Lung cancer among industrial sand workers exposed to crystalline silica

In 1997, the International Agency for Research on Cancer determined that cr ystalline silica was a human carcinogen but noted inconsistencies in the ep idemiology. There are few exposure-response analyses. The authors examined lung cancer mortality among 4,626 industrial sand workers, estimating expos ure via a job-exposure matrix based on 4,269 industrial hygiene samples col lected in 1974-1995. The average length of employment was 9 years, and esti mated average exposure was 0.05 mg/m(3) (the National institute of Occupati onal Safety and Health Recommended Exposure Limit), Results confirmed exces s mortality from silicosis/pneumoconioses (standardized mortality ratio = 1 8.2, 95% confidence interval: 10.6, 29.1; 17 deaths). The lung cancer stand ardized mortality ratio was 1.60 (95% confidence interval: 1.31, 1.93; 109 deaths). Limited data suggested that smoking might account for 10-20% of th e lung cancer excess. Exposure-response analyses by quartile of cumulative exposure (15-year lag) yielded standardized rate ratios of 1.00, 0,78, 1,51 , and 1,57 Ip for trend = 0.07). Nested case-control analyses after exclusi on of short-term workers, who had high overall morality, yielded odds ratio s by quartile of cumulative exposure (15-year lag) of 1.00, 1.35, 1.63, and 2.00 (p for trend = 0.08) and odds ratios by quartile of average exposure of 1.00, 0.92, 1,44, and 2.26 (p = 0.005). These data lend support to the l abeling by the International Agency for Research on Cancer of silica as a h uman carcinogen. There are approximately 2 million US workers exposed to si lica; 100,000 are exposed to more than 0.1 mg/m(3).