Air Quality: What Can Make You Sick?

Medically Reviewed

Q. What does it mean when an Air Quality Advisory is issued?

A. If the outdoor air in your area is unhealthy, the Environmental Protection Agency and local air-quality agencies rely on a tool called the Air Quality Index (AQI) to issue an advisory. You can find your daily local air quality report by visiting the AIRNow website.

The AQI measures ground ozone levels (formed when pollutants react with the sun), particulate matter (emanating from sources such as vehicle exhaust, power plants, forest fires, and stirred-up dust), carbon monoxide (three-quarters of which comes from vehicles), and sulfur dioxide (produced when sulfur-containing fuels such as coal and oil are burned).

Depending on how much of these offenders are in the air, the AQI can be as low as zero and as high as 500. Communities aim to keep their AQI at 100 or below; below 50 is optimal for health.

If your community issues an advisory, you may need to modify your daily schedule. An AQI between 50 and 100 is considered acceptable for all but a small number of people unusually sensitive to pollution.

An AQI between 100 and 150 because of ozone or particle pollution may affect older people, those with heart or lung disease, and individuals who are active outdoors.

Above 150, air quality can cause inflammation, respiratory distress, and asthma aggravation. At these levels, stay indoors—particularly if you plan to exercise.

Anything above 201 is considered very unhealthy or hazardous, which can affect everyone.