougher restrictions on business and a possible loss of federal transportation grants.

A wet summer was a major factor in the cleaner air. Ozone, the main ingredient in the polluted brew called smog, forms best on hot, sunny, still days.

A persistent upper-level trough over the Eastern U.S. has contributed to unsettled conditions – clouds and rain – in the Carolinas, said meteorologist Elliot Tardif. He’s with the air-quality division, which produces daily ozone forecasts.

The unsettled air held off the high-pressure formations that ozone likes, he said. The clockwise-rotating winds of a high parked off the Southeast coast, meanwhile, blew clean ocean air across rural areas and toward Charlotte.

But weather is not the whole story, said Tardif and his colleague, Nick Witcraft.

State and federal laws have slashed emissions from coal-fired power plants and motor vehicles, which cook in the atmosphere to form ozone.

Rainy summers also occurred in 2003 and 2009, with steadily improving results. The Charlotte region broke the ozone standard nine times in 2003, five times in 2009 and none so far this year.

“I think we’re seeing a trend going, and what we’re seeing partly is because of meteorology and partly because of cleaner emissions,” Witcraft said.

North Carolina’s Clean Smokestacks Act of 2002 ordered sharp reductions in emissions from coal-fired power plants, a leading source of air pollutants.

Since then, Duke Energy’s plants have cut releases of nitrogen oxides, a key ingredient of ozone, by 83 percent compared to 1998 levels.

Cleaner-burning new cars and stricter federal standards on vehicle fuels also curbed ozone-forming releases, experts say.

The American Lung Association ranked metro Charlotte 19th worst in the United States for ozone pollution in April. That was an improvement over 10th worst in 2010 and 2011.

But Mecklenburg County still has the worst ozone problem in North Carolina and a looming deadline set by the Environmental Protection Agency.

The federal ozone standard is .075 parts per million averaged over eight hours, and Mecklenburg’s compliance deadline is the end of 2015. Through 2012, Mecklenburg was well over that limit at .083 ppm.

Compliance is calculated in three-year increments, meaning the county has only this year, 2014 and 2015 to meet the standard.

Mecklenburg air quality director Leslie Rhodes isn’t counting on favorable weather to rescue the county.

“It’s a good start to a three-year average that would demonstrate attainment, but we can’t rely on this good weather to continue,” she said. “It’s going to take (emission) reductions.”

For this year, anyway, the shorter days as summer creeps toward fall move the county toward a low-smog record.

Breaking the standard is “not out of the question, but the further we go and still see this trough in place, the better we’re looking for the rest of the season,” Tardif said.

Henderson: 704-358-5051 Twitter: @bhender
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