executive summary background over the next decade power plant operators may face significant requirements to reduce emissions of sulfur dioxide so 2 nitrogen oxides no x carbon co and mercury hg at present neither future reduction nor complete timetable is known for any these airborne compli ance planning difficult in response clean air act amendments 1990 caaa90 are now process making reductions emis sions phase ii program lowering allowable an annual cap 8 95 million tons became effective on january 1 2000 more stringent standards setting new emission limits boilers also took effect states beginning efforts address visibility problems regional haze national parks wilder ness areas throughout country because contribute formation they have be further reduced improve some near it expected that ambient quality stan
