Aug. 28 (UPI) -- Exposure to certain chemicals commonly found in cosmetics and processed foods increases a child's risk for developing ADHD-like behaviors by more than 30%, according to a study published Friday by JAMA Network Open.
For every two-fold rise in concentrations of chemicals called phthalates, as measured by urinalysis, a child is 34% more likely to shows signs of the neurobehavioral disorder, the data showed.
And for every two-fold increase in urine concentrations of dichlorophenols, the risk grows by 15%, the researchers said.
Phthalates are used in plastics and are often found in cosmetics, lubricants, personal-care products, medical devices, detergents, packaging, children's toys, pharmaceuticals, food products and clothing, while dichlorophenols can be found in many food preservatives.
"Our study's results suggest that teenagers' exposure to chemicals found in many consumer products may increase behaviors that are common among individuals diagnosed with ADHD," study co-author Jessica R. Shoaff, a post-doctoral research fellow at Harvard Medical School, told UPI.
"However, we did not study the diagnosis of ADHD, [which] means our results cannot answer the question of whether these chemical exposures increase the likelihood of being diagnosed with ADHD," she said.
Up to 10% of children in the United States have ADHD, or attention deficit hyperactivity disorder, according to recent estimates.
The mental health disorder can cause above normal levels of hyperactive or impulsive behaviors, as well as difficulty focusing attention on a single task or sitting still, as described by the U.S. Centers for Disease Control and Prevention.
Earlier research by Shoaff and her colleagues linked the disorder with exposure to chemicals like phthalates and dichlorophenols, but the exact relationship remains unclear.
These chemicals are believed to affect the human endocrine system, a group of glands that produce hormones that regulate metabolism, growth and development, according to the researchers.
For this study, the group enrolled 205 adolescent participants, of whom 40% had signs and symptoms of behavioral problems and 19% had ADHD.
Participants had median urine concentrations of 0.49 micromoles per liter for personal care product phthalates and 0.02 micromoles per liter for dichlorophenols, the data showed.
It is unclear whether having detectable levels of phthalates in urine has adverse effects on health, and an estimated one in four U.S. children have detectable levels of dichlorophenols, according to the CDC.
However, evidence is mounting that exposure to these chemicals does impact health, particularly in children and adolescents, Shoaff said. The North American Network of Academic Pediatric Environmental Health Specialty Units offers guidelines for managing environmental chemical exposures in children, she said.
"Whenever it is practical to do so, it is best to reduce exposure to products containing chemicals," Shoaff said. "it is possible to select products that minimize exposure to these chemicals."