Study: Common Pesticides Linked to Attention Deficit Disorder

By Andrew Moseman | May 17, 2010 12:30 pm

Child with learning difficultiesAdd one more to the list of environmental factors that could contribute to the rise in attention deficit hyperactivity disorder (ADHD): pesticides. A new study out in Pediatrics argues that there’s a connection between high exposure to common pesticides and increased risk for children developing ADHD.

Maryse Bouchard and colleagues looked at more than 1,100 children aged between 8 and 15. All of them had been sampled by the National Health and Nutrition Examination Survey (NHANES) between 2000 and 2004, and 119 had been diagnosed with ADHD. Bouchard’s team studied their urine samples for chemicals called dialkyl phosphates, which result from the breakdown of organophosphate pesticides used to protect fruits and vegetables.

For a 10-fold increase in one class of those compounds, the odds of ADHD increased by more than half. And for the most common breakdown product, called dimethyl triophosphate, the odds of ADHD almost doubled in kids with above-average levels compared to those without detectable levels [Reuters].

According to the researchers, there are about 40 organophosphate pesticides in use in the United States, the most famous of which is malathion. It was heavily sprayed in California in the early 1980s to try to kill the Mediterranean fruit fly, and also about a decade ago to try to stop the spread of West Nile virus.

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 [MSNBC].

Using the large sample of children from NHANES allowed the researchers to adjust for location, race, and other factors that have confounded studies like this trying to link an environmental factor to a particular condition. However, the scientists admit, the weakness of their study is that using NHANES data allowed them to see just one urine sample taken at one point. Thus, they couldn’t determine the source of contamination, nor could they see how levels of the chemicals in question built up over time. And since that buildup over time is what would spur the potential neurochemical changes that would increase ADHD risk, Bouchard and colleagues write, their study shows correlation but not causation.

Bouchard’s analysis is the first to home in on organophosphate pesticides as a potential contributor to ADHD in young children. But the author stresses that her study uncovers only an association, not a direct causal link between pesticide exposure and the developmental condition. There is evidence, however, that the mechanism of the link may be worth studying further: organophosphates are known to cause damage to the nerve connections in the brain — that’s how they kill agricultural pests, after all [TIME].

So there’s a lot left to be proven. But Bouchard’s study is another reminder in favor of the old stand-by: wash your fruits and vegetables thoroughly.

Related Content:
DISCOVER: Vital Signs: There’s Hyperactivity… And There’s Hyperactivity
DISCOVER: Vital Signs: Misdiagnosing ADHD
80beats: Scientist Smackdown: Are Environmental Toxins a Huge Cancer Threat?
80beats: Herbal Remedy Doesn’t Help Kids with Attention Deficit Disorder
80beats: Why ADHD Kids Have Trouble with Homework: No Payoff
80beats: Bee Killer Still at Large; New Evidence Makes Pesticides a Prime Suspect

Image: iStockphoto

MORE ABOUT: ADHD, pesticides
  • KDdidit

    Just makes me wonder how my exposure to DDT between the ages of 8-12 and the fact that all three of my children had foot deformaties is all related. The Japanese Snow Monkeys had feet and hand deformaties from DDT exposure. There are no other foot deformaties on either side of our families to blame genetics. Thank heavens that none of my eight grandchildren have similar foot deformaties. One of my children did have ADHD. Was that DDT related?

    WHAT will we find in the future regarding the chemicals we casually use today?

  • Geraldine

    The end of the article says, “Wash your friuts and vegetables thoroughly.:
    That will not make much of a difference in the end. The plants uptake these poisons, and they become part of the fruit.

    The old adage of, “We are what we eat” is very truthful. Unfortunately, unless we grow our own foodstuffs or eat organic foods, we have no idea what has been done to our food supply.

  • jmberan

    It’s unfortunate that studies like this don’t even consider correcting for internal variables (lifestyle choices, parenting methods, etc) insofar as to suggest that a more diligent parent will select or prepare foods better for their children in coincidence with emphasis on reasonable disciplines. Whereas the lazy, unthoughtful, and sometime contemptuous parent would aim for less care as personal freedom. Such lax would also result in weekened discipline and morals in the child.

    The most unfortunate side affect from this article will be it’s gospel-like adherence of die-hard anti-inorganics.

    Don’t check your brain at the keyboard or the door when you read things like this, everyone has an agenda.

  • KDdidit

    My mother grew gladiolus as a hobby and the trend during the mid-1950s was to use DDT to kill any bugs. I remember my mother telling about the salesman who ate a teaspoon of DDT to demonstrate that it was safe. I helped her plant, clean and care for those gladioli. Of course she used DDT on the garden stuff so in theory I was eating fresh off of the farm food but it was contaminated because it was pre- Rachel Carson and her book “Silent Spring.”

    A medical person told me that at the age I was exposed to DDT my eggs were forming so the exposure I had affected their development. That’s WHY I asked about the chemicals we are being exposed to via the medical establishment aka prescriptions! Are we setting up another thalidomide issue? But perhaps it will be less obvious such as ADHD or ADD. AAARGH!

    I spent 36 years in K-8 classrooms in 5 states and overseas. There is a change in the students’ attention span and interest. I still substitute teach and I am seeing a regression in the maturity of the students in the primary and intermediate grades. I am also hearing as one of my former students who is a teacher calls it — “Twitter Live”. The students do not know the value of being silent for even a short period of time.

  • Jay Fox

    Keep looking at this and you’ll find all kinds of problems. ADHD is just the beginning. What about autism?

  • scribbler

    We will find that even with the harm done, our lives demanded the use of chemicals…

  • Linda

    Jay has an excellent point. Many researchers list ADD/ADHD as disorders falling along the autism or PDD “spectrum.”


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