Feedlot Buffer Zones May Not Protect Produce from Contamination

Current buffer zone guidelines, which recommend that produce be planted at least 400 feet away from livestock feedlots in order to prevent contamination with airborne pathogens, may not be sufficient to protect produce from E. coli O157:H7, according to new research from USDA scientists at the Agricultural Research Service, U.S. Meat Animal Research Center in Clay Center, Neb.

The study, funded in part by the Center for Produce Safety, appears in the February 2015 edition of Applied and Environmental Microbiology. In this first comprehensive long-term study of its kind, the researchers sampled leafy greens growing in nine plots—three each at 60, 120, and 180 meters downwind from the research center’s cattle feedlot—over a two-year period. They took their samples six times per year, from June to September. As would be expected, E. coli O157:H7 contamination declined with distance, but an average of 1.8 percent of leafy green samples still contained E. coli at 180 meters, or nearly 600 feet.

“There had previously not been a lot of data as to how far a pathogen can be transported, to inform these setback distances,” says lead investigator Elaine Berry, PhD, a USDA research microbiologist. “The industry has a real need to understand the risks associated with growing in close proximity to cattle production.”

The researchers would like to investigate further using more sensitive air samplers, and test produce planted at greater distances from the feedlot. “Since we found the pathogen at our maximum distance, about 600 feet, a more appropriate buffer zone distance may be higher than that,” Dr. Berry says. “But more work needs to be done to see just how far the pathogen can be transported.”

Shaw writes frequently about science, medicine, and health while serving as a regular contributor on notable medical publications.