Hog Farms and the Environment: An Investigative Series

Published November 21, 2003

Across the United States, residents in a growing number of communities are expressing concern over hog farms—a type of livestock operation technically known as concentrated animal feeding operations, or CAFOs—and their potential effects on human health.

This article is the first in a series examining the practice of hog farming, its potential effects on the environment, and mechanisms for environmental responsibility in hog farming practices.

Waste Management

Management of animal waste is the most significant environmental challenge presented by large-scale hog farming.

Most hog farms allow animal waste to seep through gaps in the floorboards of barns, collecting in a large underground pool of concentrated waste. That concentrated mix is then flushed with water through pipes into earthen containment structures called lagoons. Aerobic bacteria break down the waste, and the treated effluent is sprayed onto field crops as fertilizer. The North Carolina Department of Environment and Natural Resources has estimated some 4,000 active lagoons are in use by 2,400 hog farms in that state alone.

Dr. Mike Williams, director of North Carolina State University’s Animal and Poultry Waste Management Center, says research supports the use of the lagoon and sprayfield approach. The federal Environmental Protection Agency, which regulates hog farms and other large-scale livestock operations, has found no scientific evidence linking hog farms with serious health problems.

Nevertheless, the Sierra Club, Environmental Defense, and other activist groups allege hog farming practices endanger the health of residents living nearby. Residents themselves frequently complain that on hot, humid days, the odor of the lagoons is detectable up to a half mile away. Residents and activist groups suspect that hydrogen sulfide emanating from the lagoons causes a variety of ailments such as headaches, flu, and diarrhea.

Mixed Messages

In Iowa, state environment officials tested air quality levels in six neighborhoods adjacent to hog farms. Air information specialist Brian Button said preliminary data showed hydrogen sulfide and ammonia levels frequently exceeded the state’s recommended air quality levels. Button did not elaborate on the frequency, duration, or extent of the heightened readings, nor did he offer evidence that the heightened readings had any connections to adverse human health.

Dr. Kaye Kilburn, a professor at the University of Southern California, believes the anecdotal evidence supports a link between hog farms and adverse effects on human health. “The coincidence of people showing a pattern of impairment and being exposed to hydrogen sulfide arising from lagoons where hog manure is stored and then sprayed on fields or sprayed into the air” demonstrates a link that is “practically undeniable” said Kilburn.

“In community exposures, when they are exposed to a mixture of chemicals—hydrogen sulfide included—there have been neurological effects reported as well,” said Selene Chou, manager of the hydrogen sulfide toxicological profile for the Agency for Toxic Substances and Disease Registry.

“Based on what I see, there could be neurological effects,” said Chou, “but we don’t know at what low level of chronic exposure. That information is badly needed, because communities have experienced these effects.”

The claims of health effects are, however, controversial. Government officials, reported the Charlotte Observer on May 11, “contend that these effects are at best poorly documented. They say that studies have relied too much on the testimony of the people with medical problems, and that there is no way to prove that those problems are directly attributable to the farms.”

Most persons claiming a link between hog farms and human health “acknowledge that for many symptoms the link to the farms is circumstantial,” reported the Observer.

“The health concern issues raised by the residents are totally unfounded,” said Ron Prestage, owner of Mississippi’s Prestage Farms. “There has never been a neighbor of a farm who has come forward with any documentation of a health problem of any kind.”

“I do not think there is any way that it can be proven that that hog farm, which is a half-mile away, has any effect,” said Dick Isler, president of the Ohio Pork Producers Council. Isler cited studies showing that “any time you are more than a hundred feet away it is not a problem.”

Given the uncertainty of the underlying science, is corrective action called for? Are better farm waste management systems scientifically and economically feasible?

Part two of this series will examine efforts currently underway to improve or abandon the process of treating animal waste in concentrated, open-air lagoons.

James M. Taylor is managing editor of Environment & Climate News. His email address is [email protected].