Is there any company that makes an E Cigarette without Propylene Glycol?

Looking for an e cigarette that uses something safer than propylene glycol, is there any out there? I have read some about it, and it seems that propylene glycol is not very safe, maybe especially when inhaled. There isnt any studies or anything that I can find so its up in the air I guess. But I do know that its not good for you. I smoke american spirit cigarettes, no additives. So comparedly, and since we dont know much about PG, it could be worse if I switched, Ill add a perhaps and maybe to that statement. I have read stories of people who were in a closed room with a smoke machine (smoke machines use pg) and coughing up black stuff afterwards. So who knows how safe the stuff is when inhaled everyday for long periods of time. If you know of any pg-free e cigarettes please let me know! Thanks!