If you use e-cigarettes (or a PV) every day, what effect has this had on the number of tobacco cigarettes you smoke per day? The researchers refer to this measure as CPD.
If you did not smoke before taking up use of a PV, don't select an answer in the poll, because use of PVs by non-smokers is a different issue and deserves its own poll.
If you did not smoke before taking up use of a PV, don't select an answer in the poll, because use of PVs by non-smokers is a different issue and deserves its own poll.
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