31 Smoggy Days in ’91 Double the Total in ’90 : Environment: The number recorded this year to date is still fewer than those in the record years of 1987 and 1988, officials say.

Ventura County air in 1991 was unhealthy on twice as many days as it was last year under federal standards, Air Pollution Control District officials said as the year’s official smog season ended last week.

In addition to an increased number of days that violated standards, the concentration of smog in the air was also slightly higher in 1991 than in 1990, district officials said.

But the 31 smoggy days recorded to date in 1991, which includes the time of year that produces the bulk of smog episodes, was still a better number than records in 1988 and 1987. This year, the county also has had 20 fewer smoggy days under federal standards than the 10-year average of 51 days.

“Things are better than historical trends, and that’s good,” said Richard Baldwin, who heads the air pollution district. He said the trend is moving in the right direction.

In addition, air pollution experts had predicted that smog concentrations in 1991 would be high enough on 15 to 25 days to warrant health advisories. But only five advisories were issued, said district meteorologist Kent Field.

“It wasn’t a bad year,” Field said. “It just wasn’t a great year like 1990.”

The persistent low cloud cover that shrouded the coast and much of the county’s inland valleys with fog throughout the summer held temperatures down, reducing the heat that is necessary to produce smog.

But the same inversion layer also trapped pollutants produced by industry and cars and prevented the smog-causing emissions from dispersing into the air as they did during the clear, breezy summer of 1990.

Last year, because the pollutants dispersed easily into the atmosphere, the county had the fewest smoggy days since air pollution monitoring began in 1973.

“We did not have the typical summer smog pattern in either year,” Field said. A typical pattern includes warm temperatures and a high-pressure weather system that traps pollutants, allowing the heat to cook them into ozone.

Neil Moyer, a member of the Ventura County Environmental Coalition, said the air quality’s dependence on weather illustrates the need for county government to do more to reduce the number of cars on the road, which account for more than half the ozone-causing emissions.

“This was a mild year weather-wise,” Moyer said. “The smog could have been much worse if the weather conditions were not so favorable.” The county needs more mass transit, and its new neighborhoods should have a balance of houses and jobs, he said.

Smog-causing pollutants--nitrogen oxide and reactive hydrocarbons--combine in sunlight to produce ozone, the primary constituent of smog. Ozone decreases lung functions and is being studied as a possible cause of lung cancer.

As always, Simi Valley recorded the greatest number of smoggy days, registering 31 unhealthy days by federal standards and 89 by more stringent state guidelines.

Also following historical patterns, the Piru-Fillmore area and the Ojai Valley were the second and third smoggiest areas in the county. Ventura and Oxnard were the cleanest areas, primarily due to the ocean breeze, cool temperatures and the lack of high mountains to trap pollutants.

Countywide, air pollution was unhealthy under state standards on 100 days in 1991, compared to 93 days in 1990 and a 10-year average of 130 days.

Air quality violates state standards when concentrations of ozone in the air are greater than 0.09 parts per million. Federal standards are violated when ozone concentrations rise to 0.12 p.p.m. The state requires health advisories to schools and hospitals at 0.15 p.p.m., warning children and the infirm to curtail outdoor activities.

In 1991, the county had only a slight increase over 1990 in the number of days with levels above 0.09 p.p.m., but it had twice the number of days with concentrations above 0.12 p.p.m. Field said that is evidence that levels of ozone in the air were higher in 1991.

But some members of the Ojai City Council have questioned whether the air pollution monitoring stations provide accurate information on smoggy days in the county. During July, when a Southern Pacific train derailed at Seacliff, thousands of cars were diverted north on California 33, which runs through the Ojai Valley.

Information from the monitoring station showed that air pollution in the Ojai Valley did not exceed federal health standards on those days, an indication, some council members said, that the station was not functioning properly.

“Air quality is a major concern in every decision we make regarding land use and growth,” Councilwoman Nina Shelley said. “We need to know if the equipment is inaccurate.”

But Baldwin, who acts as the county’s air pollution control officer, said the district’s equipment meets higher standards for accuracy than the federal Environmental Protection Agency requires.

He said not enough ozone was formed those days to violate federal health standards because even large quantities of fumes from automobiles over a few days would not significantly affect air quality in the weather conditions that existed the week of the July 28 train accident.

“The meteorology during the days traffic was detoured through Ojai was not conducive to forming ozone,” Baldwin said. “The relationship between ozone levels and emissions is not linear. A pound of precursor emissions does not form a pound of smog.”

William Mount, planning manager for the district, estimated that regulations imposed by the state and local governments have forced a 30% decline in nitrogen oxide emissions and a 36% decrease in reactive hydrocarbons emissions since 1979.

He said that even with continued population growth in the county, emissions will continue to drop slightly at least through 2010 as new regulations are enacted and existing ones take effect.

Smog Levels

Chart shows the number of days that air quality in Ventura County exceeded federal and state standards for ozone, the primary component of smog. The first figure is the number of times the area exceeded federal health standards during that year. The second figure is the number of times the area’s air exceeded the more stringent state standards.

1991* 1990 1989 1988 1987 Simi Valley 31 / 89 14 / 78 40 / 94 51 / 99 22 / 79 Thousand Oaks 00 / 16 03 / 26 10 / 47 08 / 39 02 / 29 Oxnard, El Rio 00 / 11 00 / 09 02 / 18 03 / 21 05 / 29 Ventura 01 / 09 00 / 05 02 / 13 01 / 09 04 / 17 Ojai 04 / 27 02 / 26 05 / 55 03 / 51 03 / 44 Piru 05 / 39 03 / 42 05 / 40 08 / 39 05 / 61 Countywide 31 / 100 15 / 93 44 / 109 54 / 125 29 / 114

* 1991 data is year to date, through the 1991 smog season that ended Oct. 31

Measurning Smog

Air quality is determinded by the concentration of ozone in the air. State health standards for ozone are more stringent than federal standards. The Pollutants Standard Index reflects ozone concentration in numbers from 0 to 400.