Study Exposes Link Between Pesticides and ADHD

ADHD, or Attention Deficit Hyperactivity Disorder, is running rampant among the nation's children, with 15% or more of children in some states having been diagnosed with the condition at some point in their lives:

(Percent of Youth 4-17 ever diagnosed with Attention-Deficit/Hyperactivity Disorder: National Survey of Children's Health, 2007 -Source: Center for Disease Control.)

And the incidence of ADHD only continues to rise:

Researchers calculate about 5.4 million kids have been diagnosed with ADHD, which suggests that about 1 million more children have the disorder than a few years earlier.

So what accounts for this spike in the number of ADHD cases? A new 12-year study from the University of California at Berkeley and the Center for the Health Assessment of mothers and Children of Salinas (CHAMACOS) has exposed pesticides', and particularly organophosphates', role in causing ADHD. Around 40 organophosphate pesticides are registered with the EPA for use in the United States. The study followed 300 Salinas, California families of farmworkers, and specifically the health of children of mothers exposed to pesticides while pregnant.

Researchers found that prenatal exposure to certain types of organophosphate pesticides is significantly linked to attention problems in children, visible by the time they turn 5, with the effects apparently stronger among boys. The findings, published in the Environmental Health Perspectives journal last August, were the first to examine the influence of prenatal organophosphate exposure on the later development of attention problems.

Among their findings was a discovery that prenatal pesticide metabolites - compounds found in the human body that indicate an over-exposure to harmful chemicals - are linked to increased odds of 5-year old children scoring high on tests for attention disorders.

So how do pregnant women and children become exposed?

Growers are not mandated to provide protective gear to farm workers, and the lack of protective measures means that workers end up carrying pesticide residues back home in their clothes, shoes, and cars. Farm supervisors commonly report that workers are often times exposed when applicators fail to notify them before spraying pesticides in adjacent fields.

And, farm laborers in the fields aren’t the only ones affected.

Communities on the edge of fields are exposed to pesticides through drift or vapor contained in the air, dispersed by strong winds as fields are sprayed. In many cases, protective measures around schools consist of a thin wire mesh separating playgrounds from lettuce fields.

The study found at least one genetic, and age-related, predisposition to the effects of organophosphate pesticides (Scroll down to "Mechanism Studies"):

[T]he human enzyme paraoxonase (PON1) detoxifies various organophosphate pesticides with different efficiency depending on single nucleotide polymorphisms (SNPs) at various position on the PON1 gene. We analyzed blood samples from mothers and children participating in the CHAMACOS cohort to determine their PON1 genotype and activity.

We found that PON1 activity is very low in newborns, suggesting that they are more susceptible to adverse effects of pesticides than adults.

PON1 activity was particularly low in newborns with vulnerable PON1 genotype.

Based on their PON1 status, some newborns may be 26 to 50 times more susceptible to exposure to certain organophosphate pesticides than other newborns. The most susceptible newborns may be 65 to 130 times more sensitive to organophosphate pesticides than the least susceptible some adults.

This is, however, not the first study to link organophosphates with ADHD. A 2010 study of 1139 children by Bouchard et al., working from the Harvard School of Public Health, the university of Montreal Department of Environmental and Occupational Health, and Brigham and Women's Hospital found that children with higher level of organophosphate metabolites in their urine were more likely to meet the diagnostic criteria for ADHD. The study authors there sttes explicitly that the findings should be "generalizable to the US population" because the study population was nationally representative.

The upshot? Eat, and have your kids eat, organically-grown vegetables as much as you can. For now, standard, pesticide-aided vegetables should come with the standard pharmaceuticals warning: "Do not use this product if you are pregnant, or are thinking about becoming pregnant..."