A lot of it, because it's illegal, isn't grown in conditions regulated in the same way that other agricultural products are grown. Take, for example, a report

A lot of it, because it's illegal, isn't grown in conditions regulated in the same way that other agricultural products are grown. Take, for example, a report from this week about pesticides in illegal growing spots in California. I can't find the Reuters link that talked about banned pesticides but I found: http://www.newsweek.com/illegal-marijuana-farms-dump-shocking-amount-toxic-waste-647568 http://www.newsweek.com/illegal-marijuana-farms-dump-shockin...) and http://www.pressherald.com/2017/08/05/pot-laced-with-pesticides-forces-states-to-act-as-epa-stays-away/ http://www.pressherald.com/2017/08/05/pot-laced-with-pestici... So the question is, do studies on cannabis harmfulness account for this variable, the unknowns and frequently illegal pesticides and other chemicals used to grow it? I suspect I know the answer...