Objective To establish a job-exposure matrix (JEM)of occupational exposure to silica dust from 1953 to 2000 in Shanghai based on accumulated records from the surveillance database of occupational hazards in Shanghai; to draw attention and lead more discussion to silica dust exposure by introducing JEM.
Methods To sort out, analyze, regress and calculate the surveillance records of silica dust exposure by using EXCEL, ACCESS and STATA software. There were 65 561 parameters in the database. The industrial health specialists assessed the intensity levels of different industrial categories and occupational categories based on the related theories and practices; calculated 113 average concentrations by cross-classifying and combining the factors such as different time periods, occupational rates and occupational rates; then obtained the regression model based upon logarithm of measured mean concentration (dependent variables)and period of time, and industrial rate and occupational rate (independent variable); filled different time periods with dummy variables to fit the regression model with fluctuations in different periods better, and filled up the missed values with prediction through regression model.
Results This study established a JEM composed of 144 cells derived from 9 different time periods, four industrial categories and four occupational categories from 1953 to 2000 in Shanghai. The fact that the concentration of silica dust exposure in the workplace had dropped from a very high level to a level close to or compliant with the health standards in 47 years demonstrated a great achievement made in the occupational health. However, linear fluctuations also reflected the relevant problems. The meaning, usefulness, methodology, and perspective of JEM were discussed.
Conclusion This study clearly organized the accumulated surveillance records of occupational exposure to silica dust in Shanghai, established a specialized JEM for occupational health surveillance, occupational disease diagnosis, epidemiological research as well as labor capability identifying.
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