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

EPA strengthened the primary National Ambient Air Quality Standard 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. 

1-hour SO2 Design Value Trends 

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 December 14, 2023