California's San Joaquin Valley for some time has had the dirtiest air in the country. Monday, officials said gases from ruminating dairy cows, not exhaust from cars, are the region's biggest single source of a chief smog-forming pollutant.
Every year, the average dairy cow produces 19.3 pounds of gases, called volatile organic compounds, the San Joaquin Valley Air Pollution Control District said. Those gases react with other pollutants to form ground-level ozone, or smog.
With 2.5 million dairy cows -- roughly one of every five in the country -- emissions of almost 20 pounds per cow mean that cattle in the San Joaquin Valley produce more organic compounds than are generated by either cars or trucks or pesticides, the air district said. The finding will serve as the basis for strict air-quality regulations on the region's booming dairy industry.
The San Joaquin Valley, Houston and Los Angeles have the three worst air-pollution problems in America. Their relative rank varies from year to year depending in part on weather conditions. Over the last six years, however, the San Joaquin Valley has violated the federal limit on ozone smog over an eight-hour period more than any other region. That "eight-hour standard" is the U.S. Environmental Protection Agency's main barometer for the severity of smog.
The dairy industry will be forced to invest millions of dollars in expensive pollution-control technology in feedlots and waste lagoons, and may even have to consider altering animals' diets to meet the region's planned air-quality regulations. Not surprisingly, industry officials challenged the estimate as scientifically unsound.
"Science is supposed to guide this regulation, not fairy dust," said Michael Marsh, chief executive officer of Western United Dairymen, a lobbying group that said it was considering a lawsuit to block regulations based on the new finding. "It's impossible to capture emissions that scientists can't even detect."
Air-quality regulators defended their estimate as a conservative one based on the best available research. But it was criticized by some scientists -- including one whose work was used by the district to arrive at the figure.
"If you closed all the dairies in California tomorrow, you would not see much of an impact on ozone formation," said the scientist, Frank Mitloehner of UC Davis, who was hired by air-quality officials to study cow emissions and now contends his findings were misconstrued.
"We really don't have the science to back this number up," he said.
Five members of Congress and 12 state legislators had demanded that the district reconsider a similar draft estimate, calling it absurdly high. Environmentalists and some community groups, meanwhile, called the same figure too low.
The entire exercise of estimating cow emissions has been lampooned on talk radio as "fart science" run amok --although most gas actually comes from the front end of the cow.
"I'd like to challenge the people that came up with this information to enclose yourself in a shop with a cow, and at the same time have someone enclose themselves in a similar shop with a car or truck running," one critic, Steve Hofman of Ripon, Calif., wrote to the Modesto Bee. "Then let me know the results."
Cars do emit many significant pollutants that cows do not, and they are responsible for more smog-forming emissions overall. But in a region where many children suffer from asthma and officials issue smog warnings on hot summer days, supporters of strong regulations said the role of cows in emitting organic gases is no laughing matter.
"This is not some arcane dispute about cow gases," said Brent Newell, an attorney for the Center on Race, Poverty & the Environment. "We are talking about a public health crisis. It's not funny to joke about cow burps and farts when one in six children in Fresno schools is carrying an inhaler."
The dairy industry is growing fast in the San Joaquin Valley as farms driven out of the Chino area in Southern California by urbanization move into the Central Valley. Government officials estimate that over the next several years, the number of cows in the San Joaquin air basin will increase from 2.5 million to about 2.9 million.
Although air-quality officials now have a figure on the extent of the cow pollution problem, it remained unclear how far they could push dairies to reduce bovine emissions.
Most of the gases, scientists believe, come from the bovine digestive process, which consists of constantly swallowing and regurgitating food. This is known as rumination, or "chewing the cud," which produces large amounts of gas.
Cow manure is also a major source of emissions and will probably be targeted for regulation. Officials said they may also require dairies to alter the food cows eat in order to reduce flatulence.
New dairies will be required to use the best available equipment to curtail emissions. Existing dairies will face less-restrictive requirements, but will also be forced to make changes to reduce cow gases.
Possible measures include scraping manure from cow corrals more frequently so it won't fester in the heat and installing digesters to break down pollution in the lagoons where cow waste is later flushed.
"We need immediate regulation now. We know the pollutants are coming off these dairies," said Tom Frantz, a native of Shafter, Calif., who heads a group called the Assn. of Irritated Residents. He says that he developed asthma in the last five years as factory dairy farms moved into the region. "Ag hasn't been regulated in the past, but times are changing. Our lungs will not become an agricultural subsidy."