Cotinine concentration in smokers from different countries: relationship with amount smoked and cigarette type.

This four-country study examined salivary cotinine as a marker for nicotine intake and addiction among smokers in relation to numbers and types of cigarettes smoked. Smoking characteristics of cigarette smokers in Brazil, China, Mexico, and Poland were identified using a standard questionnaire. Cotinine concentration was measured using a saliva sample from each participant; its relationship with numbers and types of cigarettes smoked was quantified by applying regression techniques. The main outcome measure was salivary cotinine level measured by gas chromatography. In all four countries, cotinine concentration increased linearly with cigarettes smoked up to 20 per day [11.3 ng/mL (95% confidence interval, 10.5-12.2)] and then stabilized as the number of cigarettes exceeded 20 [6.8 ng/mL per cigarette (95% confidence interval, 6.3-7.4) for up to 40 cigarettes]. On average, smokers of regular cigarettes consumed more cigarettes and had higher cotinine levels than light cigarette smokers. Cotinine concentration per cigarette smoked did not differ between regular and light cigarette smokers. Results suggest a saturation point for daily nicotine intake and minimal or no reduction in nicotine intake by smoking light cigarettes.

Utility and cutoff value of hair nicotine as a biomarker of long-term tobacco smoke exposure, compared to salivary cotinine.

While hair samples are easier to collect and less expensive to store and transport than biological fluids, and hair nicotine characterizes tobacco exposure over a longer time period than blood or urine cotinine, information on its utility, compared with salivary cotinine, is still limited. We conducted a cross-sectional study with 289 participants (107 active smokers, 105 passive smokers with self-reported secondhand smoke (SHS) exposure, and 77 non-smokers with no SHS exposure) in Baltimore (Maryland, USA). A subset of the study participants (n = 52) were followed longitudinally over a two-month interval.  Median baseline hair nicotine concentrations for active, passive and non-smokers were 16.2, 0.36, and 0.23 ng/mg, respectively, while those for salivary cotinine were 181.0, 0.27, and 0.27 ng/mL, respectively. Hair nicotine concentrations for 10% of passive or non-smokers were higher than the 25th percentile value for active smokers while all corresponding salivary cotinine concentrations for them were lower than the value for active smokers. This study showed that hair nicotine concentration values could be used to distinguish active or heavy passive adult smokers from non-SHS exposed non-smokers. Our results indicate that hair nicotine is a useful biomarker for the assessment of long-term exposure to tobacco smoke.