Tobacco use is the leading cause of cancer-related death of approximately 1.2 million annually in the world. Cigarette smoking causes 90% of lung cancer cases and about 30% of all cancer death in the developed countries is related to tobacco use. NNK, the most carcinogenic tobacco nitrosamine (TSNA), has been classified as Group 1 human carcinogen by IARC. NNAL, the major metabolite of NNK, is not only a biomarker of exposure, but also an indicator of lung cancer risk.
This study is aimed to investigate the tobacco carcinogen levels in US cigarette smokers.
We have measured urinary NNAL in participants aged ≥ 6 years in NHANES from 2007 to 2012. Log NNAL was plotted as a function of CPD by age groups using a locally weighted polynomial regression (LOESS) function. Weighted log linear regression of NNAL concentrations on CPD controlling for other covariates was conducted.
NNAL concentrations generally increased for all age groups 1-40 CPD. NNAL levels increased more rapidly for CPD 1-10 than CPD 10-40. NNAL tend to plateau generally across all age groups at CPD < 10. NNAL levels increased as smokers’ age increased almost regardless how many cigarettes they smoked per day. Age group 45-54 resembles the lower age groups in the pattern of NNAL levels by showing higher NNAL than age group 35-44. Age group 55-64 and age group 65+ had very similar NNAL level.
NNAL in smokers is not only associated with self-reported CPD, but also related to smoker’s age. At the same CPD, older smokers have relatively higher carcinogenic NNAL concentrations, which could be translated to higher carcinogen dose and might be associated with higher risk of lung cancer. Tobacco product standards on TSNA levels are urgently needed to protect individuals addicted to nicotine and to reduce the burden of cancer around the world.