Chapter 7 
Figure 7 
Mean expired air carbon monoxide values as a function of FTC carbon monoxide yield of 
cigarettes smoked 
Key: solid line = mean; broken line = 95-percent confidence intervals. 
Source: Gori and Lynch, 1985. 
Figure 9 shows data from a crossover study of urine mutagenicity and 
nicotine intake from smokers smoking their own brand, high-yield (Camel), 
and low-yield cigarettes (True) (Benowitz et al., 1986b). The mutagenic 
activity of the urine was lower for both Camel and True compared with 
the usual brand, most likely because smokers did not like these other brands 
of cigarettes as much as they liked their own. However, the mutagenicity 
values for Camel and True were similar. The ratio of mutagenic activity 
over the 24-hour period under the nicotine plasma concentration-time curve 
(the latter being an estimate of daily nicotine intake) was used as a surrogate 
for tar-to-nicotine ratio and was the same in all conditions, although the 
machine-predicted ratios were 14.8 for smoker's own, 15.1 for Camel, and 
11.5 for True. Thus, the in vivo tar-to-nicotine ratio did not correspond to 
differences in the machine-determined tar-to-nicotine ratios for different 
brands. 
Figure 9 also shows similar data when switching to Carlton, which is an 
ultralow-yield cigarette. There was a small difference in the ratio of mutagenic 
105 
