Chapter 3 
Figure 2 
Percentage of all U.S. cigarettes with filter tips 
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inner core of the burning cone is depleted of oxygen, and thus the levels 
of carbon monoxide, hydrogen cyanide, and some other volatiles are 
selectively reduced in the smoke of cigarettes with perforated filter tips 
(Figure 3) (National Cancer Institute, 1977). Furthermore, the lower velocity 
of the generated smoke increases the efficiency of the filter. However, the 
tumorigenicity of the resulting tar does not change compared with that of 
the tar of a conventional, nonperforated cellulose acetate filter cigarette 
(National Cancer Institute, 1977). In principle, the smoke of a cigarette 
can be diluted to an unlimited degree by air; however, the consumers' 
nonacceptance of these cigarettes is the limiting factor. 
The use of charcoal particles in one of two or three sections of a filter 
tip, or sprayed onto the cellulose acetate, also offers the opportunity to 
selectively reduce certain volatile smoke constituents, such as the ciliatoxic 
hydrogen cyanide, acetaldehyde, and acrolein (National Cancer Institute, 
1977; Tiggelbeck, 1968). However, replacing one section of the filter tip 
with charcoal also leads to less reduction of TPM than can be achieved with 
19 
