Los Angeles is America's smog capital once again.
The megalopolis actually has had fewer smoggy days this year than last, continuing a relatively steady three-decade trend toward cleaner air. However, Houston and California's San Joaquin Valley, which in recent years rivaled and even surpassed L.A. as the smoggiest areas in the country, experienced exceptionally clean air this year.
As a result, the Greater Los Angeles region is again home to the worst smog in the nation, according to the federal Environmental Protection Agency's latest barometer for measuring the unhealthful haze -- a dubious distinction the region has held for most of the last half-century.
Air quality in Los Angeles, Orange, Riverside and San Bernardino counties has exceeded the federal health standard for more than 2 1/2 months this year.
"It's a tough job cleaning up the ozone at this point because there are not a lot of easy emissions to target," said Joe Cassmassi, planning and rules manager for the South Coast Air Quality Management District, the region's chief smog-fighting agency. "The low-hanging fruit, as a lot of people like to say, has been taken."
Ground-level ozone, the primary ingredient in smog, is formed when two types of air pollution react chemically while being cooked by the sun's rays. Both of the pollutants, volatile organic compounds and nitrogen oxides, are emitted during the burning of fossil fuels in cars, factories and power plants.
Scientists have linked breathing smoggy air to an array of health effects, including wheezing and coughing because of irritated lungs, increased asthma attacks, reduced lung power and even premature death.
The South Coast Air Basin, which includes all of Orange County and most of the urbanized parts of Los Angeles, Riverside and San Bernardino counties, exceeded the EPA's smog standard on 84 days this year.
Last year, the region exceeded the standard on 90 days, and in 2003, it surpassed it on 120 days. The standard limits airborne concentrations of smog, or ground-level ozone, to .08 parts per million over an eight-hour period.
By comparison, the San Joaquin Valley, which in recent years had been the nation's biggest violator of the eight-hour standard, exceeded it on just 72 days this year -- the fewest ever since regulators began recording smoggy days. The region surpassed the mark on 109 days last year and 134 days in 2003.
