Air Quality Trends - SO2
Air quality trends are used to assess if the air quality is improving and thereby determine if control and abatement strategies are effective.
Ozone • PM2.5 • Carbon Monoxide • Nitrogen Dioxide • Sulfur Dioxide • Lead
Sulfur dioxide (SO2) is a colorless gas, odorless at low concentrations but pungent at very high concentrations. It is generated primarily by the burning of fuels that contain sulfur. The main contributors to the release of SO2 in Connecticut are oil and coal fired power plants, industrial sources, residential heating and motor vehicles. All of Connecticut has been in attainment of the National Ambient Air Quality Standard (NAAQS) for SO2 since well before the Clean Air Act was amended in 1990.
EPA strengthened the primary NAAQS for SO2 on June 2, 2010. The revised primary SO2 standard is a new 1-hour standard at a level of 75 parts per billion (ppb). EPA’s evaluation of the scientific information and the risks posed by breathing SO2 indicate that this new 1-hour standard will protect public health by reducing people’s exposure to high short-term concentrations of SO2. The following chart shows that monitored 1-hour design values* in Connecticut have been below this standard since the year 2000.
Please select for a larger view of the above graph (PDF)
*To attain this standard, the 3-year average of the 99th percentile of the daily maximum 1-hour average at each monitor within an area must not exceed 75 ppb.
Content last updated February 5, 2025