Smoking and Tobacco Control Monograph No. 7 
Benowitz and colleagues (1986) looked at differences in tar, nicotine, 
and CO exposure when smokers switched from their regular brand to high-, 
low-, and ultralow-yield cigarettes. The researchers detected no differences 
in exposure among the high- and low-yield smokers. However, for smokers 
of ultralow-yield cigarettes, there were substantial reductions in exposure to 
tar (49 percent), nicotine (56 percent), and CO (36 percent). Despite these 
reductions, the investigators reported that the relative exposure to tar and 
nicotine from ultralow-yield compared with higher yield cigarettes was much 
greater than predicted by FTC machine-determined yields. 
Kolonen and colleagues (1991) examined puffing patterns of 36 smoking 
students, with different smoking histories, in a natural environment. The 
subjects included 18 smokers of low-yield cigarettes, 10 smokers of medium- 
yield cigarettes, and 8 smokers who had switched from medium- to low-yield 
cigarettes. Subjects smoked their regular brand for the first week, a low-yield 
brand for the second week, and a medium-yield brand for the third week. 
All three groups had the highest daily puff volumes when smoking low-yield 
cigarettes, and the correlations between urine cotinine concentration and 
daily puffing in the three groups were poor. However, the urinary cotinine 
concentration was significantly lower for low-yield smokers compared with 
the switchers. The investigators concluded that cotinine excretion results in 
the switchers' group were in line with earlier reports showing that long-term 
switchers have no significant decreases in plasma and urine cotinine. 
In a longer study of switching effects, Guyatt and coworkers (1989b) 
monitored 28 smokers who switched to cigarettes with lower tar and nicotine 
yields. The researchers concluded, after monitoring subjects for about 
1 year, that most effects of the switch to lower yield cigarettes did not persist 
beyond 36 weeks. The drop in cotinine levels was only 40 percent of what 
was expected from stated nicotine yields; mean puff volume increased by 
16 percent; and smokers seemed to achieve about 60 percent compensation 
when smoking lower tar cigarettes. 
YIELDS BY THE FTC Carbon monoxide yields follow somewhat surprising 
TEST METHOD AND OTHER dynamics. For example, as Rickert and colleagues 
CONSTITUENTS USING (1980) reported, efficient filters may substantially 
FTC PUFF PROFILE reduce tar yields of cigarettes but lead to increased 
delivery of CO. 
In a study of reduced-draw-resistance cigarettes, Dunn (1978) found that 
smokers can substantially vary their inhalation patterns, leading to marked 
changes in the amount of smoke that reaches the lungs as measured by 
alveolar CO levels. Although increased levels of alveolar CO were expected 
with reduced draw resistance, CO levels decreased, possibly because of 
increased delivery of nicotine. Dunn proposed that the level of CO in 
exhaled air may be a good measure of depth of inhalation. 
There appears to be substantial natural variation in the amount of 
CO inhaled by smokers, even when numbers of cigarettes smoked are 
approximately equal. Burling and colleagues (1985) studied 12 matched 
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