October 4, 2000

Pesticides can help bacteria grow on fruits and veggies, scientists say

TORONTO (CP) -- Some pesticides actually encourage the growth of life-threatening bacteria on fruit and vegetable crops, scientists at the University of Manitoba have found.
 As a result, bugs like Salmonella, E. coli and Shigella could pose a threat to people eating raw fruit and vegetables, they report in this week's issue of the journal New Scientist.
 The problem starts not with the pesticides themselves, but the water used to mix them, author Greg Blank explained in an interview from Winnipeg on Wednesday.
 Blank is a professor of microbiology in the university's department of food science. He and his colleagues were alarmed by the rise in cases of food poisoning caused by fresh produce, so set out to determine if contaminated pesticide sprays were to blame.
 Pesticides are generally purchased in concentrated form and mixed with water. "In most cases the water that the farmers are going to use is whatever is available," Blank noted.
 "If you take a look at what happened with Ontario, with Walkerton, that water's not only used for drinking but it's also used for irrigation."
 Six people died after drinking E. coli contaminated water in the town earlier this year.
 The researchers mixed a variety of common pesticides, herbicides and fungicides with water contaminated with pathogens like Salmonella or E. coli.
 Some killed the bugs quickly. But in about one-third of the pesticides, the bacteria actually flourished.
 "Numbers could increase 1,000-fold," Blank said.
 Salmonella, E. coli and Shigella grew best, particularly in the fungicide chlorothalonil.
 "If it's spread on a crop that's already standing, then you're contaminating the crop," he said, adding that "many of these fruits or vegetables ... are usually consumed raw or with minimal cooking."
 Watering fruit and vegetable crops with contaminated water also poses a threat. But the health risks are greater if that water is mixed with pesticides that foster bacteria growth.
 "I would think so. The more (bugs) the merrier," Blank said.
 While foods like chicken, eggs and dairy products were more traditionally associated with food poisoning, the incidence of illness caused by fruits or vegetables has been on the rise. Children have contracted E. coli from unpasteurized apple juice. Contaminated vegetable sprouts caused a major outbreak of E. coli in Japan.
 The diversification of food products also poses a threat, Blank said, pointing to the fact that shoppers can now buy half a watermelon or cantaloupe.
 "Somebody had to take a knife. That knife -- was it used for picking chewing gum off the floor before you sliced the watermelon? Or do they take it into a sterile room and carefully cut it?
 "What do you think?"
 Blank believes the public has heard the message that fruits and vegetables have to be carefully washed.
 "I think ... that most people today are becoming more vigilant with regards to washing their fruits and vegetables before they eat them or cook them."
 And that doesn't mean just a cursory rinse under cold running water, he noted.
 But he doesn't think everyone makes the connection when it comes to the water they use on fruit and vegetable gardens and crops. For instance, people often ask him if they can use the water from Winnipeg's Red River to water their gardens.
 "And of course this is ludicrous considering that a lot of these people are going to eat their produce raw.
 "It's almost the same thing as saying: 'Well, can I drink this water?'"