Chapter 7 
to a given daily intake of nicotine, a factor that averages 0.08. Thus, for a 
typical smoker with a level of 300 ng/mL, nicotine intake is estimated to be 
24 mg per day. Based on average cigarette consumption, that represents an 
intake of about 1 mg of nicotine per cigarette. This K factor did not vary as a 
function of whether a person was a smoker or nonsmoker, brands of cigarette 
smoked, or gender. Thus, the author is aware of no bias in using this K factor 
to estimate the dose of nicotine based on a plasma cotinine concentration. 
Data from a study of 136 smokers entering a smoking cessation program 
are shown in Figure 4 (Benowitz et al., 1983b). There was a weak relationship 
between FTC yield and cotinine level. The slope of this relationship was 
shallow and, in this study, not significant. From the lowest to the highest 
yield of cigarettes, there was only a 5- to 10-percent change in cotinine level, 
reflecting a 5- to 10-percent change in nicotine intake. There was a much 
stronger correlation between cigarettes per day and cotinine level (or nicotine 
intake). Thus, the greater the number of cigarettes a person smokes, the more 
nicotine is taken in. This is important because some studies, such as that of 
Rosa and colleagues (1992), purport to show a strong relationship between 
I Figure 4 
; Afternoon blood cotinine concentrations (Group 1) as compared by regression analysis with the 
Note: These smokers’ values were so similar that plots of individual values overlapped. The total number of subjects 
shown in Panel B is lower because data for a few subjects were incomplete. Morning blood cotinine 
concentrations (Group 2, not shown) were on average slightly lower but had similar correlations with the number 
of cigarettes (r = 0.45) and the FTC yield (r = 0.06). 
I Key: NS = not significant; 0=7 observation; • = 2 observations; A = 3 observations; □ = 4 observations. 
i Source: Benowitz et al., 1983b. 
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