Often, yes: novel compounds can have side effects which take years to understand (e.g. DDT‘a impact on bird populations lasted past the point where its effectiveness was rapidly tapering) and depending on what characteristics something was picked for you can end up with something which doesn’t biodegrade and is thus a long-term problem if it doesn’t turn out to be harmless.
The fact that these are man-made is irrelevant to their harmful effects and framing it as if it was contributes to the persistence of the natural fallacy.
The natural fallacy application doesn’t seem appropriate: the problem isn’t where they were produced but rather that they’ve never before been part of the ecosystem. We’d have the same concerns if these novel chemicals were introduced by meteors or something but that’s extremely rare whereas chemists produce a wide range of compounds every year.
That’s exactly what I’m saying. But the context is that most people operate with heuristics of the natural fallacy type. Hence this is not mere pedantry for pedantry’s sake, the intention is to provide an actually-helpful clarification/correction.
