A recent study published in JAMA Network Open, a journal of the American Medical Association (JAMA), found that e-cigarettes have a harm reduction effect and that when smokers switch completely to e-cigarettes, their physical health improves. In contrast, when e-cigarette users went back to smoking, their urine concentrations of several carcinogen metabolites increased significantly, by up to 621%
The study, supported by the National Institute on Drug Abuse (NIDA), followed more than 3,000 adult smokers across the United States for up to a year. The researchers looked at the "transition period" in which many smokers go through a mixture of cigarettes and e-cigarettes before switching completely to e-cigarettes. The results showed that when smokers became both cigarette and e-cigarette users, there was little change in the concentration of metabolites in their urine for tobacco hazards, and the mixed pattern did not make smokers any healthier.
But both smokers and dual users who switched completely to e-cigarettes had significantly lower concentrations of the metabolites responsible for tobacco hazards in their urine. For example, smokers and dual users who switched to e-cigarettes had a 92% and 96% reduction in urine NNAL concentration, respectively, which is a level 1 carcinogen and highly associated with lung cancer.
To test their conclusions, the researchers also reverse-tracked what happened to e-cigarette users when they switched to cigarettes. The data showed that concentrations of nicotine metabolites in urine increased threefold when e-cigarette users became dual users. E-cigarette users who went back to smoking were worse off: urine concentrations of PAHS metabolites increased by 155% and VOC metabolites increased by 621%. Both POLYcyclic aromatic hydrocarbons (PAHs) and VOCs (VOC) are extremely harmful carcinogens, which are associated with various diseases such as leukemia, bladder cancer and neurocognitive disorders.
The cost of returning to cigarette smoking is high, and the mixed use mode is not desirable. Only by completely switching to e-cigarettes can the harm be reduced. In recent years, a number of global studies have confirmed this conclusion. The American Heart Association (AHA) noted in 2020 that smokers who switched to e-cigarettes had improved cardiovascular outcomes, and that the common mix failed to reduce the risk of cardiovascular disease and was "completely ineffective."