Six in 10 Americans -- about 175 million people -- are living in places where air pollution often reaches dangerous levels, despite progress in reducing particle pollution, the American Lung Association said in a report released Wednesday.
The Los Angeles area had the nation's worst ozone pollution.
The report examined fine particulate matter over 24-hour periods and as a year-round average. Bakersfield, Calif., had the worst short-term particle pollution, and the Phoenix-Mesa-Scottsdale area of Arizona had the worst year-round particle pollution.
The U.S. cities with the cleanest air were Fargo, N.D., Wahpeton, N.D., and Lincoln, Neb.
The report is accurate but doesn't show how far California has come, said Dimitri Stanich, a spokesman for the California Air Resources Board.
"More than 45 percent of the days in the 1990 ozone season were considered very unhealthy (in the South Coast area). Today, 45 percent of the days are clean, more than double the number of clean days during 1990."
"So while we are still not meeting the federal air quality standards, the concentrations that Californians are exposed to are coming down dramatically," he said.
In Arizona, Benjamin H. Grumbles, the state's environmental quality director, issued a statement objecting to the methodology of the report highlighting the Phoenix area's levels of particulates such as dust.
"This finding came about because of one lonely air quality monitor near the cowtown area of western Pinal County, nearly 40 miles and across the mountains from downtown Phoenix," he said. He also called the report, based on 2006-08 figures, outdated, saying pollution levels have improved since then.
He said the state recognizes that the Phoenix area has significant air pollution problems, and "we're making some progress on dust and ozone in the Phoenix area, but not enough and not as quickly as we'd like."
The report doesn't do much to inspire pollution-plagued areas to continue working to clean their air, said Jaime Holt, chief communications officer for the San Joaquin Valley Air Pollution Control District in Fresno, which oversees the Bakersfield area.
"We are one of the dirtiest places in the nation, and we recognize that, but we are much cleaner than we used to be and we wish that side of the coin had been mentioned," she said.
The report gave Bakersfield an "F" grade - again.
"If you are a student who was getting 10 percent on tests every year and you improved to 50 percent on tests every year, you are still failing, but you've made tremendous improvements," Holt said.
But if the instructor keeps yelling that you are failing, it doesn't inspire you to keep doing the work it took to get from 10 percent to 50 percent, she said.
The Lung Association credited cleaner diesel engines and controls on coal-fired power plants for decreasing pollution such as soot and dust.
However, the report estimates that nearly 30 million people live in areas with chronic levels of pollution so that even when levels are relatively low, people can be exposed to particles that will increase the risk of asthma, lung damage and premature death.
About 24 million people live in 18 counties with unhealthy levels of ozone, short-term particle pollution and year-round particle pollution, the report said, adding that new research shows the risk of health problems from pollution may be worse than once thought, especially for infants and children.
The California Air Resources Board has tripled its estimates of premature deaths in California from particle pollution to 18,000 a year, the report said. Stanich said those numbers were taken from 2008 documents and were in the process of being updated now. He said he expected new numbers in about a month.
Freeways remain high-risk areas for everyone, the study said, increasing the risk of heart attack, allergies, premature births and infant deaths.
The two biggest air pollution threats in the United States are ozone and particle pollution, the Lung Association said. Others include carbon monoxide, lead, nitrogen dioxide, sulfur dioxide and a variety of toxic substances.
For the first time, the association included people living in poverty as one of its at-risk groups, reasoning that people with lower income levels face higher pollution risks.
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