North Carolina currently is showing full compliance with the new, more stringent ozone standard that the U.S. Environmental Protection Agency adopted on Thursday, based on preliminary data from the air quality monitors across the state.
The EPA set the new 8-hour ozone standard at 70 parts per billion, compared to the previous standard of 75 ppb that it had adopted in 2008. The federal agency will determine compliance with the new standard on Oct. 1, 2017, based on a 3-year average of the fourth-highest ozone values at each monitor for the 2014-2016 period.
No air quality monitors in North Carolina are violating the new standard based on data for the 2013-2015 ozone seasons, according to preliminary analyses by the state Division of Air Quality, or DAQ, and local air programs in Buncombe, Forsyth and Mecklenburg counties.
"This is the first time that North Carolina has been in full compliance with a new ozone standard at the time it was adopted by the EPA," DAQ Director Sheila Holman said. "We expect to comply with the new standard statewide when the EPA makes its final attainment designations in 2017 because air quality has been improving steadily across the state over the past 15 years."
EPA information released Thursday indicated that one North Carolina county (Mecklenburg) was not meeting the new standard, but that was based on older data for the 2012-2014 period. Levels of ozone and other air pollutants have further declined since then.
In July, the EPA officially recognized the Charlotte metropolitan area as complying with the 2008 ozone standard, marking the first time that North Carolina has met all air quality standards since the 1990s. The Charlotte metropolitan area had been the only region of North Carolina still designated as non-attainment, or non-compliance with the ozone standard.
In the early 2000s, about one-third of the state's counties were classified as non-attainment for ozone, and Code Red and Orange ozone alerts were a frequent occurrence during summer months. However, ozone levels during the past three years have been the lowest since the state began monitoring the air in the early 1970s - with only one exceedance of the ozone standard in 2013, none in 2014, and two in 2015.
Air quality has improved due to declining emissions from motor vehicles, power plants and other industrial sources, resulting from a series of state and federal measures. Most importantly, the Clean Smokestacks Act that the legislature adopted in 2002 required the state’s coal-fired power plants to reduce their emissions by about three-fourths. Other EPA requirements have led to lower emissions from other industrial sources, cars and trucks, as well as cleaner gasoline and diesel fuel.
Historically, ozone has been North Carolina’s most widespread air quality problem. Ozone is a highly reactive form of oxygen that is unhealthy to breathe and damages trees and crops. It forms when other air pollutants, primarily nitrogen oxides or NOx, react in the air during hot, sunny weather.