Chapter 1 1 
Human Smoking Patterns 
James P. Zacny and Maxine L. Stitzer 
: INTRODUCTION It has been established that human exposure to tobacco smoke 
constituents does not reflect package yield characteristics of cigarettes as 
determined by Federal Trade Commission (FTC) smoking machine methods. 
I This chapter describes some reasons for this discrepancy by examining 
! features of human smoking behavior and how smoking behavior interacts 
* with cigarette yield characteristics. The chapter is divided into four sections. 
I The first section describes the topography of cigarette smoking; the second 
I identifies the parameters of smoking topography that influence smoke 
I exposure; the third shows that human smoking patterns are dynamic rather 
than static; and the fourth draws conclusions about the relevance of the 
FTC methodology to human smoking patterns. 
HOW DO The first behavioral aspect of smoking involves holding the cigarette, 
t HUMANS When smoking low-yield cigarettes (nicotine yield < 0.9 mg), smokers 
' SMOKE? may knowingly or unknowingly block some or all the filter vents with 
their fingers or lips. Blockage of these vents increases the density of 
mainstream smoke that enters the mouth from the cigarette rod because S 
the opportunity for air to be drawn into the smoke stream via the vents is " 
reduced. Vent blocking essentially can turn a low-yield cigarette into a high- 
yield cigarette. Over the past 10 years, Dr. Lynn Kozlowski has performed 
a series of studies in which cigarette butts were assessed for vent blocking. 
He obtained these butts from public access places such as shopping malls. j 
From his butt analyses, he estimated the extent to which smokers in the 
United States engage in vent blocking. In one study (Kozlowski et al., 1988), . 
the incidence of partial or complete vent blocking of ultralow-yield cigarettes j, 
(0.1 to 0.4 mg of nicotine) was 58 percent. In a more recent study, Kozlowski » 
and colleagues (1994) collected butts of so-called "light" cigarettes (0.5 to 
I 0.8 mg of nicotine yield) and found that 53 percent of the butts showed 
I evidence of some degree of vent blocking. Vent blocking can be detected by 
j looking at the filter stain: Cigarettes that are not vent blocked have a dark 
stain in the middle of the filter toe with a visible white ring surrounding the 
; stain (i.e., "bulls-eye" pattern); cigarettes that are vent blocked have filter 
1 stains that encompass to varying degrees not only the middle of the filter 
j toe but also the periphery. 
! What are other features of smoking behavior? The smoker draws on 
the cigarette, inhales the smoke into the lungs, then exhales. Drawing or 
puffing parameters that can be measured include the size of the puff (puff 
volume), the duration of the puff, and the interval between puffs. Inhalation 
I parameters that can be measured include the amount of air that is mixed 
] with the smoke as it is inhaled into the lungs (inhalation volume, also 
I referred to as inhalation depth), the duration to peak inhalation, and any 
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