Breathe Better Air, Breathe Easier

摘要

This year marks the 45th anniversary of the 1970 Clean Air Act. Under the Act, the U.S. Environmental Protection Agency safeguards public health by setting national standards for six "criteria" pollutants: particu-lates, ozone, lead, sulfur dioxide, nitrogen oxides, and carbon monoxide. In 2007, the U.S. Supreme Court ruled that greenhouse gases were also air pollutants, so to comply with the Clean Air Act the EPA must now regulate greenhouse gas emissions (see Massachusetts v. EPA, 549 U.S. 497 (2007)).