Smoking and Tobacco Control Monograph No. 7 
Figure 8 
Urinary mutagenicity based on 24-hour urine collections in a habitual smoker 
smoking his or her own brand. Camel (high-yield), and True (low-yield) cigarettes 
Own Camel True Abstinence 
Note: Mutagenic activity tends to be constant from day to day and falls to the DMSO control value 
(similar to that of nonsmokers) rapidly after stopping smoking. 
Key: DMSO = dimethyl sulphoxide. 
Source: Benowitz, 1989. 
activity to tar for Carlton compared with other cigarettes, but the difference 
was not near the values of 13.5, 15.4, and 7.3, which were predicted by FTC 
values. 
rhe data of Rickert and Robinson (1981) shown in Table 3 explain the 
discrepancy between measured and predicted tar-to-nicotine ratios. These 
data, based on smoking machine tests, show that when cigarettes are smoked 
more intensely, the tar-to-nicotine ratio of low-yield cigarettes increases 
substantially. Fhus, when smokers compensate for low-yield cigarettes by 
smoking them more intensely, the tar-to-nicotine ratio increases. I'herefore, 
tar-to-nicotine ratios published by the FT’C method cannot be used to make 
estimates of what the overall tar exposure will be for actual smokers. 
CX)NCLUSIONS The suggestion that there is a meaningful quantitative relationship 
between FTC-measured yields and actual intake is misleading. I'here do 
appear to be differences in nicotine ex[)osure comparing high- vs. low-yield 
