When the liquid is heated, small amounts of aldehydes, especially formaldehyde, are formed. Formaldehyde is an endogenous metabolite that circulates in the blood and is exhaled by humans. During normal use, the vapor contains similar concentrations of formaldehyde as the ambient air. There are also frequent warnings about nitrosamines in steam. Nitrosamines are contained in almost all foods; these compounds can only be detected in trace amounts, if at all, in the aerosol of e-cigarettes. According to the basic pharmacological law of dose dependence of effects, there is always a concentration or dose of a substance that does not have a harmful effect. Otherwise, limit values ​​for pollutants in the environment and food would be meaningless. Quoted from: KARL FRANZENS UNIVERSITY GRAZ INSTITUTE OF PHARMACEUTICAL SCIENCES - Pharmacology and Toxicology - Head: 0. Univ.-Prof. Dr. Bernhard Michael Mayer