Vaping exposes you to significantly fewer toxic substances than smoking cigarettes, though it is not risk-free. The key difference comes down to combustion: burning tobacco generates thousands of chemicals, including dozens of known carcinogens, while e-cigarettes heat a liquid into an aerosol without combustion. Public Health England has stated that vaping is “at least 95% less harmful than smoking,” though that figure is an estimate based on limited data and remains debated among scientists. The Royal College of Physicians puts it more conservatively, concluding that vaping poses “a small fraction of the risk of smoking” over the short and medium term.
Carbon Monoxide and Combustion Byproducts
One of the clearest measurable differences between smoking and vaping is carbon monoxide exposure. When tobacco burns, it produces carbon monoxide that enters your bloodstream and reduces your blood’s ability to carry oxygen. This strains your heart and contributes to cardiovascular disease over time.
Exhaled carbon monoxide levels tell the story plainly. Tobacco smokers average about 6.86 parts per million (ppm) of carbon monoxide in their breath, while e-cigarette users average just 1.61 ppm. That’s roughly a fourfold difference. For context, nonsmokers typically measure between 0 and 4 ppm, meaning vapers fall within or very close to the normal range while smokers consistently exceed it.
What Happens to Your Lungs
A five-year study tracked people with chronic obstructive pulmonary disease (COPD) who switched from cigarettes to e-cigarettes and compared them to COPD patients who kept smoking. The results were striking. The group that switched to vaping showed significant, sustained improvements in lung function across the entire observation period. Their ability to exhale air forcefully and their total lung capacity both improved compared to their baseline measurements. Meanwhile, the group that continued smoking saw their lung function gradually decline, which is the expected trajectory for smokers with COPD.
The switchers also improved on a standardized walking test and reported fewer symptoms over the five years. This doesn’t mean vaping healed their lungs, but it suggests that removing combustion from the equation allowed their bodies to partially recover rather than continuing to deteriorate.
Cardiovascular Effects Are More Complicated
The heart and blood vessel picture is less clear-cut than the lung data. Several studies have found that vaping affects blood vessel function in ways that look uncomfortably similar to smoking. In one human study, exclusive e-cigarette users showed changes in blood vessel stiffness and reduced production of nitric oxide (a molecule that keeps blood vessels flexible) comparable to what’s seen in cigarette smokers.
A 2022 study added nuance to this: while both vaping and smoking impaired blood vessel dilation, the two habits affected different biological markers. Vapers showed elevations in some cardiovascular risk markers that smokers didn’t, and smokers showed elevations in others that vapers didn’t. In other words, vaping isn’t simply a milder version of smoking when it comes to your blood vessels. It may cause a different pattern of cardiovascular stress. A 2023 study also found that vaping triggered increased blood clot formation and reduced function in small blood vessels, with both effects linked specifically to the nicotine in the aerosol.
This is one area where the “95% safer” estimate looks less convincing. Your lungs clearly benefit from switching, but your cardiovascular system may still face meaningful risks from nicotine delivery regardless of the source.
Gum and Dental Health
A systematic review and meta-analysis examining periodontal health found a clear gradient of risk. Nonsmokers had the healthiest gums, e-cigarette users fell in the middle, and cigarette smokers had the worst outcomes. Among people with gum disease, cigarette smokers had significantly deeper gum pockets and more plaque buildup than vapers. Vapers still had worse periodontal health than nonsmokers, with notably higher plaque levels, but the damage was less severe than what smoking causes.
Secondhand Exposure Is Substantially Lower
If you live with other people, the difference in secondhand exposure is significant. Indoor air nicotine concentrations from cigarette smoke average about 31.6 micrograms per cubic meter, roughly ten times higher than the 3.3 micrograms per cubic meter produced by e-cigarettes. Fine particulate matter, the tiny particles that penetrate deep into the lungs of bystanders, was seven times higher from cigarette smoke (819 µg/m³) compared to e-cigarette aerosol (152 µg/m³).
Crucially, e-cigarettes produced no measurable combustion toxicants in the surrounding air. Secondhand cigarette smoke contains carbon monoxide, formaldehyde, and other byproducts of burning tobacco. E-cigarette aerosol exposed bystanders to some nicotine and particulate matter, but not to those combustion-specific toxins.
Vaping as a Quit-Smoking Tool
A Cochrane review, considered the gold standard for evaluating medical evidence, found high-certainty evidence that nicotine e-cigarettes help people quit smoking more effectively than traditional nicotine replacement products like patches and gum. People using e-cigarettes were 59% more likely to successfully quit. In practical terms, that translates to about four additional people quitting for every 100 who try, compared to nicotine replacement therapy.
That may sound modest, but smoking cessation is notoriously difficult, and any meaningful improvement in quit rates has large public health implications when applied across millions of smokers.
What We Still Don’t Know
The honest limitation is time. E-cigarettes have only been widely used since the early 2010s, and the diseases caused by smoking, such as lung cancer, heart disease, and emphysema, typically develop over 20 to 40 years. The Royal College of Physicians has noted that it will take several decades to accurately measure the long-term effects of vaping, especially in people who have never smoked cigarettes. Most existing studies involve small sample sizes, and many vapers are former smokers, making it difficult to separate the effects of vaping from residual damage caused by years of smoking.
What the current evidence supports is that vaping is considerably less harmful than continuing to smoke. It produces far less carbon monoxide, dramatically reduces secondhand exposure, preserves lung function better over time, and causes less periodontal damage. But “less harmful” is not the same as harmless. The cardiovascular data in particular suggest that nicotine delivered by any method carries real risks for your heart and blood vessels. For current smokers, switching represents a meaningful reduction in harm. For nonsmokers, there is no health reason to start.