Risk Prediction of Pulmonary Function Disorder of Workers Exposed to Silica Dust in the Stone Crushing Workshops Using Cox Regression Model

The occupational exposure conditions such as dust concentration، exposure time، smoking status and use of respiratory protection device are effective on pulmonary function disorder. The aim of this study was to determine the risk of pulmonary function disorder in the workers exposed to silica dust in the stone crushing by using Cox regression model. 117 of workers employed in the stone crushing workshops were selected through simple random approach. Information about history of occupational exposure was collected using the standard questionnaire. The results of p ulmonary function test which had been conducted using the Spirometer (Model –Vitalograph Spirotrav IV) were extracted. The result of the obtained model showed that the worker age، smoking status and use of respiratory protection device were effective in causing pulmonary function disorder. The hazard risk in the smokers was 8. 44 higher (compared with non-smokers) and also in the workers without respiratory protection device was 3. 3 higher (compared with the group who used the device). Using the Cox model could practically determine the effect of worker exposure variables on the hazard risk of pulmonary function disorder. Accordingly، this study proposed that the hazard risk of different occupational diseases should be estimated using the Cox model in order to consider protective intervention programs.