SMOGGY L.A. BETTER, BUT STILL TOPS IN NATION.

Byline: - Karen Rubin

Los Angeles' air is getting cleaner, with the lowest ozone levels on record this year, but it's still bad enough to make the city this year's smog capital of the nation, officials said Tuesday.

For a third year in a row, Los Angeles did not have a Stage 1 smog episode, but the city outpaced rival Houston for the nation's smoggiest city title.

``Despite the population growth and the distances people are driving, we are seeing a steady trend toward cleaner air,'' said Sam Atwood, a spokesman for the South Coast Air Quality Management District, the air pollution control agency for major portions of Los Angeles, San Bernardino and Riverside counties, as well as Orange County.

Los Angeles' ozone danger period - from May 1 to Oct. 31 - recorded ground-level ozone levels exceeding national health standards for 36 days. Last year, Los Angeles exceeded the national level on 40 days.

Barry Wallerstein, executive officer for the AQMD, said the air is cleaner because of regulatory programs.

``Air quality continued a long-term improving trend this year due to a number of successful air pollution control programs,'' he said.

Air is getting cleaner due to programs that demand cleaner cars, cleaner gasoline, a reduction in the amount of fumes and smoke-forming emissions, officials said.

Cleaner paints, hair sprays, nail polish and household cleaners also contribute, they said.

Air quality is considered unhealthy when the federal one-hour standards for ozone, 0.12 parts per million, is exceeded.

Still weather can play a role, and the Los Angeles area had a smog season that was generally conducive to ozone formation, Atwood said.

A hotter-than-normal summer inland created a layer of warm air over the entire region, trapping ozone-forming pollutants.

While the area saw fewer unhealthy ozone days, residents experienced a slightly higher peak air pollution level, officials said.

That level rose from 0.184 to 0.190 parts per million this year, said AQMD senior meteorologist Joe Cassmassi.

``Even though this summer was somewhat cooler than last, the meteorology was more favorable for smog formation,'' he said.

Because ozone, the principal ingredient of smog, forms when volatile organic compounds and nitrogen oxides mix with sunlight, conditions such as clouds and rain can affect ozone formation, Wallerstein said.

Wind also plays an important role, with calm winds favoring the formation of smog.

Still, Atwood said that Los Angeles low levels even under these conditions is testament to years of efforts to reduce ozone-forming emissions.