Smoking and Tobacco Control Monograph No. 7 
of TSNAs and BaP is not selective. On a gram-to-gram basis, the tars obtained 
from cigarettes with high-porosity paper still have the same tumorigenic 
activity as does the tar from control cigarettes that have conventional 
cigarette paper (National Cancer Institute, 1977). 
Reconstituted Reconstituted tobacco (RT) was first used after World War 11 as a 
Tobacco binder for cigars and until the beginning of the 1960's on a limited 
scale for cigarettes (Halter and Ito, 1979). The interest in RT grew with 
the observation that cigarettes made exclusively from RT delivered lower 
smoke yields of tar, phenols, and BaP. On a gram-to-gram basis, this tar had 
significantly lower tumorigenicity on mouse skin and in the respiratory tract 
of hamsters (Wynder and Hoffmann, 1965). In 1974 the Research Institute 
of the German Cigarette Industry reported that forced exposure of Syrian 
golden hamsters to the smoke of cigarettes filled exclusively with RT gave 
significantly lower tumor incidence in the upper respiratory tract of the 
animals than treatment with the smoke of a blended cigarette containing 
only lamina of bright, hurley, and oriental tobacco (Dontenwill, 1974). 
Reconstituted tobacco, or homogenized sheet tobacco as it is sometimes 
called, is a paperlike sheet approaching the thickness of tobacco laminae. 
RT is made from tobacco dust, fines, and particles from ribs and stems; 
various additives may be incorporated. The process for making RT can be 
divided into four general classes. The first two relate to the papermaking 
process; the third involves a slurry; and the fourth is based on the 
preparation of a tobacco paste with rollers using water or low-boiling 
solvents. For the papermaking process, a mixture of fines, midribs, and 
sometimes tobacco stems is broken up and extracted with water. The extract 
is concentrated by evaporation. The insoluble residue is macerated further, 
and the resulting material is formed into a paperlike web on a papermaking 
machine. The web is dried and then impregnated with the concentrated 
extract; this web is then further dried and cut. The shredded material is 
added to the tobacco blend. Because the water extract of the tobacco 
contains nicotine and this extract is added in concentrated form to the 
tobacco web, this process has been considered a "nicotine-enriching process." 
In one papermaking process, cellulose fiber is added to increase the filling 
power and stability of the resulting RT. 
In making RT by the slurry process, dry tobacco materials are finely 
divided and often mixed with small amounts of adhesive, then suspended 
in water. The resulting slurry is placed on a metallic band on which it is 
dried. I'he resulting sheet is shredded and added to the tobacco blend. In 
the rolling process, only small amounts of water are added to the mixture of 
tobacco fines, dust, and finely powdered ribs; this paste is placed onto rollers 
with different speeds, resulting in a sheet with limited filling power and 
tensile strength. 
The potential to produce RT in various forms with different densities 
and filling powers and thereby to modify the tumorigenicity of tars and 
whole smoke encouraged the National Cancer Institute (NCI) in the 1970's 
to explore the use of various types of R F for recommendations of a less 
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