The monitor colors on the map tell you how relatively clean or
polluted the air is, and what this might mean for your health. The
ranges are the corresponding Air Quality Index values.
More . . . about Pollutants,
Effects, and Standards;
FAQ about the
||0-50 = Good|
poses little or no risk
||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. Unusually sensitive people
should consider reducing prolonged or heavy exertion
||101-150 = Unhealthy for Sensitive
Members of sensitive groups may experience health
effects. For example, people with lung disease are at greater risk from
exposure to ozone, while people with either lung disease or heart
disease are at greater risk from exposure to particle pollution. Active
children and adults, and people with lung disease, such as asthma,
should reduce prolonged or heavy exertion outdoors. The general public
is not likely to be affected when the AQI is in this
||151-200 = Unhealthy|
Everyone may begin
to experience health effects; members of sensitive groups may experience
more serious health effects. Active children and adults, older adults,
and people with lung disease, such as asthma, should avoid prolonged or
heavy exertion outdoors. Everyone else, especially children, should
reduce prolonged or heavy exertion outdoors.
||201-300 = Very Unhealthy|
everyone may experience more serious health effects. Active children and
adults, older adults, and people with heart or lung disease, such as
asthma, should avoid all outdoor exertion. Everyone else, especially
children, should avoid prolonged or heavy exertion
poses little or no risk. Grey is used instead of green for NO2, SO2, and CO to avoid confusion
with ozone and PM2.5 on the Current Max map. Grey may also
indicate that a monitor is measuring 0 or very close to 0 (this may be
displayed as a negative value).
Health effects . . . learn
Behind the Colors &
How we determine healthy vs. unhealthy air
The colors are based on the Air Quality Index (AQI). The AQI is
calculated from the pollution level and the pollutant standards.
Pollutants have different standards, but the AQI is a number that allows
levels of different pollutants to be put on the same scale.
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 concern. For example, an AQI value of 50 represents
good air quality with little potential to affect public
An AQI value of 100 generally corresponds to the national air
quality standard for the pollutant, which is the level US EPA has set to
protect public health. 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.
For example: an AQI of 100 for ozone corresponds to an ozone
level of 0.070 parts per million (averaged over 8 hours). An AQI of 100
for PM2.5 (particles up to 2.5 micrometers in diameter) corresponds to a
level of 35 micrograms per cubic meter (averaged over 24
Source: USEPA . . . learn
What causes good or bad air?
Massachusetts currently meets the sulfur dioxide (SO2) ambient
air quality standards and does not experience unhealthy
Because SO2 is a criteria pollutant, MassDEP continues to monitor for
SO2 to ensure that SO2 levels continue to meet the standard.
Learn more about . . . . . SO2