People, particularly younger people, tend to think waterpipes, or hookahs, and e-cigarettes are safer alternatives to tobacco cigarettes. The number of waterpipe and e-cigarette users has increased significantly, with e-cigarettes becoming the most popular smoking product in the U.S. in 2014.

However, a growing body of evidence suggests that e-cigarettes are not as harmless as first believed. Researchers are trying to determine whether vaping is saving smokers’ lives or just generating a new generation of nicotine addicts.

E-cigarette vapor includes formaldehyde and acrolein, and traces of chemicals called transition metals and volatile organic compounds, which can damage cells.

An international group of scientists has published a review study comparing the effects of the three types of smoking and vaping on human health. The review found that smoking and vaping stiffens arteries, causes inflammation and damages DNA. These effects can lead to health problems such as cardiovascular disease. “All three forms of smoking and vaping lead to an increased production of free radicals in blood vessels,” lead author, Thomas Münzel, said in a statement. “Free radicals break down nitric oxide, which is important for helping blood vessels dilate, and protects against inflammation and clogging of the arteries.”

The researchers reviewed data from about 100 studies, rating them as providing a strong, good or medium level of evidence about the harm caused from smoking tobacco cigarettes and waterpipes, and vaping e-cigarettes. Based on good evidence, tobacco cigarette smokers had a more than 700 percent increased risk of chronic obstructive pulmonary disease (COPD), and strong evidence that waterpipe users had a greater than 200 percent increased risk of COPD. Vapers had a nearly 200 percent increased risk of COPD, also based on good evidence.

There was strong evidence that tobacco smokers had a more than 1200 percent increased risk of lung cancer compared to non-smokers, and waterpipe users had nearly a 125 percent increased risk of lung cancer. There was not enough evidence to draw conclusions about the link between e-cigarette use and lung cancer risk. That mode of nicotine delivery is too new.

Tobacco cigarette smoking and waterpipe use also made COVID-19 symptoms worse compared to not smoking, and increased the risk of intensive care unit admission and need of a ventilator.

The review's conclusions are consistent with what is already known: both cigarette smoking and waterpipe use are harmful to many organs in the body, including the cardiovascular and the respiratory systems, Ahmad Besaratinia, a researcher who was not involved in the study, told TheDoctor.

Vaping causes damage to many of the same systems as tobacco cigarettes, probably because e-cigarette vapor contains many of the same toxic chemicals as tobacco cigarette smoke, but at lower concentrations, Besaratinia, an associate professor of research at the Keck School of Medicine at the University of Southern California, said.

E-cigarette vapor includes formaldehyde and acrolein, and traces of chemicals called transition metals and volatile organic compounds, which can damage cells. Cigarette smoke and waterpipe smoke contain an even more complex mixture of dangerous chemicals that, according to Münzel, a member of the department of cardiology of the University Medical Centre Mainz, Germany, need further study.

Besaratini agrees. “E-cigarettes are a relatively new technology, so the long-term effects of vaping are not as well established. Cancer is a disease that develops over many decades. In order to study the cancer-causing potential of a chemical or substance in humans, we need to study users over a long period of time.”

The study is published in the European Heart Journal.