Air Quality Improves Markedly

California’s air quality took a substantial turn for the better in 2004, after three years of steadily worsening smog had sparked fears that the state was losing its decades-long war against air pollution.

The explanation for the improvement, air-quality experts say, boils down to simple meteorology: It has not been as hot this year in California.

The good news regarding bad air days demonstrates that the state’s notoriously hazy skies are not only a product of pollution, but of weather conditions that often make California a perfect hothouse for smog.

“Every year, the fleet of cars gets a little cleaner, and we see improvements in the pollutants that form smog,” said Jerry Martin, a spokesman for the California Air Resources Board. “The big unknown is the weather. You don’t get really high levels of ozone until pollution has spent several days cooking in the sun.”

Last year, Los Angeles, Orange, Riverside and San Bernardino counties surpassed a key federal health standard for ozone, the main ingredient in smog, on 64 days by the end of September -- nearly one-fourth of the time. So far this year, the region has exceeded the standard on just 27 days.

Similarly, the San Joaquin Valley, which has begun to challenge L.A. as the state’s smog capital, has violated the ozone standard on only nine days, compared with 36 at the same time a year ago.

By contrast, Houston, which has vied with regions in California for the title of the nation’s smoggiest place, experienced a slight increase in exceptionally bad air days this year.

Houston exceeded federal health standards for ozone over a one-hour period on 31 days so far this year, making it the smog capital -- at least by that test. But the San Joaquin Valley fared far worse than Houston according to another federal measure of ozone over an eight-hour period, leaving room for debate.

Breathing air with high levels of ozone can cause shortness of breath, nausea and headaches. Repeated exposure has been linked to serious health problems including asthma and heart disease.

Cars are the largest source of smog-forming emissions in California, followed by household chemicals from cleaning supplies and paints. Diesel engines powering trains, ships, buses and construction equipment also are a major contributor, and remain loosely regulated compared with other causes of pollution.

There were several smog hotspots in Southern California this year, notably Santa Clarita. It violated the federal maximum for ozone more often than any other area of Southern California.

Meanwhile, the twin ports of Los Angeles and Long Beach, a growing source of air pollution, barely registered on the smog meter, largely because the emissions they spew do not form smog until they blow farther inland.

The year’s highest smog reading -- .163 parts per million of ozone in the air -- was registered in the central San Bernardino Mountains, historically the smoggiest part of Southern California due to wind-blown pollution from the Los Angeles area.

High as it was, that reading was the lowest recorded in the region for any year since air-quality officials began carefully monitoring ozone in 1976. The same area registered a high of .216 ppm ozone a year ago. The federal health standard for ozone over a one-hour period is .12 ppm.

Scientists have long known that high temperatures help cook the chemical stew of pollutants that forms smog. Milder weather makes the stew boil more slowly, resulting in lower ozone levels.

Air-quality experts say the spring cloud layer, known locally as “June gloom,” seemed to last longer this year, lowering temperatures.

“It was a very cool early part of the summer. There were a few exceptions, but the real severe weather days were not there this year,” said Joe Cassmassi, senior meteorologist for the South Coast Air Quality Management District.

The lower occurrence of smoggy days this year conforms with a trend toward cleaner air in California, which has been aggressively regulating air pollution for more than 50 years.

“Certainly, the long-term trend shows improvement in ozone air quality,” said Lynn Terry, deputy executive officer of the Air Resources Board.

Although the air above Los Angeles still shrouds the downtown skyline in a brown pall, pollution experts say it is almost pristine compared with the thick smog the city was notorious for following World War II.

Even a decade ago, Southern California violated ozone standards nearly twice as often as it does today. Peak ozone levels were also higher, which triggered public health alerts by local officials warning people to stay indoors. Until high ozone levels required one last year, Southern California had not seen a Stage 1 health alert since 1998.

A surge of smoggy days in California in recent years, however, had undermined the pattern of reductions, leading some experts to fear that the state had begun losing ground.

In 2001, the four-county South Coast Air Basin experienced 36 days exceeding the federal one-hour ozone standard, followed by 45 days in 2002 and 64 days in 2003.

Although air quality may be improving, Southern California is still failing to meet federal standards, which are becoming tougher due to growing knowledge about the dangers of air pollution, critics note.

The Environmental Protection Agency this year announced that by 2021 cities will have to meet the ozone standard that measures the pollutant in the air over an eight-hour span. It requires levels to remain below .08 ppm.

So far this year, the South Coast area has violated that standard on 86 days -- roughly a third of the time. The San Joaquin Valley, which is expected to have a harder time meeting the eight-hour standard because its pollution lingers longer, has exceeded it on 97 days so far this year.

Although ozone has been the barometer used to measure air pollution in California, air-quality experts are increasingly concluding that particulate matter -- microscopic specks commonly released into the air by car, truck and ship exhaust -- may be more dangerous.

A recent USC study that tracked Southern California children from fourth grade until they graduated from high school found that children growing up in polluted areas were more likely to have underdeveloped lungs, leading to a lifetime of possible health problems.