Biomonitoring Summary

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL)

CAS No. 76014-81-8
Metabolite of 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone, NNK (a tobacco-specific N-nitrosamine)

General Information

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a metabolite of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which belongs to a group of chemicals termed tobacco-specific N-nitrosamines (TSNA). As the name implies, TSNA are found only in tobacco and products derived from tobacco (Hecht and Hoffman 1988). TSNA are chemically related to nicotine and other tobacco alkaloids, and they are present particularly in tobacco leaves. The TSNA content of tobacco varies depending upon soil conditions, agricultural practices, fertilizer use, and tobacco manufacturing processes (IARC, 2007). The largest amounts of TSNA are formed during tobacco curing and processing after harvesting, and additional amounts are formed when tobacco is smoked. In general, the levels of TSNA are greater in smokeless tobacco than in tobacco used in cigarettes and produced in mainstream tobacco smoke (IARC, 2007). Human exposure occurs by use of smokeless tobacco products (e.g., snuff, chewing tobacco, etc.), and by inhaling tobacco smoke during the process of active smoking or as a result of passive exposure to ambient tobacco smoke (referred to as second hand smoke, SHS, or environmental tobacco smoke). Considerably lower levels of TSNA have been detected in second hand or sidestream smoke, as in poorly ventilated rooms where heavy smoking occurred. The small amounts of N-nitrosamines that may occur in food and non-food products are several orders of magnitude lower than the content of tobacco and tobacco smoke (Hecht and Hoffman, 1988). Measurement of TSNA and their metabolites in humans provides biomarkers of exposure to carcinogens that are specific to tobacco.

NNK has no commercial use (IARC, 2007). It forms in tobacco by the reaction of nicotine with nitrite that may be naturally occurring or added during processing. NNK is released into the environment when tobacco is burned, but environmental fate has not been well characterized (HSDB, 2010). Inhalation or dermal exposure may occur in workers involved in NNK production or use. General population exposure occurs largely through inhalation of tobacco smoke, either active smoking or SHS exposure, and through ingestion of NNK in smokeless tobacco products. There is no evidence that absorption of nicotine from a patch, lozenge, or gum can lead to production of NNK in the human body (Hecht, 1998).

In the body, NNK undergoes metabolic activation and is metabolized largely (about 95%) to NNAL (IARC, 2007; Stepanov et al., 2008). Both chemicals are procarcinogens that require metabolic activation to react with DNA and other cellular molecules (IARC, 2007). NNAL is slowly eliminated in urine with an elimination half-life of 18-45 days (Goniewicz et al., 2009; Hecht et al., 1999) and can be detected for months after smoking cessation. Transplacental transfer of NNK and/or NNAL has been demonstrated by measuring urinary NNAL in newborn babies (Lackmann et al., 1999).

NNK was mutagenic in in vitro assays, including bacteria, rodent fibroblasts, and human lymphoblastoid cells (IARC, 2007). Cytotoxicity has been documented in in vitro mammalian liver and pancreatic cells (IARC, 2007). NNK carcinogenesis is thought to involve metabolic activation and formation of DNA adducts (Hecht, 1998). NNK appeared to be a lung-specific carcinogen in several animal species, primarily producing adenocarcinomas, independent of the route of administration (Hecht, 1998). NNK-induced tumors also were produced in the nasal cavity, liver, and pancreas in experimental animals (IARC, 2007). NNAL produced lung tumors in mice, and when given prenatally to mice, resulted in lung or liver tumors in the offspring (Anderson et al., 1989). Studies using animal and human cells demonstrated metabolic activation of NNK and NNAL and the formation of DNA adducts, suggesting that the mechanism of human lung cancer may be similar to that seen in experimental animals (Hecht, 1998; Richter et al., 2009).

NNAL has been extensively studied as a carcinogen biomarker of tobacco use and SHS exposure. NNAL has been detected in urine and blood of smokers (Carmella et al., 2005) and smokeless tobacco users, and in urine of individuals with SHS exposure (IARC, 2007). In general, urinary NNAL levels were well correlated with either serum or urinary cotinine levels. In smokers, NNAL levels were also correlated with the number of cigarettes smoked (Kavvadias et al., 2009; Xia et al., 2010). In non-smokers, NNAL levels were also correlated with the amount of SHS exposure (Bernert et al., 2009). In a study of nonsmokers with chronic obstructive pulmonary disease, more severe symptoms were reported when urinary NNAL levels were higher, indicative of greater SHS exposure (Eisner et al., 2009). In a case-control study, levels of NNAL measured in serum collected prospectively were associated with increased lung cancer risk (Church et al., 2009). Non-smoking women living with a partner who smoked cigarettes had urinary NNAL levels that were about 5% of the levels in their smoking partners, a percentage similar (1-2%) to that for lung cancer risk in non-smokers with SHS exposure compared to smokers (Anderson et al., 2001).

IARC considers NNK to be a human carcinogen, and NNAL is an animal carcinogen (IARC, 2007). NTP (2005) determined that NNK is reasonably anticipated to be a human carcinogen.

Biomonitoring Information

Urinary levels of NNAL reflect use of one or more smokeless tobacco products or exposure to tobacco smoke via active smoking or from SHS exposure. From NHANES 2007-2008 to 2009-2010, urine NNAL appeared to decline slightly among all groups of non-smokers except for non-Hispanic blacks (CDC, 2012). Total urinary NNAL was detectable above the limit of detection (0.6 pg/mL) in 55% of NHANES 2007-2008 participants aged six years and older, and in 41.2% of the nonsmokers (Bernert et al., 2010). Compared to non-smokers, defined as participants with serum cotinine <10 ng/mL, the 75th and 95th percentile NNAL levels in smokers were about 75 and 200 times higher, respectively (Bernert et al., 2010). For a subgroup of more highly exposed nonsmokers, defined as participants with serum cotinine 0.1 to less than 10 ng/mL, the geometric mean of 5.56 (CI, 4.8-6.4) pg/mL was similar to levels reported in studies of adults exposed to SHS (Anderson et al., 2001 and 2003; Bernert et al., 2010; Tulunay et al., 2005). Within this subgroup, non-Hispanic whites had slightly higher urinary NNAL levels than either non-Hispanic blacks or Mexican Americans. No differences were apparent between levels in males and females, but among the age groups, the highest geometric mean NNAL level was in children aged 6-11 years (Bernert et al., 2010). In contrast to nonsmokers, urinary NNAL levels in smokers in NHANES 2007-2008, demonstrated gender and racial/ethnic differences. The adjusted geometric mean (95% CI) NNAL levels were highest in females, 353 (324-384) pg/mL and non-Hispanic whites, 336 (298-379) pg/mL. Urinary NNAL levels were significantly correlated with levels of serum cotinine, urine creatinine, and the number of cigarettes per day smoked but not to the menthol type of the cigarette (Xia et al., 2011). In the U.S. population, urinary total NNAL levels were approximately 50-150 times higher in smokers compared with non-smokers (Bernert et al., 2010; Xia et al., 2011). Urinary NNAL levels in U.S. smokers appear to be similar to levels reported in smaller studies of smokers (Breland et al., 2003; Byrd and Ogden, 2003; Carmella et al., 2002).

Variability in urinary NNAL levels may be due to TSNA content of the smoked product, the frequency and intensity of smoking, and such individual factors as age and genetics (Ashley et al., 2010; Herstgaard et al., 2008; Lubin et al., 2007). Total urinary NNAL levels reported from studies of U.S. smokers varied widely, but typically, average levels ranged from 200-600+ pg/mL or pg/mg creatinine (Breland et al., 2003; Carmella et al., 2002; Church et al., 2010; Hecht et al., 1999 and 2002; Hertsgaard et al., 2008; Muscat et al., 2009; Stepanov et al., 2007). Consistent with the lower NNK levels of most cigarettes from outside the U.S., lower urinary NNAL levels, often less than 200 pg/mL were reported in smokers from countries other than the U.S. (Ashley et al., 2010; Calapai et al, 2009; Morin et al., 2010; Yuan et al., 2009).

Nonsmokers with SHS exposure typically had urinary NNAL levels below 10 pg/mL (Anderson et al., 2001; Carmella et al., 2003; Hecht et al., 1999 and 2007), but higher levels were reported following exposure under controlled conditions (Bernert et al., 2009). Studies in infants and young children suggest that they may be susceptible to inhaling large doses of SHS, as evidenced by high urinary levels of total NNAL. Children exposed to SHS in the home had average urinary NNAL levels ranging from 10-30 pg/ml, about 2-3 times higher than those reported in SHS-exposed adults (Hecht et al., 2001 and 2006; Lackmann et al., 1999). Notably higher urinary NNAL levels, averaging 29.3 pg/mL (95% CI 17.3-41.8) were found in newborns of mothers who smoked during pregnancy (Lackmann et al., 1999).

Urinary total NNAL levels are similar or slightly higher in users of smokeless tobacco products compared to active smokers, indicative of the higher levels of TSNA and NNK that may be present in smokeless tobacco. Small studies of snuff dippers and chewing tobacco users reported average NNAL levels of approximately 850 pg/mL and 600-900 pg/mg creatinine (Carmella et al., 2002 and 2003; Hatsukami et al., 2004; Hecht et al., 2002; Kresty et al., 1996; Lemmonds et al., 2005). Possibly the highest urinary NNAL levels, averaging more than 250,000 pg/mL, were measured in several Sudanese users of “toombak”, a paste of tobacco and sodium bicarbonate that is held in the mouth like snuff (Murphy et al., 1994).

Biomonitoring studies of urinary NNAL provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of NNK from SHS and tobacco than are found in the general population. Biomonitoring data can also help scientists plan and conduct research about exposure to NNK and its health effects.


Anderson KE, Carmella SG, Ye M, Bliss RL, Le C, Murphy L, et al Metabolites of a tobacco-specific lung carcinogen in nonsmoking women exposed to environmental tobacco smoke. J Natl Cancer Inst 2001;93(5):378-81.

Anderson KE, Kliris J, Murphy L, Carmella SG, Han S, Link C, et al. Metabolites of a tobacco-specific lung carcinogen in nonsmoking casino patrons. Cancer Epidemiol Biomarkers Prev 2003;12:1544-6.

Anderson LM, Hecht SS, Dixon DE, Dove LF, Kovatch RM, Amin S, et al. Evaluation of the transplacental tumorigenicity of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in mice. Cancer Res 1989;49:3770-5.

Ashley DL, O’Connor RJ, Berhert JT, Watson CH, Polzin GM, Jain RB, et al. Effect of differing levels of tobacco-specific nitrosamines in cigarette smoke on the levels of biomarkers in smokers. Cancer Epidemiol Biomarkers Prev 2010;19(6):1389-98.

Bernert JT, Gordon SM, Jain RB, Brinkman MC, Sosnoff CS, Seyler TH, et al. Increases in tobacco exposure biomarkers measured in non-smokers exposed to sidestream cigarette smoke under controlled conditions. Biomarkers 2009;14(2):82-93.

Bernert JT, Pirkle JL, Xia Y, Jain RB, Ashley DL, Sampson EJ. Urine concentrations of a tobacco-specific nitrosamine carcinogen in the U.S. population from secondhand smoke exposure. Cancer Epidemiol Biomarkers Prev 2010;19(11):2969-77.

Breland AB, Acost MC, Eissenberg T. Tobacco specific nitrosamines and potential reduced exposure products for smokers: a preliminary evaluation of Advance™. Tob Control 2003;12:317-21.

Byrd GD, Ogden MW. Liquid chromatorgraphic/tandem mass spectrometric method for the determination of the tobacco-specific nitrosamine metabolite NNAL in smokers’ urine. J Mass Spectrom 2003;38:98-107.

Calapai G, Caputi A, Mannucci C, Gregg EO, Pieratti A, Russo FA, et al. A cross-sectional investigation of biomarkers of risk after a decade of smoking. Inhal Toxicol 2009;21(13):1138-43.

Carmella SG, Han S, Fristad A, Yang Y, Hecht SS. Analysis of total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in human urine. Cancer Epidemiol Biomarkers Prev 2003;12:1257-61.

Carmella SG, Han S, Villalta PW, Hecht SS. Analysis of total 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in smokers blood. Cancer Epidemiol Biomarkers Prev 2005;14(11):2669-72.

Carmella SG, Le K-A, Upadhyaya P, Hecht SS. Analysis of N– and O-glucuronides of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in human urine. Chem Res Toxicol 2002;15:545-50.

Centers for Disease Control and Prevention (CDC). Fourth National Report on Human Exposure to Environmental Chemicals. Updated Tables. September 2012. [online] Available at URL: 12/28/12

Church TR, Anderson KE, Caporaso NE, Geisser MS, Le CT, Zhang Y, et al. A prospectively measured serum biomarker for a tobacco-specific carcinogen and lung cancer in smokers. Cancer Epidemiol Biomarkers Prev 2009;18(1):260-6.

Church TR, Anderson KE, Le C, Zhang Y, Kampa DM, Benoit AR, et al. Temporal stability of urinary and plasma biomarkers of tobacco smoke exposure among cigarette smokers. Biomarkers 2010;15(44):345-52.

Eisner MD, Jacob III, P, Benowitz NL, Balmes J, Blanc PD. Longer term exposure to secondhand smoke and health outcomes in COPD: impact of urine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol. Nicotine Tob Res 2009;11(8):945-53.

Goniewicz ML, Havel CM, Peng MW, Jacob III J, Dempsey D, Yu L, et al. Elimination kinetics of the tobacco-specific biomarker and lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol. Cancer Epidemiol Biomarkers Prev 2009;18(12):3421-5.

Hatsukami DK, Lemmonds C, Zhang Y, Murphy SE, Le C, Carmella SG, et al. Evaluation of carcinogen exposure in people who used “reduced exposure” tobacco products. J Natl Cancer Inst 2004;96(11):844-52.

Hazardous Substances Data Bank (HSDB). 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Bethesda, MD: National Library of Medicine. Available at URL: icon.12/28/2012

Hecht SS. Biochemistry, biology, and carcinogenicity of tobacco-specific N-nitrosamines. Chem Res Toxicol 1998;11:559-603.

Hecht SS, Carmella SG, Le K-A, Murphy SE, Boettcher AJ, Le C, et al. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol and its glucuronides in the urine of infants exposed to environmental tobacco smoke. Cancer Epidemiol Biomarkers Prev 2006;15(5):998-92.

Hecht SS, Carmella SG, Ye M, Le-K-A, Jensen JA, Zimmerman CL, et al. Quantitation of metabolites of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone after cessation of smokeless tobacco use. Cancer Res 2002;62:129-34.

Hecht SS, Carmella SG, Chen M, Dor Koch JG, Miller AT, Murphy SE, et al. Quantitation of urinary metabolites of a tobacco-specific lung carcinogen after smoking cessation. Cancer Res 1999;59:590-6.

Hecht SS, Carmella SB, Murphy SE, Riley WT, Le C, Luo X, et al. Similar exposure to a tobacco-specific carcinogen in smokeless tobacco users and cigarette smokers. Cancer Epidemiol Biomarkers Prev 2007;16(8):1567-72.

Hecht SS, Hoffmann D. Tobacco-specific nitrosamines, an important group of carcinogens in tobacco and tobacco smoke. Carcinogenesis 1988;9:875-84.

Hecht SS, Ye M, Carmella SG, Fredrickson A, Adgate JL, Greaves IA, et al. Metabolites of a tobacco-specific lung carcinogen in the urine of elementary school-aged children. Cancer Epidemiol Biomarkers Prev 2001;10:1109-16.

Hertsgaard LA, Hanson K, Hecht SS, Lindgren BR, Luo X, Carmella SG, et al. Exposure to a tobacco-specific lung carcinogen in adolescent versus adult smokers. Cancer Epidemiol Biomarkers Prev 2008;17(12):3337-43.

International Agency for Research on Cancer (IARC). Smokeless tobacco and some tobacco-specific N-nitrosamines. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans vol. 89. Lyon, France. 2007. Available at URL: icon. 12/28/2012

Kavvadias D, Scherer G, Cheung F, Errington G, Shepperd J, McEwan M. Determination of tobacco-specific N-nitrosamines in urine of smokers and non-smokers. Biomarkers 2009;14(8):547-53.

Kresty LA, Carmella SG, Borukhova A, Akerkar SA, Gopalakrishnan R, Harris RE, et al. Metabolites of a tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in the urine of smokeless tobacco users: relationship between urinary biomarkers and oral leukoplakia. Cancer Epidemiol Biomarkers Prev 1996;5:521-5.

Lackman GM, Salzberger U, Tollner U, Chen M, Carmella SG, Hecht SS. Metabolites of a tobacco-specific carcinogen in urine from newborns. J Natl Cancer Inst 1999;91(5):459-65.

Lemmonds CA, Hecht SS, Jensen JA, Murphy SE, Carmella SG, Zhang Y, et al. Smokeless tobacco topography and toxin exposure. Nicotine Tob Res 2005;7(3):469-74.

Lubin JH, Caporaso N, Hatsukami DK, Joseph AM, Hecht SS. The association of a tobacco-specific biomarker and cigarette consumption and its dependence on host characteristics. Cancer Epidemiol Biomarkers Prev 2007;16(9):1852-7.

Morin A, Shepperd CJ, Eldridge AC, Poirier N, Voisine R. Estimation and correlation of cigarette smoke exposure in Canadian smokers as determined by filter analysis and biomarkers of exposure. In press. Regul Toxicol Pharmacol 2010: doi:10.1016/vrtph.2010.09.020.

Murphy SE, Carmella SG, Idris AM, Hoffman D. Uptake and metabolism of carcinogenic levels of tobacco-specific nitrosamines by Sudanese snuff dippers. Cancer Epidemiol Biomarkers Prev 1994;3:423-8.

Muscat JE, Chen G, Knipe A, Stellman SD, Lazarus P, Richie Jr JP. Effects of menthol on tobacco smoke exposure, nicotine dependence, and NNAL glucuronidation. Cancer Epidemiol Biomarkers Prev 2009;18(1):35-41.

National Toxicology Program (NTP). 4-(N-Nitrosomethlamino)-1-(3-pyridyl)-1-butanone. Report on Carcinogens, 12th Edition. U.S. Department of Health and Human Services. June 10, 2011. Available at URL: iconexternal icon.12/28/2012

Richter E, Engl J, Friesenegger S, Tricker AR.Biotransformation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in lung tissue from mouse, rat, hamster, and man. Chem Res Toxicol 2009;22:1008-17.

Stepanov I, Hecht SS, Lindgren B, Jacob III P, Wilson M, Benowitz NL. Relationship of human toenail nicotine, cotinine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol to levels of these biomarkers in plasma and urine. Cancer Epidemiol Biomarkers Prev 2007;16(7):1382-6.

Stepanov I, Upadhyaya P, Carmella SG, Feuer R, Jensen J, Hatsukami DK, et al. Extensive metabolic activation of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in smokers. Cancer Epidemiol Biomarkers Prev 2008;17(7):1764-73.

Tulunay OE, Hecht SS, Carmella SB, Zhang Y, Lemmonds C, Murphy S, et al. Urinary metabolites of a tobacco-specific lung carcinogen in nonsmoking hospitality workers. Cancer Epidemiol Biomarkers Prev 2005;14(5):1283-6.

Xia Y, Bernert JT, Jain RB, Ashley DL, Pirkle JL. Tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in smokers in the United States: NHANES 2007-2008. Biomarkers 2011;16:112-9.

Yuan J-M, Koh P, Murphy SE, Fan U, Wang R, Carmella SG, et al. Urinary levels of tobacco-specific nitrosamine metabolites in relation to lung cancer development in two prospective cohorts of cigarette smokers. Cancer Res 2009;69(7):2990-5.

Page last reviewed: April 7, 2017