Smoking and Tobacco Control Monograph No. 7 
cigarettes were found to have higher CO and salivary cotinine levels. 
Rickert and colleagues (1983) found that blocking half the ventilation holes 
increased the delivery of TPM by 60 percent, and full occlusion increased 
TPM delivery by 150 percent. 
The effect of blocking on perforation ventilation (ventilation holes in the 
filter) and channel ventilation (longitudinal air channels around the filter) 
was studied by Hdfer and colleagues (1991). The researchers compared 
results of lip smoking and holder smoking of cigarettes among 72 smokers, 
divided equally by ventilation type of cigarette smoked. Hdfer and 
colleagues (1991, p. 910) found that 
under normal lip contact conditions, the CO and nicotine 
deliveries of the channel-ventilated cigarettes were higher than 
those of the perforation-ventilated cigarettes and higher than 
with holder smoking. With holder smoking, both types of 
cigarettes delivered comparable amounts of CO and nicotine 
(t-tests, n.s.). 
It appeared that the nicotine boost from channel-ventilated cigarettes was 
twice that of perforation-ventilated cigarettes; differences in CO exposure 
were less well defined. The researchers judged that there was evidence 
of blocking in 86 percent of the channel filter cigarette smokers and in 
33 percent of the perforated filter cigarette smokers. 
In a novel approach to the study of hole blocking among smokers 
of ultralow-tar cigarettes, Kozlowski and colleagues (1988) collected 
135 discarded filters from ashtrays in shopping malls. It was found that 
58 percent of the filters showed some evidence of hole blocking (as measured 
by tar stain patterns); 19 percent showed evidence of extreme hole blocking; 
and 42 percent showed no signs of hole blocking. Kozlowski and colleagues 
(1994) extended this research to "light" cigarettes (about 9 to 12 mg tar, 
about 15 to 30 percent vented): Twenty-seven percent of collected filters 
indicated extreme blockage; 26 percent showed some blocking; and 
47 percent showed no vent blocking. Although defeat of the air vents 
will have a relatively small effect on light rather than ultralight cigarettes, 
the greater sales of light cigarettes contribute to its significance for public 
health. In an earlier report, Kozlowski and colleagues (1980b) examined 
the effect of hole blocking on nicotine, tar, CO, and puffs (Table 7), noting 
that ventilated filters have been developed primarily as a way to make less 
toxic cigarettes but that smoking behavior can sabotage the benefits of 
these filters. 
Kozlowski and colleagues (1989) demonstrated that some smokers of 
vented filter cigarettes are lighter smokers who appear to be seeking lower 
smoke doses and do not block vents, whereas others are generally heavier 
smokers who block vents and derive high daily doses of nicotine. Two 
smokers, who were vent blockers, of a 1-mg tar, 0.1 -rng nicotine cigarette 
achieved salivary cotinine levels (303 and 385 ng/mL) consistent with 
smoking a high-yield cigarette. 
266 
