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Food for Thought: Pesticide Exposure and ADHD Risk in Children
Attention Deficit Hyperactivity Disorder is a neurodevelopmental syndrome in which a child's levels of attention, activity, and impulsivity are inappropriate for her age. The symptoms can interfere with learning, family and social functioning, and safety. A child with ADHD may have trouble succeeding in school, low self-esteem, poor peer relationships, and other emotional and behavioral issues. ADHD is most accurately diagnosed with a comprehensive physical, neurological, educational, behavioral, and emotional assessment. It is treated with counseling and behavioral management, educational modifications, and medications. Although the manifestations and the impact may change, some ADHD symptoms generally persist throughout the lifecycle.
ADHD has been attributed to a wide variety of causes from fetal exposure to toxins such as nicotine and alcohol, to birth complications including prematurity and low weight, to early life health problems including lead poisoning, and to socio/environmental factors such as poverty and parental mental illness. It is likely that there are many causes and many periods of vulnerability during early development whose common denominator involves a process that interferes with the normal development of the parts of the brain responsible for organization, behavior regulation, and attention.
A recent study published in Pediatrics suggests that pesticide exposure during childhood is associated with an increased risk of ADHD in children.(1) The researchers decided to test the idea that pesticides might have an impact based on the knowledge that children are a greatest risk from toxic effects of pesticides because their brains are still developing, the biochemical systems responsible for reducing toxicity of organic chemicals are not fully developed, and the pesticide exposure is distributed over a smaller body and brain weight than in adults. Previous studies have shown that infants who were exposed to pesticides prenatally had a higher risk of significant developmental delays relative to their peers.(2)(3) Other researchers have determined that exposure to pesticides after birth is associated with problems with behavior, memory, and motor skills.(4)(5)(6)
The investigators for this study chose to evaluate children whose pesticide exposure was considered to be an average rather than those whose exposure was at a toxic level. The main sources of exposure for these children were pesticide residues that remain on food and pesticide washed into drinking water from environmental exposure. They looked at a group of children who were 8-15 years old during the period 2000-2004. As part of the routine physical exam, the children's urine specimens were collected and measured for the chemical evidence of the most common pesticides. The study sample included 1139 children. Of these, 119 met diagnostic criteria for attention deficit hyperactivity disorder. By comparing the level of pesticide metabolites in the urine specimens of the children who did and did not meet criteria for ADHD, the researchers found that the children with ADHD diagnoses had significantly higher pesticide exposure levels than their peers. Children who had no detectable level of pesticides in their urine were half as likely to have ADHD than those whose levels could be detected. However, even in the positive group, the levels were consistent with those seen commonly in the pediatric population and most would be judged to be average for a child of their age.
The researchers suggest that the pesticides may negatively impact the biochemical messenger systems that are involved in attention, organization, and inhibition in the developing central nervous system. This is a similar model to that which is proposed as the mechanism for the negative effect of nicotine on attention. The authors suggest that more study is needed to learn more about how the timing and the duration of exposure to pesticides impact development and whether there are specific times in a young child's life when they are more vulnerable to the negative effects of environmental toxins such as pesticides.
Awareness about the risks of pesticides in children's diets is appropriate, but fruits and vegetables are critical sources of nutrition for good health and normal development. Parents may wish to discuss ways to safely feed their children nutritious food with their doctors or with nutritional consultants. More information about pesticide safety in the home, garden, workplace, and in food and water is available on:
May 30, 2010
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