AIR IN COUNTY STAYS CLEANER THAN IN 1970S : AIR POLLUTION FACTS.

Byline: Michael Coit Daily News Staff Writer

If Ventura County's air pollution levels were charted, they would resemble a saw-toothed blade with the highs and lows showing a downward trend.

The county's air is considerably cleaner than it was in 1973, when the county Air Pollution Control District was formed. But there can be bad stretches, triggered by weather patterns that trap smog mostly in Simi Valley and Thousand Oaks.

The six-month smog season starts in May, and pollution-control and health officials hope a downward trend started again in 1996 after bad-air days increased from 1992 through 1995.

``We're not in a summer-weather pattern yet. We haven't really transitioned yet, so we really haven't seen any of the strong inversions,'' said Mallory Ham, an APCD meteorologist. ``It's around the corner.''

The federal government designates Ventura County as an area which sometimes has bad air - too much ozone. Ozone is created when emissions from vehicles and industry cook together in intense sunlight. The gas becomes more concentrated on hot, windless days and usually is lightest when the weather is cool and breezy, officials said.

``The main weather factor is the inversion, which means there's a stable layer in the atmosphere that is hotter than the air below it. It acts as a cap, and it doesn't allow anything to mix above it,'' Ham explained. ``So everything that we produce on the ground - and that is produced as ozone - is kept beneath that layer.''

When the smog sets in, Simi Valley and Thousand Oaks on the county's east end and the Ojai Valley to the west regularly record the greatest number of days in which ozone concentrations exceed federal health-based standards.

Federal regulations require the APCD to report those days when there are more than .12 parts of ozone per 1 million parts of air, which is 100 on the pollutant standards index. There are seven monitoring sites throughout the county, officials said.

The district also issues daily forecasts that are given to schools, hospitals, health agencies, fire departments and the media.

In 1996, there were 17 days when ozone levels exceeded the federal standard. Simi Valley exceeded the ozone standard on 13 of those days and Thousand Oaks on five of those days, Ham said.

For Thousand Oaks, that was the worst smog year so far in this decade, while Simi Valley has experienced worse. In 1991, ozone levels topped the federal standard on 32 days. There were 33 days that year when the air was bad somewhere in the county - almost always in Simi.

There's not much officials in either city can do. Blame the geography.

Simi Valley gets blasted with the worst air because pollutants from the San Fernando Valley seep over the Santa Susana Pass in the morning, and pollutants are blown into Simi Valley from the Oxnard Plain during the day. Then the inversion hems it in, Ham explained.

``Simi Valley is kind of a horseshoe-shaped valley. It's open to the west, but with the ocean breeze, nothing escapes,'' he noted.

When ozone levels hit .15 parts per million, the APCD issues a health advisory for children, the elderly, and people with cardiac or respiratory ailments to cut back on outdoor activity, officials said.

During the 1990s, the number of health advisories issued by the APCD have ranged from one in 1992 and one in 1996 to seven in each of two years, 1991 and 1995, Ham said.

The United States Environmental Protection Agency has recommended more stringent air-quality standards for ozone and particulates. Congress is reviewing the proposal.

Taking advantage of greater public interest heading into summer, the American Lung Association of Ventura County has programs to make people aware of health threats from air pollution and of ways they can reduce it.

The association kicked off Clean Air Month in May with a demonstration by respiratory therapists and the launching of the county's first asthma-education program in a school. MariTna West Elementary School in Oxnard was chosen in memory of Preston Hedgepeth. He was a Marina West student who died of asthma last year, said Barbara Weinberg, the association's spokeswoman.

``We've never done this thing before,'' Weinberg noted. ``It's just that Preston died so tragically. He had asthma, and he died of an asthma attack.''

Clean Air Month also will feature a day - May 22 - when commuters will be urged to ride a bike or take a bus to work rather than drive a car, Weinberg said.

``The point is to help people realize, first of all, if you stay out of your car, you help clean the air,'' She said, ``and to encourage cities to become more bike-friendly because biking is the best way to clean our air.''

Ozone - formed when pollutants from vehicles and industry are hit by sunlight - is Ventura County's biggest air pollution concern.

Exposure to ozone irritates the respiratory tract. Ozone harms the nasal passages and lungs and narrows the airways. Symptoms include coughing, wheezing, increased phlegm, shortness of breath and chest discomfort. Vigorous outdoor exercise raises the rate of breathing, which increases the amount of ozone inhaled and the risk of harming the respiratory system.

When the air quality is poor, strenuous exercise can be bad for your health. Children, the elderly, pregnant women and people with cardiac or respiratory problems are sensitive to increased ozone levels.

The Ventura County Air Pollution Control District measures and predicts ozone levels every day. When measurements reach .15 parts per million (138 on the pollution standards index), the district calls an ozone health advisory. Hospitals, schools, convalescent homes, recreation districts and other institutions are contacted and requested to inform people to take precautionary measures.

Source: Ventura County Air Pollution Control District

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