Sulfur Dioxide           Sulfur dioxide emissions historically have been regulated under the Clean Air Act because of health concerns. Sulfur dioxide interacts in the atmosphere to form sulfate aerosol particles which can be inhaled.  In the eastern U. S. sulfate aerosols constitute about 25 percent of inhalable particles.  These particles account for about half of visibility reduction in these same areas.

     Sulfur is a contaminate in oil which makes its way into gasoline for motor vehicles.  The federal EPA wants sulfur levels of gasoline sold in the United States reduced substantially. So, in December 1999, President Clinton announced a mandated schedule for a major reduction of gasoline sulfur content. California has switched to low-sulfur gasoline and the European Union, Japan, and Canada have decided to follow suit. Calfornia regulators believe that the move to low-sulfur gasoline in 1996 was the most important step toward improving air quality since the 1975 introduction of the catalytic converter.

     Haze over national parks has been a decades-old problem. Sulfur dioxide is a major culprit. The Clinton administration proposed a rule to eliminate 90% to 95% of sulfur emissions from 26 industrial sources, particularly 600 old (1962-1977) coal-fired power plant boilers. With public opinion polls plummeting due to hard-line environmental stances, the Bush administration in 2001 supported the changes.

Last updated on Tuesday, July 24, 2001