What Is Non-Attainment?
What is non-attainment and what are the sources of the pollutants?
The United States Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS). The Carolinas’ monitor concentrations of air pollutants in the ambient air. Some of these monitors have measured concentrations of ozone and carbon monoxide exceeding the standards. Areas that have not met the National Ambient Air Quality Standards can be classified by EPA as non-attainment.
Mobile sources such as cars and trucks are the primary cause of carbon monoxide and ozone precursors. About 90 percent of the carbon monoxide emissions come from motor vehicles. In the urban areas, 60 percent of the nitrogen oxides and 25 percent of the man-made hydrocarbons or volatile organic compound emissions come from motor vehicles; the rest comes from off-road vehicles, utility and industrial boilers, petroleum marketing, factories, businesses, and households.
Nitrogen oxides react with volatile organic compounds and sunlight in warm weather to produce ozone.
Why is a county designated non-attainment?
EPA guidance recommends that an entire Metropolitan Statistical Area (MSA) be designated non-attainment when a monitor is found to be violating the National Ambient Air Quality Standards (NAAQS). This policy is due to the regional nature of certain pollutants, like ozone.
Ozone is formed in the atmosphere under complex chemical reactions. Sometimes the ozone levels are higher just downwind of urban areas because of the time it takes the pollutants to react to form ozone. Therefore, larger areas are designated nonattainment to represent the likely area contributing to the air quality problems.
Once a county is designated non-attainment, what is the process for becoming attainment?
The Carolinas’ are required by the federal Clean Air Act and EPA to produce and implement emission reduction plans and show that these plans are strong enough to produce compliance with the standards. The plans could involve resource-intensive monitoring, emissions inventory, modeling, public participation, and strategy formulation efforts. There are deadlines for producing the plans and for achieving compliance with the standards. EPA must approve the plans.
Below is the decision-making process for determining the steps that must be taken by companies who are comparing sites for expansion or location of facilities that might be impacted by EPA regulations.
PM2.5 refers to particles with a diameter of 2.5 microns (one-millionth of a meter) or less. PM2.5 comes from a wide variety of stationary, mobile, and natural sources. For example, power production, cement manufacturing, combustion, diesel trucks and forest fires are all sources of particulate emissions.
Concerns for human health from PM2.5 exposure are effects on breathing and the respiratory system. Because of its extremely small size, PM2.5 penetrates the most sensitive parts of the respiratory tract.
EPA and North Carolina have not yet reached agreement on nonattainment areas for PM2.5.
An evaluation of air quality trends versus NAAQS is published annually for each state to keep the public informed of statewide air quality, exceedances of ambient air quality standards, if any, progress in attainment or maintenance of standards, health hazards of air pollution, and air quality public participation. Below are the most recent available reports for each state.
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NC Division of Air Quality Reports |
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SC Bureau of Air Quality Reports |
