There’s little evidence to establish causation between cannabis use and mental illness, and even less suggesting a correlation between chronic use and most cancers. Also, flowers (unlike oils, waxes and other concentrates) are direct products of nature, so concerns about harmful chemicals involved in the manufacturing process disappear. If you just smoke flower, you have very little to worry about, right?
I read this eye-opening study by Nick Sullivan, Sytze Elzinga, and Jeffrey C. Raber in the peer-reviewed Journal of Toxicology about pesticide inhalation. (Full disclosure: I am interning for them at their laboratory, The Werc Shop, and so am pretty motivated to make them look good.) The authors looked at three common pesticides and a plant growth regulator, and found that a significant percentage of them do remain in the smoke one inhales upon smoking cannabis out of a pipe or bong.
What follows is a summary of the study and a correction of Dr. Gupta’s remark, along with notes from a radio interview Dr. Raber gave about the study.