Heat-not-burn (HNB) tobacco products are alternative nicotine delivery systems that provide the user with an inhalable aerosol. The central premise of these devices is to heat processed tobacco leaf to a temperature sufficient to release nicotine and flavor compounds without causing the material to burn. This approach was developed based on the understanding that the vast majority of harmful substances in traditional cigarette smoke are generated through the chemical process of combustion. By eliminating burning, manufacturers aim to significantly reduce the formation of these detrimental compounds in the resulting aerosol.
The Mechanics of Heating Tobacco
The core functionality of HNB devices relies on sophisticated electronic temperature control to prevent combustion. These devices use a battery-powered heating element, which may be a ceramic or metal blade, pin, or an external heating chamber, to warm a specially designed tobacco stick. The heating process is precisely managed to maintain a temperature typically within the range of 300°C to 350°C. This temperature range is high enough to vaporize nicotine and other volatile compounds from the tobacco but significantly lower than the approximately 900°C reached during the combustion of a conventional cigarette.
The tobacco sticks used with these systems are not standard cigarettes; they are often composed of processed, reconstituted tobacco. These sticks typically include a tobacco plug, a hollow acetate tube, and various filter segments designed to cool the generated aerosol before it is inhaled. The device’s electronic control unit continuously monitors the heating element, often cutting off the energy supply if the temperature risks exceeding the set maximum, thereby preventing pyrolysis or charring.
Aerosol Chemistry Compared to Combustion Smoke
Traditional cigarette smoke is a complex mixture containing thousands of chemicals, many classified as harmful and potentially harmful constituents (HPHCs). The aerosol produced by HNB products differs substantially in chemical composition, primarily due to the marked reduction in the levels of these HPHCs. This reduction is a direct consequence of avoiding fire. Studies consistently show that HNB emissions contain HPHCs reduced by 90% or more compared to conventional cigarette smoke.
This reduction applies to compounds like carbon monoxide, volatile organic compounds, and polycyclic aromatic hydrocarbons, all of which are byproducts of high-temperature combustion. However, while levels are significantly lower, the HNB aerosol is not chemically benign; it still contains nicotine and a variety of other compounds. Some HPHCs remain present, and new compounds unique to the heating process may be introduced, though typically at much lower concentrations than those found in smoke.
Current Scientific Understanding of Health Effects
The scientific community is currently evaluating whether the reduction in HPHCs translates into a reduction in health risk for human users. Research has focused on short-term biomarkers of exposure and biological effect, comparing users who switch completely to HNB products with those who continue to smoke cigarettes or who abstain entirely. In studies where smokers switched to HNB products, favorable changes were observed in several biomarkers related to cardiovascular and respiratory health. For example, some studies showed improvements in markers associated with oxidative stress and inflammation, such as high-density lipoprotein cholesterol (HDL-C), white blood cell count (WBC), and exhaled carbon monoxide (COHb), when compared to continued smoking.
However, when HNB use is compared directly to smoking cessation, the results are mixed, with some independent studies showing harmful effects on certain markers of cardiovascular function and platelet function. The consensus among independent researchers is that while HNB products likely pose less risk than smoking, they are not risk-free, and their long-term health consequences are not yet fully understood. Furthermore, public health concerns remain regarding their potential role as a gateway to nicotine use for non-smokers or as a product used in dual-use with traditional cigarettes, which would negate any potential benefit.
Global Regulatory Status and Public Health Oversight
Governmental bodies worldwide have adopted varied regulatory approaches to heat-not-burn products, reflecting the ongoing debate over their risk profile. In the United States, the Food and Drug Administration (FDA) authorized the marketing of a prominent HNB product through its Modified Risk Tobacco Product (MRTP) pathway, under the framework of 21 U.S.C. § 387k. This authorization permitted the manufacturer to claim reduced exposure to specific harmful chemicals compared to cigarettes, but it did not classify the product as safe or FDA-approved.
The European Union (EU) regulates HNB products under the Tobacco Products Directive (2014/40/EU), classifying them as “novel tobacco products.” This classification subjects them to reporting, notification, and packaging requirements, including mandatory text-only health warnings. Significantly, the EU recently implemented a Delegated Directive applying the ban on characterizing flavors to heated tobacco products, bringing their regulation closer to that of traditional cigarettes. Meanwhile, a number of countries in Asia and other regions have opted for outright bans on the sale and import of HNB devices, highlighting the lack of a unified global approach to this new category of tobacco product.