Smog Reaches Unhealthful Levels in Simi : Environment: Federal standards are surpassed for the first time in Ventura County this year.

Hot sunshine and sluggish onshore breezes pushed smog levels in Simi Valley over Memorial Day weekend to unhealthful levels for the first time this year in Ventura County, air quality officials said Tuesday.

The pollution standard index for ozone, a major component of smog, reached 100 Saturday, touching the unhealthful level, according to readings taken in Simi Valley by the county Air Pollution Control District. On Sunday, the level pushed up to 114.

Anything more than 100 is considered unhealthful according to the pollution standard index of the federal Environmental Protection Agency, but California’s stricter pollution standards consider air unhealthful if the smog is just three-quarters that thick.

Ozone levels dropped considerably Tuesday, but district forecasters predict that it will push upward today in Simi Valley toward levels that would violate state air quality standards.

And district data shows that Thousand Oaks violated state pollution standards Saturday and Sunday. And in Ojai, which suffered the next most severe pollution levels, the air was unhealthful by state standards Saturday and had improved only slightly Sunday.

“This is typical,” said William Mount, deputy air pollution control officer in Ventura County. “Our smog season runs May through October, and the meteorology is conducive to fairly high levels of ambient ozone in those months. Over the weekend, we got strong sunlight and fairly stagnant conditions.”

Smog hit unhealthful levels for the first time in 1993 on May 9, Mount said.

Simi Valley, Ojai and other inland areas often suffer some of the worst pollution in the county because they are in “convergence zones.” Their canyons trap smog blown in from the Oxnard Plain by sea breezes, and from the San Fernando Valley when winds are blowing out to sea, Mount said.

“Winds have been onshore for the last few days, and what happens is all the emissions from Ventura and Oxnard move onshore into the canyons,” he explained.

The high volume of holiday traffic could also have pushed the smog levels higher, Mount said. “Vehicles typically are emitting higher levels of pollutants when the traffic’s congested,” he added.

Ventura County’s May-to-October smog season parallels changes in the weather that worsen the concentration of pollutants from vehicles and industry--which actually remain fairly constant throughout the year, Mount said.

“It’s just so meteorologically specific,” he said. “That’s what people don’t seem to realize. The same amount of stuff is going through the air every day. Everybody’s driving their car the same way.

“A lot of people want to believe that our ozone problem is due to the L. A. region, but typically our worst days for ozone are when the wind is blowing from the west.”

Air pollution in Ventura County has decreased dramatically in recent years. In 1974, its air pollution levels violated the federal health standard for ozone on 122 days, but that dropped to 45 days in 1984 and only 13 days in 1993, according to district statistics.

Under the federal Clean Air Act, the county has until 2005 to reduce the number of unhealthful days to no more than three in a three-year period.