https://www.epa.gov/so2-pollution
Sulfur Dioxide (SO2) Pollution | US EPA
Information on setting and implementing the outdoor air quality standards for sulfur dioxide.
sulfur dioxidepollutionusepa
https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/sulfur-dioxide
Sulfur Dioxide | American Lung Association
Sulfur dioxide (SO2) is a gaseous air pollutant composed of sulfur and oxygen. SO2 forms when sulfur-containing fuel such as coal, oil, or diesel is burned.
american lung associationsulfur dioxide