Table 1.

Biomarkers of exposure measured in the study.

Biomarker of exposure				Associated toxicant			Matrix		Method		References
Primary end point
	Total NNALa				NNKb			24-hour urine		LC-MS/MSc	[54-57]
Secondary end points
		3-HPMAd	Acrolein			24-hour urine			LC-MS/MS		[56,58]
		3-OH-B[a]Pe	B[a]Pf			24-hour urine			LC-MS/MS		[59]
		HMPMAg	Crotonaldehyde			24-hour urine			LC-MS/MS		[56,58]
		MHBMAh	1,3-Butadiene			24-hour urine			LC-MS/MS		[56,58]
		S-PMAi	Benzene			24-hour urine			LC-MS/MS		[58]
		TNeqj	Nicotine			24-hour urine			LC-MS/MS		[56]
		Total NNNk	NNN			24-hour urine			LC-MS/MS		[56]

^aNNAL: 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol. Urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol is associated with lung cancer risk [57]; therefore, it is also considered a biomarker of potential harm for lung cancer [54,55].

^bNNK: nicotine-derived nitrosamine ketone.

^cLC-MS/MS: liquid chromatography with tandem mass spectrometry.

^d3-HPMA: 3-hydroxypropylmercapturic acid.

^e3-OH-B[a]P: 3-hydroxybenzo[a]pyrene.

^fB[a]P: benzo[a]pyrene.

^gHMPMA: 3-hydroxy-1-methylpropylmercapuric acid.

^hMHBMA: monohydroxybutenylmercapturic acid.

ⁱS-PMA: S-phenylmercapturic acid.

^jTNeq: total nicotine equivalents (nicotine, cotinine, 3-hydroxycotinine, and their glucuronide conjugates).

^kNNN: N-nitrosonornicotine.