Several health organizations and consumers have long argued that e-cigarettes are significantly safer than conventional cigarettes. However, Professor Jana Jaal, head of the hematology-oncology clinic at the Tartu University Hospital, said this view is based on outdated expert assessments. According to her, more recent studies at the cellular level suggest otherwise.

"The claim that it is 90 percent safer is certainly not accurate. Even if the damage is smaller, that does not mean there is no risk. Such statements can create a dangerous false sense of security," Jaal emphasized.

Professor Alan Altraja, head of the university hospital's lung clinic, added that vaping does not offer a safe alternative. He said e-cigarettes do not keep lungs healthy but instead cause different types of tissue damage and pathologies than conventional smoking.

Different toxins, same target

Conventional smoking produces well-known carcinogens during the combustion process, such as polycyclic aromatic hydrocarbons and nitrosamines. While these substances are not present in e-cigarette vapor, users inhale a different chemical cocktail. It consists of nicotine, propylene glycol, glycerin, volatile carbonyl compounds and flavorings. In addition, modern high-powered devices deliver toxic gases into the lungs, including nitrogen oxides and carbon monoxide, as well as a range of heavy metals such as nickel, chromium, lead, arsenic and cadmium.

According to Alan Altraja, using high-powered devices can deposit hundreds of micrograms of heavy metals in the lung alveoli with a single puff. These deposited metal particles are toxic to lung cells, cause long-term inflammation and promote fibrotic changes, or scarring of lung tissue.

Both habits directly damage cellular DNA, but through different mechanisms. Jana Jaal explained that in people who vape, oxidative stress in cells is triggered by the heat of the device and the metals found in the vapor. Sweet additives in e-liquids turn into genotoxic compounds and aldehydes when heated in the device. E-cigarette vapor also inhibits the function of enzymes that would otherwise help repair damaged DNA.

What particularly concerns oncologists is that vaping causes rapid epigenetic changes. This means chemicals alter how genes are expressed in cells, essentially programming them into a precancerous state. "Both smoking and vaping cause epigenetic changes that may promote the development of cancer. As oncologists, we can therefore only say that the risk is serious," Jaal said.

Because vaping has been widespread in society for a relatively short time, scientists still do not know whether these profound genetic changes are reversible after a person quits the habit.

Lung damage from the food industry

From the perspective of lung health, flavorings in e-liquids pose a significant risk. Substances widely used in the food industry, such as cinnamaldehyde and diacetyl, are safe when ingested and processed in the stomach. However, Alan Altraja warned that the lungs are not equipped to handle these chemicals.

"Although the respiratory organs evolved from the digestive tract, the airways and lungs are not adapted to receive or process substances that are permitted in the food industry. The lungs are adapted only for breathing air," the pulmonologist explained.

When inhaled, these compounds poison lung cells even if the liquid contains no nicotine. Flavorings disrupt the function of the cilia in the epithelial cells lining the respiratory tract, paralyzing the tiny "brooms" that normally keep airways clear of invading pollutants. Pulmonologists directly associate inhaling diacetyl with bronchiolitis obliterans, a destructive condition commonly known as "popcorn lung."

In addition to chemical toxicity, hot e-cigarette vapor impairs the function of the lungs' cleansing cells, or alveolar macrophages. This makes people who vape significantly more susceptible to viral illnesses such as influenza and coronavirus. At the molecular level, e-cigarettes increase the levels of certain inflammatory proteins in the airways, specifically type 2 cytokines, which promote allergic inflammation. As a result, vaping raises the risk of chronic obstructive pulmonary disease and asthma by nearly one and a half times.

Complex diagnoses

According to doctors, conventional smoking typically causes acute respiratory distress syndrome (ARDS), chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. Vaping, however, leads to a range of atypical lung injuries. These include EVALI (e-cigarette or vaping product use-associated lung injury), eosinophilic pneumonia, alveolar hemorrhage, or bleeding in the lung alveoli, organizing pneumonia and bronchiectasis, or permanent widening of the bronchi.

Alan Altraja said that EVALI, for example, is not simply a mild cough. In cases of acute lung injury, patients often require intensive care and mechanical ventilation. Although the notorious 2019 EVALI outbreak was primarily linked to the cannabis compound THC and vitamin E acetate, the professor noted that severe lung damage occasionally also occurs with standard nicotine liquids.

Doctors find these new conditions very difficult to diagnose because they do not always know what exactly to look for. There are also no specific tests designed for this purpose. Altraja urged physicians to suspect e-cigarette-related damage sooner rather than later in cases of atypical lung disease. This requires compiling a very thorough medical history and examining in detail which substances the patient has actually been exposed to.

Many smokers attempt to reduce health risks by using both conventional and e-cigarettes daily. The professor stressed that dual users achieve no health benefit. "Their lungs are actually under greater strain because they are exposed to both combustion byproducts and the chemicals in e-liquids," Altraja said. In addition to lung disease, dual use also significantly increases the risk of cardiovascular disease.

The professor also pointed out that using e-cigarettes to quit smoking often produces the opposite result. Nicotine dependence strengthens and lung health deteriorates. Biomarker studies show that toxin levels in dual users' bodies begin to decline only when they reduce their consumption to fewer than 10 conventional cigarettes per day. Most dual users, however, do not reach that threshold and continue to smoke heavily.

Even when a long-term smoker receives a cancer diagnosis, doctors do not recommend switching to vaping as a substitute. Jana Jaal explained that cancer treatment is always more effective in nonsmokers. If a patient with lung cancer continues to smoke or use e-cigarettes, about 10 percent of them will develop a new malignant tumor in the lung.

Ticking time bomb

Jana Jaal explained that although nicotine is not considered a primary carcinogen, it directly promotes the rapid progression of tumors that have already developed. Nicotine helps cancer cells multiply, stimulates the growth of new blood vessels in tissue and supports the formation of metastases. "Those who develop tumors and continue to use e-cigarettes are likely to have their disease detected at a significantly more advanced stage," the oncologist warned.

In addition to the lungs, vaping also poses a serious threat to other organs. Because the body eliminates many toxins through urine, doctors cautioned that, similar to conventional smoking, vaping will likely lead to bladder cancer in the future. Jaal drew a parallel with the dye industry. Just as aromatic amines derived from aniline dyes once caused bladder cancer in factory workers, harmful residual products from e-cigarettes accumulate in the bladder before being excreted.

For oncologists, the greatest concern is the long latency period of serious diseases, meaning the true extent of the damage has not yet become apparent. Establishing a link between carcinogens and the clinical manifestation of disease often takes decades. "We are at the beginning of the latency period," Jaal said. "The connection between a risk factor and cancer usually becomes evident only when researchers begin to examine why a particular cancer has suddenly become more common. At the individual level, however, it is already too late by then."

Taking all this into account, both senior physicians consider the widespread use of vaping to be devastating to public health. "From a public health perspective, the net effect on lung health is clearly negative — instead of benefit, there is harm," Altraja said. Globally, he added, e-cigarettes are bringing millions of young people into the lung disease risk group who likely would never have started smoking conventional cigarettes.

A study published last year by the National Institute for Health Development paints a clear picture of e-cigarette use among young people in Estonia. Youth vaping is rising rapidly and the age of first experimentation has dropped, most commonly to between 12 and 14 years old. By 2024, the proportion of girls who had used e-cigarettes in the past month had more than doubled compared with 2019, reaching 28 percent. Among boys, the figure was 21 percent. One in 10 young people had smoked conventional cigarettes in the past month.

Overall, this means that while in 2019 daily use of either conventional or e-cigarettes stood at 13 percent among boys and 10 percent among girls, by 2024 the figures were 13 percent for boys and 16 percent for girls.

The professor emphasized that beyond cancer risk, vaping directly threatens the anatomical development of children's and adolescents' lungs, causing a permanent decline in lung function at an early age. Early initiation also significantly prolongs the period during which carcinogens act in the body.

Jana Jaal warned that this impact does not exist in isolation — the harms of e-cigarettes add to longstanding risk factors such as alcohol use and obesity, as well as newer threats like air pollution and sugary drinks. Taken together, this cocktail will increase the overall cancer burden on society in the future.

Alan Altraja summarized the doctors' position bluntly: "Promoting vaping is a very bad and anti-public health idea. The only health-friendly measure is to quit both smoking and vaping entirely."

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