Exposure to phthalates may put young children at higher risk for hyperactivity, short attention spans, and impulsivity, say psychiatrists this week in Biological Psychiatry.

 

“The present study showed a strong positive association between phthalate metabolites in urine and symptoms of ADHD [attention deficit hyperactivity disorder] among school-age children,” write Bung-Nyun Kim, of the Seoul National University College of Medicine, and colleagues.

 

Phthalates are chemicals used to make plastics bendy, strong and transparent. Previous research in humans has suggested a link between exposure to the chemicals and birth defects, and experiments in animals have shown they can disrupt hormone systems. In rats, exposure to phthalates can lead to hyperactive and impulsive behaviour. But scientists have never before linked the chemical to such symptoms in people.

 

The researchers recruited around 260 school children aged between eight and 11 years who lived in four Korean cities. To measure the prevalence of ADHD symptoms in the group, each student’s teacher scored them for symptoms of ADHD on a standard diagnostic scale. The children also undertook computerised tests, devised to help diagnose the condition, which measured their inattention and impulsivity — both signs of ADHD.

 

Kim and colleagues also collected urine samples from the students, and tested them for the presence of three metabolic break-down products of phthalates. Statistical analysis revealed that the concentration of one of these metabolites, DEHP, in the kids’ urine was significantly associated with ADHD symptom scores given by their teachers. Another of the phthalate metabolites, DBP, was significantly associated with poor test results for attention and impulsivity.

 

The children included in the study were not clinically diagnosed with ADHD. Instead, symptoms of the condition were measured by their teachers using a tool adapted for use in schools. In addition, the study design does not allow conclusions to be drawn about a causal relationship between the exposure and the behavioural symptoms. These are limitations of the research, say the authors.

 

“However, despite these limitations, the results of this study suggest the possibility of an association between phthalate metabolites, one of the major environmental disruptors, and the inattention and hyperactive-impulsivity phenotype of ADHD,” conclude Kim and colleagues.