OBJECTIVETo understand the laws and characteristics of silicosis incidence of the workers exposed to the uranium dust from 1956 to 2002.

METHODSThe length of employment, age of occurrence of silicosis, and its duration and death age were compared between the uranium miners and uranium geological prospecting teams, and also between the miners exposed to uranium dust and those exposed to mixed uranium dust by single factor analysis method.

RESULTSWith time going on, the length of employment, age of occurrence of disease and its duration and death age were prolonged respectively in the workers exposed to uranium dust. The length of employment and age of occurrence of disease in uranium geological prospecting teams [(10.15 +/- 5.95) and (40.60 +/- 9.86) years respectively] were shorter than those in uranium miners [(14.23 +/- 8.12) and (41.38 +/- 10.98) years], but the duration (P(50)) and death age were longer [(14.29 years vs 12.52 years), (53.69 +/- 10.04) years vs (51.45 +/- 10.85) years respectively]. The length of employment and age of occurrence of disease in those exposed to uranium dust only [(11.78 +/- 8.06) and (38.04 +/- 9.89) years] were shorter than those exposed to mixed uranium dust [(12.74 +/- 6.29) years, (41.40 +/- 10.67) years], but the duration (P(50)) and death age were longer than the mixed uranium dust ones [(14.59 years vs 13.20 years), (53.93 +/- 10.60) years vs (51.82 +/- 10.20) years].

CONCLUSIONThe difference in the occurrence of silicosis in the workers exposed to uranium dust may be attributed to the physical and chemical character of the uranium dust and the different working circumstance.