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.
Learn More . . . about Pollutants, Health Effects, and Standards; FAQ about the map
||0-50 = Good|
Air pollution 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 outdoors.
||101-150 = Unhealthy for Sensitive Groups|
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 range.
||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|
Health alert: 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 outdoors.
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 more
Behind the Colors & Numbers
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 health.
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 0.075 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 hours).
Source: USEPA . . . learn more
What causes good or bad air?
Massachusetts currently meets the sulfur dioxide (SO2) ambient air quality standards and does not experience unhealthy levels.
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