Toxic Effects of Sulfur Dioxide: A Review

Sulfur dioxide (SO₂) is a colorless, pungent gas that is a significant contributor to air pollution, with well-documented environmental and health impacts. It is emitted both naturally (e.g., in volcanic activities) and anthropogenically (e.g., fossil fuel combustion, sulfuric acid production, papermaking, and wine preservation). Inhalation represents the primary route of human exposure, particularly in urban and industrial settings. Acute SO₂ exposure can lead to airway irritation, laryngospasm, bronchoconstriction, pulmonary edema, and death in severe cases. Chronic exposure, even at low concentrations, can contribute to the development of pulmonary and extrapulmonary diseases. Despite its classification as a hazardous air pollutant, a comprehensive understanding of dose-response relationships, exposure thresholds, and mechanisms of toxicity for SO₂ remains limited. This review synthesizes current knowledge on environmental sources, exposure routes, mechanisms of toxicity, and health impacts of SO₂, highlighting findings from epidemiological, toxicological, and mechanistic studies. We also discuss gaps in knowledge regarding SO₂, approaches to monitor and assess SO₂ exposure in ambient environments, the emerging role of SO₂ as a gasotransmitter, and areas where further research is needed to better understand health risks and support evidence-based public health decision-making.