Sulfur dioxide (SO2) is a colorless gas with a sharp, pungent smell. It is produced naturally by volcanic eruptions and is also released during the burning of fossil fuels, such as coal and oil. SO2 is significant in the formation of acid rain, which can harm ecosystems, buildings, and human health. In the atmosphere, SO2 can react with water vapor to form sulfuric acid, contributing to air pollution. It is also monitored as part of air quality regulations due to its potential health effects, including respiratory problems. Efforts to reduce SO2 emissions are important for environmental protection and public health.