Heated tobacco product
A heated tobacco product is a tobacco product that heats tobacco at a lower temperature than conventional cigarettes. The heat generates an aerosol or smoke for inhalation, containing nicotine, a highly addictive substance, and other chemicals. HTPs may also contain additives not naturally present in tobacco, including flavoring chemicals. HTPs generally heat tobacco to temperatures below 600 °C, which is lower than the combustion temperature of conventional cigarettes.
HTPs use embedded or external heat sources, heated sealed chambers, or product-specific customized cigarettes. Unlike e-cigarettes, which vaporize nicotine-containing liquids, HTPs typically use leaf tobacco or another solid form, though some hybrid models can use both solid tobacco and e-liquids. There are various types of HTPs. The two most common designs are battery-powered devices that heat tobacco leaf and devices that heat tobacco using a carbon ember. Similar devices exist for heating cannabis.
A 2016 World Health Organization report found no evidence supporting claims of reduced risk or health benefits compared with conventional cigarettes. A 2018 Public Health England review concluded that HTPs may pose less risk than conventional cigarettes but more risk than e-cigarettes. Some HTP aerosols have been found to contain nicotine and carcinogen levels comparable to those of traditional cigarettes. Although HTPs may be less harmful than smoking, the UK Committee on Toxicity recommends complete cessation instead of switching to HTPs. There is insufficient evidence on the effectiveness of HTPs for smoking cessation, or on the risks of second-hand exposure. Limited evidence suggests that toxic emissions from HTPs are higher than those from e-cigarettes. Some smokers have reported HTPs to be less satisfying than traditional cigarettes.
Tobacco companies began developing alternative tobacco products in the 1960s. HTPs were first marketed in 1988 but were initially unsuccessful. The industry’s renewed interest in HTPs has been partly linked to global declines in tobacco consumption. The latest generation of HTPs has been promoted as a potential—though unproven—harm-reduction option. Existing smoking bans vary in whether they apply to HTPs.
Health effects
A 2016 Cochrane review found that it was unclear whether the use of heated tobacco products would “substantially alter the risk of harm” compared with traditional cigarettes., it remained impossible to quantify the health risks of HTP use due to the limited amount of available health data. The short- and long-term adverse effects of HTPs were also unclear.
, only a limited number of independent studies had been conducted on HTPs, and further research was expected to improve understanding of their health effects.
The wide variety of HTP designs poses challenges for researchers, as different products may produce different effects. One study found that about half of users believed HTPs to be safer than traditional cigarettes.
A 2016 World Health Organization report stated that claims of reduced harm from HTPs were based largely on industry-funded research, and independent evidence to support these claims was lacking. It also reported evidence indicating that HTPs may be as dangerous as traditional cigarettes.
In 2016, Action on Smoking and Health emphasized the need for independent research, citing "the tobacco industry's long record of deceit" regarding the health risks of smoking.
Given the wide range of electronic cigarette products in the UK, it remains unclear whether HTPs provide any notable benefit as harm reduction devices. A 2018 Public Health England report stated that HTPs may be significantly safer than traditional cigarettes but less safe than e-cigarettes. A 2017 non-technical summary by the Committee on Toxicity recommended that smokers should completely stop using tobacco, even though HTPs were assessed as less harmful than smoking conventional cigarettes.
Emissions
Heated tobacco products expose users and bystanders to an aerosol. The aerosol contains levels of nicotine, volatile organic compounds, and carcinogens comparable to those in regular cigarettes, and has been found to contain higher levels of acenaphthene than cigarette smoke. Other substances typically associated with cigarette emissions—such as tar, nicotine, carbonyl compounds, and nitrosamines—are also found in HTP emissions. A 2017 study found that indoor use of HTPs increased air levels of carbon monoxide and formaldehyde by 10 percent.Another 2017 study reported that HTPs generate emissions containing metal particulates, organic compounds, and aldehydes, and found that airborne contaminant concentrations were lower than those produced by traditional cigarettes, though HTP use still decreases indoor air quality.
A 2018 Public Health England report stated that, compared with cigarettes, HTPs are likely to expose users and bystanders to lower levels of particulate matter and harmful and potentially harmful compounds, though the degree of reduction varies across studies. The report also found that less nicotine is typically inhaled from HTPs than from cigarette smoke, and that exposure to mutagenic and other harmful substances is lower. However, reduced exposure does not necessarily correlate with reduced health risk. Even low levels of exposure can raise the risk of cancers, stroke, and other cardiovascular diseases compared with non-smokers. Although lower emissions have been observed, there was no evidence as of 2018 that switching to HTPs reduces overall risk for smokers. In 2017, the Committee on Toxicity reported that HTPs do not reduce exposure to, or the potential for addiction to, nicotine; several inhaled substances remain carcinogenic.
Physiological responses to heated tobacco emissions, including inflammation, metabolic changes, and carcinogenesis across multiple organ systems, are not well characterised due to limited research, particularly in animal models. A 2018 in vitro study found a less harmful pathophysiological response in human organotypic oral epithelial cultures exposed to HTP emissions. A 2016 animal study reported that HTP emissions did not increase surfactant lipids and proteins, inflammatory eicosanoids, metabolic enzymes, or various ceramide classes in exposed mice compared with those exposed to cigarette smoke. The study also noted that excessive use can lead to eosinophilic pneumonia in humans despite reduced toxicant levels.
The population-level impact of HTP emissions is unclear. As of 2018, studies on second-hand HTP emissions varied widely and were often affiliated with manufacturers. There is disagreement over the extent and composition of HTP emissions. A reduced risk to bystanders is expected where HTPs are used instead of cigarettes. Limited evidence suggests that toxic exposure from HTP emissions is higher than from e-cigarettes. Because no safe level of exposure to carcinogens exists, it is difficult to determine how much HTPs reduce health risks overall.
Addiction and quitting
HTPs contain the highly addictive chemical nicotine. The nicotine content of HTP emissions is similar to that of traditional cigarette smoke, suggesting a comparable potential for addiction and dependence. There is insufficient evidence on whether HTPs are effective for quitting smoking.A 2018 World Health Organization report stated that "onclusions cannot yet be drawn about their ability to assist with quitting smoking, their potential to attract new youth tobacco users, or the interaction in dual use with other conventional tobacco products and e-cigarettes." In 2017, the New Zealand Ministry of Health noted that there was "limited information on product use, including whether smokers are likely to switch completely from tobacco smoking or use both types of product, as well as initiation by non-smokers." The same year, the Committee on Toxicity expressed concern that non-smokers, including children and young people, might begin using HTPs, despite the products not being risk-free.
The availability of flavours in HTPs may appeal to non-smokers, and evidence indicates that individuals who have never used tobacco products—particularly children and adolescents—may be susceptible to trying HTPs, potentially leading to subsequent traditional cigarette use. In 2017, the Committee on Toxicity further noted concern for young people initiating HTP use, given their longer potential lifetime exposure and possible increased sensitivity to nicotine.
Dual use of HTPs and combustible cigarettes is common. Trying HTPs is more frequent among adults under 30 and among regular cigarette smokers. A 2015 online survey found that 6.6% of 8,240 respondents had tried an HTP at least once. Research has shown a high overlap between HTP users and female smokers.
Four epidemiological studies reported that 10–45% of HTP users were non-smokers, with findings interpreted as evidence of marketing effectiveness by the tobacco industry. For example, IQOS use reportedly functions more often as a gateway to traditional cigarette use than as a quitting tool, with the remaining 69% being dual users; no reduced risk has been established for these users. In 2016, Philip Morris International acknowledged that IQOS is likely as addictive as traditional smoking. IQOS packaging includes a warning stating that avoiding tobacco products entirely is the best option.
IQOS devices can record user behaviour. Although Philip Morris International states that data are retrieved only when the device malfunctions, Gregory Connolly of Northeastern University suggested that tobacco companies could develop a "mega database" of smoking habits and potentially adjust puff delivery patterns to increase reinforcement and addiction potential.
As of July 2017, HTP awareness and use in the United States remained low; approximately one in twenty adults had heard of HTPs, including one in ten cigarette smokers. In Italy, HTP use was 1.4% among the general population and 3.1% among regular tobacco users. A 2018 Italian survey found that 45% of people who had experimented with IQOS, and 51% of those interested in IQOS, had never smoked before. In this context, HTPs may represent a gateway to nicotine addiction for never-smokers rather than a harm reduction alternative for current smokers.
In Germany, HTP use is uncommon and tends to be concentrated among wealthier and more educated smokers. In Japan, where HTPs have been sold since 2014, use has been high. A 2017 survey in Japan found that, among recent IQOS users, 20% had never smoked before. Eighty-six percent of IQOS users reported that the product did not satisfy them, and they continued smoking traditional cigarettes alongside IQOS. HTP use among youth remains uncertain, though monitoring is underway as of 2019.