Skip to main content.
Enviropaedia Sponsors and Supporters

Sulphur Dioxide

( Article Type: Explanation )

Sulphur dioxide (SO2) is a colourless, acrid gas formed by the combustion of sulphur. It is an oxidising and reducing agent and is used as a refrigerant, disinfectant, preservative and bleach. It reacts with water to give sulphuric acid, which means that when it is released as a gas through factory chimneys from boilers, it causes serious pollution. ‘Acid rain’ is frequently associated with sulphur dioxide pollution but a significant contributor to acid rain is carbonic acid, which forms when carbon oxides in the atmosphere combine with water. Sulphur dioxide is released from factory chimneystacks but is also released naturally in vast quantities during volcanic eruptions.

Sulphur is an important macro-nutrient for plants but as soon as its concentrations reach beyond tolerance levels, it becomes toxic and dangerous to most living things. In very high concentrations, sulphur dioxide is dangerous to health. In low concentrations, it is hazardous to young children, the aged and those with respiratory ailments. Sulphur dioxide mainly aggravates the respiratory tract and can cause secondary health impacts on those suffering from emphysema, asthma, bronchitis and illnesses of the respiratory tract and lungs, and heart disease. Sulphur dioxide is easily detectable and measurable as an air pollutant and is therefore used widely as an indicator for other common industrial air pollutants, including oxides of carbon and nitrogen, and linked photochemical pollutants.

Associated Organisations: