To provide a scientific basis for determining the health surveillance period of dust-exposed workers, data of a retrospective cohort study was re-analyzed with emphasis on natural course of silicosis. 33640 workers exposed to silica dust who were employed for at least 1 year from 1972 to 1974 in twenty Chinese mines or pottery factories were included as subjects, and were followed up till December 31, 1994. The cohort included subjects from 8 tungsten mines, 4 tin mines and 8 pottery factories. Our results showed that the mean latency of silicosis, for all the cases of the cohorts, was 22.9 +/- 9.8 y. 52.2 % of silicosis was diagnosed approximately 9.1 +/- 5.7 y after the dust exposure had ceased. The progression rates of silicosis from stage I to II and from stage II to III were 48.2 % and 18.5 %, and the duration was 4.1 +/- 0.2 and 6.8 +/- 0.2 y, respectively. The survival times of silicosis stage I , II and III, from the year of diagnosis to death, were 21.5, 15.8 and 6.8 years, respectively. There was 25 % of the silicosis patients whose survival time was beyond 33 y. The mean death age of all silicosis cases was 56.0 y. The death age increased to 65.6 y in the middle of 1990s. Among dust-exposed workers, subjects who became suspected case (0+ ) accounted for 15.0 %. 48.7 % of the suspected silicosis cases developed to silicosis, and the average year from the time of being suspected of the disease to the first stage of silicosis was 5.1 y. The natural characteristics, as mentioned above, varied with different mines and factories. We are led to conclude that silicosis is chronic in nature, but progress quickly. As a serious occupational disease it significantly reduces the life span of exposed workers. The study of its natural history is of importance for the development of health surveillance criteria for dust-exposed workers.

BACKGROUND: Spinocerebel ar ataxia is a common neurodegenerative disease characterized by slowly progressive movement incoordination of the limbs. It responds badly to common medication. OBJECTIVE: To observe the clinical effect of autologous bone marrow mesenchymal stem cells and al ogeneic umbilical cord mesenchymal stem cells tranfusion in the treatment of spinocerebel ar ataxia. METHODS: A total of 27 spinocerebel ar ataxia patients treated with mesenchymal stem cells treatment were included for comprehensive statistical analysis. Among these patients, six patients received autologous bone marrow mesenchymal stem cells lumbar puncture treatment and 21 patients received al ogeneic umbilical cord mesenchymal stem cells lumbar puncture treatment combined with intravenous infusion. The neurologic function of the patients in the two groups was evaluated with International Cooperative Ataxia Rating Scale before and after treatment. RESULTS AND CONCLUSION: There was no obvious adverse effect in the 27 spinocerebel ar ataxia patients during, before or after mesenchymal stem cells treatment. The effect of autologous bone marrow mesenchymal stem cells in six patents was not significant; for the other 21 patients treated with al ogeneic umbilical cord mesenchymal stem cells transfusion, the subjective symptoms of the patients were improved, and the International Cooperative Ataxia Rating Scale scores were decreased significantly at 3 months after treatment when compared with those before treatment (P < 0.05). The results suggest that umbilical cord mesenchymal stem cells treatment is safe and able to ameliorate the clinical symptoms and improve life quality of spinocerebel ar ataxia patients to some extent.

To provide a scientific basis for determining the health surveillance period of dust-exposed workers, data of a retrospective cohort study was re-analyzed with emphasis on natural course of silicosis. 33640 workers exposed to silica dust who were employed for at least 1 year from 1972 to 1974 in twenty Chinese mines or pottery factories were included as subjects, and were followed up till December 31, 1994. The cohort included subjects from 8 tungsten mines, 4 tin mines and 8 pottery factories. Our results showed that the mean latency of silicosis, for all the cases of the cohorts, was 22.9±9.8 y. 52.2 % of silicosis was diagnosed approximately 9. 1±5.7 y after the dust exposure had ceased. The progression rates of silicosis from stage Ⅰ to Ⅱ and from stage Ⅱ to Ⅲ were 48.2% and 18.5 %, and the duration was 4.1±0.2 and 6.8±0.2 y,respectively.The survival times of silicosis stage Ⅰ , Ⅱ and Ⅲ , from the year of diagnosis to death, were 21.5,15.8 and 6.8 years, respectively. There was 25 % of the silicosis patients whose survival time was beyond 33 y. The mean death age of all silicosis cases was 56.0 y. The death age increased to 65.6y in the middle of 1990s. Among dust-exposed workers,subjects who became suspected case (0+)accounted for 15.0%. 48.7% of the suspected silicosis cases developed to silicosis, and the aver age year from the time of being suspected of the disease to the first stage of silicosis was 5.1 y. The natural characteristics, as mentioned above, varied with different mines and factories. We are led to conclude that silicosis is chronic in nature, but progress quickly. As a serious occupational disease it significantly reduces the life span of exposed workers. The study of its natural history is of importance for the development of health surveillance criteria for dust-exposed workers.

OBJECTIVETo explore the minimum observed adverse effect level(LOAEL) and intensity of pathogenesis of tin mine dust.

METHODSA cohort study design with retrospective assessment of exposure was used. Selected 4,471 male tin miners who were exposed to tin at least one year during 1960 to 1974 and were compared with 4,797 pottery dust exposed workers in the same way designed. Statistical analysis system SAS, PROC LIFETEST were used to perform the non-parameter calculation by Life Table method.

RESULTSTin mine cohort subjects were followed up to December 31, 1994. The percentage of miners who developed silicosis was 21.7% (971/4,471). 81% of the patients had been exposed to dust before 1958. The cumulative total dust exposure(CTD) was significantly correlated with silicosis risk. The risk of silicosis was 0.012 when CTD was less than 50 mg/m-3.year-1. The risk of silicosis was increased to 0.971 when CTD was beyond 400 mg.m-3.year-1. However, the risk of silicosis was only 0.369 for dust exposed workers in pottery factories when CTD was beyond 400 mg.m-3.year-1.

CONCLUSIONThere was significant relationship between cumulative dust exposure and the incidence of silicosis in tin exposed workers. And silicosis induced by tin mine dust is more serious than the pottery dust.

Cohort Studies ; Dust ; Humans ; Mining ; Occupational Exposure ; adverse effects ; Silicosis ; etiology ; Tin