Radiological Progression and Mortality among Silica Flour Packers: A Longitudinal Study

Abstract

There are few longitudinal studies that investigated the radiological progression of silicosis among different occupational groups. Inhalation exposure to very high levels of crystalline silica can lead to acute silicosis. This longitudinal study was designed to determine association between mortality and radiological progression among individuals with rapidly progressive silicosis. Twenty-three subjects with silicosis had previously worked in the same stone-grinding factories, where they had been exposed to high airborne concentrations of silica powder dust. The diagnosis of rapidly progressive form of silicosis was made according to the National Institute for Occupational Safety and Health definition. The subjects were entered into the study if chest radiography films with acceptable quality showed small opacity shadowing of at least 1/0 profusion grade. Chest radiographs of the start and end of follow-up were independently reviewed at different times by two readers. For paired comparison, the side-by-side method of presenting radiographs was used. Data analysis was carried out by using the t-test, Fisher's exact test, and logistic regression. It was found that 65.2% of workers showed evidences of radiological progression during a period of follow up (mean 30.3 mo). The age of death for the 10 workers who died of silicosis ranged between 21 and 35 yr, with the mean and median age of 27.30 (SD 4.77) and 28.50 yr, respectively. There was a significant association between mortality and both size and profusion progression of small opacities. In conclusion, we quantified the risk of death from rapidly progressive forms of silicosis in a group of workers heavily exposed to silica. We conclude that young adult age, rapid progression in the size, and profusion of small opacities are risk factors for the development of advanced silicosis. Death occurs more quickly in silicotic patients with these criteria.