A.V. HAS CLEANEST AIR IN 7 YEARS FEWER BAD AIR DAYS, BUT VALLEY STILL VIOLATES U.S. STANDARD.

Byline: CHARLES F. BOSTWICK Staff Writer

LANCASTER -- Antelope Valley had its cleanest air in seven years this summer.

Ozone levels measured in Lancaster violated the stiff state air quality standard 22 days, the fewest bad air days since 1999 and the third best year since measurements began in 1976, records show.

``It was a big difference. This was an exceptional year for air quality,'' Antelope Valley Air Quality Management District spokeswoman Violette Roberts said.

Though bad air days were fewer, the valley remains in violation of federal air quality standards, as is all of Southern California from Kern County southward except for Santa Barbara County.

The valley violated the basic federal ozone standard 16 times this year, down from 31 last year, posting the second best reading since the standard was adopted in 1997.

The Antelope Valley AQMD also measures particulate pollution, but those readings won't be announced until the end of the year. The valley hasn't violated the federal particulate standard in more than 10 years, and in recent years has exceeded the stiffer state standard one or two days.

The Antelope Valley's air suffers from being downwind from two of the smoggiest places in the United States: the San Joaquin Valley and the Los Angeles area.

The federal ozone standard was violated 86 days as of last month in the South Coast Air Quality Management District that covers urban Southern California and 82 days in the San Joaquin Valley, the South Coast AQMD said. (Houston was third at 34 days.)

Roberts said most of the Antelope Valley's air pollution this summer blew in from the Los Angeles Basin -- as is evident to anyone who noticed the brown cloud wafting most late summer afternoons through Soledad Pass.

The Antelope Valley's ozone levels have improved markedly since the late 1970s, when Stage 1 smog alerts came every year. From 1977 through 1981, every year there were one or more days of Stage 1 smog alerts, including seven days each in 1980 and 1981, records show. The valley's last Stage 1 alert was in 1989.

The state standard is .09 parts per million (ppm), measured in hourly readings. The basic federal standard is 0.08 parts per million (ppm) averaged over eight hours.

A Stage 1 alert is called when ozone hits .20 ppm. The highest reading this summer was .13 ppm.

The Antelope Valley is most likely to get high levels of ozone on days when an inversion layer settles over the Los Angeles Basin, then gives up its pollutants to a breeze that blows them into the desert.

Antelope Valley ozone levels typically peak between 4 and 6 p.m. on summer days, after the inversion layer rises high enough to let the pollutants spill over the San Gabriel Mountains, experts say.

Because of weather patterns, most bad air happens in June and July, and the smog season is considered to end in October.

A basic component of smog, ozone can irritate air passages, reduce lung function, aggravate asthma, and inflame and damage the cells lining the lungs, the U.S. Environmental Protection Agency says. It also may aggravate chronic lung diseases like emphysema and bronchitis, may reduce the immune system's ability to fight off bacterial infections in the respiratory system and may cause permanent lung damage.

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