Heat-Not-Burn Cigarettes: Lower Concentration Does Not Mean Safe

Letter

The results provided by Stephens [1] may suggest to readers that since the concentrations of carcinogens are lower in vapourised nicotine products (VNPs), the risks of cancer are smaller compared to conventional cigarettes. The article uses the linear non-threshold model for risk assessment (a uniform cancer risk per unit dose from higher to lower doses), which is also used by most regulatory agencies. This model is considered to have a high degree of uncertainty; nevertheless, it implies that any dose of carcinogens increases the risk of cancer. Accordingly, the primary conclusion of Stephens and other’s[2] findings of the presence of carcinogens, particularly in heat-not-burn cigarettes (HNB) is that HNB poses a significant risk of cancer. In addition:
1) The article highlights a summation approach of overall cancer risk for each product, yet the individual concentrations of human carcinogens (for example, formaldehyde [3]) are still at risk level.
2) The assessment of carcinogenesis of low-level exposure to a mixture of chemicals is challenging [4]. Stephens’s summation model assumes that the effect of chemicals is independent. Even if we assume that for an individual chemical a lower concentration lowers carcinogenicity, we cannot rule out the potential effects of interactions among chemicals.
3) The analysis relies on holding consumption constant. However, manufacturer studies have suggested that consumption increases after a switch to HNB devices [5]. For non-smokers or occasional smokers to whom HNBs are introduced as a safe product, any additional burden of toxicants increases the risk of cancer.
4) The conclusion concentrates on reduced risk of VNPs compared to the most harmful product (i.e tobacco smoke) and should also calculate elevated risk of using VNPs compared to background concentration.

In summary, smoking imposes exposure to a variety of toxicants with known and/or unknown health effect regardless of name, shape and means of use. These findings suggest that HNB cigarettes should be subject to the same regulations as tobacco cigarettes. The tobacco control community should communicate the absolute risks associated with these products. In particular, there is an urgent need for tobacco control policy actors to understand the potential absolute harms of heat-not-burn (HNB) cigarettes that PMI is pushing as ‘less harmful alternatives to smoking’ in their declared movement toward a smoke-free world (https://www.pmi.com/sustainability).