Risk of stomach cancer associated with 12 workplace hazards: analysis of death certificates from 24 states of the United States with the aid of job exposure matrices

Objective-To investigate the risk of gastric cancer associated with 12 work place exposures suspected or discussed as aetiological agents in previous r eports. Methods-A case-control study was conducted based on the death certificates of several million deaths in 24 states of the United States in 1984-96. Ove rall, the data base included 41 957 deaths from stomach cancer among subjec ts aged greater than or equal to 25 years. These were 20 878 white men, 14 125 white women, 4215 African American men, and 2739 African American women . Two controls for each case were selected from among subjects who died fro m nonmalignant diseases, frequency matched to cases by geographic region, r ace, sex and 5 year age group. Each three digit occupation and industry cod e listed in the 1980 United States census was classified for probability an d intensity of exposure to asbestos, inorganic dust, metals, lead, polycycl ic aromatic hydrocarbons (PAHs), nitrogen oxides, nitrosamines, sulphuric a cid, fertilisers, herbicides, other pesticides (including insecticides and fungicides), and wood dust. These job exposure matrices were subsequently a pplied to the occupation-industry combinations in the death certificates of f study subjects, separately by sex and race. Results-Risk of stomach cancer showed a modest association with occupationa l exposure to inorganic dust (odds ratio (OR)=1.06; 95% confidence interval (95% CI) 1.03 to 1.11) with significant increasing trends by probability a nd intensity of exposure overall and by cross classification of the two exp osure metrices. Workplace exposure to nitrosamines also showed a modest ass ociation (OR=1.06; 95% CI 1.01 to 1.11), but the excess risk was even small er after adjusting for inorganic dust exposure. Risk of gastric cancer was not associated with any of the other workplace exposures considered in this study. Conclusions-Non-differential misclassification of exposure may have caused negative findings in this study, and inorganic dust may be a partial surrog ate for exposure to other unknown risk factors. Alternatively, our results suggest that occupational factors contribute little to the aetiology of gas tric cancer. Inorganic dust might act through non-specific mechanisms, simi lar to those proposed for salt, aspirin, and heat by other authors.