Press release from the N.C. Department of Environment and Natural Resources:

RALEIGH – Ozone levels in North Carolina were the lowest on record in 2014, with no exceedances of the federal ozone standard for the first time since air monitoring began in the early 1970s, due to lower air emissions and favorable weather conditions.

The 2014 ozone season, which ended Oct. 31, marked the second year in a row with record-low levels, according to air monitoring by the N.C. Division of Air Quality, or DAQ. Ozone levels statewide exceeded the federal standard on only one day in 2013, well below the previous record low of six days in 2009.

The highest number of days exceeding the ozone level was 111 days in 1999. The number of high ozone days has averaged 14 days per year during the past five years and 28 days per year during the past decade.

“North Carolina is reaping the benefits of reduced emissions from power plants, industries and motor vehicles over the past decade,” DAQ Director Sheila Holman said. “We have seen steady declines in measured levels of ozone as well as particle pollution across the state.”

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 the past two years because summers were 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.

Stricter state and federal requirements for industrial facilities as well as motor vehicles have contributed to the emissions reductions. These requirements have included:

– The Clean Smokestacks Act that the legislature passed in 2002, requiring the state’s coal-fired power plants to reduce their ozone and particle-forming emissions during the following decade.

– Stricter federal controls on emissions from power plants and other industrial sources.

– More stringent federal standards for car and truck engines as well as gasoline and diesel fuel.

A Division of Air Quality report shows that the state’s coal-fired power plants have cut their NOx emissions by more than 80 percent since the N.C. General Assembly enacted the Clean Smokestacks Act. NOx emissions totaled 41,641 tons statewide in 2012, well below the cap of 56,000 tons/year set by the act and the baseline emissions of 245,000 tons in 1998.

“Power plants have exceeded the requirements of the Clean Smokestacks Act,” Holman said. “Their emissions cuts, coupled with reductions from other industries and motor vehicles, have undoubtedly contributed to the improvements in air quality across North Carolina.”

The Clean Smokestacks Act required Duke Energy and Progress Energy (now a single company) 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.

More information on air quality issues can be found at the DAQ website,

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Angie Newsome was the executive director and editor of Carolina Public Press. Contact her at (828) 774-5290 or e-mail her at

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