Better to hold your breath? Brett Gundlock/Redux/Eyevine

Traffic fumes go to your head. Tiny specks of metal in exhaust gases seem to fly up our noses and travel into our brains, where they may contribute to Alzheimer’s disease.

Iron nanoparticles were already known to be present in the brain – but they were thought to come from the iron naturally found in our bodies, derived from food.

Now a closer look at their structure suggests the particles mostly come from air pollution sources, like traffic fumes and coal burning. The findings are a smoking gun, says Barbara Maher of …