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- Since 2002, Ann Arbor has maintained "good" Air Quality Index levels between 40 and 80 percent of the year, and "moderate" levels between 20 and 40 percent of the time. The data below show that the recent trend is few unhealthy days for sensitive groups. Although the air quality is improving overall, Washtenaw County will remain out of attainment for the 1-hour ozone standard, which recently was tightened from 0.08 to 0.075ppm.
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Source: Michigan Air Quality Reports |
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What is the Air Quality Index?
The Air Quality Index (AQI) is used for daily reporting of air quality as related to ozone, particulate matter, carbon monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide (SO2). It describes the health effects that may be associated with exposure to different levels of these pollutants, the groups most likely to be sensitive to the pollutant and simple measures that can be taken to reduce exposure.
AQI values range from 0 to 500. The higher the AQI value, the greater the level of air pollution -- and the greater the health danger. An AQI value of 100 generally corresponded to the national air quality standard for a pollutant. Thus, AQI values of less than 100 are usually considered satisfactory. When AQI values are higher than 100, air quality is deemed unhealthy for certain sensitive groups of people; as values rise, everyone becomes at risk. However, unusually sensitive people may experience health effects when AQI values are between 50 and 100. The highest of the AQI value for individual pollutants becomes the AQI value for that day. For example, if one day had certain AQI values of 150 for ozone and 120 for particulate matter, the AQI value would be 150 for that day.
What does the Air Quality Index tell us about our environment?
The higher the AQI value, the greater the level of air pollution -- and the greater the health danger. AQI values range from 0 to 500. An AQI value of 100 generally corresponded to the national air quality standard for a pollutant. Thus, AQI values of less than 100 are usually considered satisfactory. When AQI values are higher than 100, air quality is deemed unhealthy for certain sensitive groups of people; as values rise, everyone becomes at risk. However, unusually sensitive people may experience health effects when AQI values are between 50 and 100. The highest of the AQI value for individual pollutants becomes the AQI value for that day. For example, if one day had certain AQI values of 150 for ozone and 120 for particulate matter, the AQI value would be 150 for that day.
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Find out how YOU can help improve the State of Our Environment.
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Last Updated: June 2009
