Prenatal exposure to particulate matter with an aerodynamic diameter <2.5 µm (PM2.5) is associated with a decrease in corpus callosum volume in children and may increase the risk for behavioral problems, according to study results published in Environmental Research.
Prenatal exposure to air pollution may have a significant effect on the developing brain, and the early exposure can induce permanent brain injury. Previous studies have revealed that the corpus callosum may be affected by prenatal and neonatal exposure to air pollution. These changes in the brain structures may be associated with behavioral problems, such as attention-deficit/hyperactivity disorder and autism spectrum disorder.
The study was developed in the context of the Brain Development and Air Pollution Ultrafine Particles in School Children (BREATHE) project, and the goal of the current analysis was to explore the effects of prenatal exposure to fine particulate matter on brain structures. In addition, the researchers explored the association between changes in corpus callosum and lateral ventricle volumes with behavioral problems.
Based on modeled traffic-related nitrogen dioxide values, 40 schools in Barcelona were selected; between 2012 and 2013, a total of 39 representative schools and 2897 children were included in the survey. Parents of 186 children, aged 8 to 12 years (49% girls; median age, 9.7 years), agreed to complete brain magnetic resonance imaging (MRI) assessment. The Strengths and Difficulties Questionnaire (SDQ) was used to assess behavioral problems.
The exposure to PM2.5 from the prenatal period to the time of the MRI study was estimated at the geocoded postal address of each participant, using land use regression models.
Prenatal PM2.5 levels across the 3 trimesters of pregnancy had similar and normal distributions. Prenatal PM2.5 ranged between 11.8 and 39.5 µg/m3 during the third trimester of pregnancy.
An increase of approximately 7 μg/m3 in PM2.5 level during the third trimester of pregnancy was associated with a reduction corresponding to almost 5% of the mean volume of the corpus callosum body (β=−53.7; 95% CI, −92.0 to −15.5). Brain changes of this magnitude may result in an increase in attention-deficit/hyperactivity disorder symptoms (specifically hyperactivity), as well as in more general behavior problems.
The analysis revealed an association between a 50 mm3 decrease in the body of the corpus callosum and a significant higher hyperactivity subscore (rate ratio, 1.09; 95% CI, 1.01-1.17), corresponding to a subscore 9% increase, independent of age, sex, and intracranial volume. However, these associations did not survive to False Discovery Rate correction for multiple comparisons.
The researchers noted several limitations of the study, including the possibility of false-positive findings, as the associations did not survive to False Discovery Rate correction for multiple testing; insufficient power to reveal significant association between PM2.5 exposure and behavioral outcomes; as well as calculating PM2.5 levels only based on ambient estimations and not on personal history or biomarkers.
“In our sample, we observed that prenatal exposure to PM2.5, particularly during the last trimester of pregnancy, may induce structural changes in the [corpus callosum] of children aged between 8 and 12 years from the general population,” concluded the researchers.
Mortamais M, Pujol J, Martínez-Vilavella G, et al. Effects of prenatal exposure to particulate matter air pollution on corpus callosum and behavioral problems in children. Environ Res. 2019;178:108734