For the first time, an ISGlobal study takes into account exposure from conception to the first 8 and a half years of life, month by month.
A study published in the journal Environmental Pollution shows how being exposed to air pollutants in the womb and during the first eight and a half years of life alters the structural connectivity of the brain in pre-adolescence. In particular, the greatest changes occur the greater the contamination received in the first five years. The work has been led by the Barcelona Institute for Global Health (ISGlobal), a center promoted by the ”la Caixa” Foundation.
Structural connectivity is the existence of white matter fascicles or tracts that connect different regions of the brain. It is measured by studying the microstructure of the white matter and is a marker of typical brain development. An abnormal white matter microstructure has been linked to psychiatric disorders (eg, depressive symptoms, anxiety, or autism spectrum disorders).
In addition to the association between air pollution and structural connectivity of the brain, the study has also found a link between specific exposure to PM2.5 particles and the volume of a brain structure known as the putamen, involved in motor function and brain function. learning processes, among many other functions. Being a subcortical structure, its involvement is quite broad and less specialized than cortical regions. The study has observed that the greater the exposure to PM2.5, especially in the first two years of life, the greater the volume of the putamen.
“A larger putamen has been associated with some psychiatric disorders (schizophrenia, autism spectrum disorders, and obsessive-compulsive spectrum disorders),” explains Anne-Claire Binter, ISGlobal researcher and first author of the study.
“The study is novel because it identifies the periods of susceptibility to air pollution”, continues Binter. “We have used a finer time scale to consider exposure, analyzing the data month by month, when previous studies investigated trimesters of pregnancy or years of childhood. In this way, we have studied air pollution from conception to 8.5 years of age on a monthly basis.”
Even if the pollution did not exceed European levels
Another of the strengths of the study is that it was based on a large cohort: 3,515 boys and girls from the Generation R Study in Rotterdam (Netherlands).
To find out what air pollution the girls and boys had been exposed to, the daily levels of nitrogen dioxide (NO2) and particulate matter (PM2.5 and PM2.5 absorbance) were recorded where they had lived from their conception to the 8.5 years. When they were between the ages of 9 and 12, brain MRI scans were taken and various brain volumes and structural connectivity were calculated.
The NO2 and PM2.5 levels recorded in the study exceeded the current recommendations of the World Health Organization (10 µg/m3 and 5 µg/m3, respectively), but complied with the European Union regulations, which suggests that air pollution can affect brain development at levels below current air quality standards.
“One of the big takeaways from the study,” Binter notes, “is that the brain is especially vulnerable to air pollution not only during pregnancy, as has been noted in previous studies, but also during childhood.”
“It would be necessary to continue repeating measurements on these boys and girls to try to understand the possible long-term effects of exposure to air pollution on the brain,” concludes Mònica Guxens, ISGlobal researcher and last author of the study.
Binter AC, Kusters MSW, van den Dries MA, Alonso L, Lubczyńska MJ, Hoek G, White T, Iñiguez C, Tiemeier H, Guxens M. Air pollution, white matter microstructure, and brain volumes: periods of susceptibility from pregnancy to preadolescence, Environmental Pollution