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Sulfur Dioxide


What is it?
Sulfur dioxide (SO2) is a gas prevalent in crude oil, coal, and ore containing common metals like aluminum, copper, zinc, lead and iron. 

Where does it come from?
SO2 is formed when fuel-containing sulfur is burned and when gasoline is extracted from oil, or when metals are extracted from ore.  Once it is released into the atmosphere, SO2 dissolves in water vapor to form acid (acid rain).

The majority of SO2 released into the atmosphere comes from coal burning power plants.  Other sources of this pollutant are petroleum refineries, cement manufacturing, and metal processing facilities.  Also, locomotives, large ships, and some non-road diesel equipment currently burn high sulfur fuel and release SO2 emissions to the air in large quantities.

How is it harmful?
Many of the potential dangers resulting from the release of SO2 in the air are directly related to how it reacts with other materials.  One danger is the formation of acid rain, which can damage plant and animal life as well as damage buildings and monuments.  SO2 also causes potential human health respiratory and cardiovascular problems for people who have heart or lung disease or asthma. 

What's being done to help?
The amount of SO2 released from coal-fired power plants needs to continue to be reduced.  Various restrictions have been and are being put in place to limit the amount released.  With the installation of pollution control equipment at power plants along with reducing the average sulfur content in fuel has helped make large advances toward decreasing the emission of this pollutant.  However, work is needed for continued maintenance and reduction of SO2.

The Environmental Protection Agency (EPA) currently has a one-hour and three-hour standard for SO2 set at 75 parts per billion (ppb), 0.5 ppm respectively.  These standards are subject to change as updated scientific information is obtained on the effects of this pollutant on human health.

Regional Matters:
The ten-county region of North Central Texas currently falls within the one-hour and three-hour concentration limits set by the EPA.  There are currently four monitors throughout the region that measure SO2.

11/21/2017 JPL/MG %Trans

 North Central Texas Council of Governments | 616 Six Flags Drive P.O. Box 5888 Arlington, TX 76005-5888
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