Comment by schiffern
When I said "tested" I clearly meant "tested for safety," which addresses those concerns.
You're conflating the colloquial usage of the word chemical with the naturalistic fallacy. These are two different things, however they interrelated because of our collective failure to embrace the precautionary principle when it comes to novel synthetic compounds. The result is that newer compounds tend to be correlated with less safety testing, simply because less time has been available for testing, testing which isn't typically required before engaging in mass exposure of the public.
There's also a connection between corporate self-interest in covering up safety risks (well documented in history, and presumably also occurring today as well) because synthetic compounds can be patented while natural compounds cannot.
In short the connection is real, but it's more subtle than your simple definition-based logic is giving credit for.