cigarette smoke induces carcinoma of the larynx in syrian golden hamsters and is active as a tumor promoter in hamsters pretreated with a low dose of a pah , nitrosamine , or nitrosamide . 
 these tumorigenic effects are only observed with total smoke , but not with the gas phase alone . 
 this demonstrates that the tumorigenic agents reside primarily in the particulate phase . according to fractionation experiments , a number of four- and five - ring aromatic hydrocarbons serve as the major tumor initiators in tobacco smoke . 
 tumor promoters reside primarily in weakly polaric neutral subfractions and in the weakly acidic portion of the particulate matter and include certain unsaturated hydrocarbons and phenolic compounds . 
 cocarcinogenic activity is a characteristic feature of tobacco smoke and its particulates . among the cocarcinogens formed during combustion 
 are catechols and certain nontumorigenic aromatic hydrocarbons and terpenes . 
 nicotine may also serve as a cocarcinogen as is indicated by preliminary data . the action of tumor promoters and cocarcinogens in tobacco carcinogenesis , the precursors for tobacco smoke promoters and cocarcinogens , and methods for their reduction in smoke are discussed.imagesfigure 2.figure 5 .