The Environmental Protection Agency finalized an update to its national ambient air quality standard for fine particulate matter (PM2.5), including soot, December 14, setting the annual health standard at 12 micrograms per cubic meter, down from the 1997 15 ug/m3 standard. The agency made no changes to the 24-hour fine particle standard or the standard for coarse particulate matter (PM10), and 99 percent of U.S. counties are projected to meet the revised standard without any additional actions by 2020. Early in the day, Senators Orrin Hatch (R-UT), Mary Landrieu (D-LA), Roy Blunt (R-MO), Jim Inhofe (R-OK), Mike Lee (R-UT), and Rob Portman (R-OH) sent a letter urging the agency not to finalize a tighter standard because of economic dangers for nonattainment areas. While the American Lung Association, the American Public Health Association, the Environmental Defense Fund, the League of Conservation Voters, Natural Resources Defense Council, and other environmental and public health groups applauded the agency’s decision, the National Association of Manufacturers, the American Petroleum Institute, and other industry groups opposed it.