A major new study has found that breathing polluted air for long periods of time may increase your chances of developing dementia. 

The research, published this week in The Lancet Planetary Health, brings together data from over 24 million people around the world, and it confirms what scientists have suspected for years: air pollution isn’t just bad for your lungs, it could also harm your brain.

Researchers looked at 51 studies published over the last few decades and closely examined 32 of them that met strict scientific standards. These studies followed adults for at least a year and tracked their exposure to air pollution, like car exhaust, soot, and tiny particles in the air, and whether they were later diagnosed with dementia.

They found that even small increases in pollution levels were linked to a higher risk of dementia. For example, for every 5 micrograms per cubic meter increase in PM2.5 – the fine particles that can get deep into the lungs – the risk of developing dementia rose by 8 percent. These particles come mostly from vehicles, burning of fuels, and industrial activity.

Exposure to nitrogen dioxide (a gas released by cars and trucks) was also linked to a slightly increased risk of dementia. And perhaps most worrying, exposure to black carbon, the soot from diesel engines and wood burning, raised dementia risk by 13% for every 1 microgram increase.

In plain terms, people living in areas with dirtier air were more likely to develop dementia than those breathing cleaner air.

“This analysis adds to the body of evidence that outdoor air pollutants are risk factors for dementia,” the researchers wrote. “Reduced exposure to pollution could reduce dementia rates and stricter air quality standards would likely provide substantial health, social, and economic benefits.”

The researchers also pointed out that while some earlier studies had shown mixed results, the latest evidence is much stronger, especially for fine particles and traffic-related pollution.

Also read: Household air pollution affected 2.67 billion people in 2021, killed 3.11 million