Cohort Study Of Pneumoconiosis In Iron Mine Workers

Industrial dust is a very common occupational hazard all around the world, especially in developing countries. There are twenty million workers registered with exposed to dust in China until 2000. However, the actual number of industrial dust exposed-worker is far beyond above number because a lot of un-registered and short-term workers are not included.Pneumoconiosis caused by dust-exposed is the most serious occupational disease, which makes up about 70% of all reported occupational diseases each year in China. By the end of 2006, there are 616442 cases of pneumoconiosis have been reported and 146195 died, the mortality is close to 24%. Between the year 2001 and 2006, there are 8000~10000 new pneumoconiosis cases were reported annually. It is supposed that the pneumoconiosis cases would exceed seven hundred thousand in China if no effective prevention measures been taken.Metal mining industry is one of the most important industries in China. The work-flow includes mining, ore dressing, transporting and so on, and then ore was sent to smelting enterprise for further processing. A large amount of industrial dust was processed in many job titles of metal mining, such as drilling, blasting, mining and transporting. The pneumoconiosis caused by dust-exposure is the most common and severe occupational disease in this industry.Pneumoconiosis is a chronic, disabling, irreversible disease, prone complicated with pulmonary tuberculosis. And at present, it lack effective treatment. Thus, dust exposure and pneumoconiosis directly threaten workers'health and life quality. More researches should be done to evaluate the influence factors on pneumoconiosis and to control dust concentration in workplace.This study developed a cohort by selecting all workers registered in one big iron mine between Jan 1st, 1960 and Dec 31st, 1974 and had worked at least one year in this mine. The total subject is 7666, and all of them were followed to died or to the end of 2003. There are two parts in this study: PartⅠAnalysis the characteristics and influencing factors of pneumoconiosis in iron mine and provide clues for the prevention of pneumoconiosis. PartⅡAssess the dust-control measures taken in the mine and give reference to the dust-control work. PartⅠThe Characteristics and Influencing Factors of Pneumoconiosis in Iron MineThe objective of this part was to describe the characteristics of the incidence of pneumoconiosis in iron mine, and to evaluate the main influencing factors which influence the incidence of pneumoconiosis among dust-exposed workers.The subjects of 7666 were traced to the end of 2003 with a total of 261410.72 person years. The information including basic personal data, occupational history, life habit and disease data for the subjects were collected. At the end of 2005, TNF-αand hOGG1 polymorphism were analyzed using real-time polymerase chain reaction techniques on 1714 randomly chosen survivors of the cohort. The relative risks (RRs) were calculated for influencing factors rates in pneumoconiosis group to non-pneumoconiosis group.By the end of 2003, there were 314 cases were diagnosed as pneumoconiosis among 3,604 dust-exposed workers, the incidence of pneumoconiosis 0.25% and accumulative morbidity of pneumoconiosis was 8.71%. More than 75% pneumoconiosis cases started dust exposure before 1960 and the cumulative total dust exposure levels for 83.12% pneumoconiosis cases were more than 50mg/m3·y. The average latency (from the date of starting dust exposure to the date of pneumoconiosis diagnosis) of pneumoconiosis cases was 19.65 years in the iron mine, and the latency of 77.71% cases was between 10 and 30 years. The incidences of pneumoconiosis increased with cumulative total exposure level. The relative risks of pneumoconiosis for high and middle dust exposed-workers were 8.25 and 2.27 as compared with that in low dust exposed workers. The RRs(relative risks) of pneumoconiosis were 1.7 for smoking and 32.34 for tuberculosis as compared with non-smoking subjects and non-tuberculosis subjects. No significant difference was found among genotype groups of TNF-αand hOGG1 between pneumoconiosis and no-pneumoconiosis cases. PartⅡAssessment of the Dust-control Measures in Iron MineThe dust concentrations and incidence of pneumoconiosis changed after the dust control techniques were used in above iron mine. The objective of this part was to assess the effect of those dust control techniques on incidence of pneumoconiosis. And conduct cost-benefit analysis for dust control techniques.All available industrial hygiene data of dust concentrations from 1953 to 2003 were used to describe total dust exposure level and calculated cumulative total dust exposure. The incidences of pneumoconiosis were calculated based on above cohort of 7666 workers. The information of dust control techniques and their use, the economic losses of Pneumoconiosis and the cost of dust-control techniques use were collected from safety production technology section and hospital of iron mine.The average total dust concentration was 10.7mg/m3 between 1953 and 1958 in iron mine. In 1959 to 1960, wet dust suppression and other dust control techniques were used in entire processes of iron mine, the average total dust concentration was declined to 6.27 mg/m3 between 1959 and 1977. From 1978, ventilation systems were enhanced in iron mine and the average total dust concentration in workplace were dropped to 1.95 mg/m3 between 1978 and 1998. At same time, the incidence of pneumoconiosis was about 0.10% before 1970, it was ascended to 0.50% in 1975 and was 0.48% in 1985. The incidence of pneumoconiosis was declined rapidly to lower than 0.04% in the middle of 1990s. The cumulative incidence of pneumoconiosis was up to 17.94% for workers exposed to dust before 1958, and it was 1.32% for those started the dust-exposure job after 1970. The decreases of incidence of pneumoconiosis lag about 20 year of the decline of dust concentration.The number of pneumoconiosis would be 1766 cases if dust concentration in workplace maintained at the level of 1957 based on the dose-response relationship between dust exposure and cumulative risk of pneumoconiosis. In fact, only 314 cases were diagnosed as pneumoconiosis from 1950 in iron mine. The economic losses of 314 pneumoconiosis cases were about 29,451,400 yuan, including the direct economic losses of 12,375,200 yuan, and the indirect economic losses of 17,076,200 yuan. The mean economic loss for each pneumoconiosis case was 93,800 yuan. On the other hand, the total cost of dust control techniques install and use was 32,466,600 yuan from 1958 till now. The economic loss were reduced 136,497,600 yuan because a decrease of 1,452 cases of pneumoconiosis, Thus, the cost-benefit ratio is 1:4.20 for the use of dust control techniques.Conclusion1,The exposure response relationship between cumulative total exposure and risk of pneumoconiosis was observed in iron mine. Smoking and tuberculosis were important influence factor for pneumoconiosis development.2,Gene polymorphism may influence the occur of pneumoconiosis; But TNF–αand hOGG1 gene polymorphism did not play an important role in susceptibility to pneumoconiosis.3,After using of dust control techniques, the dust-concentrations were decreased to 2 mg/m3 from 10.70mg/m3 at the beginning of the mine founded, and incidence of pneumoconiosis dropped to 0.04% from 0.50%. The most effective dust control techniques are wet operation and ventilation.4,The dust control techniques used in the iron mine has good cost-benefit, and they were effective in reducing dust concentrations and protecting workers health.