There's alot of "dunno" replies to your queary. I'm not that smart, but I'm still sticking w/ foundationless and stand by; "some" foundation has extreme levels of toxins. We all can't test our wax or foundation. How would you do that? I live in the woods and frankly not that up to speed on the "science" of things. My lab is outside.
Someone asked how toxins get in the wax; the bees bring it home, both natural and man-made.
I'm not arguing with your viewpoint on chemicals in foundation. There are chemicals. The level is what is being questioned, and at what harmful effect.
For the record, I have been associated with research in one form or another over the years. And when they came out and first mentioned all the chemicals they found in foundation, I was expecting an uproar of demands. But it quickly faded. I thought maybe some researchers did not want to step on toes. Maybe they were being affected by the same money oriented research that some have suggested over the years. You know....slant your outcomes based on who is putting money in your pockets type thing.
That is why I did my own testing. No parts per billion of any BEEKEEPER applied chemical could be found from bees on commercial foundation.
What I did find, and a much bigger problem for me in one of my bee yards, was the massive amounts of chemicals my bees were bringing in from the cattle farm next door. The chemicals they were dipping their cattle in several times a year for fleas, ticks, etc., had saturated the soil over the 30-40 years they have been in operation.
So yes, chemicals are everywhere. I don't think that the levels in foundation make a difference. I think much of it is encapsulated. What your bees are dragging in is a much bigger concern. And to date, I have seen no report or study that has shown wax foundation to be detrimental to bees. That's not to say it was fully looked at. It just says that to this date, much of the comments may be based on urban legend, self promotion of some particular way of keeping bees, etc. Some websites and companies are out there making it sound as if they have definitive proof of bees being harmed on wax foundation....and they do not.
Yes, comb rotation and not putting the chemicals in the hives is the key.