If someone wants to suggest that pharmacists and USP staff don't agree, then that's fine. All we can do here is publish what qualified pharmacists tell us.
The retail quality situation isn't ideal in any case.
Contamination is always going to be a problem with inhalable products because (1) the degree of contamination does not need to be high before there is a potential problem, and (2) no one in the supply chain really cares too much as long as they think they can get away with it, because quality is too expensive to provide unless you are forced to provide it.
The best example of this is the diacetyl flavouring scandal, where the original main producer kept selling it without protection and without warning the suppliers further down the chain, even though they knew it was toxic and was already killing people - so dozens of people were killed or maimed in the supply line, as the material was processed and reprocessed into other products. They thought they could get away with it, and it made them too much money to turn the switch off.
And before you say that doesn't happen in our own business - it does. One of the largest Chinese
e-liquid vendors was caught supplying PEG-based
e-liquid with 2% DEG contamination, because they normally supplied it at up to 1.9% contamination but made a mistake and let some through with 2% contamination, and that got caught in an FDA import test (sometimes the FDA stop and analyse e-liquid imports). Their Sales Director said, to paraphrase him, "We will supply PEG e-liquid with up to 2% DEG contamination because that is the FDA limit. It is allowed below that."
As a result, following a storm of argument, they stopped supplying PEG over here (as far as I know), because they could not control the purity. But as far as they were concerned, anything up to 1.9% contamination with a known poison was just fine because that was the limit allowable. They had been supplying it contaminated up to that time.
The supply chain doesn't care because no one has to pay personally. You don't know what you are inhaling unless you have seen a certificate of full analysis of the finished retail product, and there is clearly a possibility someone in the supply chain has cut corners. There is no such thing as a certificate of analysis available for an e-liquid retail product anywhere, as far as I am aware. Please don't tell me that this is not necessary: I have just demonstrated to you that products were being sold here with around a 2% DEG contamination, and that the manufacturer was fully aware of it, and that the vendors here had no idea.
Therefore, you will probably understand why I don't consider a debate about the finer points of the meaning of USP to have much importance, considering the context it has to be placed in.
I'm just trying to point out that the risk elevation is so small compared to smoking that it probably will not be able to be identified reliably even in a population who have never smoked and who have vaped for 30 years.
