Children who are exposed to organophosphates may have an increased risk of attention deficit/hyperactivity disorder (ADHD), according to a study published in the journal, Pediatrics.

But what are organophosphates? According to the Illinois Department of Public Health, 37 of the 900 different pesticides used in the United States belong to the class of organophosphates. These widely-used insect killers work by disrupting the brain and nervous system and are known to be toxic to humans.

Humans can be exposed to organophosphates by

• working for a company that makes or applies organophosphates;
• eating or drinking something that has an organophosphate in it;
• inhaling it;
• or having contact with it through skin, especially an open wound

The objective of the study was to examine the association between urinary concentrations of dialkyl phosphate metabolites of organophosphates and ADHD in children 8 to 15 years-old.

The study group included 1,139 children who were representative of the general U.S. population. One hundred nineteen of the children met the diagnostic criteria for ADHD. Those with higher urinary dialkyl phosphate concentrations, especially dimethyl alkylphosphate (DMAP) concentrations, were more likely to be diagnosed as having ADHD.

From the journal Pediatrics:

A 10-fold increase in DMAP concentration was associated with an odds ratio of 1.55 (95% confidence interval: 1.14–2.10), with adjustment for gender, age, race/ethnicity, poverty/income ratio, fasting duration, and urinary creatinine concentration. For the most-commonly detected DMAP metabolite, dimethyl thiophosphate, children with levels higher than the median of detectable concentrations had twice the odds of ADHD (adjusted odds ratio: 1.93 [95% confidence interval: 1.23–3.02]), compared with children with undetectable levels.

While further studies are needed to find out if the association is casual, the hypothesis is that organophosphate exposure, at levels common among US children, may contribute to ADHD prevalence.

Marc Weisskopf of Harvard School of Public Health worked on the study and said, “That’s a very strong association that, if true, is of very serious concern. These are widely used pesticides. A good washing of fruits and vegetables before one eats them would definitely help a lot.”

Good Morning America also recommends these steps:

• Limit or eliminate the amount of pesticides in the home, such as bug spray.
• Limit or eliminate the amount of pesticides and chemicals you use on your lawn and buy natural products whenever possible.
• Buy fruits you can peel or fruit that has a hard exterior, such as an apple, that you can wash.
• Experts say the fruits which tend to have the highest level of pesticides are strawberries, raspberries and peaches. These fruits have soft skin and the pesticides can get in the fruit and it becomes hard to wash them out.

Symptoms of ADHD include hyperactivity, impulsivity, difficulty staying on task and controlling behavior. The cause is not identified, but a combination of genetics and environmental factors is one avenue researchers have been pursuing.

According to the Centers for Disease Control and Prevention (CDC), in the U.S.

• 4.5 million children 5-17 years of age have ever been diagnosed with ADHD (as of 2006);
• 3 percent of school-aged children have ADHD;
• diagnosis of ADHD increased an average of three percent per year from 1997 to 2006;
• and boys are more likely than girls to be diagnosed with ADHD.

For more information about ADHD visit the CDC.