Figure 14: Air Quality Index (AQI) levels of health concern. This color-coded table shows generically how AQI values correlate with levels of health concern. For a copy of this AQI table, download the booklet, "Air Quality Index - A Guide to Air Quality and Your Health," that explains the AQI and the health effects of major air pollutants, at http://www.epa.gov/airnow/aqi_brochure_08-09.pdf. (629KB, 12 pp.)
"Good" (0 - 50) Air quality is excellent and poses little or no risk.
"Moderate" (51 - 100)Air quality is acceptable; however, there may be some health concern for a small number of unusually sensitive individuals. We cannot identify groups of people that are at greater risk when air quality is in this range. However controlled human exposure studies indicate that there are individuals who experience health effects at more moderate levels of outdoor exertion or at lower ozone levels than the average person, and these individuals may experience effects when air quality is in the moderate range.
"Unhealthy for Sensitive Groups" (101 - 150)When air quality is in this range, people that are included in a sensitive group, whether the sensitivity is due to medical conditions, exposure conditions, or inherent susceptibility, may experience the effects described above when engaged in outdoor activities. However, exposures to ambient concentrations in this range are not likely to result in effects in the general population. For ozone, the sensitive group includes children and adults who are active outdoors because they are more likely to be at elevated ventilation rates for sufficiently long periods of time when ozone levels are high to experience effects. People with lung diseases are also included in this group because they often have poorer lung function to begin with, so that any additional reduction is more likely to result in symptoms, and also ozone can aggravate their underlying diseases. EPA's risk assessment (Whitfield et al., 1996) indicates that at this level for healthy individuals (adults and children) at moderate exertion: 1) approximately 18% are estimated to experience moderate or greater lung function impairment, 2) approximately 9% are estimated to experience large or greater lung function impairments, and 3) approximately 2% are estimated to experience moderate to severe aggravated cough.
"Unhealthy" (151 - 200)When air quality is in this range, any individual who is active outdoors may experience the respiratory effects described above. Members of sensitive groups are likely to experience more severe effects. EPA's risk assessment (Whitfield et al., 1996) indicates that at this level for healthy individuals (adults and children) at moderate exertion: 1) approximately 30% are estimated to experience moderate or greater lung function impairment, 2) approximately 15% are estimated to experience large or greater lung function impairments, and 3) approximately 5% are estimated to experience moderate to severe respiratory symptoms (i.e., chest pain with deep inspiration and aggravated cough).
"Very Unhealthy" (201 - 300)When air quality is in this range, it is expected that there will be widespread effects among the general population and more serious effects in members of sensitive groups. EPA's risk assessment (Whitfield et al., 1996) indicates that at this level for healthy individuals (adults and children) at moderate exertion: 1) approximately 50% are estimated to experience moderate or greater lung function impairment, 2) approximately 20% are estimated to experience large or greater lung function impairments, and 3) approximately 10-15% are estimated to experience moderate to severe respiratory symptoms (i.e., chest pain with deep inspiration and aggravated cough). Individuals with asthma or other respiratory conditions will likely be more severely impacted than healthy individuals, leading some to increase medication usage and seek medical attention, including increased emergency room and clinic visits, and increased hospital admissions.
"Hazardous" (301 - 500) If air quality gets in this range, it will trigger health warnings of emergency conditions and there will be widespread coverage in the media.