> To this day, afaik no testing of vapes is required to ensure they don't contain this toxic ingredient.

This is a pretty good example of how "testing requirements" tend to be reactionary and effectively useless.

Vapes contained Vitamin E because the sellers were cutting the product with it, the same way drug dealers cut drugs with starch or sugar or something worse. It wasn't a manufacturing mistake, they were adding it on purpose to rip off the customer. It makes sense for that to be a crime -- it's fraud and negligence -- so the argument comes that we should require testing for it.

But if you add a test for something like that, they either cut it with something else that the test won't show (which might be even worse) or they add the cutting agent to the distribution pipeline somewhere after the point where the testing requirement is imposed. Testing for something works against mistakes, not purposeful behavior.

Meanwhile the people doing it were probably idiots who didn't know it would cause physiological harmful and thought they were just ripping people off, so then the argument comes that we should be testing to make sure they're not doing that. Except there is no generic test for every possible problem, so at the point they first started adding it, the government would have had no reason to test for that in particular, and by the time it becomes generally known that adding that substance is harmful, they'd have stopped adding it because they don't want to be sued or arrested when their customers have those symptoms and then permanently testing everything for something everybody has already independently stopped doing is a waste of resources.

The problem is people want the generic test that could catch every possible problem and that isn't a real thing, and there is no point in doing the specific test for something that has already stopped happening.