Smoking camel milk is apparently common in some countries and at the bottom of the bottle there are tiny dark particles, burnt wood from the smoking process.

BBC: NEWS | UK | Magazine | Milk: One hump or two?

What exactly this dark matter consists of exotic elementary particles, lumps of rock, failed stars, burnt-out stars, even small black holes is still a mystery, since the stuff itself is invisible.

ECONOMIST: The galactic gourmand

Before people started making such a mess, the number of dust particles orbiting earth was tiny, since they would have been dragged quickly into the atmosphere by friction and burnt up.

ECONOMIST: Orbital debris