Pollution Declines by One-Third : Health: Figures from a smog study show that efforts during the last decade have paid off in the county, one official says.

Thanks largely to cleaner-running cars and good weather, air pollution in Ventura County declined by 33% during the past decade, air quality officials said Tuesday.

The decrease was less dramatic than the 50% plunge reported elsewhere in Southern California in a study released this week. Nevertheless, state and county officials were pleased.

“It’s very clear that the air quality is improving in Ventura County, just as we have found it is in other places,” said Bill Sessa, a spokesman for the California Air Resources Board, which conducted the study. “You would expect a more dramatic decline in places like Los Angeles because it has more smog to begin with.

“But it’s very clear from the statistic in Ventura County that while there are still many days and hours of the year when the air is unhealthy and there is more work that we have to do, the work we have been doing is paying off.”

Richard Baldwin, director of the Ventura County Air Pollution Control District, pointed out that smog decreased at a time when the county’s population and traffic were growing.

“Ventura County has made significant progress,” he said.

The study focused on the number of hours annually when areas exceed the state’s air quality health standard of 0.09 parts of smog per million parts of air.

The study found that Los Angeles, Orange, Riverside and San Bernardino counties exceeded the state standard half as often in 1991 as they had a decade earlier.

Ventura County recorded 823 hours exceeding the state limit in 1980, but only 552 hours last year--a 33% decrease, said Bill Mount, manager of planning for the Air Pollution Control District.

Smog periods that exceeded a less stringent federal healthy air standard plummeted 60% between 1980 and 1991, he said.

“I think they should take a modest bow,” said Neil Moyer, president of the Environmental Coalition of Ventura County. “But we should thank our lucky stars that we’ve had some good weather the past three years. We shouldn’t count on that to clean up the air indefinitely.” Mount acknowledged that weather conditions, including wind patterns, solar radiation and high temperatures, affect smog levels. Ventura County weather conditions in recent years have not been favorable for the production of smog, he said.

Although air quality countywide has improved, some trouble spots remain. There has been little improvement over the past decade in the county’s worst smog city, Simi Valley, Mount said, mainly because of wind patterns and its location within a mountain area that traps unhealthy air.

Air quality officials attributed much of the improvement in the rest of the county to California’s automobile smog-check program and its new vehicle emission standards, the toughest in the nation.

Fewer older cars, built before the stricter rules were imposed, are still on the road, they said. “An old clunker,” Mount said, “can emit 100 times as much pollution as a new car.”

County regulators also have been imposing tighter controls on other sources of air pollution, including factories, gas stations and dry-cleaning shops.

Despite the reduction in smog, environmentalists plan to keep the pressure on county air quality officials. “We still have to do a lot more,” said Stan Greene, president of the Citizens to Preserve the Ojai.

Greene’s group filed suit several years ago, seeking to force the federal Environmental Protection Agency to take a more active role in cleaning up Ventura County’s air. The agency, which wants to leave enforcement to the local level, has appealed the most recent court ruling favoring Greene’s group.