There are many studies on fine particles (PM2.5) and their fully negative effect on human health. There doesn't seem to have any positive aspect of inhaling particles, except very particular ones, but most often people smoke, and release all sort of unwanted and toxic PM2.5, same goes with for fuel combustion.
At a huge dose, we die within minutes, like in a gas chamber, at small dose below this hazardous health risk level, is it still dangerous to us? If yes, why aren't we equipped to fight them, I guess this smoke concentration and pollution level is very recent on human evolution scale, but at the lowest layer of life, bacteria may develop to break and eat toxic particles, does it happen it our blood? Is it hard to explain to a non-biologist like me?