Research: A Link Between ADHD by Kids 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.”

“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.

DNA damage

PBO induced mutagenicity in cultured human RSa cells and caused mutations in gene OuaR. PBO also caused mutations in K-ras, a gene believed to be involved in neoplastic (tumorous) changes (Suzuki H et al 1995). PBO causes sister chromatid exchanges in cultures of cells from hamster ovaries (Tayama, S. 1996).

Cancer

The carcinogenicity of PBO was in 1995 still controversial to some reviewers. In a 1995 review, the World Health Organization, identified five other studies that found no evidence that PBO exposure caused cancer (WHO and FAO Evaluations 1995 pp 288-293). At this moment much more studies do suggest the carcinogenic effect… .

Since 1995, EPA has classified piperonyl butoxide as carcinogen (a chemical that causes cancer). EPA’s classification of piperonyl butoxide is `Group C’, a possible human carcinogen (U.S. EPA 1995). A study conducted by PBO manufacturers found the incidence of lymph and thyroid tumours increased with increasing exposure to PBO (WHO and FAO Evaluations 1995 Pp. 291). By now it is reasonable to call PBO a liver carcinogen.