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.
With public opinion polls plummeting due to hard-line environmental stances, the Bush administration in 2001 supported the changes.