Air pollution is a problem that knows no geographical boundaries. When the World Health Organization studied the issue in 2016, it found that 91% of the world's entire population lived in areas where pollution was so dangerous that the air did not meet their air quality standards for safety.
But wait! There's more. A recent study by scientists in China shows that in addition to respiratory and cardiovascular issues, the air pollution was causing significant cognitive decline.
Studies of pollution and the effects it has on health have always shown that living in an area with horrible air quality raises the risk of developing heart disease, having a stroke and having trouble breathing and exercising. In some major cities with high levels of particulate matter in the air, the sky is often not visible through the smog. Residents who must be outdoors will often wear dust masks to avoid inhaling the tiny bits of metal and toxic materials.
In the study, scientists from Beijing Normal University look at math and verbal scores from 31,000 Chinese citizens. They matched that data with air quality data from 2010 to 2014 and found cognitive decline in the test scores in areas where pollution was severe. Even when the data was controlled for the natural cognitive decline that happens as people age, there was still an association between pollution exposure and dwindling mental acuity.
So how does the air we breathe impact the brain? Shouldn't the blood-brain barrier (BBB) protect cognition? Well, yes and no. Some research has shown that pollution can actually disrupt the function of this neural safeguard. A study conducted in 2008 showed that children and young adults who were exposed long-term to poor air quality had inflammation of their brain tissue, altered immune responses, and abnormalities in the function of the endothelial cells that make up the BBB. In an interview with National Geographic one of authors of the study, Xin Zhang, stated, "We speculate that air pollution probably puts greater damage on the white matter in the brain, which is associated with language ability. More research is needed to understand the mechanisms." Neuroscience research on other projects shows that women have more white matter brain tissue than men do and this could be why the China study showed a disproportionate impact on men.
It's not just a health problem either. The cost to society for dementia care is growing at an alarming rate. Speaking to BuzzFeed News, Zhang explained, "The damage on cognitive ability likely impedes the development of human capital. It is so widespread that [it] can impose substantial costs to everyone's daily life and critical decision-making. Investment in cleaning up air pollution is not only good for health, but also for the intellect of society at large." According to Dementia Australia, on a global scale, dementia care costs the world economy almost 1 trillion dollars annually. Dementia and other cognitive disorders are also on the rise, and by the year 2030, there could be close to 75 million people living with some form of cognitive decline.
The pollution problem aggravates climate change as well and must be dealt with collaboratively by all nations. The video below has more information about the research, take a look.
Sources: World Health Organization National Geographic BuzzFeed News Dementia Australia PNAS