With the TEM and physical gas adsorption techniques, porous properties of nano-ribriform silica （MLD： 92.73%） from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silic...With the TEM and physical gas adsorption techniques, porous properties of nano-ribriform silica （MLD： 92.73%） from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silica results from brucite octahedral sheets of nature chrysotile dissolved completely and Si-O tetrahedral sheets collapsed by acid leaching. Its length is at a micron or nanometer scale. There are two types of pores： pores among neighboring fibers and pores in nanoriber. These pores （less than 6.5 nm in diameter, mostly 2.1 nm and 3.8 nm） all belong to mesopores. The pores in fibers consist of those among SiO2 particles, those among aggregates, remnant nanotubes and capillary tubes. Nanoribriform silica proves better than the traditional silica as a carrier of catalyzer and a filler for reinforce rubber and plastics.展开更多
Objective To determine whether there was excessive risk of cancer among workers exposed to chrysotile fiber alone by applying a meta-analysis technique. Methods All data meeting the criteria of cohort studies on c...Objective To determine whether there was excessive risk of cancer among workers exposed to chrysotile fiber alone by applying a meta-analysis technique. Methods All data meeting the criteria of cohort studies on cancer mortality among workers exposed only to chrysotile were incorporated into meta-analysis. Pooled standardized mortality ratios (SMRs) and their corresponding 95% confidence intervals (CIs) for main cancer sites were calculated using two approaches of unweighted ratio and random effect model. The heterogeneity and its sources of the results were examined with a Q-statistic and Z-score test. The dose-response effect as reflected in the percentage of all deaths due to mesothelioma served as a proxy measure of chrysotile exposure. Results A cohort of twenty six workers exposed to chrysotile alone was summarized. The significantly elevated meta-SMRs for all deaths (1.27), all cancers (1.28), cancers of respiratory organs (2.51), cancers of lung (2.35) and cancers of stomach (1.24) were observed. The significantly elevated meta-SMRs for lung cancer within occupational strata were observed among textile workers (3.55), asbestos product manufacturers (3.30), miners and millers (2.24), cement product workers (1.22), and for stomach cancer among asbestos product manufacturers (1.49). Meta-SMRs for cancers at other sites were not significant. Meta-SMR for lung cancer showed an increasing trend with an elevated percentage of all deaths from mesothelioma, but no such trend for stomach cancer. Conclusion There are excessive risks of lung cancer and mesothelioma among workers exposed to chrysotile fiber alone, and likely no convincing indication of an etiological association between chrysotile exposure and cancers at other sites.展开更多
In order to investigate the mortality of a cohort of chrysotile asbestos miners in China and evaluate its association with exposure to chrysotile,a fixed cohort of 1932 workers in chrysotile asbes-tos mine was establi...In order to investigate the mortality of a cohort of chrysotile asbestos miners in China and evaluate its association with exposure to chrysotile,a fixed cohort of 1932 workers in chrysotile asbes-tos mine was established in 1981 and followed till June 1,2010.Information on vital status,cause of death and smoking habits was collected.The workers were divided into two groups according to their exposure status.The exposed group was composed of frontline workers who worked directly on mining or processing asbestos products.The control group consisted of those who were not directly exposed to asbestos in their work.Standardized mortality ratio (SMR) was calculated according to Chinese national death rates.Cox proportional hazards model was applied to estimate the adjusted relative risks of deaths from major causes in exposed and control groups.The results of this study showed that main causes of mortality were malignant neoplasm,cardiovascular disease,cerebrovascular disease and respiratory disease for chrysotile miners.The mortality rate was 939.20 per 100 000 person-years for workers.The SMR for all causes of death was 1.46 in the cohort.Statistically significant mortality excesses were found for lung cancer (SMR=1.51),pulmonary heart disease (SMR=2.70),respiratory disease (SMR=1.93),asbestosis (SMR=9.62),and accident (SMR=1.59).The mortalities from malignant neo-plasm,lung cancer,cerebrovascular disease and digestive disease in the exposed group were signifi-cantly higher than those in the control group.The findings indicate that chrysotile exposure is a risk factor for lung cancer,respiratory disease,cerebrovascular disease and digestive disease.展开更多
Pathological effects of asbestos are probably dependent on the special surface properties of the fibers, such as surface charge, surface metal ions. The present study was designed to determine whether the pretreatment...Pathological effects of asbestos are probably dependent on the special surface properties of the fibers, such as surface charge, surface metal ions. The present study was designed to determine whether the pretreatment of chrysotile asbestos fibers (CAF) with rare earth compounds (REC) solution can reduce their pathogenicity. The results showed that REC-pretreated CAF induced less nitrogen oxide (NO) production by alveolar macrophages (AM). In addition, the pretreatment lowered the capacity of hemolysis and the methylene blue (MB) adsorption of the native CAF. These findings suggested that the pretreatment of CAF with REC solution reduced the in vitro toxicity of CAF by lessening its surface charges. Nevertheless, the pathogenicity and the carcinogenicity of REC-pretreated CAF in vivo remain to be investigated.展开更多
Detect the change of the Expression of oncoprotein on the Chinese hamster lung cells (V79 cells) which effect with two main district of China and four alternative chrysotile fiber to investigate the factors of lung ca...Detect the change of the Expression of oncoprotein on the Chinese hamster lung cells (V79 cells) which effect with two main district of China and four alternative chrysotile fiber to investigate the factors of lung cancer. V79 cells were exposed to the suspension of Chrysotile and its substitute with different powder content, the survival rate of cells was monitored by MTT. After 48 h, the location, distribution and expression of Survivin, Cap43, Bcl-2, p16 and p53 in V79 cell were examined by immunohistochemistry and compared. In the six kinds of powder, the inhibition of rockwool on the growth of cells was weakest, the inhibition of Chrysotile from Xinkang Sichuan and Southern Shanxi on the growth of cells was strongest. Chrysotile from Xinkang Sichuan, Chrysotile from Southern Shanxi, glass fiber, ceramic fiber, rockwool and wollastonite had a certain influence on the survival rate of V79 cells. As the concentration of powder increased the survival rate of cells decreased, which showed dose-effect relationship. The expression of Survivin, Cap43 and Bcl-2 was upregulated and the expression of P16 and P53 was downregulated in V79 cells, which was obviously in the powder suspension of Chrysotile from Southern Shanxi and Xinkang Sichuan and glass fiber. The expression was mainly in cytoplasm. The influence of different kind of powder on the cells differed in degree. Chrysotile and its substitute can induce the development of cancer by upregulating the expression of Survivin, Cap43 and Bcl-2 and downregulating the expression of p16 and p53.展开更多
The chrysotile asbestos was converted to the forsterite-type compounds by calcination at 740 and 800oC (F7-740 and F7-800), which were used as a catalyst for the polycondensation of bis(hydroxyethyl) terephthalate aff...The chrysotile asbestos was converted to the forsterite-type compounds by calcination at 740 and 800oC (F7-740 and F7-800), which were used as a catalyst for the polycondensation of bis(hydroxyethyl) terephthalate affording poly (ethylene terephthalate). The obtained forsterite-type compounds did not show any catalytic activity. However, the products obtained by simply treating them with acetic acid significantly promoted the polymerization that produced a THFinsoluble polymer. It was found that the polymer prepared with the acetic acid-treated F7-740 at 160oC for 2 h showed a 93% yield and the number average molecular weight of 6.4 × 103. The observed catalytic activity was higher than that for the acetic acid-treated magnesium oxide, as well as the typical polycondensation catalysts, such as magnesium acetate and antimony oxide.展开更多
Most chrysotile deposits occur in ultramafic rocks of the ophiolite suite. The chrysotile deposits dis-cussed in the present paper were formed through metasomatism and infilling-crystallization in a continentalserpent...Most chrysotile deposits occur in ultramafic rocks of the ophiolite suite. The chrysotile deposits dis-cussed in the present paper were formed through metasomatism and infilling-crystallization in a continentalserpentinization environment after plate convergence, where ultramafic rocks were replaced byhydrothermal solutions consisting mainly of deep-circulating heated water derived from atmospheric precip-itation. The critical state for the formation of asbestos in ultramafic rock bodies might be reached bysuperposition of multiple stages of serpentinization. Favourable fracture systems and relatively stable geo-logical environment are important conditions for forming chrysotile deposits. Three subtypes of chrysotiledeposits could be formed in different tectonic settings and under different minerogenic geochemical condi-tions.展开更多
The dose-response relationship for asbestos exposure in a chrysotile product factory was studied. The past gravimetric dust concentration values, obtained from different worksites, were converted into fiber concentrat...The dose-response relationship for asbestos exposure in a chrysotile product factory was studied. The past gravimetric dust concentration values, obtained from different worksites, were converted into fiber concentration values according to conversion factors that were worked out by simultaneous sampling in this study. The conversions were made so that exposure could be expressed in fiber-years (f-yr). Asbestosis was diagnosed on the basis of chest radiographs and occupational histories. Cumulative dust exposure (f-yr) was calculated up to the date of diagnosis for asbestosis patients, and up to September 1982 for the remaining workers. A dose-response relationship expressed as fiber-years exposed vs cumulative prevalence of asbestosis was established by the life table method on the basis of these data. Predicted 3 and 1% prevalence of asbestosis corresponded to 43 and 22 f-yr exposure, respectively. Considering that a worker can work for 35 years, these doses are commensurate with dust concentrations of 1.22 and 0.63 f/ml, respectively. It is recommended that 1 f/ml be taken as the maximum allowable concentration of airborne asbestos dust for the workplace with an anticipated prevalence of about 2% asbestosis after 35 years of exposure. 1990 Academic Press, Inc.展开更多
Mesoporous MCM-41-type molecular sieves were synthesized using calcined and leached chrysotile and cetyltrimethylammonium bromide as the silica source and structure directing agent, respectively. Powder X-ray diffract...Mesoporous MCM-41-type molecular sieves were synthesized using calcined and leached chrysotile and cetyltrimethylammonium bromide as the silica source and structure directing agent, respectively. Powder X-ray diffraction (XRD), N2 isothermal adsorption-desorption, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the samples. The calcined and leached chrysotile can be employed as an inexpensive silica source for the formation of low-order MCM-41 mesoporous materials.展开更多
文摘With the TEM and physical gas adsorption techniques, porous properties of nano-ribriform silica （MLD： 92.73%） from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silica results from brucite octahedral sheets of nature chrysotile dissolved completely and Si-O tetrahedral sheets collapsed by acid leaching. Its length is at a micron or nanometer scale. There are two types of pores： pores among neighboring fibers and pores in nanoriber. These pores （less than 6.5 nm in diameter, mostly 2.1 nm and 3.8 nm） all belong to mesopores. The pores in fibers consist of those among SiO2 particles, those among aggregates, remnant nanotubes and capillary tubes. Nanoribriform silica proves better than the traditional silica as a carrier of catalyzer and a filler for reinforce rubber and plastics.
基金This study was partially supported by a grant from the Research Foundation in the year of 1997 of the Japan-China Medical Association (No. 001).
文摘Objective To determine whether there was excessive risk of cancer among workers exposed to chrysotile fiber alone by applying a meta-analysis technique. Methods All data meeting the criteria of cohort studies on cancer mortality among workers exposed only to chrysotile were incorporated into meta-analysis. Pooled standardized mortality ratios (SMRs) and their corresponding 95% confidence intervals (CIs) for main cancer sites were calculated using two approaches of unweighted ratio and random effect model. The heterogeneity and its sources of the results were examined with a Q-statistic and Z-score test. The dose-response effect as reflected in the percentage of all deaths due to mesothelioma served as a proxy measure of chrysotile exposure. Results A cohort of twenty six workers exposed to chrysotile alone was summarized. The significantly elevated meta-SMRs for all deaths (1.27), all cancers (1.28), cancers of respiratory organs (2.51), cancers of lung (2.35) and cancers of stomach (1.24) were observed. The significantly elevated meta-SMRs for lung cancer within occupational strata were observed among textile workers (3.55), asbestos product manufacturers (3.30), miners and millers (2.24), cement product workers (1.22), and for stomach cancer among asbestos product manufacturers (1.49). Meta-SMRs for cancers at other sites were not significant. Meta-SMR for lung cancer showed an increasing trend with an elevated percentage of all deaths from mesothelioma, but no such trend for stomach cancer. Conclusion There are excessive risks of lung cancer and mesothelioma among workers exposed to chrysotile fiber alone, and likely no convincing indication of an etiological association between chrysotile exposure and cancers at other sites.
基金supported by a grant from Pneumoconiosis Compensation Funding Board,Hong Kong,SAR,China
文摘In order to investigate the mortality of a cohort of chrysotile asbestos miners in China and evaluate its association with exposure to chrysotile,a fixed cohort of 1932 workers in chrysotile asbes-tos mine was established in 1981 and followed till June 1,2010.Information on vital status,cause of death and smoking habits was collected.The workers were divided into two groups according to their exposure status.The exposed group was composed of frontline workers who worked directly on mining or processing asbestos products.The control group consisted of those who were not directly exposed to asbestos in their work.Standardized mortality ratio (SMR) was calculated according to Chinese national death rates.Cox proportional hazards model was applied to estimate the adjusted relative risks of deaths from major causes in exposed and control groups.The results of this study showed that main causes of mortality were malignant neoplasm,cardiovascular disease,cerebrovascular disease and respiratory disease for chrysotile miners.The mortality rate was 939.20 per 100 000 person-years for workers.The SMR for all causes of death was 1.46 in the cohort.Statistically significant mortality excesses were found for lung cancer (SMR=1.51),pulmonary heart disease (SMR=2.70),respiratory disease (SMR=1.93),asbestosis (SMR=9.62),and accident (SMR=1.59).The mortalities from malignant neo-plasm,lung cancer,cerebrovascular disease and digestive disease in the exposed group were signifi-cantly higher than those in the control group.The findings indicate that chrysotile exposure is a risk factor for lung cancer,respiratory disease,cerebrovascular disease and digestive disease.
文摘Pathological effects of asbestos are probably dependent on the special surface properties of the fibers, such as surface charge, surface metal ions. The present study was designed to determine whether the pretreatment of chrysotile asbestos fibers (CAF) with rare earth compounds (REC) solution can reduce their pathogenicity. The results showed that REC-pretreated CAF induced less nitrogen oxide (NO) production by alveolar macrophages (AM). In addition, the pretreatment lowered the capacity of hemolysis and the methylene blue (MB) adsorption of the native CAF. These findings suggested that the pretreatment of CAF with REC solution reduced the in vitro toxicity of CAF by lessening its surface charges. Nevertheless, the pathogenicity and the carcinogenicity of REC-pretreated CAF in vivo remain to be investigated.
基金Project supported by the State Key Program of National Natural Science of China(No. 41130746)
文摘Detect the change of the Expression of oncoprotein on the Chinese hamster lung cells (V79 cells) which effect with two main district of China and four alternative chrysotile fiber to investigate the factors of lung cancer. V79 cells were exposed to the suspension of Chrysotile and its substitute with different powder content, the survival rate of cells was monitored by MTT. After 48 h, the location, distribution and expression of Survivin, Cap43, Bcl-2, p16 and p53 in V79 cell were examined by immunohistochemistry and compared. In the six kinds of powder, the inhibition of rockwool on the growth of cells was weakest, the inhibition of Chrysotile from Xinkang Sichuan and Southern Shanxi on the growth of cells was strongest. Chrysotile from Xinkang Sichuan, Chrysotile from Southern Shanxi, glass fiber, ceramic fiber, rockwool and wollastonite had a certain influence on the survival rate of V79 cells. As the concentration of powder increased the survival rate of cells decreased, which showed dose-effect relationship. The expression of Survivin, Cap43 and Bcl-2 was upregulated and the expression of P16 and P53 was downregulated in V79 cells, which was obviously in the powder suspension of Chrysotile from Southern Shanxi and Xinkang Sichuan and glass fiber. The expression was mainly in cytoplasm. The influence of different kind of powder on the cells differed in degree. Chrysotile and its substitute can induce the development of cancer by upregulating the expression of Survivin, Cap43 and Bcl-2 and downregulating the expression of p16 and p53.
文摘The chrysotile asbestos was converted to the forsterite-type compounds by calcination at 740 and 800oC (F7-740 and F7-800), which were used as a catalyst for the polycondensation of bis(hydroxyethyl) terephthalate affording poly (ethylene terephthalate). The obtained forsterite-type compounds did not show any catalytic activity. However, the products obtained by simply treating them with acetic acid significantly promoted the polymerization that produced a THFinsoluble polymer. It was found that the polymer prepared with the acetic acid-treated F7-740 at 160oC for 2 h showed a 93% yield and the number average molecular weight of 6.4 × 103. The observed catalytic activity was higher than that for the acetic acid-treated magnesium oxide, as well as the typical polycondensation catalysts, such as magnesium acetate and antimony oxide.
文摘Most chrysotile deposits occur in ultramafic rocks of the ophiolite suite. The chrysotile deposits dis-cussed in the present paper were formed through metasomatism and infilling-crystallization in a continentalserpentinization environment after plate convergence, where ultramafic rocks were replaced byhydrothermal solutions consisting mainly of deep-circulating heated water derived from atmospheric precip-itation. The critical state for the formation of asbestos in ultramafic rock bodies might be reached bysuperposition of multiple stages of serpentinization. Favourable fracture systems and relatively stable geo-logical environment are important conditions for forming chrysotile deposits. Three subtypes of chrysotiledeposits could be formed in different tectonic settings and under different minerogenic geochemical condi-tions.
文摘The dose-response relationship for asbestos exposure in a chrysotile product factory was studied. The past gravimetric dust concentration values, obtained from different worksites, were converted into fiber concentration values according to conversion factors that were worked out by simultaneous sampling in this study. The conversions were made so that exposure could be expressed in fiber-years (f-yr). Asbestosis was diagnosed on the basis of chest radiographs and occupational histories. Cumulative dust exposure (f-yr) was calculated up to the date of diagnosis for asbestosis patients, and up to September 1982 for the remaining workers. A dose-response relationship expressed as fiber-years exposed vs cumulative prevalence of asbestosis was established by the life table method on the basis of these data. Predicted 3 and 1% prevalence of asbestosis corresponded to 43 and 22 f-yr exposure, respectively. Considering that a worker can work for 35 years, these doses are commensurate with dust concentrations of 1.22 and 0.63 f/ml, respectively. It is recommended that 1 f/ml be taken as the maximum allowable concentration of airborne asbestos dust for the workplace with an anticipated prevalence of about 2% asbestosis after 35 years of exposure. 1990 Academic Press, Inc.
基金The authors gratefully acknowledge financial support from CAPES organizationas well as the NEPGN-UFRN organization for use of their Scanning Electron Micros-copy
文摘Mesoporous MCM-41-type molecular sieves were synthesized using calcined and leached chrysotile and cetyltrimethylammonium bromide as the silica source and structure directing agent, respectively. Powder X-ray diffraction (XRD), N2 isothermal adsorption-desorption, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to characterize the samples. The calcined and leached chrysotile can be employed as an inexpensive silica source for the formation of low-order MCM-41 mesoporous materials.
