Charcoal burns dirty - when it burns tiny flakes of soot are released in the air.
Can result in the development of carcinogenic compounds - Carcinogenic compounds are thought to be formed when fat from meat drips on the charcoal and then rises along with the smoke and then become deposited into the food.
Safer Charcoal use:
Use charcoal that is produced from oak hardwood charcoal and does not contain any limestone, oil, coal, petroleum or sawdust.
Well that's good.
I use only hardwood charcoal pieces (not briquettes) and I build the fire on one end and put the meat on the other end.