Moderate UCSF stance a surprise
A new review of scientific literature on vaping products has emerged from a research group at the University of California at San Francisco, and has been published in the journal of the American Heart Association.
The article is quite significant in view of its fairly moderate stance, given that one of the co-authors is Stanton Glantz, known for uncompromising opposition to the vaping movement. The other co-authors, Neal Berkowitz and Rachel Grana, are equally prominent scientists in nicotine and tobacco studies, but without the extreme anti-vaping position characteristic of their colleague. Who knows? Perhaps they're bringing him around, but all the same, don't expect Professor Glantz to march in the next "Save Vaping" rally.
The trio has reviewed 82 articles on various aspects of vaping and its dangers, and presents a review of the field, and a summary of the studies they find most significant. By and large the review is remarkably free of "cherry-picking" and negative spin, by contrast with previous blogs and studies emerging from UCSF and associates of Glantz.
After the preliminaries summarizing the basics of e-cigarettes, they take up studies of vapor toxicity. Speaking of the recent study by Miaciej Goniewicz, they note that "levels of toxicants in the aerosol were 1 to 2 orders of magnitude lower than in cigarette smoke but higher than with a nicotine inhaler," failing to note that the range went from levels equal to those from the inhaler to levels significantly higher, leaving open the possibility that further research will enable all liquids to attain the lower levels.
Turning to cytotoxicity studies, they summarize the Farsolinos study of cardiac tissue, stating that the 3 fluids exhibiting cytotoxicity were all flavored, and that cigarette smoke, by contrast, was almost universally cytotoxic. They also note that 2 other cytotoxicity studies found flavors to be implicated but not nicotine.
Turning to studies of secondhand exposure to vapor, they quote a study by Schipp to the effect that the impact of secondhand vapor is much lower for e-cigs than for cigarettes, but they don't say how much lower. Trace levels would seem to be a probability. Regarding a study by Flouris, they note that the levels appeared comparable, but they admit that the study used a vapor pump that "discharges all the nicotine into the environment," while in an actual vaping situation, the vaper would absorb 80% of it, "so the nicotine exposure may be higher in this study than would be the case with actual secondhand aerosol exposure." Even so the level of serum cotinine in nonsmokers sitting in the chamber was just over half that for cigarette smoke (average, 0.8 ng/mL for tobacco cigarette and 0.5 ng/mL for e-cigarette). Schober found probable carcinogens found but there is no mention of the concentrations. Czogala found one tenth of the contaminants in secondhand cigarette smoke.
The next group of studies the authors look at have to do with particulate matter or "nanoparticles" (teeeeeny-weenie particles) in cigarette smoke and e-cig vapor. "Particles" the authors aver, "can be variable and chemically complex, and the specific components responsible for toxicity and the relative importance of particle size and particle composition are generally not known." Indeed, this area is likely to be a hotspot in coming research and debate over vaping. The existence of such particles is clear, but their actual impact is an unknown. Opponents see this as a justification for restrictions, while proponents see it as an opportunity for further research into making the product even safer.
"Given these uncertainties," say the good scientists, "it is not clear whether the ultrafine particles delivered by e-cigarettes have health effects and toxicity similar to the ambient fine paticles generated by conventional cigarette smoke or secondhand smoke."
We do know, say the authors, that the particles seem to be dependent on nicotine levels rather than flavorings, but "the thresholdsfor human toxicity... are not known."
The review of research literature goes on to look at studies of cessation efficacy and marketing. These portions of the study will be assessed in coming blogs during the next few days.