Dairy Cows in a CAFO, 2007
Photo Provided courtesy of Shira Lane and
"Got the Facts on Milk?"
The emissions released by cows during milk production may be creating enough environmental pollution to negatively affect human health, which is why we've decided to include dairy cow emissions in our research into Milk ProCon.org's core question "Is drinking milk healthy for humans?"
The emission levels in the chart below were estimated by the United States Department of Agriculture (USDA) and the Environmental Protection Agency (EPA) using measurements taken in 2001 from confined animal feeding operations (CAFOs) - large dairy cow operations that house thousands of animals. The chemicals listed have been studied for their role/s in contributing to air and water pollution, negative human health effects, and/or global warming.
The US government does not have (as of Jan. 17, 2011) regulations for the amount of allowable air pollutants from dairy farms. In 2007 the EPA began collaborating with eight universities on a National Air Emissions Monitoring Study (NAEMS) to develop such regulations. The $14.6 million NAEMS study, led by Purdue University, was financed by a consent agreement between industry and the EPA to measure emission levels from CAFOs and to develop improved methods for estimating emissions in order to regulate CAFOs and monitor their compliance with the Clean Air Act and other environmental protection laws. Dr. Frank Mitloehner, a principal investigator of the study, emailed ProCon.org on Oct. 12, 2010 to announce that the study was complete and in the hands of the EPA. On Jan. 13, 2011, the EPA released the raw data from the NAEMS, which it will then reportedly use to create regulations on allowable levels of air pollutant emissions from CAFOs.
Dairy Cows (includes enteric fermentation and manure management)
– Dairy cows were not isolated as a separate category by the EPA's report; ProCon.org calculated these totals. The EPA report included dairy cows (and other animals such as beef cows, sheep, goats, pigs and horses) within their enteric fermentation and manure management categories shown below.
2. Natural Gas Systems
3. Enteric Fermentation (farts and burps of all livestock, including dairy cows)
4. Coal Mining
5. Manure Management (decomposition of all livestock animal waste, including dairy cows) - A single dairy cow produces about 120 pounds of manure every day.
7. Waste Water Treatment (includes the treatment /decomposition of all human and industrial waste)
12. Mobile Combustion (the majority of gasses produced in this category came from highway vehicles such as personal cars and transport trucks)
14. Iron & Steel Production
All other man-made sources (such as stationary combustion, chemical production, and agricultural processes)
"Ammonia…is produced when microorganisms break down organic nitrogen products such as urea and proteins in manure...
[Moderate ammounts of ammonia in water]...are associated with reduced species diversity, while more severe depressions can produce fish kills.
Additionally, ammonia can lead to eutrophication, or nutrient over-enrichment, of surface waters….
The degree of ammonia volatilization is dependent on the manure management system. For example, losses are greater when manure remains on the land surface rather than being incorporated into the soil, and are particularly high when the manure is spray irrigated onto land."
"Hydrogen sulfide is a colorless gas and has a strong odor of rotten eggs…Although quantitative data are lacking, toxicity studies suggest that H2S gas is absorbed rapidly through the lungs….
Human data pertaining to inhalation exposure (the expected route of ambient exposure) consist of a plethora of case reports and a variety of occupational epidemiological studies. Although these studies have limitations that preclude their use for quantitative risk assessment, they indicate that exposure to H2S (at high concentrations) has profound effects on the respiratory system leading to unconsciousness with attendant neurologic sequelae and, sometimes, death…
The effects of H2S in humans can be acute and/or chronic. The weight-of-evidence from the human and animal studies suggest that the effects of H2S are dose-dependent. The exposure-response relationship for acute effects, particularly CNS and respiratory, can be very steep. Levels in the range of 500 to 1,000 ppm (695 to 1,390 mg/m3) are life-threatening and can cause immediate unconsciousness followed by serious and debilitating neurologic and respiratory sequelae [a condition following as a consequence of a disease]. Lower levels have been associated with lung function deficit and eye, nose, and throat irritation…"
[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).]
"Health effects [of VOC exposure include] eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, dizziness.
The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed…
No standards have been set for VOCs in non industrial settings."
"PM10 is commonly defined as airborne particles with aerodynamic equivalent diameters (AEDs) less than 10 micrometers [a micrometre is one thousandth of a millimeter]
Similarly, PM2.5 refers to the particles that are collected in a Federal ReferenceMethod PM2.5 sampler, which has a 50 percent cut diameter of 2.5 micrometers...
AFOs [Animal Feeding Operations] can contribute directly to primary PM through several mechanisms, including animal activity, animal housing fans, and air entrainment of mineral and organic material from soil, manure, and water droplets generated by high-pressure liquid sprays, or they can contribute indirectly to secondary PM by emissions of NH3, NO, and H2S, which are converted to aerosols through reactions in the atmosphere…
PM2.5 can reach and be deposited in the smallest airways (alveoli) in the lungs, whereas larger particles tend to be deposited in the upper airways of the respiratory tract. It is also most effective in attenuating visible radiation, causing regional haze…
Damage seems to be most intense with the smallest particles...which can be composed of elemental carbon, absorbed complex organic molecules, heavy metals, bioaerosols, acid aerosols, ammonium nitrate, and other materials. However, substantial research interest is now directed at elucidating the aspects of PM that cause various health effects. It is worth noting that it is by no means clear that the hazards of rural PM can be inferred from research focused on urban PM."
"Nitrous oxide forms and is emitted to the atmosphere via the microbial processes of nitrification [a microbial process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate]…In the United States, total anthropogenic sources in 1990 were ~ 0.4 Tg N/yr [44,0924 tons], with animal excreta contributing about 25 percent…N2O diffuses from the troposphere to the stratosphere, where it is lost to photolysis [the splitting of molecules by means of sun/light energy] and other processes. Once emitted, N2O is globally distributed because of its long residence time (~100 years); it contributes to both tropospheric warming and stratospheric ozone depletion...
N2O has a global warming potential 296 times that of CO2 [emphasis added by ProCon.org]."
"Methane is produced by microbial degradation of organic matter under anaerobic conditions...
Of the various anthropogenic sources, the agricultural sector is the largest, with livestock production being a major component within this sector...
The primary source of CH4 in livestock production is ruminant animals. Livestock ruminants (sheep, goats, camel, cattle, and buffalo) have unique, four-chambered stomachs. In one chamber, called the rumen, bacteria break down grasses and other feedstuff to generate CH4 as one of several by-products…
In addition to enteric fermentation, CH4 emissions also occur during anaerobic microbial decomposition of manure…
Methane is a greenhouse gas and contributes to global warming. Methane has a global warming potential 23 times that of CO2 [emphasis added by ProCon.org]."
All emission levels were rounded to the nearest whole number by ProCon.org.
All data in the charts, including dairy cow populations and emission levels, refer to 2001 levels.
In chart II all the emission levels were derived from manure decomposition measurements except methane, which represents both manure and enteric fermentation (cow farts and burps) measurements.
In chart II the emission levels for ammonia, hydrogen sulfide, volatile organic compounds, and particulate matter were found using the following process: The EPA estimates of emissions were given in tons per year per 500 animal units (AU). The EPA defines one dairy cow as equivalent to .7 (AU). Thus, 500 (AU) equals 350 dairy cows. The number 350 was divided by the total number of dairy cows in each state and multiplied by the average (calculated by ProCon.org) of emission levels taken from eight different types of CAFOs.
The nitrous oxide emission levels per state were found by dividing the total emission level for 2001 given by the EPA by the total number of dairy cows in the US in 2001 (12,994,849 - USDA). This yeilded a calculation of 1.35 pounds per year per cow. This number was multiplied by the total number of cows for each state, converted into tons, and rounded to the nearest whole number.
Methane emission levels per state were found by dividing the total number of dairy cows in the US in 2001 (12,994,849 - USDA) by the total country wide methane emission levels for dairy cows given by the EPA (both enteric fermentation & manure management). This yeilded a calculation of .16 metric tons (353 pounds) per year per cow. This number was multiplied by the total number of cows for each state and rounded to the nearest whole number.