Long exposure to polluted air containing high levels of fine particles has been consistently linked to dementia, according to researchers at the Harvard Chan School of Public Health who analysed 14 earlier studies.
Around 57 million people worldwide have dementia, which currently has no cure. A reduction in annual levels of just 2 micrograms per cubic meter could lead to lower dementia rates, said Marc Weisskopf, a professor of environmental epidemiology and physiology at Harvard co-author of the analysis published BMJ medical journal, as reported by Bloomberg.
“As far as we can tell, the lower you can go, the lower your risk is,” he said in an interview, according to Bloomberg. He acknowledged that people have little control over their exposure to such pollutants but regulators have more say.
Fine particulate matter, also known as PM2.5, comprises participles around 30% of the diameter of a human hair. Their size allows them to settle deep in the lungs and even make their way into blood, according to the US Environmental Protection Agency. PM2.5 exposure has been linked to many diseases, including cardiovascular disease, type 2 diabetes and lung cancer, as well as premature death, according to Bloomberg.
The World Health Organization recommends that average annual PM2.5 levels should be below 5 micrograms — but most of the global population breathes air that exceeds these limits. The wide scope of pollution exposure makes the particulate matter a concerning risk factor for dementia, even though its estimated effect was smaller for factors like smoking, Weisskopf said.
Nitrogen dioxide and nitrogen oxide, two other pollutants, could be associated with dementia risk; however, the link was based on fewer studies and may not be as firm, according to the researchers. “Everybody has to breathe, so everybody is exposed to this,” Weisskopf said, as reported by Bloomberg. “The population-level effect could actually be quite large because the number of people exposed is massive.”
In the recent 5th Annual World Air Quality Report released by IQAir, India ranked 8th in the list of countries with the worst air quality index, and 12 of the 15 most polluted cities in Central and South Asia are currently in India, according to Mint. Furthermore, about 60% of the Indian population lives in cities where the annual PM2.5 levels are at least seven times higher than the WHO guidelines. The PM2.5 level of most polluted Indian cities stands at 53.3, according to the report.