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Nephrite jade is majorly composed of nonasbestiform tremolite. The study of the health risk in nephrite jade workers is limited.
Methods
A retrospective cohort study was designed. A cohort of 344 stone workers and their family was established in 2010. Among them, 54 workers are nephrite jade workers. Medical examination, chest radiogram and questionnaire survey were conducted. The profusion of chest radiogram was graded complied with ILO/ICRP standard in a triple-blinded manner. Both cross-sectional and longitudinal statistics were applied. In time series analysis, the follow-up started from the year of beginning their work and ended in the survey of 2010. At the end of follow-up, the development of pulmonary fibrosis profusion 1/1 or greater with lung crackle was regarded as an event, and subjects without the event were treated as right censored. Consecutive personal air samples of asbestos fiber in a full cycle of manufacturing nephrite jade were obtained.
Results
After excluding 12 subjects with history of tuberculosis and occupational history of metal casting and welding, 328 subjects were enrolled for analysis. The mean follow-up year was 25.0 and 8,137 person-years were accrued. The OR of pulmonary fibrosis profusion 1/1 or greater with lung crackle in nephrite jade workers was 2.99 (p=0.04). By using employment less than 10 years as the reference group, the OR of processing nephrite more than 20 years was 4.79 (p=0.01). Log-rank test showed that processing nephrite had an increased risk (p=0.08). The proportional hazard ratio adjusted for age, sex and pack-year of smoking was 2.30 (p=0.14) in processing nephrite. The concentration of fiber is 0.0981 f/cc in cutting, 0.5967 f/cc in crude grinding, 0.0490 f/cc in fine grinding, and 0.507 f/cc in polishing nephrite.
Discussion
The finding indicates that processing nephrite jade might release asbestiform fibers and increase the risk of lung fibrosis.