Dozens of young marijuana users in Germany were found to be suffering from lead poisoning last year, apparently as a result of dealers mixing lead flakes into packets of marijuana leaves to increase their street value.
In a letter to the New England Journal of Medicine, half a dozen German doctors have now described the detective work that led them to discover the adulteration.
The doctors were initially baffled when 29 patients were admitted to Leipzig hospitals over a period of 3-4 months with classic symptoms of lead poisoning, since Germany has strict regulations on the use of lead.
Most of the patients were suffering from abdominal symptoms and fatigue, but some had neurological effects and one experienced hallucinations and permanent nerve damage.
After eight weeks of looking for common factors, it was found that "the patients were young, were unemployed or were students, had a history of smoking, and had body piercings." All of the victims eventually admitted to being regular users of marijuana, and samples supplied by three of them revealed lead particles.
After two weeks an anonymous screening program had detected significant blood levels of lead in 95 out of the 145 persons who volunteered for testing.
Screening has continued, and about 200 victims have been identified, but it appears that the practice has now ceased.