Not only do high levels of fine particulate matter harm the respiratory tract, they also increase the risk of developing dementia. These particles are so small – with a diameter of 2.5 micrometers or smaller (PM2.5) – that they can reach deeply into the lungs and even the brain. These particles mainly originate from vehicle exhaust fumes, power plants, wood-burning appliances, and construction dust.
Source: Meta-analysis published in the medical journal Lancet Planetary Health (2025)