Everything in California has a Prop 65 warning, even aspirin. LOL.
I know man, and it gets kind of confusing I agree. It really is hard to tell the severity of the danger because everything is labeled. I saw a label at the drive through for mcdonalds warning that the food is known the state of California to cause birth defects, lol that should take your appetite away. However, as it applies to systemic pesticides or PGR's I think we have to assume that they are actually quite dangerous. I wish I could find the article I was reading about PBZ, they where talking about the triaz ring the chemical causes and that the growth retardant is one aspect, the antifungal is another, but the straight systemic poisonous aspect is another. I believe the study was funded by the state of Massachusetts in response to them wanting to use it on trees in historical downtown areas. I think that should be a good sign that we shouldn't smoke it man, they obviously had enough of a backlash over applying it to ornamental trees that they where compelled to do the study.
Your gonna have a hard time finding anyone outside of a hydro store that thinks it is a good idea, I promise.