Chapter 3 
Changes in Cigarette Design and Composition 
Over Xime and How Xhey Influence the 
Yields of Smoke Constituents 
Dietrich Hoffmann, Mirjana V. Djordjevic, and Klaus D. Brunnemann 
INTRODUCTION Since the first epidemiological reports on the association of 
cigarette smoking with lung cancer, the composition of tobacco blends 
and the makeup of commercial cigarettes in the United States as well as in 
Western Europe have undergone major changes. Measured on the basis of 
standardized machine smoking conditions, the sales-weighted average tar 
and nicotine deliveries in U.S. cigarette smoke have decreased from 38 mg 
and 2.7 mg, respectively, in 1954 to 12 mg and 0.95 mg, respectively, in 
1993. The lower emissions have been primarily accomplished by using 
efficient filter tips and highly porous cigarette paper and by changing the 
composition of the tobacco blend. The latter includes the incorporation 
of reconstituted and expanded tobaccos into the blend. Concurrent with 
the reduction of tar and nicotine in the smokestream, there also occurred 
a reduction of carbon monoxide, phenols, and carcinogenic polynuclear 
aromatic hydrocarbons (PAHs). These reductions were partially tied to an 
increase in the nitrate content of the tobacco blend used for U.S. cigarettes. 
The addition of nitrate was initially targeted at decreasing the smoke yields 
of PAHs; however, that this also would cause a gradual increase of the 
carcinogenic, tobacco-specific N-nitrosamines (TSNAs) was not recognized 
until there was awareness of those compounds as smoke constituents in 
the 1970's. 
These observations were based on measurements of yields from 
cigarettes that were smoked under standardized laboratory conditions, 
initially established in 1936, and adopted by the U.S. Federal Trade 
Commission (FTC) in 1969. These conditions do not reflect the smoking 
patterns of the smokers of filter cigarettes, who currently account for the 
consumption of 97 percent of all cigarettes produced in the United States. 
The current filter cigarette smoker tends to smoke more intensely and to 
inhale more deeply. Thus, the actual exposure to toxic and tumorigenic 
agents in the inhaled smoke of filter cigarettes is not necessarily in line 
with the machine smoking data. 
BACKGROUND In 1950 epidemiological studies reported that lung cancer was 
particularly prevalent among cigarette smokers (Wynder and Graham, 1950; 
Doll and Hill, 1950). These observations in the United States and the United 
Kingdom were confirmed by the Royal College of Physicians (1962) and by 
the U.S. Surgeon General in 1964 (U.S. Department of Health, Education, and 
Welfare, 1964). These reports and the emerging knowledge of the presence 
15 
