Tobacco Harm Reduction: Evidence Update

Summary of Study

Bottom Line: The best evidence conclusively shows that e-cigarettes are far less harmful than combustible cigarettes on a spectrum of health metrics, that e-cigarette users are far more successful in achieving smoking abstinence, and that e-cigarettes have not renormalized combustible cigarettes. They are a key part of a harm reduction approach to smoking.

The 2018 National Academies of Sciences, Engineering and Medicine (NASEM) report on e-cigarettes found that e-cigarettes are less harmful than combustible cigarettes and concluded that “completely substituting e-cigarettes for combustible tobacco cigarettes reduces users’ exposure to numerous toxicants and carcinogens” and further that, “there is substantial evidence that completely switching from regular use of combustible tobacco cigarettes to e-cigarettes results in reduced short-term adverse health outcomes in several organ systems.”

A health evidence review concludes:

  • CO emissions from e-cigarettes are approximately 99 percent lower than tradition cigarettes. As a result, the carbon monoxide levels in e-cigarette users is typically the same as those in non-smoking individuals.
  • A side-by-side comparison of combustible cigarettes and e-cigarettes demonstrate that combustible cigarettes have 18-21 times more fine PM emissions immediately after a puff, and that background particulate matter levels are roughly 100 times lower in environments consistently exposed to e-cigarettes compared to those consistently exposed to combustible ones.
  • An independent analysis of the toxic effects of heat-not-burn products showed that cells exposed to aerosol from heated tobacco had significantly decreased cell death and inflammatory biomarkers, which indicates that particulate matter from e-cigarettes is far less toxic than cigarette smoke.
  • It has also been estimated that use of e-cigarettes reduces human exposure to particulates by approximately 75 percent.
  • E-cigarette aerosol has between 9 and 450 times lower emissions of many volatile organic compounds than combustible cigarettes and these emissions are less complex in their makeup.
  • Tobacco-specific nitrosamines (TSNA) are also up to 1,800 times lower in concentration in e-cigarettes compared to combustible ones. Levels of major TSNA and volatile organic compound metabolites in e-cigarette users—a measure of actual exposure as opposed to potential exposure—were approximately 3 percent that of cigarette smokers.
  • The FDA’s scientific review of both independent studies and data provided in the recent application for marketing approval of the IQOS heat-not-burn device concludes that harmful and potentially harmful constituents in the aerosols of heat-not-burn were reduced by 54-99.9 percent compared to reference cigarettes.
  • Patients who switched completely to e-cigarettes had favorable outcomes in COPD scores compared to those who continued to smoke. There was an improvement in three specific measures of respiratory symptoms and disease progression.

Varenicline and nicotine replacement therapies (NRT)—the most traditional forms of quit tool—are not highly effective at helping smokers quit. In fact, in some cases, randomized, controlled trials show no difference between these products and placebo treatments.

In contrast, there is significant evidence that e-cigarettes help smokers quit. Heat-not-burn technology has contributed to a dramatic decline in cigarette consumption in Japan, where cigarette volumes have fallen by 33 percent in three years.

Despite fears of a youth uptick of e-cigarettes, only 5.7 percent of high school students are habitual e-cigarette users. As e-cigarette use increased, smoking prevalence has decreased, meaning there's no "gateway effect." Trajectory analysis indicates a stronger association from cigarette to e-cigarette use than the other way around. 

Read the full report here