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Mainstream smoke concentrations (μg/puff) of formaldehyde, acrolein, propionaldehyde, crotonaldehyde, 2-butanone, and butyraldehyde in reference cigarette (1R6F), Marlboro, and of two brands of hemp cigarettes. Columns with vertical bars express the mean + SD (n=4); significance is shown as *p<0.05, **p≤0.01, and ***p<0.001.
