My thoughts on the subject are that:

1. adulterated products were introduced into the supply on purpose by certain people or entities that stand to gain from this (regular tobacco companies specifically)
2. they have been adding cutting agents to vape pens for years without much regulation or knowledge on the ingredients

I quit dabbing and vaping almost 100% in early 2018 after I started getting repeated asthma attacks, some in the middle of the night, which is terrifying. I had pain in my chest and lungs and was also getting light headed often. I attributed it to vaping at too high of a temperature, or impure product, but in the end I think that we just arent meant to inhale these kinds of things into our lungs (oils, terpenes, tars, flavor chemicals).