Many of these street and synthetic drugs are “manufactured” in unclean environments (e.g. someone’s apartment, bathroom, kitchen, abandoned warehouses, etc). Some of the products being marketed as a “safe high” might be further adulterated with addictive constituents (like heroin) to ensure dependency and repeat customers.
Brain scans are beginning to reveal the damaging psychological effects these substances are having on the brain and there is no way of knowing what the longer-term effects will be. Even a casual one time experience with these unknown chemicals can have a permanent effect, impacting mental health, manifesting with depression, anxiety or psychotic behavior.