Right but specifically solid particles in the air, not just gasses (CO2, NOX, etc.).

For example smoke and soot from combustion or dust particles from tires and brakes.

Sibling comments are good. I'll add that the biggest concern is PM2.5 (particulates smaller than 2.5 micrometers). They're thought to be responsible for 70,000 excess deaths in the U.S. annually, more than homicides or drug overdoses: https://www.stateofglobalair.org/health/pm

Particulate matter is relatively large particles, so far as air pollution goes. Think things like soot or smoke, rather than specific chemicals. Burning wood and coal produces far more particulates than, say, natural gas or gasoline-gas.

Yes, it's associated with cancer, heart disease, and dementia.