"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."

This argument is fallacious, I believe, because there are many things that changed from one cohort to the next. The introduction of cigarette filters is only one such change. To assume that any observed changes in cancer risk from one cohort to the next must be attributable to one particular change - the filter - is not appropriate, in my view.

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