Modern science can only "prove" that something is not harmful on a timescale of a year or perhaps a decade, not a generation or more. If the precautionary principle had been applied in Roman times, lead would not have been considered safe. Nor asbestos, nor thalidomide, nor microplastics, nor a bunch of synthetic molecules - "proven safe" - that are routinely added to non-organic food in order to improve its yield or its cosmetic aspect or whatever. That was my point.
That is still better than organic, which doesn't even ask what science can show about chemicals. The obvious example is organic doesn't have GMOs, even though GMOs are the only foods we even try and prove safe. Everything else, what we just assumed, but nobody has ever actually checked.
The argument we are having here is essentially a classic of philosophy: empiricism versus rationalism. You keep arguing for the former; I am arguing for the latter. It is true that molecule X may not present an observable danger to health; it is also true that it may be reasonable to believe it does present one (most obviously because we do not have thousands of generations of evolutionary adaptation to it, as is the case with both lead and GMOs).
This dichotomy underpins a difference in regulation between the USA and Europe. As mentioned already, the EU Commission applies the "precautionary principle" in its legal regime for food and chemicals. This is not "unscientific". Empiricism has been more popular in the Anglophone world, but rationalism was one of the pillars of the scientific Enlightenment.
https://eur-lex.europa.eu/EN/legal-content/glossary/precauti...
Why are you allowing chemicals with proven toxicity then?