In Europe, when I stopped buying from the black market, it was reaching a point you can't even imagine! We've seen so many ways of lacing the weed, you would shit bricks if you knew the extent!
Sugar was the easiest to detect, probably the least harmful and unfortunately the least common. It consumed poorly and created pitch black ashes. But then there were at least two reported cases of lead intoxication (lead weights a lot and vaporizes at a very low temperature, the unfortunate people who experienced it now will spend the rest of their life taking chelation medicine as the metal fixed itself to their bones) but I never had any, thankfully.
What I had several times on the other hand was glass micropspheres, and sometimes worse, just finely crushed glass. These spheres are used as part of construction materials normally, from what I gathered. Those glass particles added a lot of weight and you could feel them grinding on your teeth after smoking when you chewed... horrible. Those led to much more reported cases of lung damages, many including microscopic cuts and internal bleeding. If you put the bud inside a glass of water and let it sit for 24h or more, you could see the spheres separate and deposit at the bottom of the glass.
But then at some point the Dutch started inundating the market with something different but equally pernicious: buds were processed to extract most of their trichomes, to make hash that they resold or kept for themselves, then the buds were sprayed with a can of special stuff, very similar in principle to the fake snow you can spray on your Christmas tree, but instead it consisted of fake trichomes (a sphere/ball with a tiny flagellate tail, very sticky)
It made the buds look shiny white, as if there was a very high resin content. But you could easily detect the deception by breaking apart the buds or looking on the underside of leaves that were not exposed, as it was much darker green. Microscope inspection confirmed easily that there were fake trichomes all over, at least if you knew how the real deal is supposed to look.
Some buds were dipped inside lacing liquids instead, and those ended often more mushy, as if they would never dry properly... I could go on but I'm glad those are just bad memories for me now!
