Heated cigarettes, more formally called heated tobacco products (HTPs), occupy a contested middle ground between conventional cigarettes and nicotine replacement therapies. They heat real tobacco to temperatures well below combustion, producing an aerosol that delivers nicotine along with substantially fewer toxic chemicals than cigarette smoke. Overall emissions from heated tobacco aerosols have been measured at roughly 90% or more below cigarette smoke levels, yet the products are far from harmless, and independent research paints a more cautious picture than industry marketing tends to suggest.
How Heated Cigarettes Work
A heated tobacco product consists of a battery-powered device and disposable tobacco sticks or plugs. The device contains a heating element, either a blade inserted into the stick or a surrounding chamber, that warms processed tobacco to temperatures typically below 245–350 °C. At these temperatures the tobacco never ignites. One well-characterized product, BAT’s THP1.0, heats tobacco below 245 °C; thermogravimetric analysis confirmed that the aerosol it generates comes mainly from evaporation and distillation rather than combustion or pyrolysis.1PubMed. Assessment of tobacco heating product THP1.0. Part 2: Product design, operation and thermophysical characterisation Philip Morris International’s IQOS, the most widely sold brand globally, uses an electrically heated ceramic blade that reaches roughly 350 °C at its tip. Other devices such as BAT’s glo use an external heating coil wrapped around the tobacco stick.
Because the tobacco never burns, there is no sidestream smoke in the traditional sense. The user inhales an aerosol of nicotine, glycerol, tobacco volatiles, and water vapor. That said, “no combustion” does not mean “no chemical reactions.” Independent lab work has found evidence that some thermal degradation still occurs at operating temperatures. One analysis of the polymer-film filter in IQOS sticks detected formaldehyde cyanohydrin being released at just 90 °C, well below normal operating temperature.2Tobacco Control. iQOS: evidence of pyrolysis and release of a toxicant from plastic Findings like this complicate the clean narrative that heating without burning eliminates harmful byproducts entirely.
Fewer Toxicants, but How Many Fewer
The strongest selling point for heated tobacco products is a dramatic reduction in the toxic chemicals found in their aerosol compared with cigarette smoke. A recent analysis bridging data across multiple brands and tobacco blends found that emissions from heated tobacco systems were reduced by about 94% overall compared with cigarette smoke, with consistent reductions across different devices and blends.3PubMed Central. Assessing the comparability of toxic emissions reduction from heated tobacco aerosols relative to cigarette smoke: a scientific approach to bridging datasets Polycyclic aromatic hydrocarbons and carbonyls, two classes of carcinogens abundant in cigarette smoke, are also present in HTP aerosol but at far lower concentrations.
Where things get more complicated is in the comparison with e-cigarettes. A head-to-head study measuring aerosol chemistry and its effects on human bronchial cells found that heated tobacco products emitted less of these compounds than conventional cigarettes but more than e-cigarettes. Cell toxicity followed the same pattern: HTP aerosol was less damaging than cigarette smoke, but more damaging than e-cigarette vapor.4PubMed. Comparison of the chemical composition of aerosols from heated tobacco products, electronic cigarettes and tobacco cigarettes and their toxic impacts on the human bronchial epithelial BEAS-2B cells Another study looking at genetic and epigenetic damage in the same type of lung cells found that HTPs produced a biological response similar to that of cigarettes, though only after more intensive exposure, while e-cigarettes did not produce the same damage.5PubMed Central. Impact of Electronic Cigarettes, Heated Tobacco Products and Conventional Cigarettes on the Generation of Oxidative Stress and Genetic and Epigenetic Lesions in Human Bronchial Epithelial BEAS-2B Cells So the hierarchy of harm in laboratory settings tends to be cigarettes worst, HTPs in the middle, and e-cigarettes least harmful, though all three expose lungs to substances that are absent from clean air.
What Happens Inside the Body When Smokers Switch
Short-term clinical trials have tracked biomarkers of exposure, the measurable breakdown products of toxic chemicals, in smokers who switch to heated tobacco products. In a controlled five-day study, participants who switched to a carbon-heated tobacco product saw biomarker levels for carbon monoxide, benzene, acrolein, and the tobacco-specific carcinogen NNK drop by roughly 50–95% compared with those who kept smoking cigarettes.6PubMed Central. Evaluation of Biomarkers of Exposure in Smokers Switching to a Carbon-Heated Tobacco Product: A Controlled, Randomized, Open-Label 5-Day Exposure Study A separate trial in Japan found that switching to either glo or IQOS products reduced urinary biomarkers by roughly 20–92% within five days, and in many cases the reductions in the glo group were statistically similar to quitting tobacco altogether.7PubMed Central. Changes in Biomarkers of Exposure on Switching From a Conventional Cigarette to Tobacco Heating Products: A Randomized, Controlled Study in Healthy Japanese Subjects
These are encouraging numbers, but biomarker reductions are a surrogate measure. They tell you the body is absorbing less of certain toxicants, which is promising. They do not tell you, on their own, whether disease risk actually drops proportionally, or at all, over a lifetime. That distinction matters, and it is where the marketing sometimes races ahead of what the science has established.
Cardiovascular and Respiratory Concerns
Animal and human studies examining the cardiovascular effects of heated tobacco products have raised red flags. In one study, current smokers who used a heat-not-burn product experienced acute increases in heart rate, blood pressure, and arterial stiffness similar to those caused by conventional cigarettes. Rats exposed to IQOS aerosol showed impaired blood vessel function comparable to cigarette smoke exposure.8American Journal of Physiology-Heart and Circulatory Physiology. Heat-not-burn tobacco products: an emerging threat to cardiovascular health A large cohort study of Japanese workers found that both cigarette smoking and exclusive HTP use were associated with increased risk of hypertension, leading the researchers to conclude that HTPs should not be considered reduced-harm alternatives for preventing hypertension.9International Journal of Epidemiology. Association of conventional cigarette smoking, heated tobacco product use and dual use with hypertension
The lungs tell a similarly cautious story. Mice chronically exposed to IQOS aerosol developed enlarged airspaces consistent with emphysema, increased collagen deposits in airway walls, and levels of inflammatory markers comparable to those seen in cigarette-exposed mice.10PubMed. Chronic exposure to IQOS results in impaired pulmonary function and lung tissue damage in mice In a mouse model simulating intensive HTP exposure, significant increases in pro-inflammatory immune cells and chemical signals were observed in the lungs, pointing to mechanisms that could contribute to conditions such as organizing pneumonia, COPD, and asthma.11PubMed Central. Heated tobacco product (IQOS) induced pulmonary infiltrates
What about the scenario many health officials hope for, where a smoker switches entirely to HTPs? A study using mice exposed to cigarette smoke and then switched to HTP aerosol found that bacterial clearance from the lungs and some inflammatory measures improved compared with continued cigarette smoking. However, the switching group still performed significantly worse than mice in a cessation group that stopped all tobacco exposure. Markers of lung inflammation and tissue damage like myeloperoxidase and neutrophil elastase did not improve at all after switching, while they dropped substantially with full cessation.12PubMed Central. Can switching from cigarettes to heated tobacco products reduce consequences of pulmonary infection? In other words, switching is probably better than continuing to smoke, but it does not appear to come close to the benefits of quitting.
Nicotine Delivery and Whether These Products Satisfy Smokers
Heated tobacco products deliver nicotine faster and in quantities closer to cigarettes than most e-cigarettes do, which helps explain their appeal. A pharmacokinetic study in Japanese smokers found that peak nicotine concentration and total nicotine absorption for IQOS were between 88% and 104% of what cigarettes delivered, and urge-to-smoke ratings were similar between the two products.13PubMed. Nicotine pharmacokinetic profiles of the Tobacco Heating System 2.2, cigarettes and nicotine gum in Japanese smokers Not all HTPs match cigarettes this closely, though. A study of BAT’s Pulze system found that peak nicotine levels and total absorption were significantly lower than usual-brand cigarettes, even though the time to peak concentration was roughly the same.14Scientific Reports. An assessment of nicotine pharmacokinetics and subjective effects of the pulze heated tobacco system compared with cigarettes
The addiction picture is nuanced. A pilot study found that IQOS use relieved cigarette-withdrawal cravings but did not alleviate other withdrawal symptoms.15PubMed. Switching from cigarettes to IQOS: A pilot examination of IQOS-associated reward, reinforcement, and abstinence relief Comparative research found that HTPs suppressed craving more effectively than e-cigarettes, though both products were less effective at craving suppression than conventional cigarettes. All three products, cigarettes, HTPs, and e-cigarettes, produced comparable reductions in nicotine withdrawal symptoms.16Nicotine & Tobacco Research. Nicotine Delivery and Changes in Withdrawal and Craving During Acute Electronic Cigarette, Heated Tobacco Product, and Cigarette Use Among a Sample of Black and White People Who Smoke So heated cigarettes are a plausible substitute for the nicotine habit, but they are also a reliable nicotine delivery system, which means they sustain dependence rather than treat it.
Do They Actually Help People Quit Smoking
This is the question that determines whether heated tobacco products are a net positive for public health, and the answer remains unsatisfyingly thin. A Cochrane systematic review, the gold standard for synthesizing clinical evidence, found zero completed studies reporting on the effectiveness of heated tobacco for smoking cessation.17PubMed Central. Heated tobacco products for smoking cessation and reducing smoking prevalence That does not mean HTPs cannot help people quit; it means the rigorous evidence simply has not been produced yet.
What does exist are observational data on real-world switching behavior. A study in Czechia tracked adults who smoke and were given access to an HTP. After six weeks of free use, 16% had completely switched to the heated product and about a third had cut their cigarette consumption by at least half. By 24 weeks, when participants had to buy their own supplies, roughly half were still using the HTP as a complete or majority replacement for cigarettes.18PubMed Central. Switching and substantial reductions in cigarette consumption concurrent with use of a heated tobacco product among adults who smoke in Czechia: an actual use study This looks encouraging but must be read carefully. “Switching to an HTP” and “quitting tobacco” are different outcomes, and the study measured the former.
Meanwhile, the problem of dual use looms large. Among young adults in Japan who currently used HTPs, roughly two-thirds also smoked conventional cigarettes.19BMJ Open. Prevalence and dual use of cigarettes, heated tobacco products and electronic cigarettes among young adults in Japan: findings from a 2019 Nationwide Survey Dual users do not get the full exposure reductions that a complete switch would provide, and they remain exposed to cigarette smoke’s full toxicant profile on top of whatever the HTP contributes.
The Japan Case Study
Japan is the most important real-world test case for heated tobacco products because it is the only major market where HTPs achieved mass adoption while e-cigarettes containing nicotine remained effectively banned. Between 2016 and 2018, per capita HTP sales in Japan skyrocketed at an annual rate of about 149%. Since 2018, growth has slowed to around 8% per year. During the same period, per capita cigarette sales fell dramatically, declining at roughly 10–11% annually from 2015 to 2018 and continuing at about 7% per year through 2023. Total cigarette sales between 2011 and 2023 fell by about 53%.20Tobacco Control. Transformation of the tobacco product market in Japan, 2011–2023
Does this mean HTPs caused the cigarette decline? A scoping review of trends confirmed that cigarette use dropped rapidly during HTP expansion, but the relationship is correlational.21Nicotine & Tobacco Research. Recent Trends in Cigarette and HTP Use in Japan: A Scoping Review An observational study found some indication that alternative nicotine products were competing with cigarettes rather than promoting smoking, but the authors described the findings as inconclusive because of data limitations.22PubMed. Effects of reduced-risk nicotine-delivery products on smoking prevalence and cigarette sales: an observational study Japan’s tobacco tax increases and broader health awareness campaigns during the same period make it hard to attribute the cigarette decline to HTPs alone.
Who Funds the Research Matters
One of the most important things to understand about heated cigarette science is who is paying for it. A systematic review examining 134 studies that compared HTPs with conventional cigarettes found that nearly two-thirds were affiliated with the tobacco industry. Among industry-affiliated studies, about 56% concluded that HTPs were more desirable than cigarettes. Among independent studies, only 19% reached that conclusion.23PubMed. Comparison of Publications on Heated Tobacco Products With Conventional Cigarettes and Implied Desirability of the Products According to Tobacco Industry Affiliation: A Systematic Review That does not mean every industry-funded study is wrong, but the pattern is striking enough that you should always check who funded a study before accepting its conclusions at face value. The biomarker and emissions data cited earlier in this article include both industry-sponsored and independent work, and the directional finding that HTPs expose users to fewer toxicants than cigarettes is consistent across both. Where the two camps tend to diverge is in how they frame the significance of those reductions and whether they emphasize remaining risks.
Indoor Air and Bystander Exposure
Because heated tobacco products produce no sidestream smoke, the secondhand exposure profile is very different from cigarettes. In controlled environmental chamber studies, key air pollutants like acetaldehyde, benzene, carbon monoxide, and nicotine were either undetectable or present at much lower levels after HTP use compared with cigarette smoking. Acetaldehyde, for instance, was detected at levels roughly 60–75% lower than after cigarette smoking.24Environmental Advances. Evaluation of environmental emissions from glo heated tobacco products and combustible Cigarettes
However, “much lower” is not the same as “safe for bystanders.” Modeling of indoor air quality found that acrolein concentrations from IQOS use in homes and public spaces could exceed levels of concern. The researchers concluded that heated tobacco products are a weaker indoor pollution source than cigarettes, but their impact is neither negligible nor fully understood.25Environmental Science and Technology. Heated Tobacco Products: Volatile Emissions and Their Predicted Impact on Indoor Air Quality For anyone sharing indoor space with an HTP user, the exposure is real, even if it is a fraction of what cigarettes would produce.
Regulation and the “Modified Risk” Debate
The regulatory landscape for heated tobacco products is a patchwork. In the United States, IQOS received an FDA marketing authorization as a tobacco product but its application for “modified risk” claims, meaning the ability to advertise reduced harm, has faced scrutiny. Analysis of the regulatory framework found that Philip Morris had not submitted adequate evidence to demonstrate that IQOS is significantly less harmful to users, that its labeling would not mislead consumers, or that marketing the product would benefit population health as a whole.26Tobacco Control. Heated tobacco product regulation under US law and the FCTC The FDA did later authorize IQOS with a “reduced exposure” claim, a narrower statement than “reduced risk.” The distinction matters: reduced exposure means the product delivers fewer toxicants, while reduced risk would mean it causes less disease. The first is well-supported; the second has not been proven.
Another regulatory gap involves the device itself. Because HTP devices and tobacco sticks are packaged and sold separately, the non-tobacco components have sometimes escaped tobacco control laws in countries that regulate only the tobacco-containing portion. The WHO Framework Convention on Tobacco Control calls on countries to assess new HTPs according to goals of reducing tobacco use and preventing misleading marketing.
Youth Appeal and Flavored Products
Public health researchers have raised concerns that heated tobacco products may attract young people who would not otherwise have started using tobacco. IQOS HeatSticks launched in flavored variants including menthol options, and it is well established that flavored tobacco products disproportionately appeal to adolescents and young adults. Research has shown that exposure to flavor-focused marketing and reduced-risk claims attracts young non-smokers to initiate tobacco use.27Tobacco Control. Heated tobacco products likely appeal to adolescents and young adults The concern is not theoretical: if HTPs serve as a gateway to nicotine dependence for people who would never have smoked cigarettes, the population health math changes even if each individual user is exposed to fewer toxicants.
Beyond the Lungs and Heart
Most of the health research on heated tobacco has focused on the respiratory and cardiovascular systems, but the effects may extend further. A study of over 42,000 Japanese workers found that exclusive HTP users had a roughly 46% higher odds of high-frequency hearing loss compared to people who never smoked. That was lower than the 83% increase seen in exclusive cigarette smokers, but it was still elevated, and the odds increased with heavier HTP consumption in a clear dose-response pattern.28PubMed Central. Association of conventional cigarette smoking, heated tobacco product use, and dual use with hearing loss: A working population-based study Research of this kind is a reminder that nicotine and whatever else makes it into HTP aerosol affect the entire vascular system, not just the organs directly exposed to the aerosol.
Environmental Waste From Heated Tobacco
Heated tobacco products generate a type of waste that does not fit neatly into existing categories. The used tobacco sticks contain processed tobacco, a plastic filter, and sometimes metallic or polymer components from the heating element interface. Lab tests examining the leachate from discarded HTP sticks found a “particularly strong ecotoxic effect” on microorganisms, comparable to the toxicity of conventional cigarette butts. The researchers flagged the high volume of waste as a concern for surface water and wastewater treatment systems.29PubMed. The influence of waste from electronic cigarettes, conventional cigarettes and heat-not-burn tobacco products on microorganisms This is an angle that rarely comes up in the harm-reduction conversation, which tends to focus narrowly on the user’s lungs. The sticks are not recyclable through normal waste streams, and in markets where HTPs have gained large market share, the volume of discarded sticks is substantial.
Population Modeling and What “Reduced Risk” Would Mean at Scale
Some researchers have tried to estimate what would happen if large numbers of smokers switched to HTPs. One modeling study estimated the hypothetical effect of introducing reduced-risk products in Germany starting in 1995. Under its most optimistic scenario, in which all smokers immediately switched to HTPs, the model projected about 159,000 fewer deaths and over two million additional life-years saved over two decades from lung cancer, COPD, heart disease, and stroke alone. More gradual adoption scenarios produced smaller but still meaningful reductions. Critically, these estimates assumed that switching to HTPs carries 80% of the risk reduction of quitting entirely.30Contributions to Tobacco & Nicotine Research. Estimated Public Health Gains From German Smokers Switching to Reduced-Risk Alternatives: Results From Population Health Impact Modelling That 80% figure is an assumption, not a measured outcome, and it is doing a lot of heavy lifting in the model. If the true risk reduction turns out to be smaller, as some of the animal data on cardiovascular and lung effects might suggest, the projected gains would shrink accordingly. Models like this are useful for framing what is at stake, but they tell you more about the question than about the answer.