Silicosis prevalence and associated occupational risk factors among cassiterite (tin ore) miners in eastern Rwanda: a cross-sectional analysis of mining practice and risk in an active mining cohort

OBJECTIVES: Silicosis is one of the most common forms of pneumoconiosis worldwide. In Rwanda, there is a lack of data on the silicosis burden and occupational risk among underground miners. METHODS: We conducted a cross-sectional study among all miners from eight cassiterite (tin ore) mining sites in Kayonza district, eastern Rwanda. Questionnaire data and chest radiography were collected at Rwinkwavu District Hospital. Two radiologists reviewed all the chest radiographs using International Labour Organization (ILO) criteria, with a third radiologist reviewing films with ILO rating discrepancies. Logistic regression was performed to investigate risk factors associated with radiographic silicosis. RESULTS: In total, 1021 mine workers were included in the primary outcome (risk) analysis. The median age was 32 years (IQR 26-40), and 948 participants (93%) were male. Of all participants, 94 (9%) were diagnosed with silicosis in the primary analysis. Increased odds of silicosis were associated with working in a blasting station (adjusted OR (aOR) 3.30; 95% CI 1.68 to 6.45), excavation station (aOR 2.77; 95% CI 1.09 to 7.04), drilling station (aOR 2.51; 95% CI 1.34 to 4.70), exposure to tobacco (aOR 1.92; 95% CI 1.14 to 3.24) and increased time of working in mining (aOR 1.05 per year spent in mining; 95% CI 1.01 to 1.09). CONCLUSIONS: High-risk mining tasks, tobacco use and duration of mining employment were significantly associated with increased risk of having a silicosis diagnosis. Our results indicate that screening and preliminary occupational risk analysis in a rural mining cohort is technically feasible.