Index/Advisories

Air Quality Index (AQI)/ Health Advisories

The EPA requires the use of an Air Quality Index (AQI) for reporting air quality levels to the general public. It tells you how clean or polluted your air is, and what associated health concerns you should be aware of. The AQI focuses on health effects that can happen within a few hours or days after breathing polluted air. The AQI is a system which uses five major air pollutants regulated by the Clean Air Act: particulate matter, sulfur dioxide (SO2), carbon monoxide (CO), ozone (O3), and nitrogen dioxide (NO2). For each of these pollutants, EPA has established national air quality standards to protect against harmful health effects.

The Metropolitan Washington Council of Governments (C.O.G.) is responsible for reporting daily air quality levels to the public in this region. C.O.G. collects air quality data from selected monitoring stations on a daily basis, calculates a maximum index value and forecasts the air quality levels for the following day. The AQI and it's corresponding color is reported to the local media, and TV, radio, and newspapers provide this information to the public. When the index exceeds or will probably exceed 100, and when specific weather conditions exist, a Health Advisory may be issued by C.O.G.