Evidence is accumulating that breathing in very small particles (Fine particulate matter PM2.5) over a long time is associated with an increased risk of dementia. The association suggests that the particles may actually be a cause of dementia, perhaps especially if the particles are coated with neurotoxic chemicals. These particles come from traffic (diesel more than petrol-powered vehicles), coal-fired power plants, agricultural emissions, and bush fires (US ‘wildfires’). It’s thought that the particles can enter the brain via the olfactory…..