Pesticides Breeding Ground for Bacteria
Germs thrive in certain farm chemicals, study shows
Pesticides kill insects, but new research suggests they may be a breeding ground for different types of bugs -- bacteria.
Four out of 15 pesticides tested proved to be a very friendly environment for germs that cause human diseases, says Rick Holley, professor of food microbiology at the University of Manitoba in Canada.
The meaning of the research is unclear -- it's not known whether the bacteria will survive the long trip from a pesticide sprayer to your dinner table.
If a link is established, the findings could help explain why the incidents of illness carried by plants have doubled or tripled in the last decade, Holley says.
"Normally one used to find food-borne illness associated with animal-based products," he says. "There's been a shift toward fruits and vegetables."
In his research, Holley mixed 15 kinds of pesticide -- five herbicides, five insecticides and five fungicides -- according to manufacturers' directions. He then inoculated the pesticides with bacteria, including salmonella, shigella, listeria and Escherichia coli. The pesticides sat in 71.6-degree Fahrenheit temperatures for four days.
"What we found was that in four of those pesticides, including at least one in each category, the bacteria in 24 hours increased 1,000-fold, and if we held it longer, it increased 10,000-fold," he says. "That's a significant increase in a small amount of time, and it surprised us."
The research suggests that bacteria, perhaps from contaminated water, could quickly grow in pesticide that has been mixed and left to stand for a few days, he says. Bacteria could also grow in pesticide residue that isn't cleaned out of a sprayer after use.
It's not clear why some pesticides were friendly to bacteria and others were not. It may have something to do with the inert ingredients added to pesticides to improve their stability, he says.
The next step is for researchers to determine whether the bacteria can survive the transition from pesticide sprayer to the plants themselves, he explains.
"We're very concerned about the fact that the bacteria grew in these products, but we don't know what the full impact might be," Holley says.
Jim Porterfield, a representative of the American Farm Bureau Federation, says farmers are very careful with the chemicals they use.
"Fruit and vegetable growers are conscious about how they mix, store and apply pesticides because they're expensive and they don't want to use any more than they have to," explains Porterfield.
A scientist with a pesticide manufacturers trade group adds farmers aren't likely to mix pesticides and leave them lying around for days at a time.
"It might happen once in a while, but it's not the usual practice," says George Rolofson, vice president of government affairs with the American Crop Protection Association.
"The practice is to mix what you're going to use, use it and rinse out the equipment in the same day or half day," he says.
Both Holley and Porterfield recommend consumers wash fruits and vegetables before eating them.
Even so, there's no guarantee of germ-free produce.
"I'd like to be able to say you could successfully wash away any problem bacteria, but the fact is that isn't 100 percent certain," Holley says.
What To Do
Your mother was right: You should eat your fruits and vegetables. But don't forget to wash them beforehand with cool tap water. If you're worried about bacteria, avoid pre-cut fruit slices and bagged veggies at the grocery store. Experts say they may harbor more bacteria than whole fruits and vegetables.
The Food and Drug Administration suggests that firm produce, such as melons and cucumbers, should be scrubbed with a clean produce brush. For more information, visit the Q&A compiled by the FDA. www.fda.gov
Thanks to Randy Dotinga
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