Research using data from a population-based birth cohort from Rotterdam, in The Netherlands, has found that children exposed to higher levels of air pollution when they were in womb had significantly thinner cortex in several brain regions. Some of this appeared to be related to impaired inhibitory control.
The study involved 783 children aged 6 to 10, who were given brain imaging and cognitive tests. Levels of air pollution in the mother’s environment during pregnancy were estimated using a standardized procedure. Mean fine particle levels were 20.2 μg/m3, and nitrogen dioxide levels were 39.3μg/m3. Note that the EU limit for mean fine particles is actually above that (25μg/m3), while the NO2 level is at the EU limit (40μg/m3), with 45% of the Dutch population experiencing higher levels. The World Health Organization sets a much lower level for fine particles: 10 μg/m3.
Children whose mothers were smokers were excluded from the study, as were children from areas where pollution measures weren’t available. Children included tended to be from a higher socio-economic position compared to those not included. Moreover, children with ADHD, or developmental or behavioral problems, were also excluded.
Global brain volume was not affected by fetal exposure. However, several brain regions showed significantly thinner cortex — in particular, the precuneus and rostral middle frontal regions, which partially accounted for the observed association between fetal exposure to fine particles and impaired inhibitory control (the ability to control your own behavior, especially impulsive behavior). This sort of cognitive impairment at early ages could have significant long-term consequences in academic achievement, later career success, and even in risk of mental disorders.
The findings are consistent with other studies linking acceptable air pollution levels with problems including cognitive impairment and child development.