Council on Environmental Quality

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Indicators:  Air

Clearing the Air

The data for 2007 show a positive change from 2006. The one-year change is not always consistent with the long-term trend, which is displayed on the graph.

Connecticut’ s air in 2007 was the best in decades.  Even though the summer had fewer good air days, the air during most of the year was cleaner than usual.

Air Pollution Trend

Six air pollutants -- sulfur dioxide, lead, carbon monoxide, particles, nitrogen dioxide, and ground-level ozone -- are measured across the state by the DEP. At the end of every year, the Council expresses the average level of each pollutant on a numerical scale, where zero equals no pollution and 100 represents the “unhealthful” level of the specified pollutant. The Council then takes this annual number for each of the six pollutants and averages them to yield the single index value on this graph. Levels of lead in the air have dropped so low that they barely register in this indicator. Following several years of measurable improvement, 2005 was the first year since 1994 to see all of the pollutants (excluding lead) get worse. In 2006, all pollutants except particles showed improvement, and in 2007 all pollutants except ground-level ozone showed improvement.