Silicosis in the ceramic industry: dose-response relationship

Background The dose-response relationship between silica exposure and silicosis remains controversial, particularly when comparing extrapolations from data of cumulative exposure in occupational cohorts. The aim of this study was to investigate the dose-response relationship between silica exposure and chest radiological abnormalities in two Trench ceramic industry plants. Methods. 218 subjects exposed to silica dust were included in a cross-sectional study in 1992 (mean age: 37.8 years; mean duration of exposure: 13.5 years). Three certified NIOSH B readers independently assessed radiological abnormalities on chest X-rays according to the 1980 ILO classification. Airborne dust measurements were used to estimate the individual cumulative exposure to silica dust. Results. Thirty-eight subjects (17.4%) exhibited small opacities with profusion greater than or equal to 1/0. Prevalence of small opacities greater than or equal to 1/0 clearly increased with cumulative silica exposure (4, 14, 20 and 31% in the "<0.35", "0.35-1.08", "1.08-1.77" and ">1.77 mg/m(3) x years" exposure categories, respectively; p = 0.002), This association remained significant after adjustment for age and smoking habits. Conclusions. Although most cases probably had only early stages of silicosis, these results suggest that a more stringent control of exposure to silica dust should be obtained in this plant.