|  | Public Health Safety | Public Health

Levels of Sulfur Dioxide by UN Standards

Sulfur dioxide is the predominant form of sulfur oxide present in Earth’s atmosphere. Volcanoes are natural sources of SO2 and account for between 35 and 65 percent of total emissions. Manmade sources of SO2 are thermal power plants that burn high-sulfur coal, metal smelters and domestic fuels for cooking and transportation. High exposure to sulfur dioxide can cause pulmonary damage in humans, destroy vegetation and corrode building masonry.

  1. World Health Organization

    • The World Health Organization is the public health arm of the United Nations. The WHO publishes guidelines on air quality to offer governments guidance about levels of particulate matter, ozone, nitrogen dioxide and SO2. Studies by the WHO estimate diseases caused by air pollution cause more than 2 million premature deaths annually. Half of these deaths occur in developing countries.

    Particulate Matter

    • Airborne particulate matter consists of fine particles of dirt, dust and smoke. The sources of particle matter are usually the same as SO2 emissions. But sulfates created by the reaction of SO2 with other elements and compounds in the atmosphere do not constitute a large proportion of total particulate matter. This contradiction introduces difficulties in estimating emissions guidelines for both particulate matter and SO2.

    Short-Term Exposure

    • Exposures to SO2 fumes for as little as 10 minutes can cause asthma symptoms or lung malfunction in humans. The WHO guidelines recommend SO2 concentration in air should not exceed 500 micrograms per cubic meter during 10-minute periods. Short-term exposure to SO2 depends on local sources of the emissions, such as cooking or transportation fuels and meteorological conditions.

    Longer-Term Exposure

    • Scientists have difficulty estimating the effects of separate air pollutants for exposure periods in excess of 24 hours. Studies in North America and Europe have failed to find a causal relationship between SO2 levels and mortality. These uncertainties led WHO to revise its air quality guidelines for SO2 to 20 micrograms per cubic meter for a 24-hour period.

    Annual Exposure

    • The WHO believes if nations comply with its guidelines for 24-hour exposures to SO2, then annual exposure guidelines are unnecessary. Acknowledging its 24-hour guidelines may be difficult economically for some emerging nations to achieve, the WHO has suggested two interim 24-hour targets of 125 and 50 micrograms per cubic meter for those countries. Such goals would be feasible for emerging economies to control emissions from one source at a time, such as motor vehicles and industrial plants.

Public Health - Related Articles