The results of this review are the same as those reported
earlier for 14 studies of rats and mice: minimal evidence of
respiratory tract carcinomas being produced by long-term
exposures to large amounts of mainstream cigarette smoke.
Signi cant increases in the numbers of malignant tumors
were not produced in the respiratory tracts of hamsters, dogs,
or nonhuman primates exposed chronically by inhalation to
mainstream cigarette smoke