The fine particles would drop to safe levels by 2014, officials said. The plan tightens rules on fireplace burning, glass-melting furnaces and even commercial charbroilers.

But the cleanup relies on pollution reductions expected from a proposed diesel truck rule that state officials have not even passed yet.

About 15 activists lined up outside the San Joaquin Valley Air Pollution Control District headquarters to demonstrate, and in the board room, some wore air masks.

They said that for months, they have been suggesting other options, such as advanced pollution-control technology on farm diesel engines or filters on wine fermentation tanks. The options would speed up the cleanup by at least a year, and they would be a safety net if the state's diesel rule does not produce the reductions officials anticipate.

Air officials said they have included every available measure. They said oil, farming and other industries Valley-wide are expected to pay a total of $20 billion over the next six years for new equipment and technologies.

"We did not leave anything off the table," said Seyed Sadredin, the district's executive director.

The Valley has one of the state's worst problems with fine particle pollution, called PM-2.5, which is at its highest levels in fall and winter. Some of the specks come from fires and vehicles, but much of the Valley's PM-2.5 problem occurs when chemicals combine in the air.

Oxides of nitrogen -- NOx -- from vehicles combine with plumes of ammonia coming mostly from dairies to form a chemical speck called ammonium nitrate, which accounts for nearly half the region's PM-2.5.

The Valley's biggest source of NOx is diesel trucks. The state's new diesel rule could be passed in the next year, but it has met with a lot of industry opposition. The rule's reductions are not supposed to begin until 2014, the same year the district projects completion of the PM-2.5 cleanup.

That worries health activist Kevin Hamilton, a respiratory therapist.

"We are buckling under the weight of visits to clinics for lung problems in this Valley," he said.

PM-2.5 specks are so small that 30 or 40 of them could fit across the width of a human hair. They easily pass through the lungs into the bloodstream. They can trigger asthma attacks and heart problems, and they cause early death. The state estimates PM-2.5 causes more than 1,000 people to die prematurely each year in the Valley.

Engineer Alvin Valeriano, a former air district employee, said he estimates the district could achieve the PM-2.5 standard by 2012 or 2013 -- if it pushes for new technologies.

District officials said they are studying the suggestions and will use them as they become feasible. But there are problems with some of the ideas, such as switching diesel farm pumps to electric power, they said.

"Many farmers have no access to the electricity for their pumps," Sadredin said.

After the board meeting Wednesday, activists said they had been ignored.

"Once again, our local air district is delaying clean air," said Catherine Garoupa, community organizer with Madera Coalition for Community Justice.

The confrontation in the board room resembled last year's fight between activists and the district over the Valley's ozone plan, which the board also approved in a split vote. At the time, board newcomers Henry T. Perea of Fresno and Raji Brar of Arvin voted against the ozone plan. They sided with activists who said the plan would delay healthy air.

This year, Perea and Brar were joined by Dr. John Telles, the newest district board member, as the dissenting votes. Gov. Schwarzenegger this month appointed the Fresno cardiologist to the board as a health expert.

"Is there a possibility this plan could fail?" Telles asked. "We need more contingency measures in case that happens."

But the plan was supported by seven county supervisors -- representing Fresno, Madera, Kings, Tulare, Kern, Stanislaus and San Joaquin -- and a city council member from Ceres in Stanislaus County.

Board member Ronn Dominici, a Madera County supervisor, said the district must meet a federal deadline this month to approve a plan or face sanctions that include the possible loss of $2 billion in road-building funds. He said improvements will be made as they become available.

"This plan has to go forward," he said.