The Baltimore-Washington doesn’t have the cleanest air in the nation, but made some improvements since last year, according to new rankings from the American Lung Association’s State of the Air 2010 report.

The rankings find that a decade’s worth of clean-up efforts, which include emissions reductions at coal-fired plants and a transition to cleaner diesel fuels, have made the nation’s air better in general. That helped this area reduce its levels of smog and soot.

The report says, however, that more than half the U.S. population suffers pollution levels that are often dangerous. Some cities, mostly in California, had dirtier air than in last year’s report.

 “State of the Air 2010 proves with hard data that cleaning up air pollution produces healthier air,” said Mary H. Partridge, the American Lung Association’s national board chair, in a statement. “However, more needs to be done. We are working with the U.S. Environmental Protection Agency on additional measures that will require even greater clean up of power plants. We are also calling for additional funding to install equipment to clean up the 20 million dirty diesel vehicles currently on the road polluting U.S. cities every day.”

The Baltimore-Washington area had the 16th worst air by ozone, or smog. And it had the 18th worst by short-term particle pollution, or soot. Air pollution data was collected in 2006-2008 around the nation.

Those with heart or lung disease, children and older adults are most likely to be affected by the particle pollution, according to the lung association. Some will develop irritated airways, coughing and difficulty breathing, and some may suffer heart attacks or even premature death. The smog irritate lungs and causes problems such as wheezing, coughing and asthma.

The Phoenix metropolitan was No. 1 for cities most-polluted by year-round particle levels. Bakersfield, Calif., had the most days of unhealthy short-term particle pollution. Los Angeles was the worst city for smog.

The Baltimore-Washington area had improvements in short-term level of particle pollution and smog, according to the report.

The lung association is urging the federal government to consider tighter limits on outdoor air pollution from coal plants and cars as part of the Clean Air Act Amendments of 2010. 

Baltimore Sun file photo of Brandon Shores Power Plant, which recently installed scrubbers/Kenneth K. Lam