Youngsters
with high levels of pesticide residue in their urine, particularly from
widely used types of insecticide such as malathion, were more likely to
have ADHD, the behavior disorder that often disrupts school and social
life, scientists in the United States and Canada found.
Kids with
higher-than-average levels of one pesticide marker were nearly twice as
likely to be diagnosed with ADHD as children who showed no traces of the
poison.
“I think it's fairly significant. A doubling is
a strong effect,” said Maryse F. Bouchard, a researcher at the
University of Montreal in Quebec and lead author of the study published
Monday in the journal Pediatrics.
The take-home message for parents, according to
Bouchard: “I would say buy organic as much as possible,” she said. “I
would also recommend washing fruits and vegetables as much as possible.”
Diet is a major
source of pesticide exposure in children, according to the National
Academy of Sciences, and much of that exposure comes from favorite
fruits and vegetables. In 2008, detectable concentrations of malathion
were found in 28 percent of frozen blueberry samples, 25 percent of
fresh strawberry samples and 19 percent of celery samples, a government
report found.
ADHD
affects 4.5 million U.S. kidsBouchard’s study is the
largest to date to look at the effect of pesticides on child development
and behavior, including ADHD, which affects an estimated 4.5 million
U.S. children. About 2.5 million kids take medication for the condition,
according to the Centers for Disease Control and Prevention.
Bouchard and her
colleagues measured levels of six pesticide metabolites in the urine of
1,139 children ages 8 to 15 selected from the National Health and
Nutrition Examination Survey between 2000 and 2004. The study included
119 children who were diagnosed with ADHD.
Unlike other studies of pesticides’ impact,
Bouchard’s sample provided a glimpse into average insecticide exposure
in the general population of children, not a specialized group, such as
children of farmworkers. Because certain pesticides leave the body after
three to six days, the presence of residue shows that exposure is
likely constant, Bouchard said.
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The
most alarming finding was a near-doubling in odds of ADHD diagnoses
among kids with higher-than-average levels of the most common of the six
metabolites detected. Kids with high levels of dimethyl thiophosphate
were 93 percent more likely to have the disorder than children with with
undetectable levels of the marker.
The research may
add to anxiety about ADHD, which has no known cause, said Dr. Andrew
Adesman, chief of developmental and behavioral pediatrics at the Steven
and Alexandra Cohen Children’s Medical Center of New York.
“It does seem to
suggest that at non-extreme or more typical levels, there does seem to
be some increased risk,” said Adesman, who is on the professional
advisory board for Children and Adults with ADHD, an advocacy group.
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Pesticides
prey on nervous systemBoucher studied organophosphate
pesticides, which account for as much as 70 percent of the pesticide use
in the U.S. They work by interfering with the nervous systems of
insects, but have a similar effect in mammals, including humans. Most
people in the U.S. have residues of the products in their urine.
Cheminova, the Danish
firm that is the leading manufacturer of malathion in the world,
declined to comment on the conclusions of the new research. Diane
Allemang, vice president for global regulatory affairs, said she hadn’t
seen the study.
Parents
of children with ADHD, however, said Bouchard’s work will give them one
more than thing to worry about.
“We’re all completely obsessed with food,” said Jamie
Norman, 32, of Freeburg, Ill., whose 6-year-old son, Aidan, was
diagnosed with ADHD six months ago.
The stimulant medication Aidan takes, Adderall XR,
depresses his appetite, so Norman said she’s always trying to find good
foods that he’ll want to eat. Other parents of kids with ADHD choose to
use diet, not medication, to control the disorder and they’re constantly
monitoring food, too.
News
that some of the best foods for kids might be tainted with something
linked to ADHD is worrisome, Norman said.
“I’ve known for some time that strawberries, in
particular, contain high levels of pesticide, but as far as frozen
fruit, I don’t give that a second thought,” she said.
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Buy organic,
make sure to washThe best advice for parents — and
anyone who wants to avoid pesticides — is to choose foods least likely
to contain them. The Environmental Working Group, a consumer advocacy
organization, advises
shoppers to buy organic versions of a dozen fruits and vegetables
that grow in the ground or are commonly eaten with the skin, because
they’re most likely to be contaminated.
Make sure to wash
all fruits and vegetables under cold running tap water and scrub
firm-skinned produce with a brush. Be sure to rinse frozen fruits and
vegetables, too.
But don’t wash
produce with soap. The Food and Drug Administration says that could
leave behind residues of detergent, yet more chemicals that everyone
would do best to avoid.