Table 2.

Levels of biomarkers in 22 e-cigarette users (E, 8 male), 63 non-smokers (N, 21 male), and 33 smokers (S, 16 male) in urine samples collected monthly for 4-6 months. Among the groups, the number of monthly visits completed were: e-cigarettes - 22 participants completed 6 visits; non-smokers - 55 completed 6, 3 completed 5, 5 completed 4; smokers - 29 completed 6 and 4 completed 4. Samples from all completed visits were used in the analysis.

Biomarker	Group	Geometric mean	95% CI	Group p-value	Pairwise
3-HPMA (acrolein) pmol/ml	Non-smokers	679.3	554.2, 832.4	<0.001	E vs S, p<0.001
	E-cig users	1249	885.7, 1762		E vs N, p=0.003
	Smokers	5576	4210, 7384		N vs S, p<0.001
SPMA (benzene) pmol/ml	Non-smokers	0.12	0.09, 0.17	<0.001	E vs S, p<0.001
	E-cig users	0.17	0.10, 0.30		E vs N, p=0.250
	Smokers	10.00	6.54, 15.29		N vs S, p<0.001
CEMA (acrylonitrile) pmol/ml	Non-smokers	1.74	1.31, 2.32	<0.001	E vs S, p<0.001
	E-cig users	2.72	1.68, 4.41		E vs N, p=0.120
	Smokers	531.9	358.4, 789.4		N vs S, p<0.001
HMPMA (crotonaldehyde; methyl vinyl ketone; methacrolein) pmol/ml	Non-smokers	586.5	485.4, 708.8	<0.001	E vs S, p<0.001
	E-cig users	696.3	505.5, 959.1		E vs N, p=0.363
	Smokers	4771	3673, 6197		N vs S, p<0.001
TNE nmol/ml	Non-smokers	a
	E-cig users	34.3
	Smokers	58.2

^athere were only 2 TNE values above the LOD for non-smokers