Investigation on masonry silicosis in a private quarry

Objective To understand the reality of work environment and occurrence of silicosis of workers in a privately-owned quarry, so that the effective measures against the hazards can be taken. Methods The occupational health survey was done in this privately-owned quarry; the dust level at workplaces was measured and health examination of 149 exposed workers was carried out. Results The TWA concentrations of total dust varied from 0.10-29.8 mg/m³ in different workplaces with 61.11% non-compliance rate. The highest concentration was 28.8 times as high as national limit value. The free silica content was 28.4% in the dust,and 18 cases of masonry silicosis(12 cases in stageⅠand 6 cases in stageⅡ) were found, with the detection rate of 12.08%. The mean age of victims was (38.5 ±1.58)years old (31-45 years old)and the mean of dust exposure was (5.0 ±1.2) years (2.0-7.7 years). Most cases (66.67%) engaged in blasting operation. The major symptoms of these cases were cough (83.33%), chest pain (44.44%) and dyspnea (38.89%). X-ray examination showed small round shadow like "q" (77.78%) and "p"(22.22%). One third of the victims completely lost their work ability. The high occurrence of silicosis was not correlated with the age (r_s=0.357 1, P=0.50),but there was obvious correlation between the work (exposure) time and the occurrence(r_s=1, P=0.01). Conclusion The workers engaged in blasting operation were the most serious victims, they had high exposure to dust.The prompt measures should be taken to control such hazards. We should conscientiously do a good job in the prevention and control work.