A lot of people reading this will probably baulk at the thought and think of how they would never partake of any kind of substance like this for a high, but in some cases they will already have without knowing it, that is, if they have ever partaken of any kind of illegal drugs in chemical form.
If you have ever smoked marajuana in solid form, it most likely was mixed with rubber, tyres, whatever they can get ahold of that is the same colour that will mix with the mj and burn easily.
That UK band Goldie lookin chain did a song called 22%(something like that anyway), talking about how studies of solid marajuana generally held there was only that amount of mj in it.
Same with white powdered drugs like amphetamines and cocaine, they will often be mixed with bathroom cleaner, any kind of household prodcut that is a white powder and can be mixed with the drug.
Heroin will often be mixed with glass and sand.
Helium mind bombers will usually be mixed with crushed brick powder from bouncy castles.
Midgets have been snorting rubber bands since the 50s in an effort to elasticise their bones, which is actually more difficult than it sounds. One circus performer got his inner skull tied up so tight he had to have his brain bounced.
The Irish have been gobbling up a watered down version of LSD in large quantaties, due to the difficulties in smuggling drugs into the country due to Bono. this 'LSD' is made from the debris left behind in removal trucks from carpets and linoleum, commonly known as 'Leprecaun stomach dust', again, more difficult to ingest than it sounds.
and of course, the American homeless have been snorting hamburger grease since the mid-70s. Jeff Goldblum can be seen with burger veins running down his nose in the original Death Wish, Bronson was also a big fan, the two of them apparently strapped Micheal Winner onto the back of a Pumpkin and rolled him down a hill into oncoming traffic, laughing wildly as they did so, amidst a hill of discarded buns and burgers.