 Industrial farms pollute the air in many
ways, emitting foul odors, dust and other small airborne
particles, greenhouse gases, and numerous toxic chemicals. In
the United States, these farms are among the leading producers
of noxious substances such as nitrous oxidei and
ammonia. Air pollution from industrial farms can cause health
problems in agricultural workers, in neighboring communities and
even for farm animals, and also results in significant
environmental damage. Although there are a variety of techniques
to reduce or minimize the impact of air pollution, many large
farms still do little or nothing to prevent it.
Farm operations in the United States produce more than
400 different gases.iii In addition to gases, the
other airborne particulates they create—such as dust and
organic matter known as endotoxinsiv—
can have damaging effects on air quality for both the farm and
surrounding areas. These gases and particulates are generated
during the handling and disposal of byproducts such as manure,
the production and use of animal feeds, and also in the shipping
and distribution of products.
Mountains of Manure
The USDA estimates that more than 335 million tons of manure are produced annually on farms in
the United States.v This manure is generally stored
for long periods of time in giant tanks or lagoons, where it
decomposes and gives off hundreds of gases.vi Manure
lagoons and tanks are often located directly next to animal
confinement facilities, so harmful gases are continuously
present in animal living quarters.vii They also
pollute the outdoor air when stored gases are vented out of
barns or manure slurry is sprayed onto fields as fertilizer.
Hydrogen sulfide, methane, ammonia, and carbon dioxide
are the four main hazardous gases produced by decomposing
manure,viii and they all cause a range of health and
environmental problems. The EPA estimates that methane emissions
from manure in the United States increased by 26% between 1990
and 2004, most of which it attributes to the trend towards
larger and more concentrated dairy cow and swine facilities.ix
The North Carolina hog industry alone produces about 300 tons of
ammonia per day.x
Air Pollution and Feed
While manure is the largest contributor to farm-generated air
pollution, a number of other factory farm components, such as
conventional animal feed, also increase the production of some
gases. The EPA estimated that in 2004, 20% of all man-made
methane production came from the digestion processes of
livestock—primarily cows.xi Factory farms use
low-quality feed in large amounts to fatten animals cheaply, and
this practice contributes to higher methane emissions.xii
Producing crops for animal feed also contributes to
farm-generated air pollution. Soil
management techniques (especially the use of fertilizers) are
the leading contributor to nitrous oxide emissions, accounting
for 68% of all nitrous oxide released into the air in 2004.xiii
Centralized Food
Production and Fossil Fuel Use
The centralized nature of American food production contributes
to air pollution, as food has to be stored for days and then
transported over long distances before it reaches supermarket
shelves. Conventionally-produced fruits and vegetables travel
over a thousand miles on average between being harvested and
sold.xiv Because of this, shipping agricultural
products accounted for at least 1% of all freight trucking
emissions in the United States in 2002, and that does not
include the amount of freight (in the form of feed, building
materials, etc.) shipped to farms in order to grow the
food.xv
Health Effects of
Farm-related Air Pollution
Health effects can vary widely by area, due to the various kinds
and amounts of pollutants produced on farms and the different
ways they’re vented. Below are some of the principle air
pollutants released by factory livestock facilities, and the
health problems that they may cause:
- Hydrogen Sulfide
Hydrogen sulfide is a gas that limits the ability of cells to
use oxygen. Exposure to hydrogen sulfide in
high levels can have a variety of acute affects, including
skin, eye, and respiratory irritation, neurologic and cardiac
problems, seizures, comas, and death. Chronic exposure at lower
levels can cause low blood pressure, headache, chronic coughs,
and psychological disorders.xvi Hydrogen sulfide is
generally associated with hog production facilities.
- Ammonia
Ammonia can cause irritation of the eyes, skin, and respiratory
tract.xvii Ammonia is released in largest quantities
by chicken and hog production.
- Particulate matter
Particulate matter (in the form of dust blown directly off
farms or produced chemically when some gases, like ammonia, are
present in high concentrations) can cause a variety of health
problems, especially in people who are regularly exposed to
them. These problems include bronchitis and asthma, and cardiac
problems such as arrhythmias and heart attacks.xviii
- Endotoxins
Endotoxins are produced when the cell walls of bacteria
degenerate, and are often measured in high concentrations on
large farms. These air pollutants can cause respiratory
problems even in extremely low concentrations.xix
- Carbon dioxide
Carbon dioxide is also produced in significant amounts in the
decomposition of manure. While its health effects for humans
are generally limited to shortness of breath or dizziness, it
often kills confined animals by asphyxiation due to
insufficient ventilation of their houses.xx
- Methane
Methane is an asphyxiate at extremely high concentrations, but
is not particularly toxic. It is, however, highly flammable and
poses a risk of explosion if manure storage facilities are
poorly ventilated.xxi Methane production is most
commonly associated with cows—who produce it naturally
during digestion—but it is a byproduct of most manures
stored in oxygen-depleted lagoons.xxii
Effects on Workers
Since most of the air pollutants produced by farms are in much
higher concentrations on the farms themselves than in
neighboring areas, farm workers are at
particular risk. Among workers on confined animal feeding
operations, as many as 70% experience acute bronchitis and 25%
chronic bronchitis.xxiii Additionally, a host of
other respiratory ailments in workers have been linked to
working in indoor swine production facilities for 2 hours a day
over the course of six years, most likely as a result of organic
dust inhalation.xxiv Some of the gases produced on
farms also are fatal in high concentrations, and in the US there
were 12 cases where workers were killed due to asphyxiation in
manure pits between 1992 and 1997.xxv
Effects on Communities
Neighboring communities are also at
risk for health problems from large farms. People living near
hog farms, for example, often have increased respiratory
problems.xxvi A number of studies have demonstrated
that fatigue, depression, and mood disturbances occur in higher
proportions in communities near such facilities.xxvii
A study of one town in Utah found a four-fold increase in
diarrhea-related hospitalizations and a three-fold increase in
respiratory-related hospitalizations over a five-year period
during which an industrial hog farm was constructed and became
operational.xxviii The Minnesota Pollution Control
Agency has documented that hydrogen sulfide concentrations in
excess of World Health Organization maximum exposure standards
can be found on neighboring properties of hog facilities in that
state.xxix
Environmental Effects
Air pollution from farms directly affects the environment , chiefly through the
production of gaseous nitrogen and some of the greenhouse gases
responsible for global warming. About 80% of U.S. ammonia
emissions came from livestock manure.xxx As a report
from the National Academy of Sciences explains, atmospheric
ammonia and nitric oxide—both produced on
farms—contribute to what is known as the “nitrogen
cascade,” in which each ammonia molecule “can, in
sequence, impact atmospheric visibility, soil acidity, forest
productivity, terrestrial ecosystem biodiversity, stream
acidity, and coastal productivity.”xxxi
Particulate matter emissions contribute to haze.xxxii
Through the production of greenhouse gases—primarily
methane and nitrous oxide—the agricultural industry was
directly responsible for 6 percent of the United States’
impact on global warming in 2004, according to the EPA.xxxiii
Remedies and Regulations
There are already a number of proven techniques that can reduce
the impact and total emissions of air pollutants from farms,
including better storage of manure, air-breaks positioned near
farms, and increased attention to the nutritional needs of
specific livestock.xxxiv Additionally, some measures
as simple as allowing cows to graze on pasture (which has also
been shown to be healthier than grain-feeding for both cows and
humans) have the potential to reduce greenhouse gas emissions.xxxv
Raising animals on pasture also reduces the need for cultivation
and transportation of feed, as well as storage and spreading of
manure, all of which require the use of fossil fuels and emit
significant amounts of carbon dioxide and other pollutants.
However, since most methods that reduce air pollution
from farms would increase maintenance costs without increasing
production, factory farms don’t see it as in their
interest to implement them. In addition to the financial
disincentive against regulating emissions from farms, there is
little regulatory incentive to promote their regulation. While
most farm emissions are legally regulated under the Clean Air
Act, most enforcement attention has been focused on factories
and cars—both of which are far easier to measure in terms
of their contribution to air pollution.xxxvi The
federal government has also done relatively little to handle the
problem, leaving enforcement of farm-related air pollution to
individual state governments, xxxvii and generally
leaving research on the topic to academics.xxxviii
There is also concern that better environmental regulation will
not stop much of the air pollution from farms. Instead, tighter
regulations could cause many of the largest corporate farmers to
move to overseas locations. Already, some of the biggest
American agricultural companies (including Perdue and
Smithfield) are now producing and processing foods in Canada,
Mexico, Europe, China and Brazil to reduce costs and avoid being
hindered by existing environmental regulations.xil
Because of this, the best way to get industrial farms to change
their ways is not through tightening regulations, but with
consumers’ food dollars.
What You Can Do
The problems associated with most farm emissions are primarily
local and regional, and the most efficient way to reduce air
pollution from farms is to reduce the size and increase the
number of farms. In other words, many small farms scattered
throughout the country will have less of an impact on air
quality than conventional factory farms do. Sustainable
livestock farms depend less on cheap feed and fuel-guzzling
machinery, because natural pasture systems rely on the
animal’s own energy to harvest feed and spread manure.
Because of this, sustainable farming offers a viable opportunity
to reduce farm-related air pollution.
As consumers, we can use our economic power to support
farms that supply sustainably-produced meat, eggs and dairy
products. By giving our dollars to farmers who work to minimize
their impact on the environment and protect human health, we can
vote with our wallets and help change the face of American
agriculture, so we can all breathe easier.
- Visit the Eat
Well Guide for a complete listing of small, sustainable farms
in your local area.
Did You Know?
- The odor from swine manure contains
331 separate chemical compounds.xl
- Tyson Foods recently agreed to pay
an undisclosed sum in air-quality damages to three neighboring
residents near one of their Kentucky operations.xl
Four couples in Iowa also reached settlement in 2003 with a
large neighboring hog operation for excessive odors, flies, and
toxic gas emissions.xli
- A study in Sampson County, North
Carolina indicated that ammonia concentrations in rain-water
doubled between 1985 and 1996—a period during which hog
operations in the state expanded rapidly.xlii
For More Information
Sources
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CAFO Manure Gun near houses. 
