I agree. The study was smoking and not vaping. They did mention a vape as possible mitigation. I only threw out the old study as people could not understand a possible reason why water may be worse. With this information in mind, we undertook to explore various ways of filtering marijuana smoke. Waterpipes were the most obvious candidate, being widely available in head shops and popular with many users on account of the apparent mildness of their smoke. We were especially encouraged by research showing that waterpipes could be highly effective in filtering tobacco. Unfortunately, we were to discover that these results did not hold up for marijuana. A second candidate technology that would likewise prove disappointing was cigarette filters, which are widely available and can be easily adapted to marijuana by means of a simple homemade filter holder. We did not consider the more advanced "smokeless cigarette" developed by RJ Reynolds, due to the fact that it is not actually a smoke filtration device, but rather an inhaler for artificially flavored nicotine, which is of no use for marijuana. Instead, we turned our attention to vaporizers, which have been touted as a possible ideal solution to the cannabis smoking problem. Unfortunately, because vaporizers can't be used with tobacco, they are prohibited under US paraphernalia laws, and users must accordingly resort to homemade designs. We obtained one such device from the San Francisco Cannabis Buyers' Club. Another we managed to obtain from a Canadian supplier, who is selling them on that country's newly emerged, illegal but tolerated "gray market" in Vancouver. Although neither device performed close to the smokeless ideal, our study left reasonable hope that substantial improvement is possible. Given the evident need, vaporization merits further research and development.