In 2008, Connecticut had the second-highest number of Good Air Days it has had in decades. Nonetheless, levels of ground-level ozone violated the standard that protects human health on 22 sunny summer days. Fine particles violated the standard on three of those same days and on six other days.
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A Good Air Day is a day when every monitoring station in the state records satisfactory air quality. “Satisfactory air quality” is defined here as air that meets the health-based ambient air quality standards for all of the following six pollutants: sulfur dioxide, lead, carbon monoxide, particles, nitrogen dioxide, and ground-level ozone.
Connecticut’s goal is to have air that meets health-based standards for all pollutants. Violations of health-based air quality standards have been eliminated for all pollutants except ground-level ozone and fine particulates.
Ozone is created when nitrogen oxides and organic compounds in the air react in the presence of sunlight. Weather is a big factor in year-to-year fluctuations. Motor vehicles remain a major source of ozone-forming emissions despite improvements in tailpipe standards. Much ground-level ozone originates in states to Connecticut’s west. In the past 40 years, only 2004 had fewer violations of the ground-level ozone standard than 2008.
Last year's report noted the odd pattern of ozone pollution in 2007, when coastal communities suffered fewer bad days than many inland cities and towns. In 2008, the pattern returned to normal, with southern cities and towns recording more bad days than most inland towns. With normal summertime air movement from the southwest, this pattern is to be expected.
Fine particles, such as those found in smoke and haze, are 2.5 micrometers in diameter and smaller. These particles can form when gases emitted from power plants, industries and automobiles react in the air. Violations of the standard occur mostly in summer and winter, rarely in spring and fall. All of Connecticut except for Fairfield and New Haven counties meet this standard for fine particles. Those counties must meet the new air quality goals for fine particles by 2015.
Technical Note: The federal government modified the standards for fine particles in December 2006 and for ground-level ozone in early 2008. The chart above was redrawn to illustrate the state's historical pattern of good air days by applying the new, stricter standards to all years.
