North Carolina's ozone levels lowest on record in 2013


RALEIGH – North Carolina had its lowest ozone levels on record in 2013 since air monitoring began in the early 1970s, due lower air emissions and favorable weather conditions.

Ozone levels statewide exceeded the federal standard on only one day in 2013, well below the previous record low of six days in 2009 and the average of 22 days during the previous five years. The declining ozone levels went hand-in-hand with lower emissions from the state’s power plants, the largest industrial source of nitrogen oxides (NOx), which are the primary contributor to ozone pollution in North Carolina.

A recent report by the N.C. Division of Air Quality, or DAQ, shows that the state’s coal-fired power plants have cut their NOx emissions by more than 80 percent since the General Assembly enacted the Clean Smokestacks Act in 2002. NOx emissions totaled 41,641 tons statewide in 2012, well below the cap of 60,000 tons/year set by the act and the baseline emissions of 245,000 tons in 1998.

“Power plants have not just met the requirements of the Clean Smokestacks Act, but have reduced their emissions more than required,” said Sheila Holman, director of the N.C. Division of Air Quality. “These emissions cuts, coupled with reductions from other industries and motor vehicles, have undoubtedly contributed to the improvements in ozone levels.”

Ozone is not emitted directly by sources but forms in the air when nitrogen oxides (NOx) react with hydrocarbons on hot, sunny days with little wind. Thus, the weather also contributed to low ozone levels in 2013 because the summer was cooler and wetter than usual.

NOx is considered the primary man-made contributor to ozone formation because trees and other vegetation emit most of the hydrocarbons in our air. The primary sources of NOx are power plants, industry and motor vehicles, and those emissions have been declining during the past decade.

The Clean Smokestacks Act required Duke Energy Carolinas and Progress Energy Carolinas (now both owned by Duke Energy, Inc.) to reduce ozone- and particle-forming emissions from coal-fired power plants by about three-fourths compared to 1998 levels. Utilities have achieved those reductions by installing scrubbers and other pollution controls at their largest facilities, closing some plants and converting others from coal to natural gas.

Stricter federal requirements for industrial facilities as well as motor vehicles also have contributed to the emissions reductions.More information on air quality issues can be found on DAQ’s website, .

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