AIR DISTRICTS ON WATCH; THOUSAND OAKS AREA REGISTERS HIGH LEVELS OF LUNG-DAMAGING TINY PARTICLES.

Byline: Don Holland Daily News Staff Writer

With smog season's peak nearly past, air quality officials in Ventura County and elsewhere are preparing to monitor a new health hazard on the horizon - toxic particles small enough to permeate into the bloodstream.

Particulate pollutants, some 28 times smaller in diameter than a human hair, hasten the death of some 64,000 people a year, according to the National Resources Defense Council.

And during the past 10 years, Ventura County exceeded state standards for particulate pollution an average of 19 days a year.

Now under a federal mandate, air pollution districts around the country will begin monitoring the smallest and most dangerous of these particles, called PM 2.5 because they are 2.5 microns in diameter, said Doug Tubbs, technical services manager for the Ventura County Air Pollution Control District.

In the next few months, PM 2.5 monitoring stations will be set up in Simi Valley, Thousand Oaks and on the Oxnard Plain. But recent tests using practice equipment suggest Thousand Oaks may be a trouble spot in the county.

``We saw some of our highest levels in Thousand Oaks, so we're going to locate two of our samplers there, one to measure and one to verify,'' said Ron Lawson, an instrument technician with the district. ``It may be that our original measurements were not that accurate. But our initial measurements are pointing the finger that Thousand Oaks is the dirty spot.''

PM 2.5 and the larger PM 10 come predominantly from diesel exhaust, industrial facilities, wood-burning stoves and forest fires. Because the particles are so small, they are not coughed up and can become lodged deep in the lungs. The microscopic particles can increase the severity and number of asthma attacks and aggravate bronchitis and other lung diseases, according to the California Air Resources Board.

Last week, after almost a decade of scientific study, the board designated diesel particulates as a toxic air contaminant. Officials say the move will reinvigorate efforts to control particulate pollution. The new designation triggers a round of public hearings on the need and feasibility of further controls on diesel pollution, which contains more than 40 hazardous pollutants.

Approximately 26,225 tons of diesel exhaust PM 2.5 are emitted into California's air each year, according to state officials.

Although PM 2.5 is the latest target of the Ventura County Air Pollution Control District, ozone remains the county's primary air pollution problem.

``Over the last 25 years, the statistics show the frequency and magnitude of ozone has decreased markedly, even though we've had significant population growth,'' Tubbs said.

Pollution levels in the county this year have been a little higher than usual. For the first time in two years, the county recorded a smog alert - on July 17 in Simi Valley.

Simi traditionally tops the county's bad air list because pollution from the San Fernando Valley blows through the Santa Susana Pass. Ocean breezes push pollution from Ventura and Oxnard into Simi Valley and neighboring communities.

``If we had the same amount of people and industry and were inland a little farther, we would see a lot more pollution,'' Lawson said. ``A lot of people come here to escape the bad air in the (San Fernando) Valley and the L.A. Basin. Even our worst days here are not as bad as an average day in Los Angeles or the Valley.''

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2 Photos

PHOTO (1--Color) (Ran in Conejo Edition only) Ron Lawson checks an air pollution monitor on a roof at Simi Valley High.

(2) Ventura County Air Pollution Control District technician Ron Lawson reads a bank of analyzers, each measuring a different air pollutant in Simi Valley.

Evan Yee/Daily News