Impact of CAFOs on Water Quality

Water quality has been a persistent problem with factory farms or CAFOs, in spite of claims that each new manure management technology and strategy will prevent water pollution. The “dead zones” in the Gulf of Mexico, Chesapeake Bay, and elsewhere continue to spread, and industrial agriculture is the major documented source of pollution. However, water quality becomes a matter of general public concern, rather than just an environmental issue, wherever pollution from factory farms threatens the safety of drinking water.

The public health risks posed by water polluted by livestock manure are essentially the same as those posed by human sewage. Many of the same chemicals and biological organisms that pose health risks from exposure to untreated human sewage also pose risks to human health from exposure to raw untreated hog sewage.

Raw untreated hog sewage generates over 150 gases, many of which are harmful, including ammonia and hydrogen sulfide, plus another 150 toxins. The animal waste from 2,500 hogs in a confinement feeding operation, the minimum size to be classified as a CAFO, is equivalent to the human waste from a municipality of 8,000 to 10,000 people.

There are logical reasons for requiring sophisticated, multi-stage waste treatment systems whenever 8,000 to 10,000 people choose to residence in close proximity and form a municipality. These same reasons raise legitimate public concerns when the feces and urine from animals raised in CAFOs is being stored and spread untreated on farmland. The chemical and biological wastes can seep into groundwater to pollute the wells of rural residents and can run off fields into streams that provide drinking water for municipalities on their way to oceans. A cow produces approximately 18 times the waste of one human being. That means a CAFO with 4,000 cows produces the waste equivalent of a city of 72,000 people.

Defenders of industrial agriculture claim that operators of CAFOs are responsible stewards of the environment. They extoll the virtues of traditional independent family farmers in their commitment to caring for the land and caring about the well-being of their neighbors. Even if this is true, it is simply not possible to manage the concentration of manure associated with large-scale confinement animal feeding operations without sophisticated waste treatment facilities. 

As a last defense, CAFO operators claim they are doing a better job of manure management than the traditional independent farmers they replaced. However, water quality statistics tell a different story. In 1998 the EPA found 35,000 miles of streams in 22 states and ground water in 17 states that had been polluted by industrial livestock operations.

The June 2016 Legislative Audit Bureau report found that a hog CAFO, Babcock Genetics, in the town of Holland had elevated levels of nitrate in monitoring well tests since 2005. Monitoring well test results for the Babcock CAFO from January 2010 through November 2016 showed all but one of the six wells tested had levels above the allowed concentration (10 ppm) for nitrate in the most recent tests. Out of 102 well samples tested during that period, only 12 fell below 10 ppm and 41 were above 20 ppm. The DNR did not issue a notice of violation nor a milder notice of noncompliance to Babcock Genetics even though they were in violation of their WPDES permit.3

1) Carla Klein, “The Facts about CAFOs and Health Ordinances,” Sierra Club, Ozark Chapter, 2006,

2) U.S. Department of Agriculture Natural Resources Conservation Service and U.S. Environmental Protection Agency, “Unified National Strategy for Animal Feeding Operations,” draft, September 11, 1998, as quoted in CAFO: The Tradegy of Industrial Animal Factories, Myths, Dan Imhoff, editor,


Water Quality resources used with permission from the Iowa Alliance for Responsible Agriculture.