The second issue you bring up is %100 due to the legal status of the substances - in a world where they were legal, there'd be regulations on purity and safety

The second issue you bring up is %100 due to the legal status of the substances - in a world where they were legal, there'd be regulations on purity and safety and established/trusted brands. Note, though, there are a number of drugs that are fairly easy to safely cultivate indoors (mj, psylocibin) where it's pretty easy to know the person who grew/produced the product. At that point, any concern about the safety is a bit like worrying about the food safety of drinking your friend's homebrewed beer. Also, the organization DanceSafe is doing some great work offering resources to test the purity of MDMA.