I have no idea the point of this vitriol, noway. USP grade means it meets the standards of the monograph of the substance published by the US Pharmacopeia, and this is what is generally meant by "pharmaceutical grade", which simply means pure enough to be used in a medicine. So yes, USP indeed does describe a grade, and it also describes the organization that creates the standards for USP grade. The links by Alien Traveler give a good description of this. Monographs not only give the purity standards for the substance, they often also dictate the testing methods needed.
Of course this does not mean vaping massive quantities of USP PG is perfectly safe, but it is the highest grade generally available. There is no substance as yet approved officially for vaping. The actual safety depends, as far as we know, on the tolerance a person has for PG (mine is extremely low, I only use VG), as well as the amount of thermal decomposition that can happen with high wattage. This issue of coil temperature and thermal decomp, in my opinion, especially with PG, is more important than debating if USP PG is pure enough. Spectroscopically pure PG will break down in a dry puff into the same toxins as USP PG. Any issues with inhaling non-decomposing USP grade PG are, in my opinion, trivial compared to those from decomposing 100.00% pure PG.
USP nicotine has its own standards, and there is a nicotine monograph from USP, as well as USP monographs for the different formulations of nicotine in NRT products. Which are pharmaceutical products, thus we can say USP nic is pharmaceutical grade nic. The ultra-pure nicotines on the market for vaping today probably exceed USP standards. In fact, if the nicotine just meets USP standards it would probably not be very good to most people here for vaping. It would have too strong a taste for many here. But it would be fine for NRTs.
As far as I know there are no USP grade flavorings, including tobacco flavors and extracts, let alone approved for inhalation by a government agency. These are simply Generally Recognized as Safe (GRAS) for ingestion, or else they are not GRAS (tobacco extracts, tobacco absolute).
I have been a Subject Matter Expert (chemistry consultant, PhD in chemistry) for the American E-Liquid Manufacturing Standards Association (AEMSA,
AEMSA | American E-Liquid Manufacturing Standards Association for almost three years now, and I helped write the e-liquid standards for the member manufacturers to follow, including USP grade diluents and nicotine (we often exceed USP purity for nicotine), flavors (GRAS only), laboratories, storage, handling, etc, in collaboration with other PhD chemists who do tobacco product and pharmaceutical analytical testing. I, along with other AEMSA representatives, have presented our standards to the FDA, which they
invited us to do, and have been grilled by FDA scientists over every detail. They voiced no objections to any of our standards or testing methods,
including the requirements for USP grade components, and in fact were quite impressed with the depth of our science. The FDA continues to invite us to report our progress, and AEMSA remains as an organization the FDA respects and learns from in terms of all things ecig.
And while it is true we do not now the very-long term safety of inhaling USP grade diluents, the track record since 2006 is quite remarkable, with virtually no serious problems reported. That said, you can expect some companies to cover their tails by either stating that their product is not for vaping, or some other statement that reduces their liability in case of injury. I have been using ES USP grade VG for years now with no problems, and so have thousands of others.
For someone who has been on ECF for all of six weeks to call me a liar is, to be honest, astounding. It is one thing to disagree or want clarification, that is the nature of scientific progress, but to call me a liar, and one with blind ignorance, is not only not true at all, it is very insulting, and just
really odd. And the tone you use is also insulting, and I suspect deliberately so. So people that think the advise of a PhD in chemistry are just fanboys?? Why on earth would you choose to be insulting and vitriolic over something like
USP VG?? If you have questions just ask! I have zero time for stupid fights over such trivial issues. If you don't think USP grade is good enough for you, then find spectroscopically pure diluents, and pay the premium for them. It is overkill, in my opinion, but I am not here to tell you what to vape. You have turned a simple post regarding a sale on PG and VG into very strange fight, when
this issue has been settled scientifically for YEARS now.
Where was I, noway?? I was finishing my spring semester grades for my chemistry courses (I am a chemistry faculty member for a major university), getting my research group ready for summer research (I do, in addition to ecig research, fundamental chemical physics research within my faculty position), finishing up an NIH grant proposal, and working on a publication I want to get out soon. My time for ECF is very limited, but I try to help out as I can. The underlying points of the discussion could have gone so much further in understanding had you been more civil. I'm sure this post will lead to more attacks, but I needed to speak my piece.