The fetal brain is particularly vulnerable during pregnancy because it hasn’t yet developed the mechanisms to protect against or remove environmental toxins. In fact, a new study in the Netherlands finds that exposure to pollution levels even below those considered safe by the European Union (EU) could result in brain structure abnormalities.
The study, published in Biological Psychiatry, linked fetal exposure to residential air pollution with brain changes that may contribute to impaired cognitive function in school-age children. The air pollution levels related to brain alterations were below those considered to be safe.
“Air pollution is so obviously bad for lungs, heart, and other organs that most of us have never considered its effects on the developing brain. But perhaps we should have learned from studies of maternal smoking that inhaling toxins may have lasting effects on cognitive development,” said John Krystal, M.D., editor of Biological Psychiatry.
The findings show that fetal exposure to fine particles during pregnancy affects a thinner outer layer of the brain, called the cortex, in several regions. These brain abnormalities contribute in part to difficulty with inhibitory control — the ability to exert self-control over temptations and impulsive behavior — which is associated with mental health issues such as addictive behavior and attention-deficit/hyperactivity disorder (ADHD).
The researchers used a population-based cohort in the Netherlands, which enrolled pregnant women and tracked the children from pregnancy onward. The researchers analyzed air pollution levels at home during the fetal life of 783 children. The data had been gathered by air pollution monitoring campaigns, and included levels of nitrogen dioxide (a prominent air pollutant caused by traffic and cigarette smoking), coarse particles, and fine particles.
When the children were between six and 10 years old, they underwent brain imaging scans which ultimately revealed abnormalities in the thickness of the brain cortex of the precuneus and rostral middle frontal region.
Despite the link between these brain structure abnormalities and fine particle exposure, the average residential levels of fine particles in the study were well below the current acceptable limit set by the EU — only 0.5 percent of the pregnant women in the study were exposed to levels considered unsafe. The average residential levels of nitrogen dioxide were right at the safe limit.
These findings add to those of previous works showing a link between acceptable air pollution levels with other complications including cognitive decline and fetal growth development.
“Although specific individual clinical implications of these findings cannot be quantified, based on other studies, the observed cognitive delays at early ages could have significant long-term consequences such as increased risk of mental health disorders and low academic achievement, in particular due to the ubiquity of the exposure,” said lead author MÃ²nica Guxens, M.D., of Barcelona Institute for Global Health (ISGlobal), Spain, a center supported by the “la Caixa” Foundation, and Erasmus University Medical Center, the Netherlands.