For those that don't know what BHO stands for or what it is then I suggest reading this informative article featured in Rolling Stone magazine.
I enjoy BHO and I am not afraid to admit I am concerned about the possibility of any harmful side effects besides blowing up a house making it (which many idiots have done.) I've never made BHO but I've watched enough YouTube videos on how it's made to know that it is NOT to be made indoors because fumes can build up inside causing an explosion. My main concern is the side effects of smoking it caused by any residuals left by the process of making it.. The dispensary I would get mine from uses a vacuum purge system which I don't believe many are using at home when making it.
A bud tender (someone that works the counter in a dispensary) I know, told me that if the BHO not purged properly that it could cause lesions on lungs of those with lung problems.
Check out this... could be BS but it's food for thought...
As far as I know there are no long term studies on how it can be harmful so take that into consideration.
I have friends' that are adamantly against wax. They don't like the fact that a chemical is used in making it and prefer bubble hash or solventless BHO. I know one of the main dispensaries I frequent had some very nice, honey like solventless BHO but it was pricey ($75 g).
It would be nice if someone started a study on this subject but until then... Dab at your own risk! I've cut back a lot lately and would like to make my own solvent- less wax. If anyone has the know how- let me know!
Here are some other articles of interest....
Sampling too soon http://fuckcombustion.com/threads/lung-brain-damage-from-bho.5018/
"However one of my friends collapsed a lung and had to to to the ER from a dab".... http://www.newschoolers.com/ns/forums/readthread/thread_id/731453/