Radiological progression and its predictive risk factors in silicosis

Abstract

Objectives-To investigate the risk factors predicting radiological progression in silicosis in a prospective cohort study of patients with silicosis who were previously exposed to silica from granite dust. Methods-From among a total of 260 patients with silicosis contracted from granite work, 141 with available serial chest x ray films of acceptable quality taken over a period of 2 to 17 (mean 7.5) years, were selected for study. Ninety four (66.7%) had ended exposure 5 or more years perviously (mean 10.1 years, maximum 28 years). Radiological progression was assessed by paired comparison of the initial and most recent radiographs, with two or more steps of increase in profusion of small opacities according to the 12 point scale of the International Labour Organisation (ILO) classification of radiographs of pneumoconiosis, taken from the majority reading by a panel of three independent readers. Results-Overall, 37% of patients with silicosis had radiological evidence of progression. From the initial radiographs, 24 (31.6%) of those with radiological profusion category 1, 15 (37.5%) of those with radiological profusion category 2, and 13 (52%) of those with complicated silicosis (including all seven with category 3 profusion of small opacities) showed radiological progression. As expected, progression was more likely to be found after longer periods of follow up (the interval between the two chest x ray films) with a 20% increased odds of progression for every additional year of follow up. After adjustment for varying intervals of follow up, the probability of radiological progression was found to be significant if large opacities were present in the initial chest x ray film. Progression was also less likely to be found among those who had ended exposure to silica longer ago, although the result was of borderline significance (p=0.07). Tuberculosis was also associated with increased likelihood of progression (borderline significance). Conclusions-There is a high probability of radiological progression in silicosis after high levels of exposure to granite dust among workers who were followed up for up to 17 years. A significant risk factor is the extent of radiological opacities in the initial chest x ray film. The probability of progression is also likely to be reduced with longer periods after the end of exposure. (Occup Environ Med 2001;58:467-471)

A 40-Year Follow-Up of Whetstone Cutters on Silicosis

“…During this some 40-year period of follow-up, more than a half of the workers deceased due to diseases including 29 cases of silicosis (including 9 cases of silicotuberculosis), and 6 cases of lung cancer (all confirmed by death certificates). Both duration of service and category of chest radiography at the time of the preceding health examination are among the influential factors in determining the progression of the disease (Tables 4 and 5), the former being in confirmation with the observation by Hnizdo and Sluis-Cremer 30) and the latter with that by Lee et al 23) . The latter observation was reproduced through a similar analysis of the other group of 75 whetstone cutters (Group II workers; Table 6).…”

“…Diagnostic application of modern techniques such as computerized tomography 18) is also well documented in addition to traditional chest X-ray examination and lung function tests 19,20) . With some exceptions [21][22][23] , most of the epidemiological studies reported in literature are on cross-sectional findings among miners or other groups of workers exposed to silicacontaining dust, despite the fact that silicosis is a very chronic disease requesting decades of years to develop in full, and reports on long-time follow-up of patients are relatively scarce.…”

Fibrose maciça progressiva em trabalhadores expostos à sílica: achados na tomografia computadorizada de alta resolução

“…Other authors (22) used serial X-rays to study the radiological evolution of 141 silicosis patients and found that radiological progression occurred more often in those presenting large opacities on the initial X-rays than in those who had had tuberculosis.…”

Mortality due to Silico-Tuberculosis and Lung Cancer Among 200 Whetstone Cutters.

“…Such close association was observed also among workers in other countries and even in recent years. For example, 7 cases out of 37 silicosis patients had lung TB among North American industrial sand workers 14) , and one third of 141 granite-exposed silicosis patients in Singapore had a history of lung TB 15) . Similarly, an elevated mortality due to all tuberculosis (predominantly lung TB) was reported for compensated silicosis patients 16) as well as for copper miners 17) in Japan.…”