Not a concern to me. There is increased risk when smoke is created from fat dripping onto the coals, or you char the outside of the meat. Neither of those things happen inside my charcoal smoker, and as long as you use natural lump charcoal instead of chemical injected briquettes, you aren't any worse than any other cooking method. Yes, lump charcoal still gives off hydrocarbons, but sitting around a campfire once a year probably gives me a greater dose than a year of smoking meat.
Theoretically, cooking a steak over a gas BBQ and letting the fat drippings fall onto to the burner will be worse than a smoker.
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