787 



«-ioAKtitt lltLUb AND i>MUKt BIOAV AILABIUTY Hi 



hc"v much '.^npenr.g occurs, resulting in a linear correlation of >-ie!d and iniak;(l9). 

 Brand preferences are probabU established on the basis of organoleptic, phvsicx' per- 

 formance (e.g.. draw), promotional, and kinesthetic differences. 



Figure 4 indicates that more smokers in our sample experienced intakes higher 

 than FTC yields when smoking brands yielding less than 0.8-1.0 mg of nicotine, and 

 Mce versa. Ahhoueh these figures correspond closely with independent experimental 

 Tieasures of nicotine intake (9), Fig. 4 should be interpreted only as a plausibJc ap- 

 proximation, owing to the variance of the parametric values utilized. Moreover, smok- 

 ers of less than 10 cigarettes per day or with less ihan 15 ppm CO in expired air were 

 excluded from our sample; their inclusion would have given lower MNIC estimates 

 than reported in this study, which may be vaJid only for the majority of serious smokers, 

 as direct measurements of compensation suggest (9). 



Tar Intake Esiimaies 



Retention of tar from inhaled smoke may be lower than that for nicotine (25); 

 therefore, any evaluation of tar intake from nicotine intake estimates represents max- 

 imum possible tar intake and can be calculated from nicotine intake values, after 

 adjusting for the tar-to-nicotine ratio (T/N) of the smoke inhaled. 



For U. S. market cigarettes, the FTC T/N ratios of cigarette smoke increase with 

 increasing FTC tar deliverv- (Fig. 8). In general. T/N ratios arc sensitive to blend 

 composition, puff profile, volume, and duration, interval between puffs, tampering 

 with ventilation devices, and environmental conditions (10). Methods of determining 

 the T/N ratio for individual smokers under free smoking conditions arc not yet avail- 

 able. Nevertheless, available evidence indicates that the effects of ventilation on T/N 

 ratios of sm.oke may not be extreme (10), suggesting that average T/N ratios based on 

 FTC values might be close to mean field conditions. With this in mind, if we consider 

 the range of MNIC in Fig. 4, and that of FTC T/N ratios of commercial cigarettes in 

 Fig. 8, the probable lax intakes should range between 4 and 6 mg/cigarette at the low 

 end, and between 1 5 and 20 mg/cigarertc at the high end. Thus even though there is 

 a small 0.6-fold increase in nicotine intake between low and high yield cigarettes, the 

 increase in tar inuke could be in the order of 2.5 to 5-foId. 



CONCLUSIONS 



In a large sample of relatively heavy smokers representative of market share, daily 

 cigarette consumption is unaffected by the FTC nicotine yield of the cigarettes smoked, 

 and MNIC for high yield cigarette consumers is only some 60% higher than for those 

 of very low yield brands, even though the FTC ranking scale implies a 1600% iocrtasc. 

 This intake ceiling is probably controlled by nicotine, it reflects upon CO intake and 

 plasma cotinine levels, is not significantly affected by the number of cigarcues consumed 

 daily, and appears to be of pharmacodynamic and behavioral origin, fn general these 

 findings reinforce previous reports and suggest that FTC measures have dubious 

 meaning to consumers, except perhaps for a small fraction of smokers (2-3%) using 

 very low yield cigarettes (19). The results also reinforce the desirability of cigarettes 

 with low T/N ratios (18, 38) and are consistent with epidemiologic evidence show- 

 ing that duration of exposure is of greater significance than the type of dgarette 

 smoked (II). 



