May 01, 2007
State of the Air 2007 in the United States
The upside is that smog levels declined nationwide between 2003 and 2005, aided by the appearance of more pollution controls on smokestacks, according to the report, called "State of the Air: 2007." The bad news is that the number of places in the United States reporting unhealthy levels of soot grew over the same period, the report found. Soot describes the tiny particles of pollution generated by burning fossil fuels. Soot pollution can increase hospital visits for heart and asthma problems, the American Lung Association said.