Globally, there are 1.1 billion adult smokers, 60% of them want or intend to quit. Much has been written and said about the potential of electronic nicotine delivery systems (ENDS) such as e-cigarettes to help tobacco users quit. While the evidence is still inconclusive, e-cigarettes are often used along with one or more tobacco products. As this is the practice with many ENDS users, the health effects of two or more products are combined.