Cancers of the gastrointestinal tract (esophageal, gastric, and colorectal cancer)

Abstract

The large differences in incidence within geographical areas and changes in incidence over time, suggest a predominant role of environmental factors under a multifactorial etiology model for esophageal cancer (EC), with alcohol and tobacco drinking as the main risk factors for squamous cell variety in Western countries, and chronic gastroesophageal reflux for the adenocarcinoma. Certain occupations and occupational exposures such as dry cleaning and tetrachloroethylene, rubber industry and nitrosamines, carbon black, strong inorganic acids including sulfuric acid, polycyclic aromatic hydrocarbons (PAHS) and exposure to different dusts (mainly silica dust) and fibers such as asbestos, has been related to EC risk, but whether risk varies according to histological type specifically remains unknown. Gastric cancer (GC) etiology is also clearly multifactorial, being both environmental such as Helicobacter pylori infection or diet and genetic factors involved. Most of the occupational studies on the risk of GC have focused on exposure to different dusts (mainly minerals such as crystalline silica) and fibers such as asbestos, and have found associations for industries and/or occupations with higher exposure to these agents. Evidence of an excess of GC among rubber-manufacturing workers also exists mainly related to mixing, milling, and compounding processes, and for hexavalent chromium exposure. Lastly, some studies have shown positive results for strong inorganic acids, PAHS, and pesticides. The variation in incidence within countries, along with the increase in the developing countries that are undergoing economic growth, or the rapid rise of colorectal cancer (CRC) showed in studies of immigrant populations from low- to high-risk areas, have suggested also a strong environmental influence on CRC pathogenesis. Asbestos is the most classically occupational exposure studied in relation to CRC. Certain human carcinogens, such as diesel and gasoline engine exhaust, tetrachloroethylene or specific pesticides such as chlorpyrifos or Aldicarb could also be associated with CRC risk.