Exposure-response estimate for lung cancer and asbestosis in a predominantly chrysotile-exposed Chinese factory cohort.

BACKGROUND: Cumulative fiber exposures, predominantly chrysotile, were estimated in a Chinese asbestos worker cohort and exposure-response relationships with lung cancer mortality and cumulative incidence of asbestosis were determined. METHODS: Individual time-dependent cumulative exposures were estimated for 577 asbestos workers, followed prospectively for 37 years. Occupational history and smoking data were obtained from company records and personal interviews; vital status and causes of death were ascertained from death registries and hospital records. Hazard ratios were generated for disease outcomes, with adjustments for smoking and age. RESULTS: Median cumulative fiber exposure for the cohort was 132.6 fiber-years/ml (IQR 89.3-548.4). Exposure-response relationships were demonstrated for both disease outcomes, with nearly sixfold and threefold increased risks seen at the highest exposure level for lung cancer deaths and asbestosis, respectively. CONCLUSION: Evidence using quantitative exposure estimates was provided for increased risks of lung cancer mortality and development of asbestosis in a predominantly chrysotile-exposed cohort.

Size- and type-specific exposure assessment of an asbestos products factory in China.

This study describes fibre size and type-specific airborne asbestos exposures in an asbestos product factory. Forty-four membrane filter samples were analysed by scanning electron microscopy to determine the size distribution of asbestos fibres, by workshop. Fibre frequencies of bivariate (length by width) categories were calculated and differences between workshops were tested by analysis of variance. Data were recorded for 13,435 chrysotile and 1075 tremolite fibres. The proportions between size metrics traditionally measured and potentially biologically important size metrics were found to vary in this study from proportions reported in other cohort studies. One, common size distribution was generated for each asbestos type over the entire factory because statistically significant differences in frequency between workshops were not detected. This study provides new information on asbestos fibre size and type distributions in an asbestos factory. The extent to which biologically relevant fibre size indices were captured or overlooked between studies can potentially reconcile currently unexplained differences in asbestos-related disease (ARD) risk between cohorts. The fibre distributions presented here, when combined with similar data from other sites, will contribute to the development of quantitative models for predicting risk and our understanding of the effects of fibre characteristics in the development of ARD.

Exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers.

OBJECTIVE: Whether there is a difference in the exposure-response slope for lung cancer between mining workers and textile workers exposed to chrysotile has not been well documented. This study was carried out to evaluate exposure-specific lung cancer risks in Chinese chrysotile textile workers and mining workers. SUBJECTS AND METHODS: A chrysotile mining worker cohort and a chrysotile textile worker cohort were observed concurrently for 26 years. Information on workers' vital status, occupational history and smoking habits were collected, and causes and dates of deaths were verified from death registries. Individual cumulative fiber exposures were estimated based on periodic dust/fiber measurements from different workshops, job title and duration, and categorized into four levels (Q1-Q4). Standardized mortality ratios (SMRs) for lung cancer were calculated and stratified by industry and job title with reference of the national rates. Cox proportional hazard models were fit to estimate the exposure-specific lung cancer risks upon adjustment for age and smoking, in which an external control cohort consisting of industrial workers without asbestos exposure was used as reference group for both textile and mining workers. RESULTS: SMRs were almost consistent with exposure levels in terms of job titles and workshops. A clear exposure-response relationship between lung cancer mortality and exposure levels was observed in both cohorts. At low exposure levels (Q1 and Q2), textile workers displayed higher death risks of lung cancer than mining workers. However, similarly considerably high risks were observed at higher exposure levels, with hazard ratios of over 8 and 11 at Q3 and Q4, respectively, for both textile and mining workers, after both age and smoking were adjusted. CONCLUSION: The chrysotile textile workers appeared to have a higher risk of lung cancer than the mining workers at a relatively low exposure level, but no difference was observed at a high exposure level, where both cohorts displayed a considerably high risk.

Exposure to chrysotile mining dust and digestive cancer mortality in a Chinese miner/miller cohort.

OBJECTIVES: To examine mortality from digestive cancers in a Chinese miner cohort and to explore the exposure-response relationship between chrysotile mining dust and site-specific digestive cancers. METHODS: A cohort of 1539 asbestos miners was followed for 26 years. Information on vital status and death causes was collected from personnel records and hospitals. Underlying causes of death from cancers were determined by combination of clinical manifestations and pathological confirmation. Individual cumulative dust exposures were estimated based on periodic dust measurements of different workshops, individuals' job title and employment duration, and treated as a time-dependent variable. Standardised mortality ratios (SMR) were calculated according to Chinese national data and stratified by exposure (levels 1-3, from low to high). Cox proportional hazard models were constructed to estimate HRs in relation to cumulative exposure with adjustment of smoking. RESULTS: Fifty-one deaths from digestive cancers were identified in the cohort, giving an SMR of 1.45 (95% CI 1.10 to 1.90). There was a clear exposure-response relationship between asbestos dust exposure and mortality from stomach cancer, with SMR of 2.39 (95% CI 1.02 to 5.60) and 6.49 (2.77 to 15.20) at exposure levels 2 and 3, respectively. The clear relationship remained in multivariate analysis, in which workers at the highest exposure level had HRs of 12.23 (95% CI 8.74 to 17.12). In addition, excess mortality from oesophageal and liver cancers was also observed at high exposure levels. CONCLUSIONS: This study provides additional evidence for the association between exposure to chrysotile mining dust and excess mortality from digestive cancers, particularly stomach cancer.

Interaction between occupational stress and GR gene polymorphisms on essential hypertension among railway workers.

OBJECTIVE: The aim of this study was to explore the interactions of occupational stress and glucocorticoid receptor gene (GR) polymorphisms on essential hypertension (EH) among Chinese railway workers. METHODS: A case-control study was conducted with 196 EH cases and matched controls from male railway employees. Occupational stress was scaled by a validated Chinese version of the Occupational Stress Inventory. Information on risk factors for hypertension, including smoking, alcohol consumption, family hypertension history and body mass index, was collected by face to face interviews. Genotypes of GR BCL1 and G678S genes were determined with PCR-RFLP. Conditional logistic regression was applied to examine the interactions of occupational stress and GR gene polymorphisms with adjustment for potential confounders. RESULTS: A positive relationship was observed in the CG/GG genotype compared with the CC genotype in the GRBCL1 gene. The interaction between the GRBCL1 gene and occupational stress was statistically significant on EH. The odds ratio (OR) was 1.56 (95% CI: 0.93, 2.63) when comparing the CG/GG genotype of the GRBCL1 gene with low/medium personal strain with the CC genotype with low/medium strain, whereas the OR was 3.43 (95% CI: 1.45, 8.12) when comparing the same genotype with high strain with the same reference. A similar pattern of association was observed for the CG/GG genotype of the GRBCL1 gene with low/medium occupational stress (OR=1.32, 95% CI: 0.76, 2.30) and with high occupational stress (OR=3.58, 95% CI: 1.60, 8.02). CONCLUSIONS: This study suggests that the CG/GG genotype in GRBCL1 possibly interacts with occupational stress in increasing the risk for essential hypertension in the railway workers, but more studies with larger samples are needed to confirm the finding.

Mortality in chrysotile asbestos workers in China.

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.

An updated review on asbestos and related diseases in China.

BACKGROUND: Asbestos is an industrial mineral that can cause diseases such as asbestosis, lung cancer, and mesothelioma. Asbestos consumption in China has increased steadily since the 1960s and is currently at half a million tonnes per year. Work conditions in the asbestos-related industries are poor and exposure levels frequently exceed the occupational exposure limit. OBJECTIVE: To provide an updated overview on asbestos production and consumption in China and discuss what is known about the resulting burden of asbestos-related diseases. FINDINGS: China is the world's top chrysotile consumer and second largest producer. Over a million people may be occupationally exposed, yet reliable disease statistics are unavailable and the national burden of asbestos-related disease (ARD) is not well known. Nevertheless, ARD prevalence, incidence, and mortality are expected to be high and will increase for many decades due to the volume of asbestos consumed historically, and a long latency period. CONCLUSIONS: Government policies to prevent ARD have been implemented but more actions are necessary to ensure compliance and ultimately, the complete elimination of asbestos to prevent a heavy future disease burden.

Cause-specific mortality in relation to chrysotile-asbestos exposure in a Chinese cohort.

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.

A 37-year observation of mortality in Chinese chrysotile asbestos workers.

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.

Occupational injury in rural Bangladesh: data gathering using household survey.

Occupational injuries are estimated to cause over 300,000 deaths per year worldwide. Many low- and middle-income countries often lack effective injury surveillance systems. We attempted to utilize household surveys to collect occupational injury data to develop more accurate injury incidence data. We undertook a pilot study of this approach in the rural area of Mirsarai, Bangladesh. Surveys were administered to 2,017 males and 120 females. Sixty-five percent were self-employed and over 80% worked in work places with less than six employees; over 60% worked seven days per week. Just over 50% of subjects reported at least one injury at work in the prior year. Incidence of lost-time injuries was 31%. The median number of work days lost was 7. The injury rates were higher than ILO estimates for Bangladesh, perhaps because of our study's focus on a rural population. We recommend expanding to larger and a more representative sample of the Bangladesh working community.

Asbestos-related disease in Bangladeshi ship breakers: a pilot study.

A pilot study tested the feasibility of conducting occupational health research in Bangladesh while examining prevalence of asbestos-related diseases including asbestosis, work-related respiratory symptoms, and attitudes to occupational health and safety among a group of internal migrant ship breakers. Data was collected on clinical and work history, respiratory symptoms, and occupational health and safety practices in Bengali. A B-reader read all postero-anterior chest x-rays. In the 104 male ship breakers studied, prevalence of asbestos-related disease was 12%, of which asbestosis accounted for 6%. Knowledge of asbestos and occupational health and safety measures were almost nonexistent. The prevalence of asbestos-related diseases is low compared to studies in shipbuilders and repairers, but a risk underestimate could have resulted from challenges identified during study design and implementation including: industry noncooperation and a culture of corruption; technological and language barriers; and a regional lack of physician knowledge and research on occupational diseases.