> There's no such thing as "contaminated" marijuana, that's an urban myth.
Is it a myth? In Germany black market cannabis has been found to be lined with synthetic cannabinoids in many cases. Those substances are not researched well and hundreds of their users (who typically didn't expect any synthetic drugs) required emergency medical care according to this German (sorry) source from two years ago: https://www.vice.com/de/article/m7a533/chemisch-gestrecktes-...
The German minister of health cites this situation as his main motivation for working towards legalization, so people wouldn't have to buy from questionable sources.