America's most polluted cities

NEW YORK (CNNMoney.com) -- The nation's air has gotten marginally better over the past 10 years, according to an annual report released Wednesday, but many cities still suffer from severe pollution problems.

The American Lung Association released its latest findings on the state of the air in America - and the news is not great. Despite progress in cutting air pollutants and a burgeoning "green" movement, nearly every major metropolitan area is burdened with significant air pollution problems.

The organization rates communities on three criteria: ozone, short-term particle spikes and long-term particle averages. The ratings are based on statistics compiled for the years 2005 through 2007 at monitoring stations maintained by the U.S. Environmental Protection Agency. Los Angeles, Fresno and Bakersfield, all in California, had the dubious distinction of being in the top 10 list of all three categories.

The ALA found that the worst places to breathe are: Los Angeles, Bakersfield, Visalia, all in California, for ozone pollution; and Bakersfield, Pittsburgh and Visalia in terms of average particulates.

Pittsburgh recorded the highest number of particle pollution spikes, which are jumps in the number of particles in the air that can last for many hours or even days.

Of the 25 cities with the worst ozone pollution problems, 16 recorded higher ozone levels in this year's report compared with last year. A dozen of the 25 cities with the worst average particle problem (microscopic soot, diesel exhaust, chemicals, metals and aerosols) experienced an uptick in those pollutants. Another four showed no change and nine improved. Thirteen cities recorded more days of severe spikes in particle pollution

Six of every 10 Americans - 186 million people - live in places where their lives are endangered by the air they breathe, according to Stephen Nolan, the American Lung Association National Board Chairman.

"Air pollution is a major threat to human health," he said in a prepared statement. "When 60% of Americans are left breathing air dirty enough to send people to the emergency room, to shape how kids' lungs develop and to kill, air pollution remains a serious problem."

The healthiest cities list mostly consisted of cities in the wide-open spaces of America's heartland, far from heavy industry. Cheyenne, Wyo., had the lowest long-term particle average, followed by Santa Fe, Honolulu and Great Falls, Mont.

The lowest, nearly non-existent, ozone levels, were found in cities like Billings, Mont., Carson City, Nev., and Fargo, ND. Only two eastern cities were on any of the three least-polluted lists. Portland, in heavily forested Maine, had among the lowest spikes in particle emissions, and Port St. Lucie, on Florida's Atlantic coast, had among the lowest ozone levels.

The study also reported that ozone is more destructive than originally perceived. In March 2008, the EPA lowered its standard for ozone levels needed to trigger an unhealthy rating.

The pollutant is created by tailpipe emissions that get cooked by the sun and heat and form triple molecules of oxygen, which is much less stable than conventional oxygen and much more damaging to respiratory systems.

Los Angeles, which has a lethal combination of heavy traffic, sunshine and heat, had 195 days last year in which the ozone levels were high enough to be unhealthy for sensitive groups. On another 55 days, it was unhealthy for anyone and on 11 days, the ozone in the air was judged as very unhealthy.

Particle emissions are generated mostly by diesel engines, coal-fired power plants and burning of wood and other combustibles. For coastal cities, much of their pollutants are generated by ships coming into port, according to Janice Nolen, the association's vice president for policy and national advocacy.

"Ships contribute significantly to both particle and ozone emissions," she said.

Whatever the source, some states are taking aggressive action to try to combat the problem. New York, Charlotte and Washington have succeeded in reducing pollution dramatically over the past 10 years. California is introducing cleaner diesel fuel for everything from trucks to boats.

There's some criticism of the findings based on where the EPA monitoring stations are located. In Pittsburgh, for example, one station sits near the largest coke plant in the nation. Coke, an ingredient in steel manufacturing, is made by baking coal and produces lots of ash and other particles.

But Nolen pointed out that the findings try to capture the worst cases of air pollution for each metro area because that's what will have the most negative impact on health. So it's appropriate to locate monitors where the problems are most acute.