Cross-shift peak expiratory flow changes are unassociated with respirable coal dust exposure among South African coal miners

BACKGROUND: The objectives of this study were to determine whether cross-shift changes in peak expiratory flow rate (PEFR) were related to respirable dust exposure in South African coalminers. METHODS: Fifty workers were randomly selected from a cohort of 684 miners from 3 bituminous coalmines in Mpumalanga, South Africa. Peak expiratory efforts were measured prior to the commencement of the shift, and at the end of the shift on at least two occasions separated by at least 2 weeks, with full shift personal dust sampling being conducted on each occasion for each participant. Interviews were conducted, work histories were obtained and cumulative exposure estimates were constructed. Regression models examined the associations of cross-shift changes in PEFR with current and cumulative exposure, controlling for shift, smoking and past history of tuberculosis. RESULTS: There were marginal differences in cross-shift PEFR (ranging from 0.1 to 2 L/min). Linear regression analyses showed no association between cross-shift change in PEFR and current or cumulative exposure. The specific shift worked by participants in the study showed no effect. CONCLUSIONS: Our study showed no association between current respirable dust exposure and cross-shift changes in PEFR. There was a non-significant protective effect of cumulative dust exposure on the outcome, suggesting the presence of a "healthy worker survivor effect" in this data.     

Differential respirable dust related lung function effects between current and former South African coal miners

Dust-related dose-response decrements in lung function among coal miners have been reported in several studies, with varying magnitudes across populations. Few studies have compared differences between current and former coal miners. No studies on dose response relationships with lung function have been conducted in South African coal mines, one of the top three producers of coal internationally. The objectives of this study were (1) to describe the relationship between respirable dust exposure and lung function among current and former South African coal miners and to determine whether differential dust related effects were present between these employment categories; (2) to examine dust related dose response relationships, controlling for potential confounding by smoking and a history of tuberculosis (TB). Six hundred and eighty-four current and 188 ex-miners from three bituminous coal mines in Mpumalanga Province were studied. Interviews assessing work histories, smoking profiles and other risk factors were conducted. Work histories were also obtained from company records. Standardised spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from company-collected sampling and measurements conducted by the researchers. Regression models examined the associations of CDE with per cent predicted FEV₁ and FVC, controlling for smoking, past history of TB and employment status. A statistically significant decline in FEV₁ of 1.1 and 2.2 ml/mg-year/m³ was found in representative 40-year-old, 1.7-m tall current and former miners, respectively. Significant differences were found between the highest and medium exposure categories. Ex-miners had a lower mean per cent predicted lung function than current miners for each cumulative exposure category, suggesting a healthy worker effect. Past history of TB contributed to 21 and 14% declines in per cent predicted FEV₁ and FVC, respectively. Thus, in this cohort, a dose-related decline in lung function was associated with respirable dust exposure, with a magnitude of effect similar to that seen in other studies and important differences between current and former employees. A healthy worker effect may have attenuated the magnitude of this relationship. TB was a significant contributor to lung function loss.     

Radiographic outcomes among South African coal miners

Objectives: This study, the first to document the prevalence of pneumoconiosis among a living South African coal mining cohort, describes dose–response relationships between coal workers pneumoconiosis and respirable dust exposure, and relationships between pneumoconiosis and both lung function deterioration and respiratory symptoms. Methods: A total of 684 current miners and 188 ex-miners from three bituminous-coal mines in Mpumalanga, South Africa, was studied. Chest radiographs were read according to the International Labour Organization (ILO) classification by two experienced readers, one an accredited National Institute for Occupational Safety and Health (NIOSH) B reader. Interviews were conducted to assess symptoms, work histories (also obtained from company records), smoking, and other risk factors. Spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from historical company-collected sampling and researcher-collected personal dust measurements. -Statistics compared the radiographic outcomes predicted by the two readers. An average profusion score was used in the analysis for the outcomes of interest. Because of possible confounding by employment status, most analyses were stratified on current and ex-miner status. Results: The overall prevalence of pneumoconiosis was low (2%–4%). The degree of agreement between the two readers for profusion was moderate to high (=0.58). A significant association (P<0.001) and trend (P<0.001) was seen for pneumoconiosis with increasing categories of CDE among current miners only. A significant (P<0.0001) additional 58 mg-years/m³ CDE was seen among those with pneumoconiosis compared to those without. CDE contributed to a statistically significant 0.19% and 0.11% greater decline in the percent predicted 1-second forced expiration volume (FEV₁) and forced vital capacity (FVC), respectively, among current miners with pneumoconiosis than among those without. Logistic regression models showed no significant relationships between pneumoconiosis and symptoms. Conclusions: The overall prevalence of pneumoconiosis, although significantly associated with CDE, was low. The presence of pneumoconiosis is associated with meaningful health effects, including deterioration in lung function. Intervention measures that control exposure are indicated, to reduce these functional effects.     

Ventilatory function after exposure to various respirable hazards in a population of former coal miners

The ventilatory function of 406 male former coal miners who had presented at the Cook County Hospital occupational medicine clinic between January 1976 and April 1987 was studied to determine whether subsequent exposure to respiratory hazards after leaving the coal mines adversely affected lung function. The miners were divided into five exposure groups based on their exposure to respirable hazards. These were coal dust only, coal dust plus asbestos dust, coal dust plus silica dust, coal dust plus another respirable hazard and coal dust plus two other respirable dust exposures. Duration of employment in coal mines, race, smoking history, and mean age were not significantly different between the various exposure groups. No significant difference was found in the per cent of predicted forced expiratory volume in one second (FEV1), per cent of predicted forced vital capacity (FVC), and FEV1/FVC when the coal dust only group was compared with each of the other four exposure groups using ANOVA. Among former coal miners who present for a respiratory disability determination, therefore, exposure to respirable hazards subsequent to employment in coal mines is not associated with a statistically significant deterioration in ventilatory function.     

Ventilatory function after exposure to various respirable hazards in a population of former coal miners.

The ventilatory function of 406 male former coal miners who had presented at the Cook County Hospital occupational medicine clinic between January 1976 and April 1987 was studied to determine whether subsequent exposure to respiratory hazards after leaving the coal mines adversely affected lung function. The miners were divided into five exposure groups based on their exposure to respirable hazards. These were coal dust only, coal dust plus asbestos dust, coal dust plus silica dust, coal dust plus another respirable hazard and coal dust plus two other respirable dust exposures. Duration of employment in coal mines, race, smoking history, and mean age were not significantly different between the various exposure groups. No significant difference was found in the per cent of predicted forced expiratory volume in one second (FEV1), per cent of predicted forced vital capacity (FVC), and FEV1/FVC when the coal dust only group was compared with each of the other four exposure groups using ANOVA. Among former coal miners who present for a respiratory disability determination, therefore, exposure to respirable hazards subsequent to employment in coal mines is not associated with a statistically significant deterioration in ventilatory function.     

High exposure to respirable dust and quartz in a labour-intensive coal mine in Tanzania

Labour-intensive mines are numerous in several developing countries, but dust exposure in such mines has not been adequately characterized. The aim of this study was to identify and quantify the determinants of respirable dust and quartz exposure among underground coal mine workers in Tanzania. Personal respirable dust samples (n = 134) were collected from 90 underground workers in June-August 2003 and July-August 2004. The development team had higher exposure to respirable dust and quartz (geometric means 1.80 and 0.073 mg m(-3), respectively) than the mining team (0.47 and 0.013 mg m(-3)), the underground transport team (0.14 and 0.006 mg m(-3)) and the underground maintenance team (0.58 and 0.016 mg m(-3)). The percentages of samples above the threshold limit values (TLVs) of 0.9 mg m(-3) for respirable bituminous coal dust and 0.05 mg m(-3) for respirable quartz, respectively, were higher in the development team (55 and 47%) than in the mining team (20 and 9%). No sample for the underground transport team exceeded the TLV. Drilling in the development was the work task associated with the highest exposure to respirable dust and quartz (17.37 and 0.611 mg m(-3), respectively). Exposure models were constructed using multiple regression model analysis, with log-transformed data on either respirable dust or quartz as the dependent variable and tasks performed as the independent variables. The models for the development section showed that blasting and pneumatic drilling times were major determinants of respirable dust and quartz, explaining 45.2 and 40.7% of the variance, respectively. In the mining team, only blasting significantly determined respirable dust. Immediate actions for improvements are suggested to include implementing effective dust control together with improved training and education programmes for the workers. Dust and quartz in this underground mine should be controlled by giving priority to workers performing drilling and blasting in the development sections of the mine.     

Respiratory outcomes among South African coal miners at autopsy

BACKGROUND: Studies of dose-response relationships between respiratory outcomes at autopsy and coal dust exposure are limited. The Pathology Automation System (PATHAUT) database of South African miners, is one of the largest autopsy databases of occupational lung disease. This study described the prevalence of respiratory outcomes among South African coal miners at autopsy, and determined whether dose response relationships existed between emphysema and exposure. METHODS: Autopsies conducted from 1975 to 1997 on coal miners with exclusive coal mining exposure and having exposure duration information (n = 3,167) were analyzed from PATHAUT. Logistic regression was used to determine relationships between exposure and outcomes, controlling for race, smoking and age on a subset for whom smoking history was available (n = 725). RESULTS: The mean duration of exposure was 11.0 years. Most were black miners (75.3%) with significant differences in the mean ages of black and white miners (37.9 and 55.3 years, respectively). Only 22.9% of cases had information on smoking. The prevalence of silicosis, tuberculosis (TB), coal workers' pneumoconiosis (CWP), and moderate and marked emphysema were 10.7%, 5.2%, 7.3%, and 6.4%, respectively. All diseases, except TB, were associated with exposure duration. Black miners had 8.3 and 1.2 fold greater risks for TB and CWP, respectively, than white miners. White miners had an increased risk of 1.4 and 5.4 for silicosis and moderate to marked emphysema, respectively. In models unadjusted for age, and including smoking, moderate to marked emphysema was strongly associated with exposure duration (OR = 3.4; 95% CI = 1.9-5.9 for highest tercile of exposure duration). Exposure-related risk estimates were reduced when age was introduced into the model. However, age and duration of exposure were highly correlated, (r = 0.68) suggesting a dilution of the exposure effect by age. CONCLUSIONS: There were significant dose related associations of disease, including emphysema, with coal dust exposure.     

锡矿工人接尘与矽肺危险度评价

目的探讨粉尘暴露与矽肺危险度之间的接触效应关系。方法选择广西４个锡矿１９６０～１９６５年间工作１年以上的３０１０名接尘工人进行队列研究。用生存分析法统计累积粉尘接触量和矽肺出现的关系。结果追访到１９９４年底,检出矽肺１０１５例（３３．７％）。矽肺平均潜伏期２１．３年。总粉尘浓度７．５ｍｇ／ｍ３（ＴＷＡ）。拟合生存分析模型表明：矽肺发病危险度与累积接尘量的关系适合Ｗｅｉｂｕｌ分布。累积总粉尘接触量低于１０ｍｇ·ｍ－３·ａ－１时,矽肺危险小于１％;累积总粉尘接触量超过２０ｍｇ·ｍ－３·ａ－１时,矽肺累积危险度升高加快;累积总粉尘接触量达１５０ｍｇ·ｍ－３·ａ－１时,矽肺危险超过６８％。接尘时间与接尘量和矽肺危险度呈正相关。结论矽肺危险度与累积接尘量之间存在接触效应关系。     

Quantitative relations between exposure to respirable coalmine dust and coalworkers' simple pneumoconiosis in men who have worked as miners but have left the coal industry

Present estimates of the quantitative relations between exposure to mixed respirable coalmine dust and risk of developing coalworkes' simple pneumoconiosis are based on studies of working miners. These studies did not include men who had been miners but had left the coal industry, and it was not known whether the estimates of risk were also appropriate for these men. The results are reported of a study in which the dust/disease relations in men who have been miners but have left the industry have been compared with those in men who have remained in it. A sample of 17738 men who were first examined when working in 24 British collieries in the 1950s has been followed up about 22 years later. It was possible to examine 61% of the survivors, 44% of the original sample. Simple pneumoconiosis was more frequent among men (particularly older men) who had left the industry than among those who had stayed in it. A detailed analysis did not show any systematic or statistically significant difference between men who stayed and men who left in the quantitative relations between dust exposure and simple pneumoconiosis. Present estimates of risk of simple pneumoconiosis in relation to exposure to mixed respirable dust in working miners adequately describe the relation found in men who have been miners but have left the industry.     

Quantitative relations between exposure to respirable coalmine dust and coalworkers'' simple pneumoconiosis in men who have worked as miners but have left the coal industry.

Present estimates of the quantitative relations between exposure to mixed respirable coalmine dust and risk of developing coalworkes' simple pneumoconiosis are based on studies of working miners. These studies did not include men who had been miners but had left the coal industry, and it was not known whether the estimates of risk were also appropriate for these men. The results are reported of a study in which the dust/disease relations in men who have been miners but have left the industry have been compared with those in men who have remained in it. A sample of 17738 men who were first examined when working in 24 British collieries in the 1950s has been followed up about 22 years later. It was possible to examine 61% of the survivors, 44% of the original sample. Simple pneumoconiosis was more frequent among men (particularly older men) who had left the industry than among those who had stayed in it. A detailed analysis did not show any systematic or statistically significant difference between men who stayed and men who left in the quantitative relations between dust exposure and simple pneumoconiosis. Present estimates of risk of simple pneumoconiosis in relation to exposure to mixed respirable dust in working miners adequately describe the relation found in men who have been miners but have left the industry.     

Respirable coal dust exposure and respiratory symptoms in South-African coal miners: a comparison of current and ex-miners

OBJECTIVES: Dose-response associations between respirable dust exposure and respiratory symptoms and between symptoms and spirometry outcomes among currently employed and formerly employed South-African coal miners were investigated. METHODS: Work histories, interviews, and spirometry and cumulative exposure were assessed among 684 current and 212 ex-miners. RESULTS: Lower prevalences of symptoms were found among employed compared with ex-miners. Associations with increasing exposure for symptoms of phlegm and past history of tuberculosis were observed, whereas other symptom prevalences were higher in the higher exposure categories. Symptomatic ex-miners exhibited lower lung function compared to the nonsymptomatic. CONCLUSIONS: Compared with published data, symptoms rates were low in current miners but high in ex-miners. Although explanations could include the low prevalence of smoking and/or reporting/selection bias, a "survivor" and/or a "hire" effect is more likely, resulting in an underestimation of the dust-related effect.     

外周血淋巴细胞热应激蛋白72和73水平与煤矿粉尘暴露及慢性阻塞性肺病的关系

目的探讨煤矿工人外周血淋巴细胞热应激蛋白Hsp72和Hsp73在慢性阻塞性肺病(COPD)患者和煤矿工人中的表达及Hsp72和Hsp73与粉尘暴露的关系。方法选择山西某煤矿工人中男性COPD患者50例,按性别、年龄匹配该矿健康煤工对照50例。分别测定肺功能,用流式细胞仪测定各组外周血淋巴细胞在体外基础状态、受热应激及二氢二醇环氧苯并(a)芘(BPDE)染毒后细胞内Hsp72和Hsp73的表达水平。结果(1)煤工COPD组和健康煤工组外周血淋巴细胞Hsp72及Hsp73的基础状态与体外受热和染毒应激后的表达呈一致性趋势,差异无统计学意义(P＞0．05)。(2)煤工COPD组外周血淋巴细胞Hsp72(17．7±4．9)表达低于健康煤工组(22．6±10．0),差异有统计学意义(P＜0．01),而Hsp73水平(33．5±11．7)明显高于健康煤工组(19．6±5．9),差异有统计学意义(P＜0．01)。(3)外周血淋巴细胞Hsp72表达水平与累积呼吸性粉尘暴露量呈正相关(健康煤工组：r= 0．30,P＜0．05；煤工COPD组：r=0．45,P＜0．01),而Hsp73表达与累积呼吸性粉尘暴露量无明显关系。结论煤工COPD患者中应激诱导的外周血淋巴细胞Hsp72表达下调,Hsp72表达与机体耐受粉尘毒性的能力可能相关。