Study: Common pesticide affects developing brain
April 30th, 2012
06:38 PM ET

Study: Common pesticide affects developing brain

Chlorpyrifos, a common pesticide, may be subtly influencing brain development in children, according to a new study.  The brain abnormalities, found among a very small population of school-aged children, may have occurred while they developed in utero.

What is troubling, according to scientists, is that relatively low levels of chlorpyrifos appear to have caused the cascade of brain changes.

"It's out there and we do not know what the longer term impact is of lower levels," said Virginia Rauh, professor of Clinical Population and Family Health at Columbia University Mailman School of Public Health, and the study's lead author.  "But it does seem to be associated with cognitive damage and structural changes in brain."

In the study, 40 children, ages 6 to 11, were given MRI scans.  Half of the children had relatively low levels of chlorpyrifos based on samples of their cord blood at birth, and the other half had relatively high levels.

The abnormalities found among children with higher-than-normal exposure to chlorpyrifos included overgrowth, and undergrowth, in areas of the brain associated with attention, emotion, behavior - even IQ.

"When the brain is developing and cells are migrating to various places in the brain they're intended to go, that process is being disrupted," said Rauh.

But the makers of chlorpyrifos say that the small population of children studied mars the findings.

"Because of the small number of blood samples and the small group of children evaluated, even a slight misclassification of 'high' vs. 'low' exposure classifications could drastically skew the results of the MRI imaging comparisons that are the focus of this article," said Garry Hamlin, a spokesperson for Dow AgroSciences, makers of chlorpyrifos, in an email.

Chlorpyrifos was a common household pesticide until it was phased out for residential use by the Environmental Protection Agency in 2001, according to the study.  But it is still used commercially in public places and - most importantly for a wider swath of the population - in agriculture.

One theory, which is not well-studied, is that chlorpyrifos could be entering the womb by way of the fruits and vegetables consumed by pregnant women.

"The mother is exposed, the chemical crosses the placenta and essentially enters bloodstream of the fetus," said Rauh, deputy director of the Columbia Center for Children's Environmental Health.  "That is a transport system to all parts of the child's body."

On its website, EPA reports that "Dietary exposures from eating food crops treated with chlorpyrifos are below the level of concern for the entire U.S. population, including infants and children."

"There is this general sense that chemicals have one known function, that they only do that one thing and not anything else," said Dr. David Carpenter, director of the Institute for Health and the Environment at the University at Albany.  "This study shows that's clearly not the case... there are gross changes in the structure of brain."

"I think this is a very, very important study," he added.

The concern among environmental health experts is not just chlorpyrifos, but a host of other pesticides falling under the umbrella of organophosphates.  The suggestion of studies in animals, and more recently in humans, is that during critical stages of brain development, organophosphates could be irreparably altering brain development - and that the changes may persist as the child ages.

An interesting finding of the current study, published in the journal Proceedings of the National Academy of Sciences, involves the possibility that chlorpyrifos interferes with sexual differentiation in the brain early in development.

"We have some evidence that among highly exposed children, those differences are slightly blurred," said Rauh.  "Meaning... the brain of an average boy looks less like the brain of a boy, and a little more like the brain of a female."

Since the study population is still pre-pubescent, the real world implications of that finding are not known.

soundoff (34 Responses)
  1. onlyfacts61

    It's a sad proven fact that if congress voted today on banning these dangerous chemicals, Republicans would vote against the ban because it would harm the profits of the companies that produce them. They would use the excuse,"the science isn't proven". I don't know how they (repubs) sleep at night!

    May 1, 2012 at 07:43 | Report abuse | Reply
  2. Sara

    Now will you pay a little more for organic produce? Since pregnant women are encouraged to eat a healthy diet with lots of fruits and veggies, it would behoove the medical profession to encourage pregnant women to try and buy organic produce whenever possible. You know since they are so adamant about pregnant women abstaining completely from alcohol, hot dogs, and certain cheeses.

    May 1, 2012 at 09:21 | Report abuse | Reply
  3. Greenfield

    DowAgroSciences should waste less time and money on defending chlorpyrifos and more on R&D into non-toxic alternatives if they want to stay ahead of the market. On the other hand, while I have no problem paying 25 to 75% more for organic produce, I do not like the idea of being held hostage to paying twice or three times as much for produce that at best is 95% pesticide free (the USDA definition). Pricing of organic produce is creating an unpleasant stratification of society. Well to do folks that can eat safely and poorer folks that can't do the same. I hate to say it but I believe some organic farmers are profiteering off of public health concerns. I understand the extra costs of lower yield and shorter shelf life of organic produce (which I read is around 25 to 50% more than conventional farming) but please, there has to be some reasonable pricing. Safe food is a basic need.

    May 1, 2012 at 10:51 | Report abuse | Reply
  4. medschoolkid

    Could be a problem but I would like to see a study done with more than 40 test subjects. Kind of limited statistically and really too small to develop a conclusion from.

    May 1, 2012 at 15:28 | Report abuse | Reply
  5. lilly

    Check out chlorpyrifos on Wikipedia's page some interesting facts not in the article.

    May 1, 2012 at 20:32 | Report abuse | Reply
  6. soulCatcher

    40 people is enough to test cosmetics for allergic reactions. Any reactions are bad. I think mothers should be looking into this instead of vaccines as the cause of ADHD. These chemicals are used in everyone's lawn that your children play in.

    May 3, 2012 at 08:34 | Report abuse | Reply
  7. Mukesh

    Bt sprays are apilped to the exterior of crops and break down in sunlight within a couple of days. Most crops genetically engineered (GE) to produce Bt proteins produce them within every cell in the plant so it remains in the GE corn or eggplant, etc. that reaches consumers. The possibility that it reaches consumers through eating the meat of animals which were fed Bt crops should be followed up on; Bt proteins are infamous for not breaking down under gastrointestinal conditions (e.g. the taco shell incident of 2000 centered around a Bt protein that did not break down readily in gastric juices).Rachel Carson supported the use of Bt sprays. I don't think she'd have done the same for GE Bt crops at least not in the way that the technology is being utilized today.

    August 1, 2012 at 19:01 | Report abuse | Reply
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