Indicators:  Air

On a Good Air Day, 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, particulates, nitrogen dioxide, and ground-level ozone. Connecticut’s goal is to have air that meets health-based standards for all pollutants except particulates by the year 2010.

Violations of the 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. Looking at ground-level ozone data from the past seven years, we see that 2005 was worse than average but that 2006, with 13 days when health standards were violated, was a little better than average. The graph above does not reflect any “bad air days” for particulates, but it probably will in future reports. In December 2006, the federal government tightened the daily standard for fine particulates in the air. (A “fine” particulate is less than 2.5 micrometers in diameter.)

Monitoring records from recent years show that the levels of fine particulates at some coastal Connecticut locations would have been considered violations if the tighter standard had been in effect during those years. Because the new standard was not in effect, the number of “good air days” counted in this indicator was not affected. Beginning next year, this indicator will be revised to take into account the new standard. Connecticut must meet the new air quality goals for fine particulates by 2015.