OCCUPATIONAL EXPOSURES AND GASTRIC-CANCER ETIOLOGY

Epidemiological studies have frequently reported that many occupations are associated with an increased risk of gastric cancer. However, the diversity of occupations and inconsistencies across studies have mean t that positive findings are often explained by confounding dietary an d life-style factors related to low socioeconomic status and manual wo rk. Nevertheless, exposure to preformed nitrosamines and to precursors of endogenous nitrosation occurs via inhalation and dermal absorption in a number of occupations and industries. It is still unclear whethe r such exposures alone contribute to gastric cancer aetiology, or whet her they act in combination with diet and life-style risk factors. N-n itroso compounds, may directly or through the formation of free radica ls or nucleophilic intermediates, damage the nucleic acids of gastric mucosal cells and act as initiators of the carcinogenic process. Other physical agents, such as organic and inorganic dusts (including asbes tos and other mineral dusts) may irritate the gastric mucosa and act a s co-carcinogens when swallowed with mucus, causing superficial gastri tis and increasing cell proliferation, which can promote initiated clo nes. Dusts can also act as carriers, delivering carcinogens to the gas tric mucosa. Further research in this area is necessary to clarify dos e-response curves and to elucidate the carcinogenic process.