The Study On The Hazard Of Occupational Dusts Of Pottery Factories And Tungsten Mines

The workplace dust is usually referred to as solid particulates formed during production and can stay in the air for a long time. The productive dusts not only pollute the environment, but also affect the health of employees. Former studies suggested that dusts have been associated directly or indirectly with the development of silicosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD), and lung cancer in workers, and shorten the life span of workers. The number of workers exposed to dust is about 100,000,000 globally. In China, the dust-exposed workers in registration had reached 20,000,000 by 2000, though the number was only an angle of the iceberg since it did not include dust-exposed workers in personal enterprises and informal workers and casual workers in state-owned enterprises.Pneumoconiosis is a fibrotic disease of the lungs produced by the inhalation and deposition of dust. It is of serious damage to the health of workers and takes the largest proportion in the occupational diseases in China. According to the Health Ministry, by 2006 the number of accumulative cases of pneumoconiosis has researched 616,442, and the mortality was 24%, which meant that more than 140,000 cases had died. If no interference was exerted, the number of silicosis patients would reach 720,000 by 2015.There are many types of productive dusts. Exposure to the different types of dusts can result in different outcomes. Even for dusts with the same type but of different sources, like commercial quartzes of different sources, their abilities to damage and activate PAM (Pulmonary Alveolar Macrophage) were different [1]. Our former study on tin dust particles found that the results from in vitro tests were in accordance with epidemiological reports in a cohort study of four tin mines, which showed increased mortality of all cancers and lung cancer and elevated pneumoconiosis risk. To testify the result of the former research, and further assess the bioactivity of dusts from pottery industry and metal mines (tungsten mines) and their impacts on the health of dust-exposed workers, historical dust monitoring data and dust samples from 4 pottery factories (3 in Jiangxi Province and 1 in Hunan Province) and 4 tungsten mines (1 in Hunan Province and 3 in Jiangxi Province) were collected. And the follow-up of former-established cohorts was continued till the end of 2003 and the SMRs of different diseases were analyzed. The research includes three parts: (1) The monitoring and the analysis of the productive dusts from pottery factories and tungsten mines. (2) The assessment of the bioactivities of the dust particles. (3) The SMR analysis of dust-exposed workers in pottery factories and tungsten mines.Part 1 The Monitoring and the Analysis of Productive Dusts from Pottery Factories and Tungsten MinesThrough collecting historical dust-monitoring data of working places in pottery factories and tungsten mines, combining the dust determinations in work sites, the change of dust concentrations and particle distribution in the pottery factories and tungsten mines from 1952 or 1972 to 2004 were analyzed. The study aimed to provide scientific evidence for the enacting of the dust control and protection measures for the same kind of industries.Dust monitoring in these 4 pottery factories and 4 tungsten mines started in 1972 and 1958 respectively. For missing data before 1972 in pottery factories and before 1958 in tungsten mines, consensus estimates were made by industrial hygiene experts, public local supervisors based on the history of control measures and major changes in technical processes in the factories and mines. The items of dust monitoring included the dust concentrations, the free silica containment in the dusts, the dispersity of the dusts and the elements in the dusts. To ensure the quality of the monitoring data, dust monitoring was organized in the working sites of pottery factories and tungsten mines during 1987-1988 and 2005-2006.The results showed that (1) In 1950s the average total dust concentration of pottery factories was as high as 16.1 mg/m3,and it maintained between 10 and 12 mg/m3 from 1960s to 1980s. In the end of 1980s, the concentration was below 10 mg/m3, and it was 3.8 and 1.6 mg/m3 in 1993 and 2004 respectively. The average total dust concentration of tungsten mines in the end of 1950s was 13.3 mg/m3, and it fell to 5.7 mg/m3 in 1958. And after that, the concentration continued to decline. The concentration was around 2.4 mg/m3 in the early 1970s, and was 1.4 mg/m3 in 2004. Despite of the improvement in the dust-control of these two types of industries, the average concentrations were still beyond the Chinese National Standard of dust concentrations in workplace (1mg/m3).(2) For pottery factories and tungsten mines, the free silica containment was around 30% and 50% in the collected dusts and was 26.37% and 39.48% in the respirable dusts respectively. In a whole, the free silica containment was higher in the tungsten dusts.(3) The analysis of the dispersity of the dusts showed that the proportion of the dusts with a diameter less than 10μm was 73.45% and 84.65% for the pottery factories and tungsten mines respectively, and it was 29.46% and 56.7% for dusts with a diameter less than 5μm respectively.(4) The average containment of As, Ni, Cd, Fe, Cu and Mn elements in pottery collected dusts was 18.2,8.7,2.0,5957.0,24.0 and 417.7μg/g respectively and the above elements were richer in tungsten collected dusts namely 102.9,20.4,17.9,19067.9,907.7 and 1201.4μg/g. The Al containment in the pottery collected dusts was 22373.3μg/g, almost twice of that in tungsten collected dusts.Part 2 The Assessment of the Bioactivities of the Dusts from Pottery Factories and Tungsten MinesTo evaluate the role of in vitro study in the assessment of the dust hazard, and provide base for assessing the occupational hazards in the dust-exposed working places by analyzing the physic-chemical characteristics and assessing the bioactivities of dusts from pottery factories and tungsten mines.Dusts from different working places in above 4 pottery factories (namely A, B, C and D factories) and 4 tungsten mines (namely E, F, G and H mines) were analyzed for the physic-chemical characteristics. And the LDH activity, cell viability, ROS and TNF-αrelease of guinea pig PAM were chosen to assess the bioactivities of dusts by using China Standard Quartz as control. The results showed that (1) The Al in pottery dusts was richer, while the As, Fe and Mn etc were richer in tungsten dusts. The element containments were different between even among dusts of the same kind.(2) Dose-response relationship between the enhancement of LDH activity and the dust concentration was found in both dusts from pottery factories and tungsten mines. Stronger ability to induce LDH activity was found in dusts from D, E and F factories (mines) and the variability to enhance LDH activity was small in pottery factories but was comparatively great in tungsten mines.(3) The cell viability decreased as the dusts'concentrations increased. The cell viabilities induced by pottery dusts were similar to that of control; while those induced by tungsten dusts was a bit lower than that of control.(4) Except for dusts from H mine, dose-response relationship was found between dust concentrations and the release of ROS. The ability of H mine to induce the release of ROS was lower than that of control while the other dusts were of the similar ability compared with the control.(5) The ability to induce TNF-αwas found in all the dusts under all the concentrations. Except for dusts from H mine, which could induce relatively high dose of TNF-αunder every set concentration, dose-response relationship was found between dust concentrations and the releases of TNF-α. Compared with the control, the dusts from C factory and H mine were easier to induce the release of TNF-αwhile the dust from E mine was on the contrary. Totally, except for the highest dust concentration(120μg/ 106 cells), the dusts from tungsten mines were more able to induce TNF-αthan those from pottery factories under the other concentrations (15,30 and 60μg/ 106 cells).Part 3 The Standardized Mortality Rate Analysis of Workers from Pottery Factories and Tungsten MinesThis part aimed to find the main diseases endangering the health and the life span of workers from pottery factories and tungsten mines, and provide instructions for the health care of the workers in these industries by the SMR analysis of workers from cohorts of pottery factories and tungsten mines.Cohorts were established basing on the above pottery factories and tungsten mines by choosing workers registered during Jun 1st 1972 and Dec 31st 1974 and with at least one working year. The cohorts were followed-up till the end of 2003 and the causes of death were analyzed and the SMR was calculated based on the domestic agespecific mortality from Health Ministry.Results (1) The number of workers in pottery factories was 4957, among which 3648 were males and 1309 were females. Totally 130783.6 person-years was calculated till the end of 2003. The main diseases caused the death were cancer (6.56%), cardiovascular diseases (6.54%), respiratory diseases (5.71%) and vascular diseases (4.72%) by the cumulative mortality. The diseases with the mortalities above the domestic level were namely silicosis, infective diseases, tuberculosis, and respiratory diseases, and their SMRs were namely 36.35, 5.08, 4.06 and 1.30.(2) The number of workers in tungsten mines was 12978, among which 11673 were males and 1305 were females. Totally 336417.8 person-years was calculated till the end of 2003. The main diseases caused the death were cardiovascular diseases (9.22%), respiratory diseases (7.30%), cancer (6.03%) and tuberculosis (4.73%) by the cumulative mortality. The diseases with the mortalities above the domestic level were namely silicosis, tuberculosis, respiratory diseases and liver cancer, and their SMRs were namely 65.27,3.90,1.90and1.38.ConclusionsBased on the cohorts of 4 pottery factories and 4 tungsten mines, the occupational dust hazard monitoring, the bioactivity of dusts and the SMR analysis of the cohorts were analyzed in the research to study the impacts of dust on health. And several conclusions were drawn as follows:(1) The average total dust concentration was higher than 13 mg/m3 in both pottery factories and tungsten mines in the early 1950s. And the concentrations have fallen obviously since the end of 1950s, and they were around 1.5 mg/m3 in 2004. This suggested that the reform in the working procedure and the combined dust proof and protection measures were of great efficiency.(2) The bioactivities of the dusts were in line with the impacts that they brought on the health of the dust-exposed workers.The changes in the LDH activity and cell viability by both types of dusts were obvious, indicative of their strong cytotoxicity, and these were coherent with the former cohort studies on dust-exposed workers of pottery factories and tungsten mines which found that the dusts from these two industries could obviously affect the health of the dust-exposed workers. Compared with the pottery dusts, the tungsten dusts were a bit higher in the membrane cytotoxicity to PAM but lower in the impact on the cell viability of PAM, probably due to the variability of the element containments in the dusts.The DNA impairments induced by ROS might be the base of mutation. Strong ability to induce ROS in PAM by both types of dusts compared with the control was found in this study, and this might contribute to the high incidence of cancer in both pottery factories and tungsten mines.TNF-αhas been found to play an important role in the process of the lung fibrosis. In this study, stronger ability to induce TNF-αunder lower concentrations (15, 30,60μg/106 cells) was found in tungsten dusts, more respresentative of the actual dust concentrations in the workplaces. Besides, higher containment of the free silica and higher disperity in tungsten dusts were also found in the monitoring data, these would be help to understand why higher SMR of silicosis was found in tungsten workers compared with that of pottery workers despite of higher average dust concentrations in the pottery mines.SummaryObvious threat of these two types of dusts to workers health was observed by selecting dust samples from 4 pottery factories and 4 tungsten mines on the base of the cohort studies of these factories/mines. The average dust concentrations of these factories/mines were beyond the Chinese National Standard of dust concentrations in workplace. Definite cytotoxicity on PAMs and obvious impacts on the health and lifespan of dust-exposed workers by these two types of dusts were observed in this study. The SMRs of silicosis in the cohorts of these pottery factories and tungsten mines were 36.35 and 65.27 respectively, which were in accord with fibrogenic ability of their dusts. The ability to induce ROS was found in both two types of dusts, and this concorded with the high prevalence of cancers especially lung cancer and hepatoma in these cohorts. By the bioactivity analysis of dusts based on the cohort study, this research aimed to provide reference for future studies on the hazard of dusts from similar factories/mines.