By the time a bill reaches you, it has passed through thousands of hands -- and in all likelihood, a few noses as well. Some trace amounts of drugs on paper money could just be dust that collects on it while it's in the possession of someone guilty of possession. Most of the residue, however, comes from drug snorters' inhaler of choice: Money rolled up like a straw and inserted into the nose.
"Some bills are so riddled with cocaine that we can't chemically clean them adequately -- every year, at least $10 million in paper currency has to be taken out of circulation and destroyed for that reason," says the Treasury insider.