Vaping: Summary of health risks

Vaping, long touted as an alternative to combustible tobacco, is now the subject of a growing body of research assessing its specific effects, independent of smoking. The aerosols emitted by electronic devices contain nicotine—a substance with high addictive potential—as well as other compounds known to be harmful, such as fine particles, carbonyls, and certain metals. According to the World Health Organization, these emissions can pose risks not only to users, but also to those passively exposed.

Recent studies differ from previous work by increasingly focusing on "exclusive vapers," that is, individuals who have never smoked tobacco. These new data show that, even among people who have never smoked, regular e-cigarette use can be associated with various adverse health effects.

This development is all the more worrying as the consumption of vaping products is increasing, particularly among young people, and increasingly affects non-smokers.

Definition and composition of aerosols

E-cigarettes heat a liquid to produce an inhaled aerosol, a liquid that most often contains nicotine as well as solvents (propylene glycol, glycerol), and flavorings. Emissions include ultrafine particles, carbonyls (formaldehyde, acrolein), and metals released by the heating components. Health authorities point out that these emissions are harmful to users and, at lower but real levels, to people passively exposed.

Nicotine dependence and acute toxicity

The nicotine delivered by e-cigarettes is the main factor in addiction. The latest generation of devices, particularly those using high-concentration nicotine salts, allow for rapid absorption, comparable or even superior to that of a combustible cigarette. This rapid absorption promotes the development of addiction, which is even more pronounced in adolescents, whose brains are more vulnerable to the neurobiological effects of nicotine. The report[1] of the National Academies of Sciences (NASEM) points out that there is substantial evidence that e-cigarette use leads to nicotine addiction and increases the risk of later initiation of combustible tobacco use. The WHO remember also that exposure to nicotine leads to lasting addiction and increased risks of brain development disorders in adolescents.

Nicotine also has physiological effects, including an increase in heart rate and blood pressure, stimulation of the central nervous system and the release of catecholamines (hormones and neurotransmitters such as adrenaline and noradrenaline, involved in the stress response and increases in heart rate and blood pressure), which can lead to long-term cardiovascular consequences.

Regarding acute toxicity, several thousand cases of accidental exposure to e-liquids are reported to poison control centers each year, particularly among children under five years old. An analysis of the American National Poison Data System (NPDS) shows that nearly 90% of poisonings occur in this age group, often following accidental ingestion of flavored liquids. Although these exposures must be taken into account to be prevented, they are fortunately very rarely serious.[2]

Finally, handling concentrated e-liquids can lead to skin or eye exposure, causing chemical burns and transient neurological symptoms. These accidents remain rare but are documented in pharmacovigilance databases.

Respiratory system: symptoms, asthma, COPD and acute injuries

E-cigarette use is now associated with an increase in respiratory problems. Clinical studies show that vapers experience symptoms such as coughing, wheezing, and shortness of breath more often than non-users. A 2023 systematic review with meta-analysis concluded that these symptoms are significantly more common in both exclusive users and those who both vape and smoke (vape-smokers). [3].

Regarding asthma, several large-scale studies provide precise numerical data. A meta-analysis published in 2022, involving more than 450,000 adolescents, indicates that vapers have a 39% increased risk of being diagnosed with asthma compared to non-users, and a 44% increased risk of experiencing exacerbations of attacks.[4]. Finally, theumbrella review published in 2025 in Tobacco Control confirms the robustness of these associations and highlights their consistency in various contexts, despite the heterogeneity of the methods[5].

Scientific attention has recently focused on the long-term respiratory effects of vaping, particularly the risk of chronic obstructive pulmonary disease (COPD). A large longitudinal study published in 2025 by the University of Oxford

The effects of vaping on the lungs have also manifested in severe acute forms, in a particular situation. In 2019, the United States experienced an epidemic of severe lung injuries grouped under the term EVALI (E-cigarette or Vaping Product Use-Associated Lung Injury). More than 2,800 hospitalizations and 68 deaths have been recorded (American Lung Association – EVALI). But these serious accidents were related to the misuse of electronic cigarettes. Indeed, the investigations revealed that the majority of cases were linked to vaping liquids containing THC adulterated with vitamin E acetate, which was detected in almost all of the bronchoalveolar fluids of affected patients. This type of event is a reminder, given the widespread practice of "do it yourself", that only products duly labeled for vaping should be used. It also illustrates the pulmonary vulnerability to various chemical additives that could be in certain vaping products[7].

Cardiovascular system: hemodynamic and vascular effects

The impact of vaping on the cardiovascular system has been the subject of extensive research. While data on long-term effects are still limited, experimental and clinical studies already show an impact on intermediate markers.

The acute effects of nicotine inhaled via e-cigarettes are comparable to those produced by nicotine inhaled from a cigarette, namely a transient elevation in heart rate and an increase in systolic blood pressure within minutes of inhalation, compared to baseline. These findings have been documented in several laboratory clinical trials[8]A 2022 meta-analysis of 23 studies confirms these trends, concluding that e-cigarette use causes an average increase in heart rate of 5 to 8 beats per minute.[9].

Vascular health data also suggests changes in various markers. A meta-analysis published in 2024 showed that people who vape regularly have blood vessels that dilate less well than those of non-users. The observed decrease is on average 1.5 % (identical to that caused by a combustible cigarette), which reflects an alteration in endothelial function (the ability of the vessel wall to dilate and regulate circulation).[10]A study in healthy young adults found that regular vaping reduced the ability of small blood vessels to dilate properly by about 14 %. This is linked to a reduced action of nitric oxide (NO), a key molecule that normally helps vessels widen and regulate circulation properly.[11].

Biological analyses show that vapers have blood markers linked to inflammation and oxidative stress that are on average 20 to 30 % higher than non-users. In concrete terms, this means that their bodies show more signs of inflammation and cell damage caused by free radicals, two phenomena known to increase the risk of cardiovascular disease.[12]These mechanisms contribute to a theoretical cardiovascular risk, even if long-term follow-up data are still insufficient to draw a definitive conclusion.

Major public health institutions are urging caution. The National Academies of Sciences (NASEM) report states that there is strong evidence that exposure to e-cigarette aerosols immediately causes autonomic nervous system stimulation and effects on blood circulation (increased heart rate and blood pressure). However, the available data do not yet definitively confirm a direct link with heart attacks, strokes, or cardiovascular mortality.[13].

In summary, studies converge to show that vaping induces immediate hemodynamic changes (increase in heart rate and blood pressure), measurable damage to endothelial function and arterial stiffness, as well as an increase in markers of oxidative stress. These effects, although often less intense than those associated with smoked tobacco, reflect real cardiovascular toxicity, which requires long-term monitoring to quantify the clinical consequences.

Carcinogenicity: state of knowledge

E-cigarette aerosols contain several known or possible carcinogenic compounds. formaldehyde is classified as “carcinogenic”[14] for humans (Group 1)” by IARC/CIRC, and its involvement in certain cancers (nasopharynx, leukemia) is established, which justifies considering any inhaled exposure as a long-term risk[15]-[16]. L'acetaldehyde, frequently measured in aerosols, is classified as “possibly carcinogenic to humans (Group 2B)”[17]Metals from resistors (notably nickel and chromium) are sometimes detected; nickel compounds and hexavalent chromium compounds (a toxic and carcinogenic chemical substance used in industry, particularly in anti-corrosion treatments and pigments) are classified as carcinogenic (Group 1), which fuels concern when their emissions are high.[18].

In terms of real-life exposure, the data converge: among exclusive e-cigarette users, exposure to many toxicants drops sharply compared to that of smokers. In a study by Shahab et al., the urinary biomarker NNAL (a metabolite of a powerful tobacco carcinogen, NNK) is very significantly reduced by around ~97 % in exclusive vapers compared to smokers.[19]. Representative cohort analyses show, in a more nuanced way, that 16 to 18 non-nicotine biomarkers of exposure (BOE) are significantly lower in exclusive vapers than in smokers, and 9 biomarkers do not differ from non-users, confirming a strong overall reduction in exposure, provided that vaping is associated with complete smoking cessation.[20]. In smokers who switch to e-cigarettes, NNAL levels decrease by 55 % to 84 %, depending on the time since quitting. The decreases are greatest after six months, highlighting the importance of completely and sustainably replacing cigarettes with vaping to reduce exposure.[21]Conversely, dual use (tobacco + vaping) does not provide the same benefits: most non-nicotine biomarkers remain close to the smoker profile, with little or no decrease when cigarette consumption remains high.[22]-[23].

The formation of carbonylates (formaldehyde, acetaldehyde) varies greatly depending on the device, the power and the way of drawing (puff topography). Studies have shown very high levels of aldehydes in so-called "dry puff" conditions (but in these conditions, acrid puffs, not tolerated by the vaper), whereas in normal usage conditions, emissions are significantly lower; this does not cancel out the risk but replaces the orders of magnitude of exposure[24]-[25]. Other experimental studies, in conditions of longer or larger puffs or higher powers, show on the contrary a significant increase in carbonyls, recalling that use in real situations can increase the dose received if we compensate for a less nicotine liquid with more intense puffs.[26].

Biologically, some markers of inflammation and oxidative stress (excess free radicals that can cause cellular damage) remain higher in vapers than in non-smokers, even though they are lower than in smokers. This therefore reflects an intermediate exposure.[27]-[28]. Several studies that have directly compared different user profiles – exclusive smokers, vapers who have completely quit smoking, dual users, and non-users – confirm this trend. Exclusive vapers are thus in an intermediate position, with reduced exposure compared to combustible tobacco, but which does not disappear entirely. These results show that, even without tobacco, vaping is not without measurable biological impact. They also highlight the need for large-scale longitudinal studies to determine the extent to which these markers translate into long-term clinical consequences. Recent research shows that vaping can modify the DNA of certain cells in the mouth, with changes partially similar to those observed in smokers and linked to mechanisms of cancer development. This constitutes a warning signal, but there is still no direct evidence of an increased risk of cancer at this stage.[29][30][31].

Regarding metals (lead, nickel, chromium, antimony) and other contaminants in some recent devices, recent publications report sometimes high levels in pod/disposable aerosols, with great variability between products. Consumption patterns also play an important role: heating power, frequency and depth of puffs directly influence the quantity of metal particles inhaled. These factors increase the uncertainty about the extent of actual exposure and its long-term effects. This heterogeneity requires separate independent characterizations to estimate the potential carcinogenic risks linked to repeated exposures to metals classified as carcinogens (e.g. nickel or chromium VI compounds).[32].

From an epidemiological perspective, the latency of cancers and the recent nature of vaping still limit the possibility of firm conclusions. The National Academies (NASEM) concluded in 2018 that there was insufficient data to quantify a cancer risk linked to vaping; recent updates mainly confirm reductions in exposure and mechanistic signals (biological indices such as inflammation, oxidative stress or DNA damage, suggesting potential disease mechanisms without establishing a direct clinical risk at this stage). The excess risk of incidence in long-term exclusive users had not been established.[33][34]. THE  analyses Ongoing studies and recent presentations now suggest associations in former smokers who continue to vape, but residual confounding by smoking history requires cautious interpretation and calls for better-controlled cohorts.

In summary, current data confirm that vaping significantly reduces (often > 50 %) exposure to many carcinogens compared to smoked tobacco when use is exclusive and long-term, but that it is not devoid of carcinogenic/suspect compounds or biological effects compatible with carcinogenic potential. In the absence of sufficient epidemiological hindsight, uncertainty remains regarding the long-term cancer risk in exclusive users; the avoidance of dual use and the maximum reduction of exposure (regulated products, moderate power/puff settings) remain decisive in practice. However, it should be remembered that, in the management of smoking cessation, there are already validated, effective and risk-free treatments, which constitute the reference options for supporting smokers.

Oral health

The study "Electronic Cigarettes and Oral Health"[35] published in 2021 highlights that, although clinical evidence remains limited, several signals converge towards negative effects of vaping on oral health. Laboratory research shows that e-cigarette aerosols can cause cytotoxicity, oxidative stress, and inflammation of oral mucosal cells. On the microbiological level, changes in the oral microbiota have been observed, suggesting a more favorable environment for the development of pathogenic biofilms. Available clinical studies report a higher frequency of dry mouth, irritation, and gingival sensitivity in users, as well as an intermediate risk of gingival and periodontal diseases, higher than that of non-smokers but lower than that of tobacco smokers. Some epidemiological data also report an increase in the use of tooth extraction for caries or periodontal disease among daily vapers. Although knowledge remains incomplete due to the lack of perspective and the diversity of practices, these elements call for caution and confirm the need to closely monitor the impacts of vaping on oral health.

Pregnancy and reproduction

A meta-analysis showed that pregnant women using e-cigarettes had a 39% increased risk of preterm birth, 64% low birth weight, and 59% small for gestational age.[36]These results, consistent with established data on smoked tobacco, reinforce the need to discourage vaping among pregnant women. Another French meta-analysis[37] A recent study comprising 9 studies and including more than 400,000 pregnancies confirms these results, with an increase of 40% in premature births, 49% in low birth weight and 32% in small for gestational age. Note, however, that these deleterious perinatal effects are lower than those observed in pregnant women who continue to smoke or who use tobacco + vape.[38]However, these results reinforce the need to discourage vaping among pregnant women.

Effects on male fertility are also beginning to be documented. A large cross-sectional study in Denmark of over 1,200 young men from the general population found a significant association between daily e-cigarette use and a decrease in total sperm count. Daily users had an average of 91 million sperm, compared to 147 million in non-users—a substantial reduction comparable to that observed in tobacco smokers. These findings suggest that repeated exposure to e-cigarette aerosols may impair spermatogenesis.[39].

In summary, the available data indicate that the use of e-cigarettes during pregnancy is associated with a 40 to 50 % increase in the risk of obstetric complications (prematurity, low birth weight, growth retardation), and that in men, it is linked to a reduction of approximately 40 % in sperm production. Learned societies and international organizations therefore recommend total abstinence from tobacco products and vaping during pregnancy and advise against the use of e-cigarettes as a means of weaning in this context, in favor of validated methods, such as cognitive behavioral therapies and, failing that, supervised pharmaceutical nicotine replacement.

Mental health

The link between vaping and mental health is receiving increasing attention in the scientific literature. Several observational studies have highlighted significant associations between e-cigarette use and depressive and anxiety symptoms, particularly among adolescents and young adults. A CDC analysis of American middle and high school students found that 42.1% of young vapers experienced moderate to severe symptoms of depression or anxiety, compared to 21% of non-users—about twice as often.[40]However, the cross-sectional nature of this study does not allow us to establish a cause-and-effect relationship.

A study published in 2025 confirms these results: among adolescents who had only used e-cigarettes, 35.9 % reported depressive symptoms and 40.5 % anxiety symptoms, compared to 21.8 % and 26.4 % respectively among non-users. After adjustment, e-cigarette use was associated with an increased risk of 67 % for depression, 48 % for anxiety, and 63 % for psychological distress.[41].

The mechanisms explaining these links remain debated. The most commonly put forward hypothesis is that of a bidirectional effect: on the one hand, young people with depressive or anxiety symptoms would be more likely to experiment with vaping as a coping strategy; on the other hand, nicotine could exacerbate mood disorders via its action on the dopaminergic and cholinergic systems (this system plays a key role in memory, attention, muscle control, as well as in certain involuntary functions such as heart rate or digestion), promoting addiction and psychological vulnerability.

Passive exposure

Contrary to popular belief, e-cigarette aerosols are not just "water vapor": they contain nicotine, fine particles, and various volatile organic compounds that can expose those around vapers. Environmental studies have shown that nicotine concentrations in ambient air during e-cigarette use are lower than those observed with tobacco smoke, but not zero. These data are confirmed by biomarkers. Under controlled conditions, e-cigarettes increase the nicotine concentration in indoor air, but to levels much lower than those caused by cigarettes: in the reference study (exposure chamber), the average airborne nicotine was approximately 3.3 µg/m³ with an e-cigarette compared to 31.6 µg/m³ with a cigarette (i.e., ≈ 10 times lower), while remaining non-zero.[42]In real life (at home), non-users living with vapers absorb nicotine: a study[43] ambient nicotine levels and biomarkers (saliva/urine, cotinine) shows that they are higher in homes where exclusive vapers reside compared to homes without tobacco/vaping. However, these levels are significantly lower than those observed in cohabitants of smokers. In children, another study[44] shows that nicotine absorption is ~84 % lower in cases of passive exposure to vaping than in cases of exposure to cigarette smoke, but it is higher than that of unexposed children. More generally, literature reviews confirm that the use of e-cigarettes degrades indoor air quality (increase in fine/ultrafine particles), but this degradation is generally lower than that induced by tobacco products which contain a very large number of toxic elements[45].

WHO remember that passive exposure to e-cigarette aerosols can pose risks, particularly for children, pregnant women, and people with respiratory or cardiovascular conditions. The WHO emphasizes that while exposure levels are generally lower than those induced by smoked tobacco, they are far from harmless and justify the application of the same protection policies in enclosed spaces.

In conclusion, the data show that a complete replacement of cigarettes with e-cigarettes reduces exposure to many toxicants compared to smoked tobacco; nevertheless, “less harmful than smoking” does not mean risk-free, and uncertainty remains about long-term effects, particularly for cardiovascular disease and cancer. The clinical priority remains to prevent initiation in non-smokers and to prevent dual use in smokers.

Furthermore, these data also encourage the widespread and priority use of cessation aid treatments that have long been validated and recommended by health authorities (HAS, HCSP). And when the electronic cigarette has been used for the purpose of cessation, it is appropriate to support the user for optimal and safest management, and given the uncertainties about the long-term effects, help them stop using it as soon as possible as soon as tobacco cessation is sufficiently assured.

©Generation Without Tobacco

AE

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