On a clear day, San Joaquin looks like a bucolic farming community, complete with almond groves, cornfields and orange trees. But most of the time the valley -- trapped between the Sierra Nevada and the Coast Ranges, with two major highways running north to south through it -- is smoggy, filled with air that has fostered widespread respiratory disease.
Fifteen percent of the region's children have asthma, a rate three times the national average. Fresno -- the valley's biggest city -- has the third-highest rate of asthma in the country, and the San Joaquin Valley rivals Los Angeles and Houston for the dubious title of worst air quality in the nation. On bad air days, some schools hoist a red flag so parents can keep their children indoors; on good days, they raise a green flag.
Agriculture does not occupy a prominent place in America's environmental policy debates, but farming has arguably more of an impact on the land, air and water than any other sector in the U.S. economy, environmental and industry experts say. In addition to producing airborne emissions, farms take up nearly half of the nation's land, and nutrient-laden runoff from farms affects such waterways as local streams and the Gulf of Mexico.
"The sheer scope of farmland means that unless it is extremely well-managed, it's going to create serious problems," said Tim Searchinger, an agricultural policy specialist at the advocacy group Environmental Defense. "But with some tweaks and a few bold approaches, farmers and ranchers could do a lot of good."
Michael Kleeman, an environmental and civil engineering professor at the University of California at Davis, estimates that agriculture accounts for as much as half of the valley's air pollution.
The health problems caused by agriculture emboldened state Sen. Dean Florez (D-Shafter) to push to abolish farming's exemption from state air pollution laws. California was at risk of losing federal highway funds because of poor air quality, and Florez argued that farms had to curb their emissions like factories and power plants. By spewing smog-forming gases into the air, the legislature declared, cows had joined cars and trucks as major polluters.
"I wanted them to understand they've got to be part of the solution, not part of the problem," Florez said. "It's a cultural change for them."
Although California farmers are now legally accountable for emissions, environmentalists, regulators and farmers are feuding over how far the government can go in regulating things such as cow emissions and aging diesel equipment in the San Joaquin Valley. About a fifth of the country's milk production now takes place in this region, well more than that produced in Wisconsin.
This summer, the state Air Resources Board ruled that any existing farm with more than 1,000 milk cows had to apply for a permit on the grounds that dairies -- which release volatile organic compounds and ammonia -- rank as major polluters. Volatile organic compounds create smog when combined with nitrogen oxide, while ammonia reacts with that smog to form fine-particle pollution.
Dairy farmers have assailed the science underlying the rules and blocked a plan that would have made them install technology to capture methane and other gases that cows emit.
"We're not convinced our cows are worse than all the cars and trucks in the world," said Michael Marsh, who heads Western United Dairymen, which represents just over half of the area's 1,900 dairy farmers. Marsh estimates that installing manure digesters could cost the industry $1 billion. "If we're going to have this kind of mandate, how are we going to pay for it?" he asked.
Tom Mendes's family has been dairy farming in California's Central Valley for three generations, ever since his grandfather arrived from Portugal. But Mendes has told his 19-year-old son not to follow him into what he calls a dying way of life.
"I don't see a very good future for agriculture," said Mendes, whose son goes to college in nearby Stockton. "We're an industry under attack, and I don't want it for my kids."
Activists such as Brent Newell, a lawyer at the Center for Race, Poverty and the Environment, said farmers' recalcitrance and the local authorities' willingness to weaken their proposed rules have undermined the new law.
"The fact that the regulated industry fights it every step of the way is the saddest part of the whole thing," he said. As for San Joaquin regulators, he added, "They just look the other way and let it go."
Residents have formed a citizens' group to fight large dairy producers. Tom Frantz, a Shafter native who heads the Association of Irritated Residents, said area farms are "like a factory in your midst."
"We're really irritated because our lungs are being used as an agricultural subsidy," said Frantz, who has asthma. His group notified farmer Rick Vanderham this month that residents plan to sue him for building a new 2,800-cow dairy without a Clean Air Act permit.
California's debate is not unique: Public health advocates in states including North Carolina and Iowa have pushed to regulate hog, poultry and dairy farms -- known as "confined animal feeding operations" -- with varying degrees of success.
In the Washington area, farms account for more than 30 percent of the pollutants that cause "dead zones" in the Chesapeake Bay -- where algae blooms deplete the oxygen, and fish and crabs cannot breathe. Maryland, Virginia and Pennsylvania have all tried to make farmers reduce the amount of fertilizer and manure washing off their fields. But environmentalists say their efforts, including pollution caps on some large farms, are not enough.
Under a 2000 agreement between North Carolina pork producers and the state attorney general, North Carolina State University professor C.M. "Mike" Williams has spent five years researching how to treat manure from the state's 10 million hogs in an affordable way. Williams, who has identified five effective technologies but is still gauging their costs, said the state needs to clean its waste load even if no "silver bullet" exists.
"I do not feel like that system is long-term sustainable," he said.
Large-scale livestock farms have mushroomed in recent decades -- 5 percent of U.S. farms now account for 54 percent of beef and dairy cattle, according to the Agriculture Department -- presenting a new challenge to regulators. Environmental Protection Agency officials began investigating the massive operations in the mid-1990s after nearby residents complained of respiratory and eye problems.
The government scored some initial wins: Missouri-based Premium Standard Farms agreed to monitor emissions at its hog farms in 1999, and the company has spent $9.5 million on technology that converts hog waste and emissions into commercial dry fertilizer. But Bush administration officials ordered the EPA to stop investigating farm emissions in 2001.
Last month, the administration struck a deal with more than 2,700 livestock firms, exempting them from prosecution for air pollution violations until mid-2008 while the agency researches the issue. Each firm must contribute $2,500 to help fund a study of two dozen livestock operations and pay a penalty on a sliding scale to address past violations.
"What the agency is trying to do is figure out the best way to get the most information, in a comprehensive way, in the most expeditious manner to determine if a problem may exist," said Jon Scholl, counselor to the EPA administrator for agriculture policy.
David Townsend, Premium Standard's vice president for environmental affairs, and other industry officials praised the deal, saying, "You have to have some reasonable data to say where [the industry] needs to go."
Environmentalists, on the other hand, assailed the pact as an industry giveaway. Aloma Dew, a Sierra Club organizer in Kentucky who monitors poultry farms, said: "It's not just a stink that's coming out of these farms. It's a real health threat."
But the EPA's amnesty for major livestock producers may amount to a temporary reprieve as even farmers' most loyal political allies are sensing a shift in public sentiment. Calvin M. Dooley, a former central California farmer who served in the House for 14 years, said local attitudes hardened during his time in office, which ended this year.
"There's a different political environment in the Central Valley today," said Dooley, a Democrat who now heads the Food Products Association. "More and more people have become increasingly concerned about the health and environmental consequences of our air quality."
Staff writer David A. Fahrenthold and researcher Carmen Chapin contributed to this report.