Sulfur Dioxide
Basic Information
The Clean Air Act requires EPA to set national ambient air quality standards for “criteria pollutants.” Currently, sulfur dioxide and five other major pollutants are listed as criteria pollutants. The others are ozone, lead, carbon monoxide, nitrogen oxides, and particulate matter. The law also requires EPA to periodically review the standards and revise them if appropriate to ensure that they provide the requisite amount of health and environmental protection and to update those standards as necessary.
Everywhere in the country has air quality that meets the current SO2 NAAQS. Only three monitoring sites in the Hawaii Volcanoes National Park recorded violations of the current SO2 standard between 2007-08. The state has suggested that these data should be considered part of an “exceptional event” (volcanic activity) and not considered for regulatory purposes.
Annual average ambient SO2 concentrations, as measured at area-wide monitors, have decreased by more than 70% since 1980. Currently, the annual average SO2 concentrations range from approximately 1 - 6 parts per billion.