Carcinogen Exposure among Canadian Tobacco Users: Changes in NNK Exposure from 2007-2009 through 2012-2013

Background: Tobacco-specific nitrosamines (TSNAs) are a class of carcinogens found in tobacco products, whose levels can vary considerably depending on tobacco blends and manufacturing processes. The current study examined whether recent increases in levels of the TSNA NNK [4-(methylnitrosamino-1-(3-pyridyl)-1-butanone] in Canadian cigarettes translated into differences in exposure among Canadian tobacco users.Methods: Nationally representative data from the Canadian Health Measures Survey (CHMS) were used to measure levels of total urinary NNAL [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol], a metabolite of the TSNA NNK, among tobacco users. Data from CHMS Cycle 3 (2012-13) were used to examine NNAL, and linear regression was used to examine predictors. Data from CHMS Cycle 1 (2007-09) and Cycle 3 (2012-13) were used to examine changes in NNAL over time.Results: From 2007-2009 through 2012-2013, levels of creatinine-corrected NNAL increased by 64% (P < 0.0001). Levels of NNAL in 2012-2013 were higher among older respondents (P = 0.04), among females (P = 0.03), among respondents identifying as "white" and "Aboriginal" (P < 0.0001), and among those with greater daily cigarette consumption (P < 0.001), as well as greater levels of urinary free cotinine (P < 0.0001) and urinary creatinine (P < 0.0001).Conclusions: The findings indicate that exposure to the TSNA NNK among Canadian tobacco users has increased considerably from 2007-2009 through 2012-2013, in parallel to changes in TSNA levels in Canadian cigarettes. In the absence of epidemiologic data, it is unclear whether this change translates into increased risk.Impact: The study findings have potential implications for tobacco manufacturers, who bear a responsibility to reduce levels of tobacco carcinogens to the full extent possible. Cancer Epidemiol Biomarkers Prev; 27(3); 262-7. ©2018 AACR.