What is Air Pollution?

Air pollution consists of gases, solid particles, and aerosols that change the natural composition of the atmosphere.  Some gases that are normal components of clean air, such as carbon dioxide, become dangerous when concentrations are higher than normal.  Air pollution has the potential to be harmful to human health and to damage other parts of the environment, including soil and water. 

Air pollution can come from two sources:  natural and human (anthropogenic).  Natural sources can include forest fires, trees and plants, and even sea salt in coastal areas.  Anthropogenic pollution occurs from a wide range of human activities, such as car and truck exhaust, industrial processes, power plants, mining activities, and landfills. 

What Governs Air Pollution?

The Clean Air Act (CAA) is the federal law that governs air pollution and efforts to improve air quality.  The CAA sets standards for how much of certain pollutants can be in the air. These standards are health-based, meaning the amount of pollutants in the air is not supposed to harm human health.  The goal of these standards is to ensure that everyone has the same basic health and environmental protections.

What Pollutes Georgia's Air?

Half of all Georgians now live in areas with air that may be harmful to their health.  The air pollutants of concern in Atlanta are ground-level ozone and particulate matter. 

 Ground level-ozone (smog):  Ozone can be good or bad depending on where it is located.  Ozone in the stratosphere high above Earth protects human health and the environment, but ground-level ozone is a serious health concern.  Ozone is produced by a combination of two pollutants, nitrogen oxides (NOx) and volatile organic compounds (VOCs), from many sources, including cars and trucks, smoke stacks, paints and solvents, and even trees.  These smog-forming pollutants react with one another in the atmosphere in the presence of sunlight to form ground-level ozone. 

Ozone levels can vary throughout the day, but the highest concentrations tend to occur between 2 and 7 pm.  Ground-level ozone increases throughout the day as temperatures rise.  May 1 – September 30 is Georgia’s official ozone season, but unhealthy ozone levels can happen anytime there is enough heat and sunlight to form ozone in the atmosphere. 

Until 2004, 20 counties in the Atlanta area had been trying to meet the old CAA ozone standard, which is known as the 1-hour standard.  In 2004, however, a new, more protective ozone standard, the 8-hour standard, became effective.  One of the differences between the two standards is the time period over which the level of ozone in the air is measured (one hour v. eight hours).   

Atlanta finally met the 1-hour standard in 2004, but Atlanta, areas around Macon, and an area in Georgia near Chattanooga do not meet the new 8-hour standard.  The state is developing plans to bring Atlanta and the other areas into compliance with the 8-hour standard.  Atlanta is classified as a “marginal” non-attainment area, which means it is required to meet the standard by 2007.  Atlanta will likely not meet this deadline and will be bumped up to a “moderate” non-attainment area, which will postpone the attainment date to 2010. 

Particulate matter (PM): this is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets.  Particles can be suspended in the air for long periods of time.  Some particles are large or dark enough to be seen as soot or smoke.  Others are so small that they can only be detected with an electron microscope.

Some particles are directly emitted into the air and come from a variety of sources such as cars, trucks, buses, factories, construction sites, tilled fields, unpaved roads, stone crushing, and burning of wood.  Other particles may be formed in the air when gases from burning fuels react with sunlight and water vapor.  These particles can result from fuel combustion in motor vehicles, at power plants, and in other industrial processes. 

In 2005, EPA designated 21 counties around Atlanta as non-attainment for PM.  EPA also designated areas around Macon and in Georgia near Chattanooga as PM non-attainment areas.  The state is also developing plans to bring these areas into attainment with the standard by 2010. While ozone violations are typically associated with the hot spring and summer months, unhealthy levels of particulate matter can happen in any time of year. In addition to public health concerns, particulate matter can corrode metals and building facades, inhibit the growth of plants, and reduce visibility.  

Sources:  Georgia Institute of Technology, American Lung Association, Clean Air Campaign, U.S. Environmental Protection Agency