A new study in the journal Pediatrics associates exposure to pesticides with cases of ADHD . ADHD rates of diagnosis have risen 3% a year between 1997 and 2006. Increasingly, research suggests that chemical influences, perhaps in combination with other environmental factors — like video games, hyperkinetically edited TV shows and flashing images in educational DVDs aimed at infants — may be contributing to the increase in attention problems.
Researchers at the University of Montreal and Harvard University examined the potential relationship between ADHD and exposure to certain toxic pesticides called organophosphates which are commonly used in North America on non-organic strawberries, blueberries and celery. Children are most likely to ingest the chemicals through their diet — by eating fruits and vegetables that have been sprayed while growing
The team analyzed the levels of pesticide residue in the urine of more than 1,100 children ages 8 to 15 and found that those with the highest levels of dialkyl phosphates, which are the breakdown products of organophosphate pesticides, had the highest incidence of ADHD.
“I was quite surprised to see an effect at lower levels of exposure,” says Bouchard, who used data on ADHD from the National Health and Nutrition Examination Survey, a long-term study of health parameters of a representative sample of U.S. citizens.
Bouchard’s analysis is the first to home in on organophosphate pesticides as a potential contributor to ADHD in young children. Organophosphates are known to cause damage to the nerve connections in the brain — that’s how they kill agricultural pests, after all. The chemical works by disrupting a specific neurotransmitter, acetylcholinesterase, a defect that has been implicated in children diagnosed with ADHD. In animal models, exposure to the pesticides has resulted in hyperactivity and cognitive deficits as well.
“I am very confident in the correlation in this study, because we controlled for quite a few things that we thought could play a role,” says Bouchard. “Adjusting for those things did not change the results very much. Which indicates that there is very little potential for confounding in this association between pesticides and ADHD.”
The study also raises the possibility of setting a national threshold for safe levels of exposure; the study authors note that according to the U.S. Pesticide Residue Program report, organophosphates were detected in 28% of frozen blueberries and in 19% of celery samples tested for pesticides. It is not clear whether those levels pose a threat to cognitive function in children, but the current study’s findings suggest it may be wise to figure that out.
In the meantime, Bouchard suggests that concerned parents try to avoid using bug sprays in the home and to feed their children organically grown fruits and vegetables, if possible. While pesticide-free fruits and greens may be more costly, Bouchard says they may be worth the price in terms of future health. While one article suggested that, parents should be careful to scrub all produce to reduce residue when using non-organics, another one pointed out that washing the fruit does nothing to get rid of the pesticides as they penetrate the skin and reside in the part of the fruit that we eat.
The sad news is that neurologist have known that pesticides are harmful to cognitive function for a long time. They have seen children exposed to pesticides on farms suffer cognitively as a result of organophosphate exposure and have warned against having young children close to fields during fumigation.
What they did not know is that even very small levels of exposure are harmful. The Environmental Protection Agency (EPA) limits how much residual pesticide can be left on food but this allowed amount, as it turns out, is harmful. In a way this is very similar to the lead story. The EPA set limits on the lead exposure that was considered ‘safe’ and but the allowed exposure level can actually cause cognitive problems and ADHD.
Pet products can also contain toxic pesticides so avoid pet shampoo, flea collars and other flea medicines with organophosphates and avoid using toxic pesticides in the home and garden.
The study was published online in the Journal Pediatrics on May 17 2010.
I found a guide of which other fruits and vegetables are high in pesticide residue at Foodnews, which is part of the Environmental Work Group.