Smoking and Tobacco Control Monograph No. 7 
Table 1 a 
Effect of filament diameter on filter efficiency^ 
Approximate 
Pressure Drop 
Tar Removed 
Filament Diameter (p) 
(mm of H 2 O) 
(percent) 
22 
55.7 
30 
20 
55.7 
33 
17 
53.1 
36 
14 
55.7 
38 
12.6 
53.1 
43 
Table 1 b 
Effect of filter length on efficiency** 
Filter Length 
Pressure Drop 
Tar Removed 
(mm) 
(mm of H 2 O) 
(percent) 
15 
42 
26.2 
20 
57 
33.3 
25 
71 
39.7 
30 
85 
45.5 
35 
99 
50.8 
® Cellulose acetate, 1 7 mm in length, 25-mm circumference. 
“ Cellulose acetate, 24.6-mm circumference. 
Key: n = micron (W^ meter); Hfi = water. 
Source: Kiefer and Touey, 1967. 
a filter tip of the same length but made entirely of cellulose acetate (Figure 4) 
(Brunnemann et al., 1990). Charcoal-containing filter tips are efficient in 
selectively reducing certain volatile aromatic hydrocarbons, such as benzene 
and toluene, from the smoke of the early puffs; yet, they release these 
hydrocarbons during the later puffs (Brunnemann et al., 1990). 
I'oday, more than 70 percent of all cigarettes sold in Japan have 
charcoal-containing filter tips (Wynder and Hoffmann, 1994). Only a few 
percent of the cigarettes sold in the United States have such filters. Although 
more Japanese men smoke comparable numbers of cigarettes per day than 
American men do and the smoke yields per cigarette in Japan are similar 
to those in the United States, Japanese men have a significantly lower lung 
cancer incidence rate (Wynder and Hoffmann, 1994; Wynder et al., 1992). 
Among other factors, the lower yields of ciliatoxins, such as acrolein and 
hydrogen cyanide, in the smoke of cigarettes with charcoal filter tips may 
be partly responsible for the lower lung cancer rate in Japan. 
20 
