As mentioned previously, I’ve found another study to have a look at. This time, it isn’t about vaping (shock!). Instead, it’s about that divisive product – Heat-not-burn.
Considering that whenever heat-not-burn gets mentioned by a vaper (such as myself) on social media the response is, sadly, predictable. As I’ve mentioned elsewhere on this blog (notably here, and here) heat-not-burn products are essential to give smokers (and the odd vaper) the widest array of choices possible. Let the market do what it does best.
Heated tobacco products (HTPs) are a form of nicotine delivery intended to provide an alternative to traditional cigarettes. These products were introduced for the first time in 1988, in the USA, as “Premier” from R.J. Reynolds. As in the case of electronic cigarettes, this technology initially did not gain wide popularity and was discontinued shortly after its introduction. Recently, the tobacco industry has made another attempt to introduce HTPs to the market [2–6]. In 2014, a heated tobacco system from Philip Morris International (PMI), marketed as IQOS (I-Quit-OrdinarySmoking), was introduced [3–6]. Other tobacco companies introduced their own HTPs in 2016. British American Tobacco (BAT) created an HTP called “glo” , while a heated tobacco and e-cigarette hybrid was developed by Japan Tobacco (JT) and marketed as “Ploom TECH” .Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
So far so good. A brief history lesson demonstrating that heat-not-burn, similar to its current form, has been around for quite a while and that, despite the capabilities and resources of the various tobacco companies, it took a long time to get it close to right – i.e. commercially viable.
Just as an aside, I’ve tried the Glo from BAT, albeit a very early pre-market model and I was disappointed. I haven’t tried it since, nor have I tried Ploom.
This study is a meta-analysis so it’s going to be looking at the current, applicable, evidence from both independent and industry papers. The results, in some cases, will no doubt surprise some of you.
Considering how young, relatively speaking, commercially viable heated tobacco products are, the fact that 289 articles were identified via the various keywords is a bit of a surprise. Only 97 made it through to the analysis proper as illustrated in the above image. Still, not bad.
Chemical composition of tobacco sticks
All papers rightly confirm that the sticks contain real tobacco (well, duh!) in a variety of “flavours”. Slight correction there, they aren’t ‘flavours’ per se, more like blends. Having tried all the various HEETS from PMI; Amber, Sienna and Yellow all taste predominantly the same with some subtle variations in intensity and underlying tone. Naturally, menthol is a flavour.
According to PMI, the total chemical composition of a HEET looks something like this:
Which, if you’ve been paying attention, should draw a line under the somewhat ridiculous video that has been circulating around twitter. Especially as the list shown in the video comprises the entirety of the HEET, including the paper (which isn’t burned or melted) and thus, has little to no biological effect. Furthermore, should someone decide to look at the ingredients added to the tobacco section, and total up the amount of flavouring, it’s a massive… 2.9%. Hardly worth all the fuss really. Especially if you follow Toxicology 101.
Additionally, independent research from Dr Farsalinos and Kanae Bekki indicates that an IQOS contained ~70-80% of the nicotine concentration found in conventional tobacco.
Out of the 13 independent studies identified in the analysis that looked at the chemical composition of the tobacco sticks (and aerosol, which I’ll come to shortly) it can be summarised thus:
- Comparable nicotine concentration to traditional cigarettes
- Emits substantially lower levels of carbonyls than cigarettes
- Lower levels of formaldehyde (av 91.6%), acetaldehyde (av 84.9%), acrolein (av 90.6%) and crotonaldehyde (av 95.3%) than cigarettes
- Toxic compounds not completely removed (but are substantially reduced)
From the industry research:
- carbonyl concentrations (formaldehyde, acetaldehyde, acetone, acrolein, propionaldehyde, crotonaldehyde, methyl-ethyl-ketone, and butyraldehyde) were lower compared to those measured in cigarette smoke
- increased acetaldehyde and nicotine concentrations in indoor air, but these concentrations were considerably lower than those found in conventional cigarettes
- except for nicotine, harmful and potentially harmful constituents were reduced by 90% in the THS2.2 aerosol in comparison with the reference cigarette
So far, both industry and independent research agrees. Heated tobacco products provide a similar amount of nicotine, substantially reduced toxins (though not as reduced as found in e-cigs, but then I would never expect that to be the case). Thus far, based solely on chemical composition and aerosol analysis (and using that god-awful PHE figure) heated tobacco is close to being ~85-90% less harmful than cigarettes.
The tobacco industry claims that the aerosol formed during the heating process has around 90–95% lower levels of toxicants than conventional cigarette smoke [13–15,23,24]. This was partially confirmed by independent studies [27,28]. Li et al. reported that, compared to conventional cigarettes, IQOS delivered a > 90% lower concentration of harmful and potentially harmful constituents (HPHCs) except for carbonyls, ammonia, and N-nitrosoanabasine, where the levels were about 50–80% lower . Farsalinos et al. showed that IQOS use emitted substantially lower levels of carbonyls than a commercial cigarette but higher levels than an e-cigarette .Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
The strange thing in this analysis is the focus on saying “produces less than tobacco cigarettes, but more than e-cigarettes”. Totally missing the bloody point!
Heated tobacco is an alternative to lit tobacco. While, yes, some use both heated tobacco and e-cigarettes (like me), the products are not as reduced risk as e-cigarettes. The point is the products are reduced risk in comparison to cigarettes.
Interestingly, there is one independent outlier in this section:
Controversial results were presented by Auer et al. who showed that in the IQOS aerosol, volatile organic compounds, polycyclic aromatic hydrocarbons, and carbon monoxide were detected . Moreover, the smoke released during the use of IQOS contained elements from pyrolysis and thermogenic degradation, similar to the harmful constituents of conventional cigarette smoke .Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
Apparently, this study identified pyrolysis and thermal degradation of the filter material. Along with Davis et al (2018) who also found that cleaning after every 20 sticks caused more pyrolysis. As with all good science, each independent study that looked at chemical composition and aerosol have not since identified the same issue.
I’ll ignore the in vitro (animal and cell studies) for this, as is the norm. These studies are usually pointless for comparing to the real world. So, on to potential health impacts.
Potential health impacts of heated tobacco
Based on studies sponsored by the tobacco industry (Table 3), among healthy Japanese adult smokers, the results have shown that HTPs effectively deliver nicotine and achieve similar pharmacokinetic profiles to combustible cigarettes [12,36,73]. Brossard et al. showed that the nicotine pharmacokinetic profile of IQOS was close to that of conventional cigarettes with similar urge-tosmoke levels . The use of IQOS or glo reduced the exposure to smoke toxicants in a manner comparable to quitting tobacco use [74,75]. After switching from conventional cigarettes to HTPs (IQOS or glo), a significant reduction in the levels of biomarkers of exposure to harmful and potentially harmful constituents was observed [76–78].Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
It seems that independent studies have yet to fully catch up in this area (as with the in vitro area also) and, aside from an analysis of PMI’s Modified Risk Tobacco Product application to FDA by Glantz, independent studies tend to agree with the tobacco industry papers. Funny that.
To summarise, what is a lengthy post, in the areas that are most applicable (I couldn’t really give a rats ass about marketing and usage patterns), both independent studies and tobacco industry studies are more or less in agreement (save a few percentage points in either direction).
The results of in vitro and in vivo assessments of HTP aerosols revealed reduced toxicity, but these were mainly based on studies sponsored by the tobacco industry. Independent human-based studies indicated that there was a potentially harmful impact of the active and passive HTP smoking on human health.Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
This is a lazy argument. It also highlights a groaning bias within public health, in case you didn’t notice. The industry-sponsored studies, including lengthy exposure biomarker studies in humans, were done by the industry of necessity to convince a sceptical regulator that their products are ‘appropriate for the protection of public health’ – an effort that one company has so far been successful with a heated tobacco product.
What this meta-analysis does show is that over half (52%) of the research conducted on heated tobacco products to date is from the industry. Amusingly, for me, the fact that the independent research is actually doing what science does best – replication, replication, replication. If an outcome can be consistently replicated (with a margin for error, natch) then it must be true. As this paper states in its conclusion:
Heated tobacco products are gradually gaining in popularity. A chemical analysis of aerosols has revealed that heated tobacco products release lower levels of toxic chemicals compared to conventional cigarettes. However, toxic compounds are not completely removed from the HTP aerosol and these products are still not risk-free. The nicotine levels delivered to the aerosol by heated tobacco products were almost the same as those of conventional combustion. Health consequences of HTPs as well as their role in smoking aid are unknown.Jankowski, M., Brożek, G. M., Lawson, J., Skoczyński, S., Majek, P., Zejda, J. E. (2019). New ideas, old problems? Heated tobacco products – a systematic review. International Journal of Occupational Medicine and Environmental Health. https://doi.org/10.13075/ijomeh.1896.01433
Harm reduction at its finest.