By Karissa Minn
kminn@salisburypost.com
SALISBURY — Rowan County’s record of high air pollution can leave some people breathless.
In the Charlotte metropolitan area, the biggest air quality problem is ozone — not the beneficial layer surrounding the earth’s atmosphere, but the harmful kind that stays near the surface.
See a full-sized map of top emitters here.
Ozone is formed when certain chemicals in the air react with water vapor and sunlight. The substance can cause or worsen breathing difficulties in children, older adults and people with conditions like asthma.
There are more than 1,000 students with asthma in the Rowan-Salisbury School System, said lead school nurse Susan Thomas.
Thomas said those children have more trouble breathing on “code orange” days, meaning that the air is unhealthy for sensitive groups. On “code red” days according to the Air Quality Index, outdoor activity could be unhealthy for anyone.“We talk to teachers about children with asthma,” she said. “If it’s bad asthma, they may need to stay indoors on those days.”
It also affects animals and even plants, said John Wear, director of the Center for the Environment at Catawba College.
“In studies where they’ve looked at agricultural crops, they’ve demonstrated that high ozone levels can actually reduce crop output, meaning the growth of the plant and the amount of crops produced,” Wear said.
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The Charlotte metropolitan area is the only region of North Carolina that is considered non-attainment for ozone, meaning that it doesn’t meet federal standards for ozone levels. (See related story on 1A.)
Laura Boothe, attainment planning branch supervisor for the Division of Air Quality, said the Metrolina non-attainment region is within the standards for all other criteria pollutants, including fine particulate matter.
Its ozone levels have dropped over the past several years, she said, but so have the maximum limits set by the U.S. Environmental Protection Agency.
As part of the six-county region, Rowan County has consistently been ranked as one of the worst in North Carolina for ozone. In 2011, it had the ninth most polluted air overall, according to the Southern Environmental Law Center.
The major chemical precursors to ozone are nitrogen oxides, or NOx, and volatile organic compounds, or VOCs.
NOx is emitted into the air whenever fossil fuels are burned. That can include industry sources like power plants — especially coal burning ones — or mobile sources like cars and even lawn equipment.
But wind can carry air pollution far from where it originated, and Wear said he thinks that’s why one of Rowan’s two official air quality monitors shows such high ozone readings.
In a study conducted last year with backyard monitors, the center showed that all counties in the region have about the same ozone levels.
“In truth, all of the counties around us have a similar issue,” Wear said. “It’s just that we’ve got a monitor.”
On days when that Enochville monitor shows ozone violations, the wind is often blowing strongly from the southwest, according to data from the Division of Air Quality at the N.C. Department of Environment and Natural Resources.
That means that prevailing winds are carrying air pollution from Mecklenburg and Iredell counties to Rowan and Cabarrus counties.
Rowan County has its own sources of nitrogen oxides, too, and air quality officials say the traffic on Interstate 85 is one of the biggest.
Boothe said older, larger and more poorly maintained vehicles tend to produce the most emissions.
“Those motor vehicles individually aren’t a whole lot, but when you put them all together, you’re talking about some significant emissions over the course of a day that rival large power plants,” Boothe said.
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According to 2010 emissions reports, Duke Energy’s Buck Steam Station in Spencer is by far the highest point source of NOx in Rowan County. It sent more than 1,100 tons of nitrogen oxides into the air that year, along with 6,500 tons of sulfur dioxide.
But those numbers are set to change. Last year, Duke built the Buck Combined Cycle Station, which uses natural gas and steam instead of coal to generate electricity. It then shut down two more of its six coal-fired units. Two others already shut down several years ago, and the final two are scheduled to close in 2015.
“All that will be left there is natural gas combustion units, which emit significantly less NOx than coal-fired units,” Boothe said. “Starting in 2013, you’re going to see much, much lower emissions there.”
That means the region’s ozone levels should drop. Fine particulate matter pollution should go down as well, Boothe said, because natural gas combustion also produces less sulfur dioxide.
According to Duke Energy representatives, emissions of nitrogen oxide at the Buck plant will be reduced to 64 tons per year — down 94 percent from 2011 levels. Sulfur dioxide emissions will go down nearly 100 percent to fewer than 5 tons per year.
After the Buck Steam Station, the largest emitters of NOx in 2010 were Carolina Stalite Company in Gold Hill with 435.4 tons and Southern Power near Cleveland with 116.1 tons.
Officials with Carolina Stalite said the company has been “very aggressive” about controlling emissions, and its emissions control technology is considered one of the best in the industry.
“We live here, and we want to do a good job,” said Charles Newsome, general manager. “We set the industry standard.”
He said the company also looks for ways to reduce the amount of energy and fuel that it takes to produce its lightweight aggregate product.
Wear said local industry has actually done a lot to reduce emissions, either in response to stricter laws like Duke or as voluntary measures.
The Center for the Environment has developed materials for schools and businesses that want to develop “no idling” programs, he said.Wear said businesses also can encourage their drivers to carpool or use public transportation during the bad ozone season in summer. At home, people can use gas-powered lawn equipment in the morning or evening, when it’s less likely to create ozone.
Because ozone needs sunlight to form, its levels usually peak at mid-afternoon on hot, sunny days.
Wear said people can look up that day’s Air Quality Index on weather websites and now mobile phone applications.
“It’s very useful if a mother wants to make sure her children are playing outside when the air quality is best,” he said. “And a runner, for instance … can look at the report and shift to doing more of their running earlier on certain days.”
For a detailed forecast, visit www.airnow.gov.
Contact reporter Karissa Minn at 704-797-4222.
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