In October 2015, the Environmental Protection Agency reset the eight-hour standard to 70 parts per billion, compared to the 75 parts per billion standard that had been in effect since 2008. The federal agency will determine compliance or attainment with the new standard in October 2017, based on a 3-year average of the fourth-highest ozone values at each monitor for the 2014-2016 period.

However, with the 2016 ozone season now coming to an end, state officials say that North Carolina is fully complying with the new standard. No air quality monitors in North Carolina violated the new standard during the 2013-2015 ozone seasons, according to final analyses by the state Division of Air Quality and local air programs, and preliminary analysis shows that the same is true for 2016. 

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 frequent during summer months. However, ozone levels during the past few years have been the lowest since the state began monitoring in the early 1970s. Declining emissions from motor vehicles, power plants and industry are largely responsible for the improved air quality. North Carolina’s 2002 Clean Smokestacks Act required coal-fired power plants to reduce their emissions by about three-fourths, and EPA requirements have led to lower emissions from other industrial sources, cars and trucks, as well as cleaner gasoline and diesel fuel.