Air Pollution May Increase Risk of ADHD in Children

ADHD risk was higher in children of women exposed to air pollution while pregnant

(RxWiki News) Polycyclic aromatic hydrocarbons — usually shortened to PAH — are a component of air pollution. And new research suggests they may raise the risk of ADHD in children whose mothers are exposed to them.

In a new study, children whose mothers were exposed to PAH while pregnant were much more likely to have ADHD symptoms than children whose mothers were not exposed.

This study was the first to examine the connection between PAH exposure in pregnancy and ADHD in school-age children, the authors noted.

The study was conducted by a team led by Frederica P. Perera, DrPH, PhD, director of the Columbia Center for Children's Environmental Health at the Mailman School of Public Health.

Dr. Perera and team studied 233 women from pregnancy until their children were 9 years old. The women all lived in New York City and did not smoke. By the time the children whose mothers had been exposed to PAH were 9 years old, they were five times more likely to have ADHD symptoms than children whose mothers had not been exposed.

The study authors took blood samples from the mothers at the time they delivered their babies. They also tested the children's blood for signs of PAH at ages 3 and 5. They assessed the children’s behavior with a standardized rating scale.

The researchers found that the children exposed to PAH were most likely to show symptoms of inattentive-type ADHD, in which the child is easily distracted and has trouble focusing. Children with inattentive-type ADHD also tend to be disorganized.

ADHD, or attention deficit hyperactivity disorder, is a mental disorder that affects children’s behavior. Children with ADHD may be easily distracted and have trouble sitting still and concentrating. They may also be impulsive and have learning problems.

In past studies, the Centers for Disease Control and Prevention (CDC) has found that PAH may affect children’s brains. Children exposed to PAH may have developmental delays by age 3. PAH exposure in children may also cause reduced IQ by age 5. By age 6 and 7, children exposed to PAH may have symptoms of anxiety and depression, as well as attention problems.

The CDC reports that about 5 percent of US children have ADHD.

Although genetics may be responsible for some cases of ADHD, environmental factors are also suspected to increase the risk. PAH can be released into the air from car exhaust, residential boilers, and electric plants that use oil or gas. Dr. Perera and team said they were not sure exactly how PAH exposure affected the children’s brains.

The study was published online Nov. 5 in PLOS One.

The study was funded by grants from the National Institute of Environmental Health Sciences, the US Environmental Protection Agency, the John & Wendy Neu Family Foundation, the New York Community Trust and the Blanchette Hooker Rockefeller Fund. The authors disclosed no conflicts of interest.


Review Date: 
November 5, 2014