It's just not so.

PART OF THE PROBLEM: Highway 101 is choked with bumper-to-bumper traffic during the morning commute in San Francisco. However, experts on both sides of the Coastal Range agree the Bay Area's smog is not the key to the Valley's dirty-air problem. (Mark Crosse / The Fresno Bee)

Experts on both sides of the Coastal Range agree the Bay Area's smog is not the key to the Valley's dirty-air problems. It never has been.

The argument between Bay Area and Valley air pollution enforcers always has been about whether a "significant" amount of smog blows into the Valley. Can it nudge Valley air to an unhealthful level of smog and cause a violation of federal law?

Valley officials say it is possible, adding that the Bay Area wind blows pollution into the Valley, which then is responsible for cleaning up the mess. Bay Area officials say there is not enough evidence to show that smog from the San Francisco area is causing air violations in the Valley.

The debate was on the front burner again this year with both the San Joaquin and Sacramento valleys suing the state over smog floating into the Central Valley. Gov. Davis in late September made the lawsuits unnecessary by signing a measure requiring the more stringent vehicle review program, called Smog Check II, in the Bay Area.

The Bay Area, already very close to attaining the federal standard for ozone, was the only major metropolitan area in the state that did not have the tougher vehicle inspections. Officials now believe Bay Area pollutants will be cut back by more than 20 tons a day.

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San Joaquin Valley Air Pollution Control District officials say that cutback could help the downwind residents in the Valley, though they acknowledge they need a reduction of 300 tons a day to achieve healthful air.

But will the more stringent smog program in the Bay Area really make a difference in the Valley? Terri Lee, spokeswoman for the San Francisco Bay Area Air Pollution Control District, says the previous science is uncertain.

The 1990 research shows 27% of the smog in Stockton comes from the Bay Area, 11% in Fresno and 9% in Bakersfield. Nobody really understands if those numbers apply every day or if they really are creating violations in the Valley.

"The study that they're talking about is more than 10 years old," she says. "It was gathered on one bad day in August at the western-most monitoring station in Stockton. Then a [mathematical] model was used to estimate how much Bay Area smog was going throughout the Valley."

Other evidence indicates the Bay Area is not having a big impact every year. In 2001, the Valley's three northernmost counties, San Joaquin, Stanislaus and Merced, had no violations of the federal ozone standard, the level at which lung damage can begin.

PART OF THE PROBLEM: The Chevron oil refinery, at Point Richmond in the Bay Area, produces smog-forming chemicals. Some of these chemicals may blow east into the San Joaquin Valley. (Mark Crosse / The Fresno Bee)

Air officials on all sides say they hope multimillion-dollar research, called the Central California Ozone Study, will settle the dispute. Though that study won't be completed until 2005, some results are expected next year.

Meanwhile, it's a mistake to think huge plumes of pollution from the Bay Area float daily into the Valley, say officials at the state Air Resources Board. Ultimately, the state is responsible for making sure one area's pollution doesn't hurt another area, and the Air Resources Board says the existing research is being misunderstood.

State officials say Bay Area smog may only come into the Valley on a few of the worst days. The Valley has far more problems with homegrown air pollution.

Valley air officials agree on that point. But they argue that in the Air Resources Board's 2001 review of migrating pollution, the Bay Area's wind-blown smog is an "overwhelming" factor on dirty-air days in Stockton, Modesto and Merced.

But Bay Area spokeswoman Lee says the Valley district still is playing a blame game.

"The northern part of the San Joaquin Valley is the cleanest part of the district – the central and southern parts of the district are the problems," she says. "This is being wildly misconstrued for political purposes to point the finger at the Bay Area for the Valley's air problems."