The requirements are likely to stir plenty of debate and questions.
Because ports are magnets for such a wide variety of mobile pollution sources -- ships, trains and trucks -- it's not clear yet what is practical and politically feasible to limit.
The Bay Area Air Quality Management District Board, however, is determined to curb emissions from ports, especially at Oakland, a hot spot for concentrations of toxic diesel soot that can aggravate the risk of asthma attacks and heart and lung problems, regulators say.
"Ports are vitally important to our Bay Area economy, but we cannot afford to overlook the health effects of port air pollution any more," said Mark Ross, a Martinez city councilman who chairs the air district.
"We need to work with the ports on how to do this," Ross said. "We're forcing their hand so they come up with emission reductions plans, so we don't have to impose it on them."
Port representatives said it's hard to assess the proposed rule or its compliance costs because it leaves so many issues to be worked out.
"We agree more needs to be done to improve air quality, whether there is a rule or not," said Marilyn Sandifur, spokeswoman for the Port of Oakland.
The port already has taken
Environmentalists say it's not fair for port neighbors to breathe dirtier air so Americans can get cheaper tennis shoes imported through local ports.
An air district study last year found that areas downwind of ports and freeways have the region's highest concentrations of toxic air emissions, including diesel. Ports also add to regional pollution loads.
Some 6 percent of the Bay Area's fine soot particles --_ called particulates -- comes from sources at the Port of Oakland, the fourth-busiest container port in the nation, according to a port study last year.
Under a draft rule proposal now out for public comment, the air district would require an inventory to estimate the tons of fine particles, sulfur dioxide and smog-forming gases from each of the five ports.
The district would set an overall pollution cap and a series of targets for percentage cuts to be met. Compliance measures could include getting cleaner engines and fuels for trucks and trains, or getting ships to plug into the electric grid for power while in port instead of spewing soot from their diesel engines.
Even as it demanded cuts, the air district would continue to offer grants and subsidies for trucks, ships and trains to covert to cleaner technology to cut diesel emissions, said Jack Broadbent, executive officer of the nine-county air quality district.
"It's a carrot-and-stick approach," Broadbent said.
The district also is looking into a different approach to the rules that would not involve an overall emissions cap.
The district might require measures such as cleaner engines in a certain number of trucks by a certain time.
Jim Matzorkis, executive director of Richmond's port, said ports are concerned that an overly strict pollution cap could hurt them.
"If we are told we can only accept certain kinds of trucks or trains, that could put out us out of business," he said. "The plan needs to be realistic. All the ports are committed to having cleaner air."
Cutting pollution at public ports such as Richmond and Oakland is complicated because private companies or individuals own the trucks, trains and ships that haul cargo in and out of the port. Some terminal operations are privately operated, too.
This raises the question: How can ports get their many users to act in concert to get cleaner air?
Ross said he believes ports have contractual and business relationships with ships, truckers, railroads and other port users that gives ports leverage to demand cleaner operations.
Environmentalists say that whatever rule is adopted, the air district should write the measure to produce specific gains in improving public health, such as reducing the number of childhood asthma cases in West Oakland.
"It's not enough to set some tonnage goal to meet. We need to find the spots where the pollution is causing a health impact and fix it at a local level," said Brian Beveridge, executive director of the Oakland Environmental Health Indicators Project, a community group.
Beveridge said the air district will be in a better position to write its rules when the state and the air district release a study later this year on the health risks in West Oakland of breathing pollution.
Henry Clark, executive director of the Richmond-based West Contra Costa Toxics Coalition, said he is glad the air district is taking steps to reduce port pollution, as Southern California officials have done in recent years with the Long Beach and Los Angeles ports.
"Port pollution has been largely ignored for a long time," Clark said. "It would be a great leap forward for environmental justice to provide relief for people living near the ports."
Reach reporter Denis Cuff at 925-943-8267 or email@example.com.