By Steve Gorman
LOS ANGELES (Reuters) - Los Angeles may boast some of the best weather among U.S. cities while scoring high in celebrity sightings, but the Southern California metropolis remains unable to shake off its more notorious No. 1 rankings for worst smog and heaviest traffic.
Los Angeles, the nation's second-largest city, again topped the charts for ozone pollution, and finished fourth for particulate pollution such as dust and soot, in the American Lung Association's annual national air quality report card, released on Wednesday.
The farming town of Bakersfield, California, was rated No. 1 for particulates.
The greater Los Angeles area has ranked every year but one since the association's first report in 2000 as the city with the worst levels for ozone, a key component of smog formed when sunlight reacts with hydrocarbon and nitrous oxide emissions.
A major source of ozone pollutants is tailpipe emissions from automobiles, which in turn account for Los Angeles' No. 1 ranking this year as the nation's most traffic-clogged city, according to a separate annual study released on Wednesday.
Honolulu dropped from first to second place in traffic congestion, followed by San Francisco at No. 3, the traffic-data company Inrix, based in Seattle, reported.
Inrix also found road and highway congestion in the Los Angeles area was back on the rise in early 2013 after two straight years of decline, a likely reflection of an improved economy.
Los Angeles has roughly 10 times more roads than Honolulu, but the Inrix study provides a comparative gauge of travel time it calls the "gridlock index," which measures the intensity of traffic congestion to local drivers as it occurs.
According to Inrix, the average Los Angeles motorist wasted 59 hours last year in jammed traffic, compared with 50 hours for the average Honolulu driver.
In terms of air quality, California as a whole dominated the list of the most polluted U.S. cities, accounting for seven of the top 10 for ozone and eight of the top 10 for annual levels of particulate pollution, the American Lung Association said.
Nearly 90 percent of Californians, or 33.5 million people, live in areas plagued by unhealthy air, especially in Los Angeles, the so-called Inland Empire region east of the city, the state capital of Sacramento, and the agricultural heartland of the San Joaquin Valley, the group's study found.
Those residents are at greater risk for asthma attacks, heart attacks and premature death, the association said.
However, many California cities have shown steady progress on improving air quality, particularly the Los Angeles region, whose ozone levels have fallen by 36 percent since the organization's first State of the Air report card in 2000.
The region's annual particle pollution has dropped by 43 percent in that time and is now close to meeting the federal year-round standard for particulates.
The U.S. cities ranked as having the cleanest air in the latest report were Ames, Iowa, for ozone and Cheyenne, Wyoming, for annual particulate pollution.
(Reporting by Steve Gorman; Additional reporting by Dana Feldman; Editing by Cynthia Johnston and Eric Beech)