Geez I remember racing at Scarborough and following an outfit around the circuit during our 15 minute morning practice, my eyes were streaming it was like being in a car spray shop without any respirator . As it emerged they were adding Toluene at a small percentage to the fuel. By doing this during combustion it would allow the engine run cooler enabling you to up the compression.
If i remember correctly there was an article where a guy had cleaned an alloy bike casing using brake cleaner and then tig welded the damaged area, he noticed a small pool of the cleaner was still present in one corner but thought this will burn off not knowing that that introducing argon when hot this produces Phosgene which caused irreversible damage to the welders organs.
I cant find the article i may be wrong on that it may have been trichloroethylene present in the brake cleaner.