Cannabis can be very bad for your health, but especially so when it is contaminated with glass beads or, as is reported in the the April 10th issue of the New England Journal of Medicine, with lead - causing 29 cases of lead poisoning in the Leipzig area of Germany, 16 of them emergency admissions (read a pdf of the report here). Such are the whims of totally unregulated illegal markets controlled by profit seeking criminal entrepreneurs.
After describing how a screening process discovered a further 95 people with elevated lead levels in their blood that required treatment, the letter notes that:
"The current working hypothesis of the police is that because of its high specific gravity and inconspicuous grayish color, lead was used to increase the weight of street marijuana sold by the gram and thereby to maximize profits among dealers. In the material that was obtained, the lead content on average was 10% by weight, which translates into a profit increase of approximately €1,000 ($1,500.00) per kilogram of marijuana. Lead particles smoked in a joint, which can have a core temperature of 1200°C, are very effectively absorbed in the respiratory tract."
There can, therefore, be no doubt that this episode was a direct result of the illegal status of the drug and the fact that it is supplied through criminal channels that are entirely free of the quality controls we expect for legal drugs such as alcohol and tobacco, prescription drugs, or indeed State or Federal Government supplied medical cannabis in the US and Canada.