Actually BHO also has toxins in it depending on where the Butane comes from. Most folks use the canisters of Butane and while the butane itself is fairly safe the things mixed in with it as propellents to get it to come out of the canister, will turn to neurotoxins when they're heated to the same temps or higher as needed to vaporize cannabis resin.
What are the propellents that you speak of and why are they needed for butane? Butane is a propellent'