Siegel is right with what he says about this study and the ridiculous response of the ACS. The study was actually a good one for the separation and analysis method they present, but the part about free-base nic = more addictive is not only something they do not prove, it is not true, mainly because it over simplifies a very complex mechanism.
The current addiction model for cigarettes has little to do with the form of nicotine. In terms of the actual physiology, it has far more to do with the high and rapid absorption of nicotine from inhaling cigarette smoke. Some is free-base, some is salt form, but the majority of nic, regardless of the form, penetrates to the lungs. Thus the rapid and high absorption. Regardless of the physical habit of inhaling and seeing smoke, hand to mouth, the ritual, etc, the absorption of nic is high and rapid. It is a strong spike of nicotine in the blood and to the brain.
This is to a large extent one of the main reasons thought for smoking addiction. That fast hit of nic to the brain. But ecigs, for the most part, are unable to do this as well. Most of the nic is absorbed orally and in the throat and nose, with much less penetrating to the lungs. Yes, free-base does absorb orally faster than the salt form, but orally is still much slower than lung absorption, and those little droplets of the vapor aerosol, which encapsulate the nicotine, are in general too large for effective lung penetration. Very high wattage can improve this, but even at 9 W, it takes an hour of vaping to reach 2/3 the level of one cigarette. Its a slow ramp up because of poor lung penetration.
And unfortunately this is also thought by medical professionals studying ecigs for cessation purposes that this is why ecigs do not work better for getting the masses to quit smoking. The majority of ecigs do not do a good job of getting nic to the lungs. And so, at least in large part, they are also not as addictive as cigarette smoking...regardless of the form of nicotine.
It is true, as I said, that orally absorbed nicotine is faster if it is in free-base form. Thus the "kicked" snus where sodium bicarbonate is added to the tobacco to promote free-base formation. Still slower than smoking, but faster than the predominant salt form found in tobacco when used orally.
But when smoked, the salt form gets to the lungs as solid particles adhered to smoke particles, and so is absorbed rapidly. Yes, free-base in gaseous form absorbs in the lungs faster than the salt form does, but any lung absorption is going to be faster than oral absorption, regardless of the form.
I know of at least one PV manufacturer that is working on decreasing the vapor droplet size, which in turn, should increase lung absorption. Thus, it should be a PV that better mimics the high and rapid absorption of smoking, making it a much better smoking cessation tool. But perhaps also enhancing some of the character that increases addiction. And yes, I am very aware of the loosely used term "addiction", rather than "dependence". But frankly endlessly debating these terms among ourselves is IMHO a waste of time. And it plays into the word game rather than the effectiveness game or the absorption game. Word salad that distracts from the actual science.
A few years ago a company tried to bring another nicotine inhaler to the market. It was a nebulizer/propellant device, not a thermal-vaporizing device. Did they use free-base nic? No! Why? Because the salt form, nicotinium pyruvate...salt form with pyruvic acid, when propelled properly, penetrates to lungs better than free-base does. It worked well in trials, but for whatever reasons, maybe money, it never came to market. If it was pleasant, would have it been effective? Probably better than gum or lozenges.
If e-liquid manufacturers pH adjust to promote salt form (I know of at least one company that does this, with citric acid, for smell/taste reasons), will this liquid have better lung absorption? Probably not, because the salt will still be wrapped up in liquid droplets we call visible vapor, and at present those droplets are too big for effective lung penetration. I have had discussions in ECF regarding this possibility for e-liquids, and I don't think it will help. But there are no studies supporting or refuting this either, so the jury is still out. One would have to measure blood levels over time to see, and no one has done a salt-form e-liquid vapor study that I am aware of.
Perhaps the ACS is under pressure politically to demonize vaping however they can. This is not the first demonizing article out of the ACS about vaping, but it is the most simple-minded and inflammatory statement they have made (also parrots the debunked flavors = kids myth), and it denies the complex chemistry and biochemistry of vaping and nicotine absorption, and how this relates to "addiction" as well as smoking cessation effectiveness. It denies the still far from perfect record in smoking cessation for vaping. If vaping was more addictive than smoking, everyone that tried vaping would quit smoking right away, and this is far from true. And it also, obviously, completely negates the importance of harm reduction, as well as contradicting the efforts of BP to improve absorption rates and magnitude of nicotine in their products, which is one of the big reasons why NRTs are so ineffective for cessation. Thus their new, but famously unpleasant, nicotine spray. Designed for better lung penetration, and thus rapid nicotine absorption! Of course, BP is huge in the ACS. The ACS is the largest professional organization in the world.
By the way, the original Nicorette nicotine inhaler, that little white mouth piece thing with the sponge of nicotine in it, and the new spray-type inhaler both contain...wait for it...free-base nicotine!
Yes, really. Two BP over-the-counter nicotine products for inhalation contain the evil, addictive free-base nicotine. And yet, they don't work very well at all. And basically suck. Huh. What a surprise.
Or a Krystal/WhiteCastle.
My last word on the matter....
