I do farm but not a cannabis farmer
There are some fairly well studied links between certain herbicides and cancers...they deal primarily w ingesting the substance. It's why one of the issues re: cannabis that's meant for smoking is tough because there isn't much literature on what happens when you burn these herbicides/pesticides and then inhale the smoke. Now you may not run into that issue but there are a lot of home gardeners who might.
As far as I understand it, inhaling the product of combustion of anything isn't great for your health. That goes for tobacco, cannabis, campfires, whatever. full disclosure I used to smoke cigs also and was a heavy cannabis user in my youth