The manure generated by thousands of cows or pigs doesn't just stink - it may seriously affect human health.
New research examining two decades' worth of livestock production data finds a positive relationship between increased production at industrial farms and infant death rates in the counties where the farms reside. The study reported in the February American Journal of Agricultural Economics implicates air pollution and suggests that Clean Air Act regulations need to be revamped to address livestock production of noxious gases.
The new work is in line with several studies documenting the ill effects of megafarms, which typically have thousands of animals packed into small areas, comments Peter Thorne, director of the Environmental Health Sciences Research Center at the University of Iowa in Iowa City. Higher rates of lung disease have been found in workers at large poultry and swine operations and respiratory problems increase in communities when these large-scale farms move in, Thorne notes.
"This study is a very important contribution," says Thorne. "This is an industry we really need - it provides food and a lot of jobs - the answer isn't for everyone to become vegetarians." But, he says, "I think we need a fundamental change in the way this industry is going. There's a very strong case that under the Clean Air Act the EPA should be looking seriously at the livestock industry."
The study, by economist Stacy Sneeringer of Wellesley College in Massachusetts, examined birth and death records from the National Center for Health Statistics and the increase in "animal units" per county across the United States from 1982 to 1997. (Animal units are a normalizing unit used by the U.S. Department of Agriculture. One animal unit equals roughly 1,000 pounds of average live weight; or 250 layer chickens (for eggs); or 1.14 fattened cattle; or 2.67 breeding hogs.) An increase of 100,000 animal units in a county corresponded to 123 more infant deaths per year per 100,000 births. Doubling livestock numbers was linked to a 7.4 percent increase in infant mortality.
Several potentially confounding variables were taken into account, such as per capita income, the availability of health care, climate, land and housing use, possible effects of other industries and whether large farms move to areas that already have poor infant health.
"I was surprised to see this association - I kept expecting it to go away but it didn't," Sneeringer says.