Pulverized coals were burntin a laboratory-scale drop tube furnace to studytheswellingcharacteristicofcharparticlesand itsinfluenceon emission of particulate matter (PM) duringcombustion.
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.
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.