ADHD and pesticides, to start with, is not a new research topic. Studies have been done before, frequently focusing on the children of migrant farm workers who have a higher pesticide exposure risk. Correlations have been made between pre- and post-natal exposure to organophosphates, lower scores on the Bayley MDI¹, and higher incidence of PDD² diagnoses.

However, as other articles point out, this is the first study to look at "the effects of exposure in the population at large." It is, to date, the largest study of its kind - measuring the levels of pesticide byproducts in the urine of 1,139 children, aged 8 to 15. But, this is where I start having a small problem.

The samples were collected during the National Health and Nutrition Examination Survey, conducted annually by the CDC on about 5,000 people in 15 counties across the United States. Only one sample was collected from these specific participants. One sample, upon which all subsequent conclusions were based, with no follow-up.

Briefly, the study found that children with higher levels of pesticide byproducts in their urine were more likely to be diagnosed with attention-deficit problems. It does not say that pesticide exposure causes ADDs. It also cannot, due to the lack of subsequent sampling, verify that the urine levels may fluctuate, may have been a one-time elevation, or that non-ADD-diagnosed children also experienced periodic higher levels.

Nonetheless, the connection does make sense to me. Organophosphates work by attacking the nervous system of pests. It is believed that they interfere with the function of acetylcholinesterase³, which controls acetylcholine⁴ levels and prevents excessive firing of neurons.

It can, therefore, be extrapolated that inhibited acetylcholinesterase / excess acetylecholine can be expected to negatively impact motor skills, learning, memory, and mood. Obviously, further extended studies are needed.

¹ - The Bayley Mental Development Index (MDI) is one-third of The Bayley Scales of Infant Development and "evaluates several types of abilities: sensory/perceptual acuities, discriminations, and response; acquisition of object constancy; memory learning and problem solving; vocalization and beginning of verbal communication; basis of abstract thinking; habituation; mental mapping; complex language; and mathematical concept formation." The other two scales measure motor skills and behavior. Together they are used to identify children who may be at risk for developmental delay.

² - NINDS (the National Institute of Neurological Disorders and Stroke) defines Pervasive Developmental Disorders (PDDs) as "a group of disorders characterized by delays in the development of socialization and communication skills." They include Autism, Asperger's Syndrome, and Rett's Syndrome.

³ - Acetylcholinesterase, according to MedicineNet.com, is "an enzyme that breaks down the neurotransmitter acetylcholine at the synaptic cleft (the space between two nerve cells) so the next nerve impulse can be transmitted across the synaptic gap. Pesticides of the organophosphate and carbamate types act ... by inhibiting ... acetylcholinesterase."

⁴ - Chemistry Encyclopedia explains that Acetylecholine is a neurotransmitter involved in "skeletal muscle movement ... the regulation of smooth muscle and cardiac muscle ... learning, memory, and mood." For nerve signals to transfer from neuron to neuron or muscle cell, acetylecholine must diffuse; higher levels in neuromuscular junctions inhibits signal movement.