Exposure to Pesticide Linked to ADHD for Children: Study

New research indicates that there may be a link between attention-deficit/hyperactivity disorder (ADHD) and a family of pesticides known as organophosphates, which are used on many commerically grown fruits and vegatables.  

The ADHD pesticide study was conducted by scientists from Harvard and the University of Montreal, and published online this week by the medical journal Pediatrics. Researchers found that children with higher levels of certain pesticides in their urine were more likely to be diagnosed as having ADHD.

Organophosphates overall are one of the most important biochemicals, essential in DNA and RNA, as well as other compounds. Pesticides made from organophosphates attack the nervous system of insects, and can also affect human and animal nervous systems as well. Some organophosphates pesticides include parathion, malathion and phosmet. It is also used to create some of the most deadly nerve agents classified as weapons of mass destruction, including sarin and VX gas nerve agents.

Overall, there are about 40 organophosphate pesticides in use in the U.S., and about 73 million pounds of it was used in 2001 alone, according to the U.S. Environmental Protection Agency.

Researchers used the National Health and Nutrition Examination Survey (NHANES) of 1139 children, identifying 119 who met the diagnostic criteria for ADHD. The researchers looked for dimethyl alkyphosphate (DMAP), a byproduct of organophosphate pesticides, in the children’s urine. They found that children with high concentrations of the most commonly detected DMAP metabolite, dimethy thiophosphate, were twice as likely to be diagnosed with ADHD as other children. On average, children 8 to 15 years old with 10 times the levels of any kind of DMAP metabolite in their urine were 55% to 72% more likely than other children to meet ADHD diagnosis criteria.

“These findings support the hypothesis that organophosphate exposure, at levels common among US children, may contribute to ADHD prevalence,” researchers concluded. “With respect to the importance of these findings, organophosphates are among the most widely used pesticides, and the concentrations of [dialkyl phosphate] metabolites among children did not decrease from 2000 to 2003-2004.”

The researchers said that future studies should focus on the collection of more data on exposure over time, hopefully leading to a better assessment of chronic exposure and to determine if there is a critical window of exposure at a certain age that is most likely to lead to ADHD.