PESTICIDE sprays encourage life-threatening bacteria to grow on crops, a
researcher in Canada has discovered. The bugs could pose a threat to people
eating raw fruit and vegetables such as strawberries, raspberries and
lettuce.
Alarmed by the rise in cases of food poisoning caused by fresh produce, Greg
Blank and his colleagues at the University of Manitoba in Winnipeg wondered if
contaminated sprays could be to blame. To find out, they prepared formulations
of a dozen or so common herbicides, fungicides and insecticides approved for
spraying on raw fruit or vegetables.
After diluting each with water, they added strains of bacteria that cause
food poisoning. These included Shigella, Salmonella,
Listeria and Escherichia coli O157:H7 which can cause kidney
failure.
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The researchers found that bacteria thrived in around a third of the
pesticides, growing best in the fungicide chlorothalonil, the weedkiller linuron
and the insecticides permethrin and chlorpyrifos. 鈥淣umbers could increase
one-thousandfold,鈥� says Blank. Salmonella, E. coli and
Shigella grew best, he says, particularly on chlorothalonil.
Blank acknowledges that when farmers irrigate their crops they may spray on
far larger volumes of contaminated water. What鈥檚 different with pesticides, he
says, is that the bacteria multiply in tanks where the solution is stored, and
so can reach far higher concentrations. He is now investigating whether the bugs
survive to the point of consumption.
Ross Dyer, technical manager of the Crop Protection Association in Britain,
says that the problem is caused by farmers using dirty water rather than by the
pesticides: 鈥淚f the water supply is contaminated, it鈥檚 that that鈥檚 supplying the
bacteria in the first place.鈥�
