Sulfur Dioxide

Sulfur dioxide is a colorless irritating gas having the same pungent odor as a struck match. Most people can detect its taste at a level of about 0.3 to 1 part per million. SO2 is highly soluble in water, forming sulfurous acid. On a worldwide basis, SO2 is considered to be one of the major pollution problems. It is emitted mainly from stationary sources that utilize fossil fuels (coal, oil) such as power plants, ore smelters, and refineries.

The health effects of sulfur dioxide appear to be always associated with high levels of particulates or other pollutants. The world's major recorded air pollution disasters have been associated with high levels of sulfur dioxide and particulates. The excess deaths attributed to these pollutants were due to respiratory failures and occurred predominantly, but not exclusively, in the elderly and infirm. Atmospheres containing high levels of sulfur dioxide are associated with elevated concentrations or other sulfur compounds such as sulfates and sulfuric acid mists, which are corrosive and potentially carcinogenic.

The corrosiveness of SO2 and its derivatives also causes crop and material damage. Its transport and transformation into sulfurous and sulfuric acids contribute to acid precipitation, causing soils and lakes to become seriously acidified.

There are two existing Primary national Ambient Air Quality Standards for sulfur dioxide. The first is a long-term one year arithmetic average of 0.03 parts per million (ppm). The second is a short-term 24-hour average standard where concentrations are not to exceed 0.14 ppm more than once per year. The current Secondary NAAQS for SO2 is a 3-hour average concentration of 0.5 ppm not to be exceeded more than once per year.

In addition there are three State standards for sulfur dioxide. The first is a long-term one-year arithmetic average of .022 parts per million. The second was a short-term 24-hour average standard of .088 ppm not to be exceeded. The third was a short-term 3-hour average concentration of .439 ppm not to be exceeded. During 1987 both of the short-term standards were amended to allow for one exceedance per year.

Sulfur dioxide is currently being monitored at the McFarland Hill site in Acadia National Park and beginning in January, 2008 will be monitored at a new site near the Deering Oaks Park in Portland using continuous monitoring equipment utilizing the pulsed fluorescent method. Data from the McFarland Hill monitor is currently available on the air quality web site and data will be added from the new site in Portland as soon as it is in operation. Long term trends in sulfur dioxide concentrations from three areas of the state can be viewed in the latest annual air quality report .

Monitoring

Sulfur Dioxide