Exposure to air pollution in the womb and early childhood linked to abnormal brain development

I talk a lot about the need for us to clean up air pollution as part of our climate response, despite the fact that doing so speeds up the warming. Air pollution has been linked to a wide array of health problems, and higher temperatures mean more poisonous air. We didn’t need another reason, but now we have one. I feel like this isn’t a big shock, but researchers have now found a link between in-utero and early childhood pollution exposure, and abnormalities in brain development:

A study published in the journal Environmental Pollution has found an association, in children aged 9‑12, between exposure to air pollutants in the womb and during the first 8.5 years of life and alterations in white matter structural connectivity in the brain. The greater the child’s exposure before age 5, the greater the brain structure alteration observed in preadolescence. The study was led by the Barcelona Institute for Global Health (ISGlobal), a research centre supported by the ”la Caixa” Foundation.

Tracts or bundles of cerebral white matter ensure structural connectivity by interconnecting the different areas of the brain. Connectivity can be measured by studying the microstructure of this white matter, a marker of typical brain development. Abnormal white matter microstructure has been associated with psychiatric disorders (e.g., depressive symptoms, anxiety and autism spectrum disorders).

In addition to the association between air pollution and white matter microstructure, the study also found a link between specific exposure to fine particulate matter (PM2.5) and the volume of the putamen, a brain structure involved in motor function, learning processes and many other functions. As the putamen is a subcortical structure, it has broader and less specialised functions than cortical structures. The study found that the greater the exposure to PM2.5, especially during the first 2 years of life, the greater the volume of the putamen in preadolescence.

“A larger putamen has been associated with certain psychiatric disorders (schizophrenia, autism spectrum disorders, and obsessive-compulsive spectrum disorders),” says Anne-Claire Binter, ISGlobal researcher and first author of the study.

“The novel aspect of the present study is that it identified periods of susceptibility to air pollution” Binter goes on to explain. “We measured exposure using a finer time scale by analysing the data on a month-by-month basis, unlike previous studies in which data was analysed for trimesters of pregnancy or childhood years. In this study, we analysed the children’s exposure to air pollution from conception to 8.5 years of age on a monthly basis.”

As someone with a somewhat “abnormal” brain, I think it’s important that we not dismiss or dehumanize the “victims” of this sort of thing. Groups like Autism Speaks and the anti-vax movement have done real harm by treating autism as a fate worse than death, and acting as though autistic people have no agency, thoughts, or lives worth living. I want a world in which people of all neurotypes are able to thrive, not a eugenical fantasy of uniformly “normal” brains.

I think it’s a clear good for us to have a better understanding of how air pollution affects us. Obviously it’s not enough to doom our species at this stage, but it’s worth remembering that it is affecting us in a myriad of ways, some of which are not immediately obvious.

Another strong point of this study is that the data analysed came from a large cohort of 3,515 children enrolled in the Generation R Study in Rotterdam (Netherlands).

To determine each participant’s exposure to air pollution during the study period, the researchers estimated the daily levels of nitrogen dioxide (NO2) and particulate matter (PM2.5 and PM2.5 absorbance) at their homes during the mother’s pregnancy and until they reached 8.5 years of age. When participants were between 9 and 12 years analysed of age they underwent brain magnetic resonance imaging to examine the structural connectivity and the volumes of various brain structures at that time.

The levels of NO2 and PM2.5 recorded in the present study exceeded the annual thresholds limits specified in the current World Health Organization guidelines (10 µg/m3 and 5 µg/m3, respectively) but met European Union (EU) standards, an indication that brain development can be affected by exposure to air pollution at levels lower than the current EU air quality limit values.

“One of the important conclusions of this study” explains Binter “is that the infant’s brain is particularly susceptible to the effects of air pollution not only during pregnancy, as has been shown in earlier studies, but also during childhood.”

“We should follow up and continue to measure the same parameters in this cohort to investigate the possible long-term effects on the brain of exposure to air pollution” concludes Mònica Guxens, ISGlobal researcher and last author of the study.

There’s a part of me that worries this information will be either ignored, or abused. Ignored, because those most exposed to air pollution tend to be those with the least power. I also worry about what governments and corporations might try to do with this knowledge.

There’s also a part of me that tends towards excessive optimism and hopefulness. I don’t know if it’s as strong as my pessimistic side, but it’s there nonetheless. That side of me hopes that research like this – in addition to helping make the case for change, will also open the way for new treatments. There’s a lot that I like about how my brain works, but there are many aspects of it I could do without. It seems to me that understanding the causal factors at work here should shed new light on the development of our brains in relation to our environment, and possibly even ways to tinker with that even into adulthood. It also seems like it moves us closer to figuring out more targeted medications for temporary effects.

This may be another one of those studies that seems important, but is never heard from again, but I don’t think it’s likely.

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  1. Katydid says

    One of the theories about crime in the cities is that the children growing up in them are exposed to pollution. Crime rates dropped in the cohort born after cars switched over from leaded to unleaded gasoline.

    Why many rural areas have a higher per-capita rate of crime when the residents are not constantly exposed to pollution is not clear.

  2. Katydid says

    Regarding autism: it’s complicated. I have an autistic cousin who’s on the extreme low end; functions on roughly the 9-month-old to 18-month-old age. Her brother, born in the same house to the same parents 18 months later, is neurotypical.

  3. says

    Absolutely. I also know that you can have people who shared the same womb at the same time, and have that same division. My take is that this is one factor that seems to be connected to that part of development. I think it would also be reasonable to look into whether things like pollen and spores affect this stuff, as well as wood smoke, airborne bacteria, and so on.

    So, for example, this is not grounds for condemnation of parents whose kids grew up in more polluted areas – there’s already ample evidence that that does not guarantee any outcome in particular, let alone autism, ADHD, or any other neurotype. It’s probably much more a matter of degrees and tendencies.

  4. says

    I also think there’s something to the lead theory, but none of this stuff is universally explanatory. A poison that reduces impulse control and increases aggression *to some degree* is going to affect everybody differently. Ideology, socialization, economic conditions, political conditions, other poisons and pollutants – The reality is that even INFORMATION can our brain development, so things like that can only really be talked about in terms of broad trends, once you’re outside more serious lead-poisoning cases like Freddy Gray.

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