May 1, 2008 -- Up to 125 million Americans are breathing air that puts their health at risk, a report released Thursday by the American Lung Association estimates.
The report shows that dozens of U.S. cities and counties regularly have unsafe levels of particulate and ozone smog pollution. Such pollution is a risk factor for worsening illness in people with asthma and other diseases but could also pose risks to healthy people, the report states.
The annual report ranks U.S. cities and counties on the number of unsafe air days throughout the year.
"Los Angeles remains the most ozone-polluted city in the nation," American Lung Association Vice President Janice Nolan told reporters. The city also scored at the top of the list for worst year-round particulate exposure.
Ozone pollution is produced when exhaust from cars, power plants, and other sources reacts chemically in sunlight. Particle pollution is a mix of solid particle and liquid droplets in the air. It can include soot, dust, pollen, chemicals, and metals.
"This process wreaks havoc in people with chronic lung disease," says Norman H. Edelman, MD, the American Lung Association's chief medical officer.
Overall ozone levels dropped about 7% nationwide between 1997 and 2006, according to Environmental Protection Agency (EPA) data. But the EPA angered environmental groups in March when it set a more lax ozone pollution standard than scientific advisors said was necessary to protect human health.
A report issued last week by the National Academy of Sciences (NAS) confirmed that ozone pollution poses risks to children, the elderly, and people with chronic diseases. But NAS experts also issued a statement declaring that "premature deaths are not limited to people who are already within a few days of dying."
After Los Angeles, cities with the worst year-round particle pollution included:
After Los Angeles, cities with the worst ozone pollution included: