"Two environmental groups petitioned U.S. EPA today to set national limits for greenhouse gases using the Clean Air Act.

The Center for Biological Diversity and 350.org petitioned (pdf) EPA to designate greenhouse gases as "criteria" air pollutants, which would require EPA to establish allowable nationwide concentrations for the gases. The groups are asking the agency to cap atmospheric concentrations of CO2 at 350 parts per million (ppm) -- a level the groups and some scientists say is necessary to avoid the worst effects of global warming."

Robin Bravender reports for Greenwire December 2, 2009. [2]