The Environmental Protection Agency (EPA) has sent its final greenhouse gas (GHG) endangerment finding to the White House Office of Management and Budget for a 90-day review and approval. The agency’s action follows the U.S. Supreme Court’s ruling in April 2007 finding that GHGs are pollutants. As the next step, EPA must determine whether such pollution endangers human health or welfare. In its April 2009 Proposed Rule, the agency found that GHGs endanger both human health and welfare, and that emissions from new motor vehicles are contributing to the mix of heat-trapping gases. If the agency’s final determination is consistent with its proposal, the endangerment finding would set the stage for broad EPA regulations aimed at curbing heat-trapping emissions under the federal Clean Air Act. Medium and heavy-duty trucks are specifically referenced in the Proposed Rule.