 cofactors involved in respiratory tract carcinogenesis were studied in syrian golden hamsters or in rats using benzo(a)pyrene as the carcinogenic agent . 
 these factors included severe tissue damage induced by electro - coagulation , glass fibers administered by intratracheal instillation , acetaldehyde as irritant vapor , food restriction , and nutrients such as vitamin a and saturated and unsaturated fats . in addition , the effects of a combined exposure to four different major gaseous cigarette smoke components -- methyl nitrate , isoprene , methyl chloride and acetaldehyde -- and to one solid cigarette smoke component -- norharman -- were examined in short- and long - term inhalation studies . 
 an interesting finding was the carcinogenicity of acetaldehyde , of which the possible mechanism is briefly discussed . 
 another conspicuous observation was the substantial increase in number and size of lipid droplets in alveolar fibroblasts of hamsters fed a high vitamin a diet.imagesfigure 1.figure 2.figure 3.figure 4.figure 5.figure 6.figure 7 . 
Images