And Dr. Terry failed to stop the study in 1965, even after the 1964 World Health Organization's Helsinki Declaration clearly articulated the ethical imperative of informed consent for human medical experimentation.

"It is not known how much nicotine or other potentially harmful chemicals are inhaled by users, nor is it known whether e-cigarette use may lead to use of other tobacco products. Neither are the benefits of using e-cigarettes over traditional products known."

Whether e-cigarette use precedes smoking or smoking precedes e-cigarette use is a critical question, but it is one which needs to be answered through longitudinal research. We need studies that follow the trajectory of teen tobacco/e-cigarette use over time. That is the only way to determine which comes first.

In fact, one of the complaints in the comment is that "E-cigarette companies are marketing e-cigarettes as healthier alternatives to cigarette smoking."

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