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?'"
