New Harvard Research Shows Link Between ADHD and Pesticides


Boston - A study recently published in Pediatrics demonstrates a link between Attention Deficit Hyperactive Disorder and organophosphate pesticides.

The Harvard-based study involved one Canadian and three American scientists. Titled Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides, the study reviewed existing health records, building on the information by interviewing parents. The four researchers, Maryse F. Bouchard (University of Montreal & Harvard), David C. Bellinger (Harvard University), Dr. Robert O. Wright (Boston Children's Hospital), and Marc G. Weisskopf (Brigham and Women's Hospital) found a strong correlation between the level of pesticides detected in the urine of children and the condition known as Attention Deficit Hyperactive Disorder. Those children with more pesticide exposure were more likely to have ADHD. The researchers concluded:

"These findings support the hypothesis that organophosphate exposure, at levels common among US children, may contribute to ADHD prevalence. Prospective studies are needed to establish whether this association is causal."

Describing the research on her Harvard webpage, Bouchard said:

"Children with higher concentrations of urinary dialkyl phosphate (DAP), especially dimethyl alkylphosphates (DMAP), were more likely to be diagnosed with ADHD. A 10-fold increase in DMAP concentration was associated with an odds ratio (OR) of 1.55 (95% confidence intervals [CI], 1.14–2.10), after adjusting for sex, age, race/ethnicity, poverty-income ratio, fasting duration, and urinary creatinine concentration. For the most commonly detected DMAP metabolite, dimethylthiophosphate, children with levels higher than the median of detectable concentrations had double the odds of ADHD (adjusted OR, 1.93 [95% CI, 1.23–3.02]) compared with those with non-detectable levels."

Attention Deficit Hyperactivity Disorder (ADHD) "... is one of the most common childhood disorders and can continue through adolescence and adulthood. Symptoms include difficulty staying focused and paying attention, difficulty controlling behavior, and hyperactivity (over-activity)," says the National Institute of Mental Health. The Center for Disease Control said 3% to 7% of school-aged children in the United States had ADHD in 2003, with 2.5 million children medicated for the condition.

A study on organophosphate pesticides published in 2007, Organophosphate Pesticide Exposure and Neurodevelopment in Young Mexican-American Children found a tentative link between the exposure to pesticides and brain development. The authors of the report noted:

"... More than one billion pounds of pesticides are used annually in the United States, three-quarters of which are used in agriculture. Recent biological monitoring studies indicate that pesticide exposures are widespread in the U.S. population, including to pregnant women and children."

Scorecard, the Pollution Information Site states:

"Organophosphate pesticides account for about half of the insecticides used in the United States. A large number of organophosphate pesticides metabolize to dialkyl phosphate metabolites and other specific metabolites. There are six dialkyl phosphate metabolites; each of these can be produced from the metabolism of more than one organophosphate pesticide.

Organophosphate pesticides act by interfering with the transmission of signals in the nervous systems of both insects and humans, if humans are exposed in high enough amounts. Organophosphate pesticides injure and even kill large numbers of people around the world every year, and have been associated with chronic nervous system damage in people who survive poisoning."

Exposure, says the Center for Disease Control, does not have to be direct. Eating foods that have organophosphates sprayed on them can contribute to effects on an individuals' health.

There are dozens of organophosphate pesticides on the market, including the better known brands, Diazinon, Malathion and Trichlorphon.
A coalition of five US groups launched a lawsuit in 2008 in an attempt to have four organophosphate pesticides removed from the market. The lawsuit is still in legal limbo, and there is no indication as to when it might be resolved.

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