Air Quality

National Ambient Air Quality Standards

The Clean Air Act requires the U.S Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for wide-spread pollutants.  The Clean Air Act established two types of standards. Primary standards set limits on pollutant levels in order to protect public health, including the health of “sensitive” populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings.  The EPA has set NAAQS for six principal pollutants, known as “criteria pollutants”. Criteria pollutants include Carbon Monoxide, Lead, Nitrogen Dioxide, Ozone, Particulate Matter and Sulfur Dioxide.  Several years ago, the Roanoke Valley was struggling to meet the NAAQS for Ozone and Particulate Matter (PM).  Today, even after more stringent standards have been adopted, the Roanoke Valley is in attainment (does not exceed the standard) for Ozone and Particulate Matter, as well as the other criteria pollutants.

Listed below are the current NAAQS standards for both ozone and PM 2.5., taken from the EPA website. These standards show the amount of ozone and PM 2.5 that Roanoke should strive to not exceed. PM 2.5 refers to particles that are 2.5 microns or less in width. To put the size of PM 2.5 into perspective, the size of this matter is about thirty times smaller than that of a human hair. Therefore, it is fairly easy for these particles to enter human lungs on a daily basis. More information regarding PM 2.5 can be found here. If there are six criteria pollutants, why are the standards below only listed for ozone and PM 2.5? In the Roanoke Valley, ozone and PM 2.5. are the main criteria pollutants that are currently present in the air.

The charts display units of concentration referred to as “ppm” and “ug/m3”. The abbreviation “ppm” stands for “parts per million”, which shows the ratio of a pollutant to a solution, in this case, the ratio of ozone to air. The abbreviation “ug/m3” stands for the amount of air pollutant, measured in micrograms, per each cubic meter of air.

Ozone NAAQS – Current Standard adopted March 2008

July 18, 1997 Primary Standard 8-Hour Average 0.08 ppm
Secondary Standard 8-Hour Average 0.08 ppm

 

March 27, 2008 Primary Standard 8-Hour Average 0.075 ppm
Secondary Standard 8-Hour Average 0.075 ppm

PM 2.5 NAAQS – Current Standard adopted December 2012

July 18, 1997 Primary Standard 24-Hour Average 65 ug/m3
Secondary Standard 24-Hour Average 65 ug/m3
Primary Standard Annual Average 15.0 ug/m3
Secondary Standard Annual Average 15.0 ug/m3
Oct. 17, 2006 Primary Standard 24-Hour Average 35 ug/m3
Secondary Standard 24-Hour Average 35 ug/m3
Primary Standard Annual Average 15.0 ug/m3
Secondary Standard Annual Average 15.0 ug/m3
Dec. 14, 2012 Primary Standard 24-Hour Average 35 ug/m3
Secondary Standard 24-Hour Average 35 ug/m3
Primary Standard Annual Average 12.0 ug/m3
Secondary Standard Annual Average 15.0 ug/m3

 

Air Quality Index

The air quality index (AQI) is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be of concern to you. The AQI focuses on the health effects that you may experience within a few hours or days after breathing in polluted air.  The AQI is color coded and broken down by the severity of health impacts. The air quality index calculator shows what level of a pollutant poses a threat to human health and therefore should be avoided.  Each day, the Virginia Department of Environmental Quality (VA DEQ) forecasts the AQI for the next day.  Both the VA DEQ and EPA websites display the current AQI for the Roanoke Valley. As mentioned previously, for the Roanoke Valley, Ozone and Particulate Matter 2.5 are the main criteria pollutants that are forecasted on a daily basis.  For more Roanoke Valley air quality information, visit Ride Solutions or to sign up for VA DEQ Air Quality Forecasts and Health Alerts, visit their website.

AIr Quality Index Matrix

The AQI Matrix below shows the level of PM 2.5 and Ozone that is considered healthy versus hazardous.

 

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