Over 20 million residents live in CA cities with worst air quality in US due to smog, report says

LOS ANGELES (KABC) -- A new report shows over 18 million residents living in the Los Angeles and Long Beach area continue breathing the unhealthiest air in the country due to smog.

According to the American Lung Association's latest State of the Air report, these are the top five U.S. cities polluted by ground-level ozone air pollution, or smog, with four of them located in Southern and Central California:

1. Los Angeles-Long Beach, California

2. Visalia, California

3. Bakersfield, California

4. Fresno-Madera-Hanford, California

5. Phoenix-Mesa, Arizona

The top 5 U.S. cities with the cleanest air are:

1. Honolulu, Hawaii

2. Johnson City, Tennessee

3. Lincoln, Nebraska

4. Bangor, Maine

5. Wilmington, North Carolina

"Air pollution can shorten lives. Particle pollution can contribute to lung cancer. Ozone and particle pollution can add to asthma burden and cause asthma attacks," said Will Barrett, national senior director for Clean Air Advocacy.

Dr. Sarah Rees with South Coast Air Quality Management District said several factors contributing to ozone pollution come from human influences.

"Most of the pollution that forms ozone in our region is coming from mobile sources, so things like trucks, ships, trains and aircraft, and those are subject to federal authority," Dr. Rees said.

The report also looked at particle air pollution, or soot, which comes from things like wildfires and diesel engines.

Bakersfield, Fresno and Visalia rank among the top 5 cities with worst air quality when graded on both short-term and year-round particle pollution, affecting over 2 million Californians.

"The amount of commerce going through the valley," Barrett said, "You've got the heavy-duty trucking corridors. You have a lot of agricultural equipment, you have the oil and gas operations there, and it's a valley. So a lot of the time, those particles can get trapped and settle for days on end."

Despite Southern California's hazardous air quality ranking, the report shows smog pollution has improved across the country over the last 25 years, with ozone levels at about half of what they were historically.

"We've seen tremendous progress. We've seen many months of unhealthy air days come off the books over that time period," Barrett said.

Experts say achieving cleaner air will require local, state and federal officials working together to reduce emissions.