> People do not get addicted to non-narcotic adulterants and become prostitutes. A cutting agent like caffeine or sugar is probably the safest ingredient...

The biggest physical danger of heroin use is the risk of overdose. The main reason people overdose is because of the adulterants - they don't know how potent the stuff is. x mg of batch A might be a good high, whereash x mg of batch B will kill you from an overdose.

Even if the adulterants are themselves safe, the presence of them is a risk to the users, because they make it impossible to determine dosage.