Imaging study shows prenatal exposure to air pollution disrupts brain development

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Prenatal exposure to polycyclic aromatic hydrocarbons (PAH), neurotoxic air pollutants resulting from car emissions and industrial coal burning, hinders brain development and could lead to learning disabilities and behavioral issues, according to results of a study published online March 25 in JAMA Psychiatry.

PAHs are ubiquitous environmental contaminants that can be particularly harmful to pregnant women and their unborn children, according to study lead author Bradley Peterson, MD, of Children's Hospital Los Angeles, and his colleagues. ”Polycyclic aromatic hydrocarbons are neurotoxicants that readily cross the placenta and damage the fetal brain, likely by inducing inflammation, oxidative stress, and vascular injury,” wrote Peterson, et al. “Animal models have shown that prenatal PAH exposure impairs subsequent development of behavior, learning, and memory.”

The researchers set out to assess the effects of prenatal PAH exposure on human brain development. To do so, they conducted MRI studies on the brains of 40 urban children, from fetal stages through the ages of 7-9 years old. Surveys were also conducted among mothers of the test subjects.

Their results showed a direct correlation between prenatal PAH exposure and disrupted brain development, specifically of white matter in the left hemisphere, which was associated with learning disabilities and behavioral issues. “These findings suggest that PAH air pollutants are important contributors to slower processing speed, ADHD symptoms, and externalizing problems in urban youth via the disruptive effects of prenatal PAH exposure on the development of left hemisphere white matter,” wrote Peterson et al, “particularly in the frontal, parietal, and temporal lobes, which subserve attention and impulse control.”

The researchers believe their results are significant, due to the potential harm to developing brains and the ubiquitous nature of PAHs “Our findings raise important concerns about the deleterious effects of air pollutants, and PAHs in particular, on brain development in children, as well as the consequences of those brain effects on cognition and behavior,” wrote Peterson et al. “If confirmed, our findings have important public health implications given the ubiquity of PAHs in air pollutants among the general population.”