Lung function and functional exercise capacity in underground semi-precious stone mineworkers.

BACKGROUND: Semi-precious stone mining may cause occupational lung disease. The impact of inhaling silica on workers' exercise capacity has only been partially studied. OBJECTIVES: To study lung function, exercise capacity, and identify factors associated with functional impairment. METHODS: In a cross-sectional study of 193 current miners from Ametista do Sul, Rio Grande do Sul, Brazil, medical and occupational data were collected. The diagnosis of silicosis was established by the history of dust exposure and chest radiographic findings. All workers performed a spirometry and a 6-minute walk test (6MWT). RESULTS: Of the sample 51 (26.4%) had silicosis. Time working in mine was 14.7±8.7 years. Spirometry showed a normal, restrictive or obstructive ventilatory pattern in 75.1 %, 13 % and 9.3 % of the workers, respectively. The diagnosis of silicosis and length of time working in mining negatively affected lung function, although exercise capacity was preserved. In the multivariate analysis, time working in mining, diagnosis of silicosis and education remained significant for forced expiratory volume in one second (FEV1; r = 0.60; r2 = 0.36; p < 0.001) and age and height for distance in 6MWT (r = 0.66; r2 = 0.43; p < 0.001). CONCLUSIONS: Our results show impaired lung function and preserved exercise capacity in current mineworkers exposed to silica. Length of time working in mining, presence of silicosis and lower education were factors associated with reduced lung function.