Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry.
The potential carcinogenicity of crystalline silica to humans remains a controversial issue. The authors conducted an historical cohort mortality study of 2,342 male workers exposed to crystalline silica, predominantly cristobalite, in a diatomaceous earth mining and processing facility in California. During the years 1942-1994, mortality excesses were detected for nonmalignant respiratory diseases (NMRD) (standardized mortality ratio = 2.01, 95% confidence interval (CI) 1.56-2.55) and lung cancer (standardized mortality ratio = 1.29, 95% CI 1.01-1.61). NMRD mortality rose sharply with cumulative exposure to respirable crystalline silica; allowing for a 15-year latency, the rate ratio for the highest exposure stratum (> or = 5.0 mg/m3-years) was 5.35 (95% CI 2.23-12.8). The rate ratio for lung cancer reached 2.15 (95% CI 1.08-4.28) in the highest exposure category. These associations were unlikely to have been confounded by smoking or asbestos exposure. The findings indicate a strong dose-response relation for crystalline silica and NMRD mortality. The lung cancer results, although less convincing, add further support to an etiologic role for crystalline silica.
Checkoway
H
H
Department of Environmental Health, University of Washington, Seattle 98195-7234, USA.
Heyer
N J
NJ
Seixas
N S
NS
Welp
E A
EA
Demers
P A
PA
Hughes
J M
JM
Weill
H
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001194:Asbestos / Q000009:adverse effects; D002140:California / Q000453:epidemiology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D008175:Lung Neoplasms / Q000139:chemically induced* / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D012140:Respiratory Tract Diseases / Q000139:chemically induced* / Q000401:mortality*; D012306:Risk; D012822:Silicon Dioxide / Q000009:adverse effects*
D001194:Asbestos; D012822:Silicon Dioxide