How to Read the EPA's Air Quality Index

Knowing how to read the EPA's Air Quality Index (AQI) will tell us how clean or polluted the air is on any given day. The EPA's AQI will also reveal other important factors that are relevant to the health of individuals as well as specific groups of people who may suffer certain respiratory ailments. If one understands how to read the EPA's Air Quality Index, then one can be assured to take measures to protect him or herself, or loved ones when the air quality (AQI) is at unacceptable levels that can put people at risk of health issues.

Air Quality Index Calculations

The Air Quality Index, or AQI, measures the quality of the air based on five major air pollutants, as regulated by the Clean Air Act. Those five pollutants are particulate pollution which is also referred to as particulate matter, the ground level ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide. The AQI has a range from 0-500. The lower the AQI, the better the air quality. The higher the AQI, the poorer the air quality and higher pollution levels that may put individuals at risk for breathing problems, especially those at high risk. When the AQI goes over 100, people in high risk groups, such as those already suffering from respiratory problems are at risk due to unhealthy air quality. As the AQI increases on upward from 100, others become at risk from suffering from pollution effects. Any AQI measurement of 300 or above poses significant risk as the air has reached hazardous levels, according to EPA standards.

Categories and Colors of the Air Quality Index

The EPA divides the AQI into six different categories so that people can easily understand how to interpret the EPA's Air Quality Index (AQI) and what the air quality can mean where one's health is concerned. The first category is green, which designates good air quality with an AQI of 0-50. There is little to no risk at this level. The next category is moderate, which has an AQI range of 51-100, and is represented by the color yellow. At this level, air quality levels are still considered acceptable. However, specific pollutant particulates may affect small groups of people. The next level is the orange level, which consists of an AQI in the range of 101-150. This AQI range is considered unhealthy for sensitive groups. People with heart diseases, both children and adults, will be more sensitive to air pollutants and people with lung diseases will show sensitivity to elevated ozone levels. In the AQI range of 151-200, the health risks increase. When the AQI reaches this red level, the air quality is unhealthy, and there can be some health effects on everyone. Persons with respiratory or other at-risk health issues can suffer significant adverse effects of the elevated, red level AQI. With an AQI reading of 201-300, everyone can suffer more serious health effects. If the AQI reaches this purple level, a health alert would be issued to indicate that everyone may suffer some adverse effects from the high pollution levels indicated by the AQI. When the EPA's Air Quality Index reaches the highest level, of over 300, represented by the color maroon, the air quality is at an extremely dangerous level, considered "hazardous" by EPA standards, which would lead to a warning that the entire population can expect to be affected by the high levels of pollution.

Protect Yourself by Knowing the EPA's Air Quality Index

Of the five pollutants considered when determining the AQI, particulate matter and ground-level ozone pose the greatest health risks to people. Whenever the AQI is at unacceptable levels anyone participating in activities that are strenuous or require being outdoors for extended periods of time, such as for yard work, one takes in more pollution when breathing. This is also true of people who exercise or work outdoors or in hazardous environments. When the AQI reaches a level of over 100, or in the red level, reduce exposure to the outdoors and avoid strenuous activities. This is critical for those in sensitive groups, especially. The EPA's daily AQI is available online, on many TV stations and in many daily newspapers. By knowing the AQI on a daily basis, one can better plan activities to avoid being exposed to high pollution levels.

Sources

cfpub.epa.gov/airnow/index

epa.ohio.gov/dapc/airohio/forecast

epa.state.il.us/air/aqi