Yes, a lot of folks don't stop to wonder if their smoke was grown in pesticide drenched soil. Just thinking back on Chlordane, for example. People were told not to plant a garden for 20 years in any soil that was treated with Chlordane. I could still smell it for even longer periods than that in crawlspaces that had been treated even longer ago. Suppose someone treated soil with a pesticide having that type of longevity, and sold the property after ten years with no disclosure. New owners totally unaware and unprepared.
I mean, that's just one facet of many possible negative occurances. Throw in some fungus, or other variables. Ugh, I'm feeling icky (over)thinking about it.