Do Cows at Large Dairy Farms Cause Significant Air Pollution?

General Reference (not clearly pro or con)

[Editor's Note: Animal feeding operations (AFOs) and confined animal feeding operations (CAFOs) are animal farming operations where dairy cows (and other livestock aimals) are housed. Animals in AFOs and CAFOs are fed on site rather than being allowed to graze or otherwise find food in pastures, fields, or on rangeland. There are approximately 450,000 AFOs in the United States.

Concentrated animal feeding operations (CAFOs) are large scale AFOs that house thousands of animals. The "regulatory definitions of large CAFOs, medium CAFO, and small CAFOs" (25 KB) (25 KB) are maintained by the US EPA.

Volatile organic compounds (VOCs) are organic gasses that react with the atmosphere to create air pollution. Dairy cows primarily emit the VOC gases methanol, ethanol and acetone through their farts and burps (enteric fermentation).]

The U.S. Environmental Protection Agency provided the following information in its Aug. 15, 2001 draft report "Emissions From Animal Feeding Operations," posted on

"Animal feeding operations can emit ammonia (NH3), nitrous oxide (N2O), hydrogen sulfide (H2S), carbon dioxide, methane (CH4), total reduced sulfur (TRS) compounds, volatile organic compounds (VOC), hazardous air pollutants (HAP), and particulate matter (including PM 10 and PM 2.5). The substances emitted and the quantity of emissions can vary substantially depending on the design and operation of each facility...

These emissions have a variety of effects. The compounds primarily responsible for the odors associated with AFOs [animal feeding operations] are VOC, hydrogen sulfide, and other reduced sulfur compounds. VOC also contributes to the formation of atmospheric ozone, which is a respiratory irritant. Some VOC are designated in the Clean Air Act as hazardous air pollutants...Carbon dioxide, methane, and nitrous oxide are odorless and nontoxic, but are considered to be greenhouse gases."

Aug. 15, 2001 - U.S. Environmental Protection Agency (EPA) 

PRO (yes)

Barbara Boxer, Democratic Senator from California, stated in her Sep. 6, 2007 opening remarks at the U.S. Senate Committee on Environment & Public Works hearing titled "An Examination of the Potential Human Health, Water Quality, and Other Impacts of the Confined Animal Feeding Operation Industry":

"I want to ensure that there is a clear picture of the significant environmental and health issues that stem from these facilities [CAFOs]...

[E]nvironmental protection laws...ensure that where there has been damage caused by these facilities - and there have been numerous instances of air and water pollution and contamination of wells and other water supplies - the parties responsible can be held accountable and pay to clean up their messes...

CAFOs can create significant air pollution, including foul odors, ammonia, volatile organic compounds and hydrogen sulfide. CAFOs' air pollution can exceed the amounts emitted by industrial facilities."

Sep. 6, 2007 - Barbara Boxer 

Catharine Fitzsimmons, Chief of the Air Quality Bureau of the Iowa Department of Natural Resources, provided the following testimony on Sep. 6, 2007 during the Senate Environmental and Public Works Committee hearing "An Examination of the Potential Human Health, Water Quality and Other Impacts of the Confined Animal Feeding Operations Industry":

"Air emissions from CAFOs can harm human health and the environment. These harmful emissions include ammonia, hydrogen sulfide and particulate matter, including fine particulate matter...

Human exposure to ammonia triggers respiratory problems, causes nasal and eye irritation and in large amounts can be fatal. Ammonia also contributes directly to the formation of [fine particulate matter] which causes severe health effects in humans, including death, heart attacks and increased severity of asthma attacks, as well as visibility impairment. Hydrogen sulfide is a toxic air pollutant that can cause severe health effects, even death, at high concentrations of exposure.

CAFO ammonia emissions represent half the U.S. ammonia emissions inventory. In California, livestock ammonia emissions contribute 38 percent of the state's entire inventory of ammonia emissions. In San Joaquin Valley, 70 percent of the area's ammonia emissions are from livestock...

Monitoring of Premium Standard Farms (PSF) conducted by EPA (under a settlement agreement) in 2004 shows that PSF releases 3 million pounds of ammonia annually from barns and lagoons at its Somerset facility, making it the fifth largest industrial emitter of ammonia in the country...

In summary, the well-documented adverse health effects and substantial levels of air emissions from CAFOs - including ammonia and hydrogen sulfide - warrant rigorous application of environmental laws to these sources."

Sep. 6, 2007 - Catharine Fitzsimmons, MA 

The San Joaquin Valley Air Pollution Control District wrote in its Aug. 1, 2005 report "Air Pollution Control Officer's Determination of VOC Emission Factors for Dairies":

"Dairies are significant sources of smog-forming volatile organic compounds and of fine particulate matter in the San Joaquin Valley. Volatile Organic Compounds are emitted directly from the Valley's approximately 2.5 million dairy cows, and also from the decomposition of hundreds of millions of pounds of dairy waste excreted each day from dairy cows in the San Joaquin Valley. Although a wide range of VOC emission factors has been proposed recently, by any of the common current estimates, dairies are among the largest sources of VOCs in the Valley, and these smog-forming VOC emissions have a significant adverse impact on efforts to achieve the health-based air quality standards."

Aug. 1, 2005 - San Joaquin Valley Air Pollution Control District 

James Owen, Staff writer for National Geographic, wrote in an Aug. 16, 2005 article titled "California Cows Fail Latest Emissions Test," published in National Geographic, that:

"Standing around chewing the cud, cows don't look especially threatening. But dairy herds in California are the latest livestock to be branded an environmental health risk on account of their flatulent behavior...

A dairy cow annually emits almost 20 pounds (9 kilograms) of smog-forming gases known as volatile organic compounds (VOCs)-more than a car or light truck...

The San Joaquin Valley is home to a thriving dairy industry that includes some 2.5 million cattle. With more new dairy operations planned, an additional 400,000 cows are expected to arrive in the valley within the next few years.

But the dairyland is also known for its smog. Over the last six years the valley has violated the federal limit on smog levels more often than any other region in the country."

Aug. 16, 2005 - James Owen 

CON (no)

James M. Inhofe, Republican Senator from Oklahoma, stated in his Sep. 6, 2007 opening remarks at the U.S. Senate Committee on Environment & Public Works hearing titled "An Examination of the Potential Human Health, Water Quality, and Other Impacts of the Confined Animal Feeding Operation Industry":

"Oklahoma is among the states with the most concentrated animal feeding operations. Concerns have been raised about the possible environmental impacts of these facilities...

Today's hearing will focus on several aspects of environmental protection, including clean air. One of our witnesses' works with the Iowa Department of Natural Resources (DNR), yet is not representing Iowa. I wonder if that is because when Iowa's DNR studied the issue of odor, it found that relatively few problems, with fewer than four percent of the measurements taken near public areas, homes and businesses exceeding acceptable odor levels. Further, another Iowa study out of the University of Iowa found that every-day products, pets and smoking were the cause of ammonia emissions and not CAFOs."

[Editor's Note: could not locate the specific University of Iowa study about the ammonia emissions of every-day products, pets and smoking that Senator Inhofe referenced. Mar. 31, 2008]

Sep. 6, 2007 - James M. Inhofe 

The American Farm Bureau Federation stated the following in a Sep. 6, 2007 statement, presented by Chris Chinn, to the Senate Committee on Environment and Public Works:

"Contrary to anti-livestock rhetoric, this nation's livestock industry is proficient at producing safe and abundant food while protecting our natural resources. The industry is highly regulated and farmers often surpass requirements when fulfilling their roles as caretakers of the environment and good citizens of their communities...

The vast majority of farmers and ranchers live on or near their livestock operations. This means they and their families breathe the same air as their neighbors. Most livestock farms are proactively instituting practices to reduce air quality concerns for the welfare or their workers, neighbors, animals, and their own families. Most operations are now using natural barriers such as tree screens to help mitigate air quality issues...

A 2003 study conducted by the National Research Council of the National Academy of Sciences and commissioned by the U.S. Environmental Protection Agency determined that there is insufficient data to fully understand the environmental and health impacts of large animal operations."

Sep. 6, 2007 - American Farm Bureau Federation 

Harry Cline, Editor of the Western Farm Press wrote in his Jan. 4, 2006 editorial "Dairy Cows Pollute Less Than Oak Trees," in the Western Farm Press that:

"The ludicrous debate over how much dairy cows contribute to air pollution in California's central valley is apparently just that - absurd.

Current regulatory estimates and environmental radicals say dairy cows emit smog forming so-called volatile organic gasses (VOCs) at rates higher than automobiles.

In reality, oak trees may be bigger contributors to smog than cows."

Jan. 4, 2006 - Harry Cline 

The Community Alliance for Responsible Environmental Stewardship (CARES), an organization of dairy farmers, milk processors and support industries, wrote in an Aug. 2007 press release titled "Judge Upholds San Joaquin Valley Dairy Air Rules, Rejects Activists' Claims as 'Nonsensical'" published on the Dairy Cares website, that:

"A Fresno County judge this month ruled to uphold new air quality rules for dairies, firmly rejecting claims by anti-dairy activists that the rules were too lax and violated the law...

'Dairy producers have invested a great deal of time and money in research efforts to understand dairy air quality issues and to develop mitigation measures that are based in sound science, and we will continue to improve upon these efforts' said Paul Martin, Director of Environmental Services for Western United Dairymen, and chairman of CARES' regulatory committee.

'This is the most comprehensive and significant air quality regulation of dairy farms in the United States, making California dairies the most regulated in the nation.' The facts are clear: California dairies operate under the most stringent air and water quality regulations in the nation, and continue to lead the nation in environmental performance."

Aug. 2007 - Community Alliance for Responsible Environmental Stewardship (CARES)