What is the AQI?
The AQI is an index for reporting daily air quality.
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. EPA uses the AQI for five major air pollutants regulated by the
Clean Air Act: ground-level ozone, particulate matter, carbon monoxide,
sulfur dioxide, and nitrogen dioxide. For each of these pollutants,
EPA has established national air quality standards to protect against
harmful health effects.
You can think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health danger. For example, an AQI value of 50 represents good air quality and little potential to affect public health, while an AQI value over 300 represents hazardous air quality.
An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. So, AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as AQI values get higher.
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Understanding
the AQI Each category corresponds to a different level of health concern. For example, when the AQI for a pollutant is between 51 and 100, the health concern is “Moderate.” Here are the six levels of health concern and what they mean: |
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“Good” The AQI value for your community is between 0 and 50. Air quality is considered satisfactory and air pollution poses little or no risk.
“Moderate” The AQI for your community is
between 51 and 100. Air quality is acceptable; however, for some pollutants
there may be a moderate health concern for a very small number of individuals.
For example, people who are unusually sensitive to ozone may experience
respiratory symptoms.
“Unhealthy for Sensitive Groups” Certain
groups of people are particularly sensitive to the harmful effects of
certain air pollutants. This means they are likely to be affected at lower
levels than the general public. For example, children and adults who are
active outdoors and people with respiratory disease are at greater risk
from exposure to ozone, while people with heart disease are at greater
risk from carbon monoxide. Some people may be sensitive to more than one
pollutant. When AQI values are between 101 and 150, members of sensitive
groups may experience health effects. The general public is not likely
to be affected when the AQI is in this range.
“Unhealthy” AQI values are between 151 and
200. Everyone may begin to experience health effects. Members of sensitive
groups may experience more serious health effects.
“Very Unhealthy” AQI values between 201 and
300 trigger a health alert, meaning everyone may experience more serious
health effects.
“Hazardous” AQI values over 300 trigger health
warnings of emergency conditions. The entire population is more likely
to be affected.