Effects of work related confounders on the association between silica exposure and lung cancer: a nested case-control study among Chinese miners and pottery workers.
OBJECTIVE
The role of silica in the causation of lung cancer is an ongoing debate. In order to explore whether observed association between silica exposure and lung cancer is confounded by exposure to other occupational carcinogens, we updated a previously nested case-control study among a cohort of male workers in 29 Chinese mines and factories on the basis of an extended follow-up.


METHODS
Five hundred and eleven lung cancer cases and 1,879 matched controls were selected. Exposure to respirable silica as well as relevant occupational confounders were quantitatively assessed based on historical industrial hygiene data. The relationship between exposure to silica and lung cancer was analyzed by conditional logistic regression analysis adjusted for exposure to arsenic, polycyclic aromatic hydrocarbons (PAHs), radon, and smoking.


RESULTS
In a crude analysis adjusted for smoking only, a significant trend of increasing risk of lung cancer with exposure to silica was found for tin, iron/copper miners, and pottery workers. But after adjustment for relevant occupational confounders, no relationship between silica and lung cancer can be observed. Instead, there is a significant association between lung cancer mortality and cumulative exposure to inorganic arsenic (OR = 1.86, 95% CI: 1.14, 3.04 for each mg/m(3)-year increase) and carcinogenic PAHs (OR = 1.35, 95% CI: 1.08, 1.69 for each 100 microg/m(3)-year increase).


CONCLUSIONS
This analysis does not provide any evidence to show that exposure to silica causes lung cancer in the absence of confounding factors.
Chen
Weihong
W
Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Bochmann
Frank
F
Sun
Yi
Y
D000395:Air Pollutants, Occupational / Q000009:adverse effects; D001151:Arsenic / Q000009:adverse effects; D016022:Case-Control Studies; D002516:Ceramics / Q000009:adverse effects; D002681:China / Q000453:epidemiology; D015986:Confounding Factors, Epidemiologic; D005500:Follow-Up Studies; D006801:Humans; D008175:Lung Neoplasms / Q000209:etiology / Q000401:mortality*; D008297:Male; D019216:Metals, Heavy / Q000009:adverse effects; D008906:Mining; D009784:Occupational Diseases / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D016017:Odds Ratio; D011084:Polycyclic Aromatic Hydrocarbons / Q000009:adverse effects; D017687:Radon Daughters / Q000009:adverse effects; D012822:Silicon Dioxide / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects
D000395:Air Pollutants, Occupational; D019216:Metals, Heavy; D011084:Polycyclic Aromatic Hydrocarbons; D017687:Radon Daughters; D012822:Silicon Dioxide; D001151:Arsenic