[xkcd-sucks]

Like what specifically? It is certainly true that there's little difference between naturally and synthetically sourced chemicals of the same identity (ideally, where supply chain doesn't affect composition)

But at least naively, these all seem like the least concern: Fairly well behaved nutrient stuff like phosphate rock, nitrates, sulfur, etc.; while all the concerning compounds are synthetic or semisynthetic (besides arsenic lead etc. which have been out of use for a long time right?!)

AFAIK there is no natural source for most of the concerning pesticides/herbicides like glyphosate, chlormequat, paraquat, aminopyralid, maybe synthetic/semisynthetic pyrethrenoids etc. while the much smaller list of "natural" pestidides (pyrethrum, any others?) aren't concerning because they degrade quickly etc.

But I'm also assuming here that "approved for organic use" means "the substance can be trivially extracted from natural sources" which might not be true

[chihuahua]

Rotenone is another example. It used to be allowed for use in organic farming, but in 2019 it was shown to be dangerous and was banned for organic farming. If one organic pesticide that was once considered harmless turned out to be dangerous, there can be others that we don't know about yet.

[xkcd-sucks]

ooh good example thanks. yeah it's super scary mitochondrial ~~uncoupler like MPTP and paraquat~~ actually a scary mitochondrial inhibitor? but its soil/water half life is only a few days