Vaping vs Smoking

This question matters most for two groups: people who smoke and are considering switching, and people who vape and want to know what they are actually exposed to. The answer is different for each, because the right comparison depends on what you are deciding.

What the toxicology shows

Cigarette smoke contains over 7,000 chemicals, at least 70 of which are established carcinogens. E-cigarette aerosol contains many of the same compounds but at dramatically lower levels. A 2014 analysis found that carcinogens in e-cigarette vapor were 9 to 450 times lower than in cigarette smoke [3].

The reduction is not uniform across all compounds. Some toxicants are reduced by orders of magnitude; others, particularly those formed by the thermal decomposition of propylene glycol and glycerin (like formaldehyde and acrolein), are present at lower but not negligible levels. The specific device matters: higher-wattage devices operating at higher temperatures produce more thermal degradation products, narrowing the gap with cigarette smoke for those particular compounds [5].

A biomarker study by Shahab and colleagues compared long-term exclusive vapers, NRT users, and smokers. Exclusive vapers had significantly lower levels of tobacco-specific nitrosamines (a major carcinogen class) and volatile organic compounds than smokers, and their levels were comparable to NRT users [4]. The key word is “exclusive”: dual users, people who vape and smoke, showed little reduction.

That dual-use finding is important because a significant proportion of vapers continue to smoke as well. If you smoke five cigarettes a day and vape the rest of the time, you are still getting the combustion exposure from those five cigarettes. The harm reduction only materializes when the switch is complete.

The 95% figure

In 2015, Public Health England published an expert review estimating that e-cigarettes are roughly 95% less harmful than combustible cigarettes [1]. This figure has been widely cited and also widely debated. The criticism is not that the estimate is wrong in direction (vaping clearly produces fewer and lower-level toxicants) but that “95%” implies a precision the evidence cannot support, and that the estimate focused on toxicant exposure rather than measured long-term health outcomes.

The 2018 National Academies of Sciences report offered a more cautious framing: “there is conclusive evidence that completely substituting e-cigarettes for combustible tobacco cigarettes reduces users’ exposure to numerous toxicants and carcinogens present in combustible tobacco cigarettes” [2]. The direction is clear; the exact magnitude remains a reasonable estimate rather than a measured outcome.

There is an important distinction between toxicant exposure and health outcomes. A 95% reduction in toxicant exposure does not necessarily translate to a 95% reduction in health risk. Some effects may have thresholds below which they do not matter; others may not. The relationship between exposure and disease is not always linear, and the long-term outcomes data that would answer this question does not yet exist.

What cigarettes actually do

To understand the comparison, it helps to know what makes cigarettes as dangerous as they are. Cigarette smoke is a product of combustion: burning organic matter at 600-900 degrees Celsius in the coal and 400 degrees during a puff. This combustion generates tar (a collective term for the particulate matter), carbon monoxide, hydrogen cyanide, ammonia, and thousands of other compounds, many of them carcinogenic.

Carbon monoxide binds to hemoglobin with roughly 200 times the affinity of oxygen, reducing the blood’s oxygen-carrying capacity. This is a major contributor to smoking-related cardiovascular disease. Tar deposits in the lungs, impairing gas exchange and driving the chronic inflammation that leads to COPD and emphysema. The carcinogens in smoke directly damage DNA, initiating the mutations that can lead to cancer.

Vaping eliminates the combustion. There is no burning, no tar, no carbon monoxide. The aerosol is produced by heating liquid to roughly 200-300 degrees Celsius, well below the temperatures that generate the most harmful combustion products. This is the fundamental reason the toxicant profile is so different.

The nicotine question

Nicotine is the addictive compound in both products. It raises heart rate, constricts blood vessels and has real cardiovascular effects [6]. But nicotine is not the primary reason cigarettes kill people. The mortality from smoking is driven by combustion products: tar, carbon monoxide, and the carcinogens formed when tobacco burns. Remove the combustion, as vaping does, and you remove the largest share of the toxicant burden.

This is why NRT, which also delivers nicotine, is considered safe enough for over-the-counter sale. The addictive potential of nicotine is a separate problem from the toxicity of the delivery system.

That said, nicotine is not benign. Its cardiovascular effects are real: chronic sympathetic nervous system activation, increased heart rate and blood pressure, and elevated oxidative stress markers in habitual users [6]. For someone who switched from smoking to vaping, the nicotine burden is similar (or higher, with modern pod devices), even though the combustion-related burden is gone. The cardiovascular risk is reduced but not eliminated.

The exposure comparison in practice

For a smoker who switches completely to vaping, the reduction in harmful exposure is substantial and begins immediately. Carbon monoxide levels drop to normal within 24 hours. Carcinogen biomarkers decline measurably within days to weeks [4]. The respiratory irritation from tar stops. The chronic CO-mediated reduction in oxygen-carrying capacity resolves.

These are real, meaningful health improvements. For someone who smokes a pack a day, switching completely to vaping is one of the most significant harm-reduction steps available short of quitting nicotine entirely. The evidence for this is consistent and strong.

For a never-smoker who vapes, the comparison to cigarettes is irrelevant. The baseline is not smoking; the baseline is not using any nicotine product. Against that baseline, vaping introduces nicotine dependence, airway irritation, cardiovascular stimulation, oral health effects, and exposure to aerosolized compounds that the lungs were not designed to process. The question for this group is not “is this better than smoking?” It is “what am I adding to a body that otherwise would not have these exposures?”

Where the comparison breaks down

The comparison to cigarettes is useful for harm reduction: if you smoke and cannot or will not quit nicotine entirely, switching to exclusive vaping reduces your toxicant exposure substantially. But the comparison is the wrong frame for someone who vapes and is deciding whether to quit.

“Less harmful than cigarettes” sets the bar at the single most deadly consumer product ever manufactured. Almost anything clears it. For a current vaper, the relevant comparison is not “is this worse than cigarettes?” It is “what am I exposed to that I would not be exposed to if I quit?” And the answer to that is: nicotine, propylene glycol, vegetable glycerin, flavoring compounds, and lower levels of some toxicants that are still present [5].

The device is not a health product. It is a nicotine delivery system that happens to be dramatically less toxic than the previous dominant delivery system. That is a meaningful improvement for someone transitioning away from cigarettes. It is not a reason to start, and it is not a reason to continue if you are considering stopping.

What remains uncertain

The long-term cancer risk from exclusive vaping is unknown. The exposure levels of established carcinogens are lower, which is encouraging. Whether those lower levels translate into meaningfully lower cancer risk over 20 or 30 years is a question that requires 20 or 30 years of data. We are roughly halfway through the first generation of that data.

The respiratory long-term picture is similarly incomplete. Cigarettes cause COPD through decades of cumulative damage. Whether the lower-level but chronic irritation from vaping causes a comparable condition at lower rates, at a slower pace, or not at all is the question the current research cannot answer. The acute effects are documented; the chronic trajectory is the unknown. Some researchers have raised concerns about the effects of propylene glycol and vegetable glycerin on airway inflammation over years of daily inhalation, but the data to support or refute those concerns at the population level does not yet exist.

What we do know is the direction of every piece of evidence: less toxic than cigarettes, more exposure than not using either. The magnitude of the harm from long-term exclusive vaping is what remains to be measured.

If you are a smoker considering switching: the evidence supports vaping as a harm-reduction step, and the reduction in toxicant exposure is real and large. If you are a vaper considering quitting: the evidence supports quitting, and the question of whether vaping is safer than smoking is not the one that matters for you. The question that matters is whether you want to continue inhaling an aerosol your lungs were not designed for, at a dose your cardiovascular system notices, for a benefit that consists primarily of managing the dependence the device created.

The harm-reduction frame is valuable when it moves someone from a more dangerous product to a less dangerous one. It stops being useful when it becomes a reason to stay on the less dangerous product indefinitely. “Better than cigarettes” is a reason to switch. It is not a reason to keep vaping once the switch has served its purpose and quitting becomes the next step. That next step is achievable, the withdrawal follows a predictable timeline, and the tools that help are well-documented on this site.

If you’d like support quitting, the Quitline (1-800-QUIT-NOW in the US) and smokefree.gov have free resources. Your doctor or pharmacist can also advise on NRT.