As a person completely naive to the finer points of plastics manufacture-do these additives tend to be drawn from a fairly small and well-understood universe of chemicals and combined in predictable ways, or is it a bit more DIY at the level of a specific manufacturing plant or product spec or batch run?

I guess my mind is instinctively reaching for the ways FDA attempts to ensure food safety by compelling manufacturers to publish ingredient lists, and by maintaining registries [0] of hopefully-well-understood additives (and banning the rest, in historically dangerous categories like colorants).

Sure from time to time agitators take that information out of context to whip up a scare about one ingredient or another, and sure some of the food that comes in from overseas has after-the-fact labeling that’s a little sus. But at least there’s an expectation that the information must exist and be legible.

[0] https://www.fda.gov/food/food-ingredients-packaging/determin...