Pesticides and ADHD Strongly Linked

Recent studies  have estimated that 8.6% of American children have ADHD, which has exploded with a 400% increase in the past twenty years. 

A study released this week examined data for over 1000 children, looking at urine metabolite levels from organophosphate pesticides.  The complete Pediatrics article is available for free; it was also widely reported in the media. 

Some background from this article and other sources as indicated:

• About 37 out of 900 (!) pesticides used in the U.S. belong to the class called organophosphates; these chemicals "kill insects by disrupting their brains and nervous systems."   Organophosphate pesticides include malathion and chlorpyrifos.
• Organophosphates are used for insect control programs, agriculture, and residential applications. 
• In 2001, 73 million pounds of organophosphates were used in the U.S.
• The U.S. has a sampling program for measuring pesticide residues.  The most recent report contains data from 2008.  According to this report, malathion and chlorpyrifos were found in the following percentages of samples:

	Malathion	Chlorpyrifos
Corn	33.7	17.8	% of samples
Blueberries (frozen)	27.8	5.6
Celery	19.3	3.2
Kale	19	1.6
Strawberries	24.6	0.9
Peaches	0	17.2
Broccoli	0.4	8.1

Children are at greater risk from pesticide exposure because:

• They put many things in their mouths, they are closer to the ground, and they spend lots of time exploring the outdoors (reference)
• They are growing quickly and take in more pesticides per unit weight than adults (reference)
• Their bodies are not the same as adult bodies.  In particular, their bodies may offer less protection from pesticide exposure due to differences in enzymatic and immune activity (ibid).
• Many of children's favorite foods appear in the EWG's "dirty dozen" of pesticide residues, including apples, strawberries, and potatoes.  Many children have limited diets and so eat more of their favorites than an adult might.   

Now - back to the ADHD / organophosphate study.  The authors state that prenatal and postnatal organophosphate exposures have been linked to developmental and behavioral problems problems, including delayed mental development, poorer short-term memory and motor skills, and longer reaction times.


After analyzing the data for various metabolites and looking for confounding factors, they determined that:

• 93.8% of the children had at least one of the 6 metabolites at a detectable level
• Metabolite levels were higher in 2003-4 than in 2000
• Children with a particular metabolite, dimethyl triophosphate, above median values, had twice the odds of having been diagnosed with ADHD; other metabolites also are associated with up to a 72% increased risk of ADHD

They conclude that "[d]evelopmental exposure to organophosphates might have persistent effects on multiple neural systems that may underlie ADHD behaviors, such as inattention and cognitive deficits, similar to the effects of developmental nicotine exposure."


The good news is that organophosphates cannot be used on organic produce.   According to this study, "organophosphates are eliminated from the body after 3 to 6 days," so moving to more organic foods could have a nearly immediate effect.