title: The changing cigarette.
abstract: BACKGROUND
  Epidemiologic surveys have revealed accelerated increases in adenocarcinoma but less rapid increases in squamous cell carcinoma of the lung among cigarette smokers in recent decades. Changes in the makeup of cigarettes and corresponding changes in smoke composition along with nicotine-compensating smoking patterns, such as the frequency of puff drawing and depth of inhalation, are suggested to have contributed to the observed epidemiologic profiles of these major histologic types of lung cancers.
  
  
  METHODS
  The various changes in cigarette makeup leading to declining smoke yields from sales-weighted averages of 38 mg "tar" and 2.7 mg nicotine to 12 mg "tar" and 0.9 mg nicotine per cigarette are described.
  
  
  RESULTS
  Higher nitrate content of tobacco blends is shown to be one of the major influences on lower smoke yields of carcinogenic polynuclear aromatic hydrocarbons (PAH) while causing increased yields of carcinogenic, tobacco-specific N-nitrosamines (TSNA). In vivo and in vitro bioassays incriminate PAH as inducers of squamous cell carcinoma, while TSNA are known to elicit primarily adenocarcinoma of the lung.
  
  
  CONCLUSIONS
  The product changes, the smokers' dependence on nicotine which governs their smoking patterns, and the modified smoke chemistry support the hypothesis that differences in PAH and TSNA exposure may be linked to the observed different incidences of squamous cell cancer and adenocarcinoma of the lung.
authors.affiliation: American Health Foundation, Valhalla, New York 10595, USA.
authors.forename: D
authors.initials: D
authors.lastname: Hoffmann
authors.forename: M V
authors.initials: MV
authors.lastname: Djordjevic
authors.forename: I
authors.initials: I
authors.lastname: Hoffmann
mesh_terms: D000230:Adenocarcinoma / Q000453:epidemiology / Q000209:etiology; D001580:Benzopyrenes / Q000009:adverse effects / Q000378:metabolism; D002273:Carcinogens / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000453:epidemiology / Q000209:etiology; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology; D009538:Nicotine / Q000008:administration & dosage / Q000378:metabolism; D009602:Nitrosamines / Q000009:adverse effects / Q000378:metabolism; D010947:Plants, Toxic; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology / Q000639:trends; D014026:Nicotiana / Q000737:chemistry*; D019460:Tobacco Industry / Q000639:trends*; D014481:United States / Q000453:epidemiology
chemical_list: D001580:Benzopyrenes; D002273:Carcinogens; D009602:Nitrosamines; D009538:Nicotine