Pesticide Exposure and ADHD

byJoy Granetz, Ph.D.

It is well established that exposure to organophosphates, the basis for many insecticides and herbicides, is associated with adverse effects on the neurodevelopment of populations with high levels of exposure. For instance, exposure to organophosphates has been linked to cognitive and behavioral problems in farm workers and their families. It is believed that children are at greater risk for toxicity from pesticides because their brains are still developing and the dose per weight is larger for children. This month, a new study published in the journal Pediatrics has added to the accumulating evidence of a link between pesticide exposure and poor developmental outcome. More specifically, researchers found an almost doubling of odds of an ADHD diagnosis in children with high levels of metabolites of pesticides in their urine. This has caused a great deal of alarm in parents of young children, as the foods implicated are what we consider to be some of the healthiest food options for our children.

The authors of the study examined 1,139 children between the ages of eight and fifteen. They found that in their sample, those children with higher urine levels of organophosphate metabolites were more likely to meet diagnostic criteria for ADHD than children with low levels of metabolites. In fact, there was almost a doubling of odds of an ADHD diagnosis in kids with higher levels of metabolites, a robust effect. Whether there was an association with a specific subtype of ADHD was unclear because of the small number of cases in the study. More research is necessary to better understand this association. ADHD is a complicated neurodevelopmental disorder with multiple causes. It will be critical for studies to replicate these findings and importantly, to better understand if there are underlying causal links to this association.

For now, there are a few take home points. Obviously, it is not recommended that children stop eating fruits and vegetables. There are a few simple things to do to minimize potential exposure that will likely benefit everyone in the family. First, it is always a good idea to wash fruits and vegetables well, including frozen fruits and vegetables. Do not use soap, though, as soap leaves residue on produce. The recommended procedure is to use cold tap water and scrub with a brush if the produce is firm-skinned. Secondly, buy locally grown organic produce as much as possible. This is especially true of the fruits and vegetables on the “dirty dozen” list. Fruits and vegetables that grow in the ground or are eaten with the skin are at highest risk for exposure. Organic fruits and vegetables are known to contain fewer pesticides. It has been estimated that avoidance of non-organic “dirty dozen” fruits and vegetables may reduce pesticide exposure by up to 80%. The dirty dozen are:

  1. Peaches
  2. Apples
  3. Bell peppers
  4. Celery
  5. Cherries
  6. Nectarines
  7. Strawberries
  8. Kale
  9. Lettuce
  10. Imported grapes
  11. Carrots
  12. Pears

In the meantime, longer term studies will be necessary to help us to better understand the link between pesticide exposure and attention-related challenges.