Cleber Ferreira Graça Filho
Graduando em Engenharia Ambiental
15/7/2009
AIR QUALITY INDEX (AQI)
Local air quality affects how we live and breathe. The U.S. Environmental
Protection Agency (EPA) and others are working to make information about
outdoor air quality as available to the public as information about the weather. A
key tool in this effort is the Air Quality Index, or AQI. EPA and local officials use
the AQI to provide the public with timely and easyto-understand information on
local air quality and whether air pollution levels pose a health concern.
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. So, AQI values below 100 are generally thought of as
satisfactory.
To make the AQI as easy to understand as possible, EPA has divided
the AQI scale into six categories, shown below:
“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.
“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.
EPA has assigned a specific color to each AQI category to make it easier
for people to understand quickly the significance of air pollution levels in their
communities. For example, the color orange means that conditions are
“unhealthy for sensitive groups”; the color red means that conditions may be
“unhealthy” for everyone, and so on.
