1.
a) If DAP is not considered "GRAS" for inhaling, then you should not make any implicit statement that your product is fit for such purpose (i.e. sell it as a "Mix of PG VG DAP" on e-bay or a general chemicals store, not as e-liquid in a vaping store) or disclose its presence, quantity and possible side-effects (like pharma does with pills or California does with "this product contains a known carcinogen" labels on about anything)
GRAS by who's standards? I'm convinced, given available evidence that we currently have that DAP is GRAS. My evidence would be zero incidents of harm for what is plausible to have some indication of harm in 7 years or less.
You seem to be saying (or are asserting) that only listing ingredients, and not purpose for what the product was intended for, is "truthful labeling." IMO, it is closer to CYA, and with supplementing data (i.e. possible side-effects) that are debatable, thus not necessarily truthful.
b) the testing should be done at "highest technological standards" i.e. using accurate, calibrated, correctly maintained and sufficiently sensitive instruments for the intended purpose.
According to who? I would very much want to scrutinize the heck out of these 'technological standards' both on technical side of things, the economic side of things (why any cost at all?), and practical standards with regards to truth telling. Another might not wish to scrutinize and go with faith that a third party has all this taken care of, and that the pricing is 'fair.' So, we are on a thread where the test costs around $60, but I'm guessing many of us would scrutinize the standards of the equipment, possibly concluding that based on price alone, it can't be all that good. And that someone charging $2000 for a test is probably doing it legitimately, or to a higher standard. But how would average vendor know? And more importantly, why should they care? I know how that last question reads, but will be glad to follow up on it, as I think it is at heart of 'truth telling' with regards to labeling, and how that could tear apart the industry in ways that might have very little to do with truth telling.
c) if you don't understand what the detected DAP means or does, hire someone qualified that could explain it to you, preferably in writing as to engage legal responsibility
What would this person provide that a layperson couldn't accomplish via truth telling?
2.
a) see 1 b) for technological standards.
I did, and I scrutinized the heck out of this proposition. I will await your reply.
b) for scientific, you should review all the available literature regarding the substance in question and its effects for a specific use (or hire someone qualified to do it for you); if there are standing concerns then you have to either not suggest that specific use or disclose the substance
I would say this is impractical. I think many will do this, and that it will still lead to issues given the fickle nature of vaping consumers on this topic. I have an ongoing wager that pertains to how I see this playing out going forward.
c) for legal, you should review and observe all the standards and regulations regarding said substance in said intended use, as published by EPA/OSHA/NIOSH/FDA/etc; also any components in your mixture shall be sourced from manufacturers that observe similar scientific/tech/legal standards
What if EPA, OSHA, etc. are not telling the truth regarding DAP and that this can be shown, but is ignored by them as they are convinced that they are being accurate with the information?
3.
If there's no consensus and there are plausible indications that DAP is hazardous when inhaled then you have to disclose. "We don't know the long term effects" is not a plausible indication. "We have 120 cases of BO where subjects inhaled high quantities of DAP" is.
In conclusion: if your liquid contains 0.5% water you don't have to disclose it other than as "GRAS impurities". If it contains 0.5% arsenic then you disclose and don't suggest anyone to vape it.
So, the consumer would have to decipher what GRAS impurities means, rather than going with something akin to full disclosure from vendor and/or truth telling by the vendor.
I give you (anyone) hard time on the DAP labeling because it is prime example of something that based on evidence to date is GRAS, but is not allowed that designation by some who have demonstrated desire to control the industry / market based on own agenda, or bias. I feel I can back up my take on DAP and thus far the backing up of DAP as potentially harmful is based on speculation or things that do not necessarily apply to vaping.