LA Times did an excellent article on how toxic chemicals/pesticides used to grow marijuana effect the body

Twenty-five of 42 legal cannabis products that The Times and WeedWeek purchased from retail stores and had tested at private labs showed concentrations of pesticides either above levels the state allows or at levels that exceed federal standards for tobacco. The contaminants include chemicals tied to cancer, liver failure, thyroid disease and genetic and neurologic harm to users and unborn children.

Click here for info graphic.