The Experts below are selected from a list of 3549 Experts worldwide ranked by ideXlab platform

D M Bernstein - One of the best experts on this subject based on the ideXlab platform.

  • the health risk of Chrysotile Asbestos
    Current Opinion in Pulmonary Medicine, 2014
    Co-Authors: D M Bernstein
    Abstract:

    Purpose of review The word Asbestos is a poorly attributed term, as it refers to two very different minerals with very different characteristics. One is the serpentine mineral of which the white Asbestos, Chrysotile, is the most common. The other is the amphibole Asbestos, which includes the blue Asbestos crocidolite and the brown Asbestos amosite. Although today Chrysotile is the only type used commercially, the legacy of past use of amphibole Asbestos remains. This review clarifies the differences between the two mineral families referred to as Asbestos and summarizes the scientific basis for understanding the important differences in the toxicology and epidemiology of these two minerals. Recent findings Biopersistence and sub-chronic inhalation toxicology studies have shown that exposure to Chrysotile at up to 5000 times the current threshold limit value (0.1 fibers/cm) produces no pathological response. These studies demonstrate as well that following short-term exposure the longer Chrysotile fibers rapidly clear from the lung and are not observed in the pleural cavity. In contrast, short-term exposure to amphibole Asbestos results quickly in the initiation of a pathological response in the lung and the pleural cavity. Summary Significant progress has been made in understanding the factors that influence inhalation toxicology studies of fibers and epidemiological studies of workers. Evaluation of the toxicology and epidemiology studies of Chrysotile indicates that it can be used safely under controlled use. In contrast, even short-term exposure to amphibole Asbestos can result in disease.

  • a biopersistence study following exposure to Chrysotile Asbestos alone or in combination with fine particles
    Inhalation Toxicology, 2008
    Co-Authors: D M Bernstein, U Decker, P Kunzendorf, Ken Donaldson, S Gaering, Jorg Chevalier, S E Holm
    Abstract:

    In designing a study to evaluate the inhalation biopersistence of a Chrysotile Asbestos that was used as a component of a joint-compound, a feasibility study was initiated to evaluate the shortterm biopersistence of the Chrysotile alone and of the Chrysotile in combination witht the sanded reformulated joint-compound. Two groups of Wistar rats were exposed to either 7RF3 Chrysotile (Group 2) or to 7RF3 Chrysotile combined with aerosolized sanded joint-compound (Group 3). In addition, a control group was exposed to filtered-air. The Chrysotile used in the Ready Mix joint compound is rapidly removed from the lung. The Chrysotile alone exposure group had a clearance half-time of fibers L > 20 µm of 2.2 days; in the Chrysotile plus sanded exposure group the clearance half-time of fibers L > 20 µm was 2.8 days. However, across all size ranges there was approximately an order of magnitude decrease in the mean number of fibers remaining in the lungs of Group 3 as compared to Group 2 despite similiar aerosol exposures. Histopathological examination showed that the Chrysotile exposed lungs had the same appearance as the filtered-air controls. This study uniquely illustrates that additional concurrent exposure to an aerosol of the sanded joint-compound, with large numbers of fine-particles depositing in the lungs, accelerates the recruitment of macrophages, resulting in a tenfold decrease in the number of fibers remaining in the lung. The increased number of macrophages in the Chrysotile/sanded joint exposure group was confirmed histologically, with this being the only exposure-related histological finding reported.

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in . This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer tha...

  • the biopersistence of canadian Chrysotile Asbestos following inhalation final results through 1 year after cessation of exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Rick A Rogers, Paul Smith
    Abstract:

    Chrysotile Asbestos, a serpentine mineral, has been shown to be notably different from amphibole Asbestos such as amosite, crocidolite, and tremolite in that Chrysotile once inhaled is rapidly removed from the lung while the amphiboles persist. This has been demonstrated for three different Chrysotile samples from Canada, the United States, and Brazil. The initial results of the inhalation biopersistence study on the Canadian Chrysotile were reported earlier. This article presents the full results through 365 days after cessation of exposure. In order to fully understand the dynamics of the clearance of Chrysotile from the lung, the study included a standardised inhalation biopersistence study following the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers () in which the lungs were digested to evaluate fiber content remaining. In addition, confocal microscopy was used to examine lungs in three dimensions to determine where and w...

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in Bernstein et al. (2003). This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (Bernstein & Riego-Sintes, 1999). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 microm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The Chrysotile samples were specifically chosen to have 200 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. Calidria Chrysotile has been found to be one of the most rapidly cleared mineral fibers from the lung. The fibers longer than 20 microm in length are cleared with a half-time of 7 h. By 2 days postexposure all long fibers have dissolved/disintegrated into shorter pieces. The fibers between 5 and 20 microm in length were cleared with a half-time of 7 days. This length range represents a transition zone between those fibers that can be fully phagocytosed and cleared as particles and the longer fibers that cannot be fully engulfed by the macrophage. The fibers/objects shorter than 5 microm in length were cleared with a half-time of 64 days, which is faster than that reported for insoluble nuisance dusts such as TiO2. By 12 months postexposure, 99.92% of all the remaining Chrysotile was less than 5 microm in length. Following the 5 days of repeated exposure to more than 48,000 Chrysotile fibers/cm3 (190 fibers L > 20 microm), histopathological examination revealed no evidence of any inflammatory reaction either after the cessation of the last exposure or at any time during the subsequent 12-mo period. This is in marked contrast to the amphibole tremolite, which was also investigated using the same inhalation biopersistence protocol. The long tremolite fibers, once deposited in the lung, remain over the rat's lifetime with essentially an infinite half-time. Even the shorter fibers, following early clearance, also remain with no dissolution or further removal. At 365 days postexposure, there was a mean lung burden was of 0.5 million fibers L > 20 microm and 7 million fibers 5-20 microm in length with a total mean lung burden of 19.6 million fibers. The tremolite exposed rats, even with exposure to 16 times fewer total fibers than Chrysotile, showed a pronounced inflammatory response with the rapid development of granulomas as seen at day 1 postexposure, followed by the development of fibrosis characterized by collagen deposition within these granulomas and by 90 days even mild interstitial fibrosis. With the short exposure, this study was not designed specifically to evaluate pathological response; however, it is quite interesting that even so there was such a marked response with tremolite. These findings provide an important basis for substantiating both kinetically and pathologically the differences between Chrysotile and the amphibole tremolite. As Calidria Chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.

Paul Smith - One of the best experts on this subject based on the ideXlab platform.

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in . This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer tha...

  • the biopersistence of canadian Chrysotile Asbestos following inhalation final results through 1 year after cessation of exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Rick A Rogers, Paul Smith
    Abstract:

    Chrysotile Asbestos, a serpentine mineral, has been shown to be notably different from amphibole Asbestos such as amosite, crocidolite, and tremolite in that Chrysotile once inhaled is rapidly removed from the lung while the amphiboles persist. This has been demonstrated for three different Chrysotile samples from Canada, the United States, and Brazil. The initial results of the inhalation biopersistence study on the Canadian Chrysotile were reported earlier. This article presents the full results through 365 days after cessation of exposure. In order to fully understand the dynamics of the clearance of Chrysotile from the lung, the study included a standardised inhalation biopersistence study following the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers () in which the lungs were digested to evaluate fiber content remaining. In addition, confocal microscopy was used to examine lungs in three dimensions to determine where and w...

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in Bernstein et al. (2003). This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (Bernstein & Riego-Sintes, 1999). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 microm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The Chrysotile samples were specifically chosen to have 200 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. Calidria Chrysotile has been found to be one of the most rapidly cleared mineral fibers from the lung. The fibers longer than 20 microm in length are cleared with a half-time of 7 h. By 2 days postexposure all long fibers have dissolved/disintegrated into shorter pieces. The fibers between 5 and 20 microm in length were cleared with a half-time of 7 days. This length range represents a transition zone between those fibers that can be fully phagocytosed and cleared as particles and the longer fibers that cannot be fully engulfed by the macrophage. The fibers/objects shorter than 5 microm in length were cleared with a half-time of 64 days, which is faster than that reported for insoluble nuisance dusts such as TiO2. By 12 months postexposure, 99.92% of all the remaining Chrysotile was less than 5 microm in length. Following the 5 days of repeated exposure to more than 48,000 Chrysotile fibers/cm3 (190 fibers L > 20 microm), histopathological examination revealed no evidence of any inflammatory reaction either after the cessation of the last exposure or at any time during the subsequent 12-mo period. This is in marked contrast to the amphibole tremolite, which was also investigated using the same inhalation biopersistence protocol. The long tremolite fibers, once deposited in the lung, remain over the rat's lifetime with essentially an infinite half-time. Even the shorter fibers, following early clearance, also remain with no dissolution or further removal. At 365 days postexposure, there was a mean lung burden was of 0.5 million fibers L > 20 microm and 7 million fibers 5-20 microm in length with a total mean lung burden of 19.6 million fibers. The tremolite exposed rats, even with exposure to 16 times fewer total fibers than Chrysotile, showed a pronounced inflammatory response with the rapid development of granulomas as seen at day 1 postexposure, followed by the development of fibrosis characterized by collagen deposition within these granulomas and by 90 days even mild interstitial fibrosis. With the short exposure, this study was not designed specifically to evaluate pathological response; however, it is quite interesting that even so there was such a marked response with tremolite. These findings provide an important basis for substantiating both kinetically and pathologically the differences between Chrysotile and the amphibole tremolite. As Calidria Chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.

  • comparison of calidria Chrysotile Asbestos to pure tremolite inhalation biopersistence and histopathology following short term exposure
    Inhalation Toxicology, 2003
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    The differences between Chrysotile Asbestos, a serpentine mineral, and amphibole Asbestos have been debated extensively. Many studies have shown that Chrysotile is cleared from the lung more rapidly than amphibole. In order to quantify the comparative clearance of Chrysotile and the amphibole Asbestos tremolite, both fibers were evaluated in an inhalation biopersistence study that followed the European Commission recommended guidelines. In addition, the histopathological response in the lung was evaluated following the short-term exposure. This article presents the results of this study through 90 days after cessation of exposure. Following the termination of the study, a subsequent article will provide the complete results through 12 mo after cessation of exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and of a long-fiber t...

  • the biopersistence of brazilian Chrysotile Asbestos following inhalation
    Inhalation Toxicology, 2003
    Co-Authors: D M Bernstein, Rick A Rogers, Paul Smith
    Abstract:

    With the initial understanding of the relationship of Asbestos to disease, little information was available on whether the two different groups of minerals that are called Asbestos were of similar or different potency in causing disease. Asbestos was often described as a durable fiber that if inhaled would remain in the lung and cause disease. It has been only more recently, with the development of a standardized protocol for evaluating the biopersistence of mineral fibers in the lung, that the clearance kinetics of the serpentine Chrysotile have been shown to be dramatically different from those of amphibole Asbestos, with Chrysotile clearing rapidly from the lung. In addition, recent epidemiology studies also differentiate Chrysotile from amphibole Asbestos. The biopersistence studies mentioned have indicated that Chrysotile from Canada and California clear rapidly from the lung once inhaled. However, variations in Chrysotile mineralogy have been reported depending upon the region. This is most likely a...

Xiaorong Wang - One of the best experts on this subject based on the ideXlab platform.

  • cancer mortality in chinese Chrysotile Asbestos miners exposure response relationships
    PLOS ONE, 2013
    Co-Authors: Xiaorong Wang, Eiji Yano, Ignatius Taksun Yu, David C Christiani
    Abstract:

    Objective This study was conducted to assess the relationship of mortality from lung cancer and other selected causes to Asbestos exposure levels. Methods A cohort of 1539 male workers from a Chrysotile mine in China was followed for 26 years. Data on vital status, occupation and smoking were collected from the mine records and individual contacts. Causes and dates of death were further verified from the local death registry. Individual cumulative fibre exposures (f-yr/ml) were estimated based on converted dust measurements and working years at specific workshops. Standardized mortality ratios (SMRs) for lung cancer, gastrointestinal (GI) cancer, all cancers and nonmalignant respiratory diseases (NMRD) stratified by employment years, estimated cumulative fibre exposures, and smoking, were calculated. Poisson models were fitted to determine exposure-response relationships between estimated fibre exposures and cause-specific mortality, adjusting for age and smoking. Results SMRs for lung cancer increased with employment years at entry to the study, by 3.5-fold in ≥10 years and 5.3-fold in ≥20 years compared with <10 years. A similar trend was seen for NMRD. Smokers had greater mortality from all causes than nonsmokers, but the latter also had slightly increased SMR for lung cancer. No excess lung cancer mortality was observed in cumulative exposures of <20 f-yrs/ml. However, significantly increased mortality was observed in smokers at the levels of ≥20 f-yrs/ml and above, and in nonsmokers at ≥100 f-yrs/ml and above. A similarly clear gradient was also displayed for NMRD. The exposure-response relationships with lung cancer and NMRD persisted in multivariate analysis. Moreover, a clear gradient was shown in GI cancer mortality when age and smoking were adjusted for. Conclusion There were clear exposure-response relationships in this cohort, which imply a causal link between Chrysotile Asbestos exposure and lung cancer and nonmalignant respiratory diseases, and possibly to gastrointestinal cancer, at least for smokers.

  • mortality in Chrysotile Asbestos workers in china
    Current Opinion in Pulmonary Medicine, 2013
    Co-Authors: Xiaorong Wang, Midori N Courtice, Sihao Lin
    Abstract:

    Purpose of review China has been the world's top Chrysotile Asbestos consumer and producer. However, the national mortality rate for Asbestos-related diseases, particularly from malignancies, is unknown. This review elaborates recent studies on cancer mortality and nonmalignant respiratory diseases in Chinese Chrysotile Asbestos workers. Recent findings Studies conducted in Asbestos products factory workers and miners have demonstrated strong associations between exposure to Chrysotile and mortality rates for lung cancer and nonmalignant respiratory diseases. Mortality rates for lung cancer and nonmalignant respiratory diseases in both Asbestos workers and miners are four and three times higher, respectively, than expected, which are greater than those seen in studies from western countries, likely a reflection of heavier exposures and less effective protection for workers. An increased risk of gastrointestinal cancer was also detected in Chrysotile miners. There have been surprisingly few reported cases of mesothelioma, however, which could, at least partially, indicate a problem in diagnosis. Summary Given the substantially increased death risks for lung cancer and nonmalignant respiratory diseases, urgent efforts must be made to implement occupational health and safety regulations and decrease workers' exposures to prevent a future heavier disease burden. Meanwhile, improvements in diagnostics and systematic recording of the incidence and mortality of Asbestos-related diseases are needed.

  • cause specific mortality in relation to Chrysotile Asbestos exposure in a chinese cohort
    Journal of Thoracic Oncology, 2012
    Co-Authors: Sihao Lin, Xiaorong Wang, Eiji Yano, Midori N Courtice, Hong Qiu, Mianzhen Wang
    Abstract:

    Introduction: The carcinogenic potency of Chrysotile Asbestos remains a contentious topic, and more data are needed to address this issue. We examine cause-specific mortality, especially lung cancer, and its association with Chrysotile-Asbestos exposure in a Chinese cohort. Methods: A cohort of 577 workers from a Chrysotile-textile plant was followed prospectively from 1972 to 2008. Occupational history, exposure information, and smoking data were obtained from company records and personal interviews; vital status and causes of death were ascertained from death registries and hospitals. Workers were classified into three exposure levels on the basis of exposure assessments of different workshops. Standardized Mortality Ratios (SMRs) were calculated in terms of exposure levels and other indices. Results: Among 259 identified deaths, 53 died from lung cancer, with an SMR of 4.08 (95% confidence interval 3.12, 5.33), and 96 from all cancers with an SMR of 2.09 (1.71, 2.55). In addition, two deaths from mesothelioma were observed. Increased mortality from respiratory diseases was also observed (SMR 3.38, 95% confidence interval 2.72, 4.21). Asbestos-exposure levels, exposure years, and birth cohorts showed a clear trend of risk for lung cancer and respiratory diseases. Conclusion: The current analysis indicated that exposure to Chrysotile Asbestos was closely associated with excess mortality from lung cancer and respiratory diseases.

  • mortality in a chinese Chrysotile miner cohort
    International Archives of Occupational and Environmental Health, 2012
    Co-Authors: Xiaorong Wang, Eiji Yano, Ignatius Taksun Yu, Mianzhen Wang
    Abstract:

    Background Few data were available to address cause-specific mortality in Asbestos miners in China. This study observed a cohort of workers from the largest Chrysotile Asbestos mine to evaluate the association between Asbestos exposure and cause-specific mortality.

  • exposure response relationship between Chrysotile exposure and mortality from lung cancer and Asbestosis
    Occupational and Environmental Medicine, 2012
    Co-Authors: Qian Deng, Xiaorong Wang, Mianzheng Wang
    Abstract:

    Objectives To describe mortality in workers exposed to Chrysotile Asbestos, and determine exposure–response relationships between Asbestos exposure and mortality from lung cancer and Asbestosis by fitting and comparing different models. Methods A prospective cohort consisting of 586 workers in an Asbestos textile factory was followed from 1 January 1972 to 31 December 2006. A structured questionnaire was administered to collect personal information and exposure data. Paired concentration samples measured in the workshops were used to convert dust concentrations to fibre concentrations. Individual cumulative Asbestos exposure was estimated as the product of fibre concentrations and duration of employment in each job and expressed as fibre-years/ml. The vital status of cohort members was followed annually. Poisson regression analysis was applied to fit log-linear, log-quadratic, power, additive relative risk and categorical models to estimate exposure–response relationships between cumulative fibre exposure and mortality from lung cancer and Asbestosis. Results Of the 226 deaths (14.6 per 1000 person-years) over the 35-year follow-up, 51 were from lung cancer (3.29 per 1000 person-years) and 37 from Asbestosis (2.39 per 1000 person-years). A significant exposure–response relationships with either lung cancer or Asbestosis (p Conclusions The study confirmed strong associations between exposure to Chrysotile Asbestos and lung cancer and Asbestosis, in which clear exposure–response relationships were observed.

Eiji Yano - One of the best experts on this subject based on the ideXlab platform.

  • cancer mortality in chinese Chrysotile Asbestos miners exposure response relationships
    PLOS ONE, 2013
    Co-Authors: Xiaorong Wang, Eiji Yano, Ignatius Taksun Yu, David C Christiani
    Abstract:

    Objective This study was conducted to assess the relationship of mortality from lung cancer and other selected causes to Asbestos exposure levels. Methods A cohort of 1539 male workers from a Chrysotile mine in China was followed for 26 years. Data on vital status, occupation and smoking were collected from the mine records and individual contacts. Causes and dates of death were further verified from the local death registry. Individual cumulative fibre exposures (f-yr/ml) were estimated based on converted dust measurements and working years at specific workshops. Standardized mortality ratios (SMRs) for lung cancer, gastrointestinal (GI) cancer, all cancers and nonmalignant respiratory diseases (NMRD) stratified by employment years, estimated cumulative fibre exposures, and smoking, were calculated. Poisson models were fitted to determine exposure-response relationships between estimated fibre exposures and cause-specific mortality, adjusting for age and smoking. Results SMRs for lung cancer increased with employment years at entry to the study, by 3.5-fold in ≥10 years and 5.3-fold in ≥20 years compared with <10 years. A similar trend was seen for NMRD. Smokers had greater mortality from all causes than nonsmokers, but the latter also had slightly increased SMR for lung cancer. No excess lung cancer mortality was observed in cumulative exposures of <20 f-yrs/ml. However, significantly increased mortality was observed in smokers at the levels of ≥20 f-yrs/ml and above, and in nonsmokers at ≥100 f-yrs/ml and above. A similarly clear gradient was also displayed for NMRD. The exposure-response relationships with lung cancer and NMRD persisted in multivariate analysis. Moreover, a clear gradient was shown in GI cancer mortality when age and smoking were adjusted for. Conclusion There were clear exposure-response relationships in this cohort, which imply a causal link between Chrysotile Asbestos exposure and lung cancer and nonmalignant respiratory diseases, and possibly to gastrointestinal cancer, at least for smokers.

  • cause specific mortality in relation to Chrysotile Asbestos exposure in a chinese cohort
    Journal of Thoracic Oncology, 2012
    Co-Authors: Sihao Lin, Xiaorong Wang, Eiji Yano, Midori N Courtice, Hong Qiu, Mianzhen Wang
    Abstract:

    Introduction: The carcinogenic potency of Chrysotile Asbestos remains a contentious topic, and more data are needed to address this issue. We examine cause-specific mortality, especially lung cancer, and its association with Chrysotile-Asbestos exposure in a Chinese cohort. Methods: A cohort of 577 workers from a Chrysotile-textile plant was followed prospectively from 1972 to 2008. Occupational history, exposure information, and smoking data were obtained from company records and personal interviews; vital status and causes of death were ascertained from death registries and hospitals. Workers were classified into three exposure levels on the basis of exposure assessments of different workshops. Standardized Mortality Ratios (SMRs) were calculated in terms of exposure levels and other indices. Results: Among 259 identified deaths, 53 died from lung cancer, with an SMR of 4.08 (95% confidence interval 3.12, 5.33), and 96 from all cancers with an SMR of 2.09 (1.71, 2.55). In addition, two deaths from mesothelioma were observed. Increased mortality from respiratory diseases was also observed (SMR 3.38, 95% confidence interval 2.72, 4.21). Asbestos-exposure levels, exposure years, and birth cohorts showed a clear trend of risk for lung cancer and respiratory diseases. Conclusion: The current analysis indicated that exposure to Chrysotile Asbestos was closely associated with excess mortality from lung cancer and respiratory diseases.

  • mortality in a chinese Chrysotile miner cohort
    International Archives of Occupational and Environmental Health, 2012
    Co-Authors: Xiaorong Wang, Eiji Yano, Ignatius Taksun Yu, Mianzhen Wang
    Abstract:

    Background Few data were available to address cause-specific mortality in Asbestos miners in China. This study observed a cohort of workers from the largest Chrysotile Asbestos mine to evaluate the association between Asbestos exposure and cause-specific mortality.

  • a 37 year observation of mortality in chinese Chrysotile Asbestos workers
    Thorax, 2012
    Co-Authors: Xiaorong Wang, Eiji Yano, Midori N Courtice, Ignatius Taksun Yu, Mianzhen Wang
    Abstract:

    Objectives This 37-year prospective cohort study was undertaken to provide additional evidence for mortality risks associated with exposure to Chrysotile Asbestos. Methods 577 Asbestos workers and 435 control workers in original cohorts were followed from 1972 to 2008, achieving a follow-up rate of 99% and 73%, respectively. Morality rates were determined based on person-years of observation. Cox proportional hazard models were constructed to estimate HRs of cause-specific mortality, while taking into account age, smoking and Asbestos exposure level. Results There were 259 (45%) deaths identified in the Asbestos cohort, and 96 died of all cancers. Lung cancer (n=53) and non-malignant respiratory diseases (n=81) were major cause-specific deaths, in contrast to nine lung cancers and 11 respiratory diseases in the controls. Age and smoking-adjusted HRs for mortality by all causes and all cancers in Asbestos workers were 2.05 (95% CI 1.56 to 2.68) and 1.89 (1.25 to 2.87), respectively. The risks for lung cancer and respiratory disease deaths in Asbestos workers were over threefold that in the controls (HR 3.31(95% CI 1.60 to 6.87); HR 3.23 (95% CI 1.68 to 6.22), respectively). There was a clear exposure–response trend with Asbestos exposure level and lung cancer mortality in both smokers and non-smokers. Conclusion Data from this prospective cohort provide strong evidence for increased mortality risks, particularly from lung cancer and non-malignant respiratory diseases, associated with exposure to Chrysotile Asbestos, while taking into account of the smoking effect.

  • cancer mortality among chinese Chrysotile Asbestos textile workers
    Lung Cancer, 2012
    Co-Authors: Xiaorong Wang, Eiji Yano, Ignatius Taksun Yu, M Z Wang, David C Christiani
    Abstract:

    Abstract To determine mortality associated with exposure to Chrysotile Asbestos, a cohort of Asbestos workers from an Asbestos textile factory in China was followed prospectively from 1972 to 2008. A total 577 workers were successfully followed, achieving a follow-up rate of 98.5% over 37 years. Employment data and smoking information were obtained from factory and individual workers. Vital status was ascertained from factory personnel records and the municipal death registry. Workers were categorized into high, medium and low exposure groups in terms of their job titles and workshops. Follow-up generated 17,508 person-years, with 259 deaths from all causes, 96 all cancers and 53 lung cancers and 2 mesotheliomas. The highest cancer mortality was observed in the high exposure group, with 1.5-fold age-adjusted mortality from all cancers and 2-fold from lung cancer compared to the low exposure group. Age and smoking adjusted hazard ratio in the high exposure group was 2.99 (95%CI, 1.30, 6.91) for lung cancer and 2.04 (1.12, 3.71) for all cancers. Both smokers and nonsmokers at the high exposure level had a high death risk of lung cancer, with a clearer exposure-response trend seen in smokers. This study confirmed increased mortality from lung cancer and all cancers in Asbestos workers, and the cancer mortality was associated with exposure level.

Jorg Chevalier - One of the best experts on this subject based on the ideXlab platform.

  • a biopersistence study following exposure to Chrysotile Asbestos alone or in combination with fine particles
    Inhalation Toxicology, 2008
    Co-Authors: D M Bernstein, U Decker, P Kunzendorf, Ken Donaldson, S Gaering, Jorg Chevalier, S E Holm
    Abstract:

    In designing a study to evaluate the inhalation biopersistence of a Chrysotile Asbestos that was used as a component of a joint-compound, a feasibility study was initiated to evaluate the shortterm biopersistence of the Chrysotile alone and of the Chrysotile in combination witht the sanded reformulated joint-compound. Two groups of Wistar rats were exposed to either 7RF3 Chrysotile (Group 2) or to 7RF3 Chrysotile combined with aerosolized sanded joint-compound (Group 3). In addition, a control group was exposed to filtered-air. The Chrysotile used in the Ready Mix joint compound is rapidly removed from the lung. The Chrysotile alone exposure group had a clearance half-time of fibers L > 20 µm of 2.2 days; in the Chrysotile plus sanded exposure group the clearance half-time of fibers L > 20 µm was 2.8 days. However, across all size ranges there was approximately an order of magnitude decrease in the mean number of fibers remaining in the lungs of Group 3 as compared to Group 2 despite similiar aerosol exposures. Histopathological examination showed that the Chrysotile exposed lungs had the same appearance as the filtered-air controls. This study uniquely illustrates that additional concurrent exposure to an aerosol of the sanded joint-compound, with large numbers of fine-particles depositing in the lungs, accelerates the recruitment of macrophages, resulting in a tenfold decrease in the number of fibers remaining in the lung. The increased number of macrophages in the Chrysotile/sanded joint exposure group was confirmed histologically, with this being the only exposure-related histological finding reported.

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in . This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer tha...

  • comparison of calidria Chrysotile Asbestos to pure tremolite final results of the inhalation biopersistence and histopathology examination following short term exposure
    Inhalation Toxicology, 2005
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    Calidria Chrysotile Asbestos, which is a serpentine mineral, has been shown to be considerably less biopersistent than the durable amphibole mineral tremolite Asbestos, which persists once deposited in the lung. The initial results of this inhalation biopersistence study in rats that demonstrates this difference were reported in Bernstein et al. (2003). This article presents the full results through 1 yr after cessation of the 5-day exposure. This study was based upon the recommendations of the European Commission (EC) Interim Protocol for the Inhalation Biopersistence of synthetic mineral fibers (Bernstein & Riego-Sintes, 1999). In addition, the histopathological response in the lung was evaluated following exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial-grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and that of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 microm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The Chrysotile samples were specifically chosen to have 200 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. Calidria Chrysotile has been found to be one of the most rapidly cleared mineral fibers from the lung. The fibers longer than 20 microm in length are cleared with a half-time of 7 h. By 2 days postexposure all long fibers have dissolved/disintegrated into shorter pieces. The fibers between 5 and 20 microm in length were cleared with a half-time of 7 days. This length range represents a transition zone between those fibers that can be fully phagocytosed and cleared as particles and the longer fibers that cannot be fully engulfed by the macrophage. The fibers/objects shorter than 5 microm in length were cleared with a half-time of 64 days, which is faster than that reported for insoluble nuisance dusts such as TiO2. By 12 months postexposure, 99.92% of all the remaining Chrysotile was less than 5 microm in length. Following the 5 days of repeated exposure to more than 48,000 Chrysotile fibers/cm3 (190 fibers L > 20 microm), histopathological examination revealed no evidence of any inflammatory reaction either after the cessation of the last exposure or at any time during the subsequent 12-mo period. This is in marked contrast to the amphibole tremolite, which was also investigated using the same inhalation biopersistence protocol. The long tremolite fibers, once deposited in the lung, remain over the rat's lifetime with essentially an infinite half-time. Even the shorter fibers, following early clearance, also remain with no dissolution or further removal. At 365 days postexposure, there was a mean lung burden was of 0.5 million fibers L > 20 microm and 7 million fibers 5-20 microm in length with a total mean lung burden of 19.6 million fibers. The tremolite exposed rats, even with exposure to 16 times fewer total fibers than Chrysotile, showed a pronounced inflammatory response with the rapid development of granulomas as seen at day 1 postexposure, followed by the development of fibrosis characterized by collagen deposition within these granulomas and by 90 days even mild interstitial fibrosis. With the short exposure, this study was not designed specifically to evaluate pathological response; however, it is quite interesting that even so there was such a marked response with tremolite. These findings provide an important basis for substantiating both kinetically and pathologically the differences between Chrysotile and the amphibole tremolite. As Calidria Chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.

  • comparison of calidria Chrysotile Asbestos to pure tremolite inhalation biopersistence and histopathology following short term exposure
    Inhalation Toxicology, 2003
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    The differences between Chrysotile Asbestos, a serpentine mineral, and amphibole Asbestos have been debated extensively. Many studies have shown that Chrysotile is cleared from the lung more rapidly than amphibole. In order to quantify the comparative clearance of Chrysotile and the amphibole Asbestos tremolite, both fibers were evaluated in an inhalation biopersistence study that followed the European Commission recommended guidelines. In addition, the histopathological response in the lung was evaluated following the short-term exposure. This article presents the results of this study through 90 days after cessation of exposure. Following the termination of the study, a subsequent article will provide the complete results through 12 mo after cessation of exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and of a long-fiber t...

  • comparison of calidria Chrysotile Asbestos to pure tremolite inhalation biopersistence and histopathology following short term exposure
    Inhalation Toxicology, 2003
    Co-Authors: D M Bernstein, Jorg Chevalier, Paul Smith
    Abstract:

    The differences between Chrysotile Asbestos, a serpentine mineral, and amphibole Asbestos have been debated extensively. Many studies have shown that Chrysotile is cleared from the lung more rapidly than amphibole. In order to quantify the comparative clearance of Chrysotile and the amphibole Asbestos tremolite, both fibers were evaluated in an inhalation biopersistence study that followed the European Commission recommended guidelines. In addition, the histopathological response in the lung was evaluated following the short-term exposure. This article presents the results of this study through 90 days after cessation of exposure. Following the termination of the study, a subsequent article will provide the complete results through 12 mo after cessation of exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial grade Chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 microm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The Chrysotile samples were specifically chosen to have 200 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm3 longer than 20 microm in length present in the exposure aerosol. Calidria Chrysotile fibers clear from the lung more rapidly (T1/2, fibers L > 20 microm = 7 h) than any other commercial fiber tested including synthetic vitreous fibers. With such rapidly clearing fibers, the 5-day exposure would not be expected to result in any pathological change in the lung, and the lungs of animals that inhaled Calidria Chrysotile showed no sign of inflammation or pathology and were no different than the lungs of those animals that breathed filtered air. Following this 5-day exposure to tremolite, the tremolite fibers once deposited in the lung parenchyma do not clear and almost immediately result in inflammation and a pathological response in the lung. At the first time point examined, 1 day after cessation of exposure, inflammation was observed and granulomas were already formed. By 14 days postexposure these microgranulomas had turned fibrotic, and by 90 days postexposure the severity of the collagen deposits had increased and interstitial fibrosis was observed in one of the rats. These findings provide an important basis for substantiating both kinetically and pathologically the differences between Chrysotile and the amphibole tremolite. As Calidria Chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.