Index Value Level of Health Concern What it Means 301 - 500 Hazardous Health warnings of emergency conditions. The entire population is more likely to be affected. 201 - 300 Very Unhealthy Health alert: everyone may experience more serious health effects. 151 - 200 Unhealthy Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects. 101 - 150 Unhealthy for Sensitive Groups Members of sensitive groups may experience health effects. The general public is not likely to be affected. 51 - 100 Moderate Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. 0 - 50 Good Air quality is considered satisfactory, and air pollution poses little or no risk.

AirCompare provides comparisons of air quality based on factors that have been shown to increase risk from air pollution. These factors can include life stages (children and older adults), specific health conditions (heart or lung disease), and increased likelihood of exposure from being active outdoors. The Air Quality Index (AQI) is the official index for air quality across the United States. The AQI ranges from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern.

When AQI values are between 101 and 150, or code orange, members of sensitive groups may experience health effects. This is because they are more likely to be affected at lower air quality levels than everyone else. For example, children and older adults, people with lung disease, and people who are active outdoors (outdoor workers) are at greater risk from exposure to ozone. Older adults and children, and people with heart or lung disease are at greater risk from exposure to particle pollution. Everyone is more likely to be affected when the AQI values are above 150, or code red and higher.

Learn more about the AQI and how air quality affects health