Air pollution also harms brain and mental health – large-scale analysis documents effects on brain regions linked to emotions

A research brief is a summary of an interesting academic paper.

The big idea

People who breathe polluted air experience changes in the areas of the brain that control emotions, and as a result are more likely to develop anxiety and depression than those who breathe cleaner air. These are the main findings of a systematic review that my colleagues and I recently published in the journal NeuroToxicology.

Our interdisciplinary team reviewed more than 100 scientific articles from animal and human studies that focused on the effects of outdoor air pollution on mental health and the areas of the brain that regulate emotions. The three main areas of the brain we focused on were the hippocampus, the amygdala, and the prefrontal cortex.

In our analysis, 73% of studies reported higher psychiatric symptoms and behaviors in humans and animals, such as rats, that were exposed to higher than average levels of air pollution. Some exposures that resulted in adverse effects occurred in air pollution ranges currently considered “safe” by EPA standards. Furthermore, we found that 95% of studies examining brain effects found significant physical and functional changes in emotion regulation brain regions in those exposed to elevated levels of air pollution.

Most of these studies have found that exposure to elevated levels of air pollution is associated with increased inflammation and changes in the regulation of neurotransmitters, which act as the brain’s chemical messengers.

Why it matters

Research on the physical health effects associated with exposure to polluted air, such as asthma and respiratory problems, has been well documented for decades.

But only in the last 10 years have researchers begun to understand how air pollution can affect the brain. Studies show that small air pollutants, such as ultrafine particles from vehicle exhaust, can affect the brain either directly by passing through the nose and into the brain, or indirectly by causing inflammation and altered immune responses in the body, which after this can cross into the brain.

At the same time, researchers are increasingly documenting the link between air pollution and its negative effects on mental health.

Unfortunately, research shows that air pollution will only get worse as climate change intensifies and carbon emissions remain unregulated.

For this reason, more research on the health effects of air pollution exposure that goes beyond respiratory health outcomes in the field of biological psychiatry is urgently needed. For example, the neurobiological mechanisms by which air pollution increases the risk of psychiatric symptoms are still poorly understood.

What is not yet known

In addition to our primary findings, our team also identified some notable research gaps that need to be addressed to paint a more complete picture of the relationship between air pollution and brain health.

Relatively few studies have examined the effects of air pollution exposure during early life, such as infancy and toddlerhood, as well as during childhood and adolescence. This is of particular concern given that the brain continues to develop into young adulthood and may therefore be particularly susceptible to the effects of air pollution.

We also found that of the studies examining the effects of air pollution on the brain, only 10 were conducted in humans. While animal studies have widely shown that air pollution can cause numerous changes in the brain of animals, research on how air pollution affects the human brain is much more limited. Moreover, most of the existing research on the human brain has focused on physical changes, such as differences in overall brain size. More research is needed that relies on a technique called functional brain imaging, which may allow researchers like us to detect subtle or smaller changes that may occur before physical changes.

In the future, our team plans to use brain imaging methods to investigate how air pollution increases the risk of anxiety during adolescence. We plan to use a variety of techniques, including personal air monitors that children can wear during the day, allowing us to more accurately assess their exposure.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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