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.