Ambient air quality is monitored depending on the type of pollutant and its effects, the way in which it is released, and its physical and health hazards.
What is Ambient Air Quality?
Ambient air quality is the measure of the quality of air in any particular region. The term “ambient” means surroundings, and that is what it refers to — the air that surrounds us on a daily basis.
Ambient Air Quality is a measure of how clean or polluted the outside air is. It is measured by monitoring levels of pollutants such as carbon monoxide (CO), nitrogen dioxide (NO2), and particulate matter (PM10 and PM2.5). In Europe, the EU Ambient Air Quality Directive [sets standards for these pollutants in ambient air.
The European Environment Agency reports on ambient air quality in Europe and monitors progress towards meeting EU standards. There are also national monitoring programs that report on ambient air quality in individual countries.
What Pollutants Affect Ambient Air Quality?
Air pollutants that most commonly affect ambient air quality include particulate matter (PM), sulfur dioxide, ozone, nitrogen dioxide, and carbon monoxide. However, the specific pollutants that affect ambient air quality depend on the location and time. For example, during forest fires or volcanic eruptions, additional pollutants like ash may be present in the air.
Ambient Air Quality Standards
The EPA has set National Ambient Air Quality Standards (NAAQS) for six common pollutants: PM2.5 (fine particles), PM10 (fine particles), sulfur dioxide, nitrogen oxide, carbon monoxide, and ozone. These standards specify the maximum concentration of each pollutant allowed in the air over an eight-hour period. If an area’s pollution levels exceed these standards for more than one day per year, it is considered a non-attainment area and must take action to reduce its pollution emissions.
How can be Measure the Ambient Air Quality?
Ambient air quality can be measured in a number of ways. The most accurate is by direct sampling of the pollutant. Direct sampling can be performed by taking a sample of the air, either on-site or in a laboratory, and analyzing it for the chemical components of interest.
However, direct sampling is not practical over large distances and typically only provides data for that particular moment in time. Longer-term monitoring is usually needed to give an indication of air pollution levels over an extended period of time. For this type of monitoring, indirect methods are generally used. These include continuous monitors that measure the concentration of a specific pollutant, as well as bio-indicators such as lichens and mosses which provide an indication of the level of general air pollution.