EPA recently denied a petition from environmental organizations imploring the agency to regulate carbon dioxide and other greenhouse gas emissions from automobiles. The petitioners -- Greenpeace, the Sierra Club and the International Center for Technology Assessment -- argued that EPA is obligated by the Clean Air Act to regulate greenhouse gases emitted from mobile sources. The agency countered that it does not have such authority and stated its belief that “setting GHG [greenhouse gas] emission standards for motor vehicles is not appropriate at this time.” In fact, the Clean Air Act requires the EPA to limit all air pollution from automobiles that “may reasonably be anticipated to endanger public health or welfare.” (Section 202 (a)(1)) Greenhouse gases do not directly harm humans, but scientists blame them for global warming, which poses an enormous threat. “Refusing to call greenhouse gas emissions a pollutant is like refusing to say that smoking causes lung cancer,” said Melissa Carey, climate policy specialist with Environmental Defense. “It's time to stop the denial and start focusing on solutions." The Bush administration has continually denied the problem of global warming, ignoring scientific consensus. Most recently, the White House forced EPA to drop a section of a report on climate change that blamed human activity -- such as rising concentrations of smokestack and tail pipe emissions -- for contributing to the problem. The environmental groups are now expected to sue EPA in an effort to force the agency to impose regulatory controls. Meanwhile, Congress is expected to consider legislation imposing greenhouse gas restrictions in the coming months.