Los Angeles, April 28 (IANS) Air pollution poses a threat to the health of about 154 million Americans or more than half of the US population, the American Lung Association (ALA) stated Wednesday.

The air is so polluted in some areas that it is often dangerous to breathe, Xinhua quoted the ALA stating in its annual report on air quality across the US.

About 48 percent of US residents live in counties where smog (ozone) is too high, 20 percent live in areas where there are too many short-term spikes in pollution and six percent live in areas with harmful year-round soot (particle pollution), said the report.

About 17 million Americans live in areas afflicted by all three air pollution hazards, the report noted.

The report listed California as the most polluted state, where people are breathing some of the worst air.

Compared with other states, California has more polluted places, including Los Angeles, Long Beach, Riverside, Bakersfield and Fresno, the report said.

Research suggests air pollution threatens human health -- and not just the lungs.

Small particles of pollution can lodge deep in the lungs, triggering an inflammatory process that, over time, can spread elsewhere in the body and damage blood vessels and the heart, said Norman Edelman, the ALA's chief medical officer.

In addition to posing both long-term and short-term risks, pollution can also contribute to low birth weights, diabetes, cardiovascular disease, heart attack, stroke and, ultimately, shorter life spans, he warned.