Pharmacokinetics<unk>  has an in vivo half-life of approximately 20 hours, and is typically detectable for several days (up to one week) after the use of tobacco. The level of<unk>  in the blood, saliva, and urine is proportionate to the amount of exposure to tobacco smoke, so it is a valuable indicator of tobacco smoke exposure, including secondary (passive) smoke. People who smoke menthol cigarettes may retain<unk>  in the blood for a longer period because menthol can compete with enzymatic metabolism of<unk> . African American smokers generally have higher plasma<unk>  levels than Caucasian smokers. Males generally have higher plasma<unk>  levels than females. These systematic differences in<unk>  levels were attributed to variation in CYP2A6 activity. At steady state, plasma<unk>  levels are determined by the amount of<unk>  formation and the rate of<unk>  removal, which are both mediated by the enzyme CYP2A6. Since CYP2A6 activity differs by sex (estrogen induces CYP2A6) and genetic variation,<unk>  accumulates in individuals with slower CYP2A6 activity, resulting in substantial differences in<unk>  levels for a given tobacco exposure. Detection in body fluids Drug tests can detect<unk>  in the blood, urine, or saliva. Salivary<unk>  concentrations are highly correlated to blood<unk>  concentrations, and can detect<unk>  in a low range, making it the preferable option for a less invasive method of tobacco exposure testing. Urine<unk>  concentrations average four to six times higher than those in blood or saliva, making urine a more sensitive matrix to detect low-concentration exposure.<unk>  levels <10 ng/mL are considered to be consistent with no active smoking. Values of 10 ng/mL to 100 ng/mL are associated with light smoking or moderate passive exposure, and levels above 300 ng/mL are seen in heavy smokers - more than 20 cigarettes a day. In urine, values between 11 ng/mL and 30 ng/mL may be associated with light smoking or passive exposure, and levels in active smokers typically reach 500 ng/mL or more. In saliva, values between 1 ng/mL and 30 ng/mL may be associated with light smoking or passive exposure, and levels in active smokers typically reach 100 ng/mL or more.<unk>  assays provide an objective quantitative measure that is more reliable than smoking histories or counting the number of cigarettes smoked per day.<unk>  also permits the measurement of exposure to second-hand smoke (passive smoking). However, tobacco users attempting to quit with the help of nicotine replacement therapies (i.e., gum, lozenge, patch, inhaler, and nasal spray) will also test positive for<unk> , since all common NRT therapies contain nicotine that is metabolized in the same way. Therefore, the presence of<unk>  is not a conclusive indication of tobacco use.<unk>  levels can be used in research to explore the question of the amount of nicotine delivered to the user of e-cigarettes, where laboratory smoking machines have many problems replicating real-life conditions. Serum<unk>  concentration has been used for decades in US population surveys of the Centers for Disease Control and Prevention to monitor tobacco use, to monitor levels and trends in exposure to environmental tobacco smoke, and to study the relationship between tobacco smoke and chronic health conditions. An estimated one in four nonsmokers (approximately 58 million persons) were exposed to secondhand smoke during 2013-2014. Nearly 40% of children aged 3–11 years were exposed as were 50% of non-Hispanic blacks.
Cotinine
Haloalkane
Carbon monoxide
Mustard gas
3-Indolepropionic acid
Benzene
Hydrogen water
Vinyl chloride