A small neuroimaging study suggests prenatal exposure to polycyclic aromatic hydrocarbons (PAHs), the toxic air pollution caused in part by vehicle emissions, coal burning and smoking, may be bad for children’s brains and may contribute to slower processing speeds and behavioural problems, including attention-deficit-hyperactivity-disorder (ADHD) symptoms, according to researchers from Children’s Hospital Los Angeles. The study is published in JAMA Psychiatry.
The team explain that PAHs are caused by the incomplete combustion of organic materials. In addition to outdoor air pollution, sources of indoor air pollution caused by PAHs can be cooking, smoking and space heaters. PAHs can cross the placenta and damage fetal brains and animal experiments suggest prenatal exposure can impair behaviour and learning, according to study background.
The group conducted a neuroimaging study that included 40 minority urban school-aged children born to Latin (Dominican) or African American women. The children were followed from the fetal period to ages 7 to 9 years old. Their mothers completed prenatal PAH monitoring and prenatal questionnaires.
The current study found an association between increased prenatal PAH exposure and reductions in brain white matter in children later in childhood that was confined almost exclusively to the left hemisphere of the brain and involved almost its entire surface.
Reduced white matter surface on the left side of the brain was associated with slower processing during intelligence testing and behavioural problems, including ADHD symptoms and conduct disorder problems, according to the results. The neurodevelopmental outcomes in children were also checked through intelligence and behaviour testing.
The team note the small size of their study as well as other limitations in the research but add that if confirmed, the findings have important public health implications given the ubiquity of PAHs in air pollutants among the general population.