Tuesday?is the beginning of Air Quality Awareness Week, a cooperative effort among Environmental Protection Agency, state environmental agencies and the National Weather Service of the United States to remind the public to protect their health by paying attention to local air quality.

With the onset of warmer weather, the EPA urges citizens to be aware of the increased risk of ground-level ozone air pollution and fine particle air pollution (when combined, often referred to as smog), and take health precautions when poor air quality is predicted.

Air quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species and or to any human need or purpose.

Air quality indices (AQI) are numbers used by government agencies to characterize the quality of the air at a given location. As the AQI increases, an increasingly large percentage of the population is likely to experience increasingly severe adverse health effects.

To compute the AQI requires an air pollutant concentration from a monitor or model. The function used to convert from air pollutant concentration to AQI varies by pollutant, and is different in different countries.

Air quality index values are divided into ranges, and each range is assigned a descriptor and a color code. Standardized public health advisories are associated with each AQI range. An agency might also encourage members of the public to take public transportation or work from home when AQI levels are high.

Air quality forecasts are issued daily by the state air agencies. Current air quality conditions and next day forecasts are available each day at the state's web site. People can also sign up to receive air quality alerts. The alert system automatically notifies participants by e-mail or text message when poor air quality is predicted in their area.

The higher the air quality index and the higher the related risk. Good or low corresponds to acceptable or low risk situations. High values present an unhealthy high risk for respiratory ailments.

Ozone, particulates, NOx, and SO2 are common sources of poor air quality. To protect one's health, citizens should limit their strenuous outdoor activity on air quality alert days, and help take steps to reduce emissions when air quality is unhealthy.

Warm summer temperatures aid in the formation of ground-level ozone and fine particle pollution. In 2008, EPA strengthened the ozone air quality health standard. The new ozone standard is set at 0.075 parts per million on an 8-hour average basis. Air quality alerts (for example) are issued when ozone concentrations exceed, or are predicted to exceed, this level.

Poor air quality affects everyone, but some people are particularly sensitive to air pollutants, including children and adults who are active outdoors, and people with respiratory diseases, such as asthma. When air quality is predicted to be unhealthy, EPA and the states will announce an air quality alerts for the affected areas.

It is recommended that people in these areas limit strenuous outdoor activity, and reduce certain usages as follows:

-Use public transportation or walk whenever possible;

-Combine errands and car-pool to reduce driving time and mileage;

-Use less electricity by turning air conditioning to a higher temperature setting, and turning off lights, TVs and computers when they are not being used;

-Avoid using small gasoline-powered engines, such as lawn mowers, chain saws and leaf blowers on unhealthy air days.

Cars, motorcycles, trucks, and buses are a primary source of the pollutants that make smog. Fossil-fuel burning at electric-generating stations, particularly on hot days, also generates significant smog-forming pollution. Other industries, as well as smaller sources, such as gasoline stations and print shops, also contribute to smog. In addition, household products like paints and cleaners, as well as gasoline-powered lawn and garden equipment, also contribute to smog formation.