Cumulative Respirable Dust Research Articles

The risk of pulmonary tuberculosis in underground copper miners in Zambia exposed to respirable silica: a cross-sectional study.

BackgroundPulmonary tuberculosis (PTB) among underground miners exposed to silica remains a global problem. Although well described in gold and coal mining, risk in other mining entities are not as well documented. This study aims to determine dust-related dose response risk for PTB among underground miners exposed to silica dust in Zambia's copper mines.MethodsA cross sectional study of in-service miners (n = 357) was conducted at Occupational Health and Safety Institute (OHSI), Zambia. A systematic review of medical data over a 5-year period from assessments conducted by doctors at OHSI and statutory silica exposure data (n = 16678) from the Mine Safety Department (MSD) were analysed. Lifetime cumulative exposure metrics were calculated. Multivariate logistic regression analysis was used to determine the association between PTB and lifetime exposure to silica, while adjusting for various confounders.ResultsThe median respirable silica dust level was 0.3 mg/m3 (range 0.1–1.3). The overall prevalence of PTB was 9.5 % (n = 34). High cumulative respirable silica dust category showed a statistically significant association with PTB (OR = 6.4 (95 % CI 1. 8–23)) and a significant trend of increasing disease prevalence with increasing cumulative respirable silica dust categories was observed (ptrend < 0.01). Smoking showed a statistically significant association with PTB with OR = 4.3 (95 % CI 1.9–9.9).ConclusionsOur results demonstrate the association of increased risk for certified active TB with cumulative respirable dust in a dose related manner among this sample of copper miners. There is need to intensify dust control measures and incorporate anti-smoking interventions into TB prevention and control programmes in the mines.

Lung function loss in relation to silica dust exposure in South African gold miners

ObjectiveTo estimate exposure-response relationships between respirable dust, respirable quartz and lung function loss in black South African gold miners.Methods520 mineworkers aged >37 years were enrolled in a cross-sectional study. Gravimetric...

Respiratory symptoms and lung function impairment in underground gold miners in Ghana

This is the first study in Ghana in the Obuasi gold mines where the silica content of the respirable dust is 10%, less than in previously studied gold mines, with only 23% of the miners having ever smoked. The study was to assess the prevalence of respiratory impairment in the Ghanaian gold miner and to quantify the effects of the respirable dust on pulmonary function A cross sectional epidemiological study The study was carried out using MRC respiratory symptoms questionnaire, spirometry, and personal respirable dust measurements. A total of 1236 miners were studied. The mean age was 39.7 +/-5.8 (SD) years with a mean of 12.6 +/- 6.7 (SD) years underground service and a mean total cumulative exposure to dust of 10.34 +/-5.61 (SD) mg.m(-3).years. The prevalence of chronic bronchitis was 21.2% and not clearly related to cumulative exposure. MRC breathlessness grade>/=2 was 31.3%, significantly related to cumulative respirable dust exposure after adjustment of age and smoking. There was however significant reduction in FEF(25-75%) with increasing dust exposure and an interaction with ever smoking. There was no correlation between cumulative exposure to respirable dust and FEV(1) % predicted in any group, suggesting that exposure to respirable silica at a mean level of 0.06 mg/m(3) had no deleterious effect on FEV(1) in a population with little tuberculosis, good housing and a low level of cigarette smoking. The prevalence of chronic bronchitis in the Ghanaian gold mine is related more to smoking than any occupational factors.

High prevalence of respiratory symptoms among workers in the development section of a manually operated coal mine in a developing country: A cross sectional study

BackgroundFew studies of miners have been carried out in African countries; most are from South Africa, where the working conditions are assumed to be better than in the rest of Africa. Several studies have focused on respiratory disorders among miners, but development workers responsible for creating underground road ways have not been studied explicitly. This is the first study assessing the associations between exposure to dust and quartz and respiratory symptoms among coal mine workers in a manually operated coal mine in Tanzania, focusing on development workers, as they have the highest exposure to coal dust.MethodsA cross-sectional study was carried out among 250 production workers from a coal mine. Interviews were performed using modified standardized questionnaires to elicit information on occupational history, demographics, smoking habits and acute and chronic respiratory symptoms. The relationships between current dust exposure as well as cumulative respirable dust and quartz and symptoms were studied by group comparisons as well as logistic regression.ResultsWorkers from the development group had the highest dust exposure, with arithmetic mean of 10.3 mg/m3 for current respirable dust and 1.268 mg/m3 for quartz. Analogous exposure results for mine workers were 0.66 mg/m3 and 0.03 mg/m3, respectively; and for other development workers were 0.88 mg/m3 and 0.10 mg/m3, respectively.The workers from the development section had significantly higher prevalence of the acute symptoms of dry cough (45.7%), breathlessness (34.8%) and blocked nose (23.9%). In addition, development workers had significantly more chronic symptoms of breathlessness (17.0%) than the mine workers (6.4%) and the other production workers (2.4%). The highest decile of cumulative exposure to respirable dust was significantly associated with cough (OR = 2.91, 95% CI 1.06, 7.97) as were cumulative exposure to quartz and cough (OR = 2.87, CI 1.05, 7.88), compared with the reference consisting of the group of workers with the lowest quartile of the respective cumulative exposure.ConclusionThe development workers in a coal mine had more acute and chronic respiratory symptoms than the mine and the other production workers. In addition, there was an association between high cumulative coal dust and respiratory symptoms.

Airflow limitation among workers in a labour-intensive coal mine in Tanzania

To describe the relationship between cumulative respirable dust and quartz exposure and lung functioning among workers in a labour-intensive coal mine. The study population comprised 299 men working at a coal mine in Tanzania. Lung function was assessed using a Vitalograph alpha III spirometer in accordance with American Thoracic Society recommendations. Multiple linear regression models were developed to study the relationship between forced expiratory volume in 1 s (FEV(1)), forced vital capacity (FVC) and FEV(1)/FVC and the cumulative dust or quartz exposure while adjusting for age, height and ever smoking. To evaluate trends for dose response, cumulative exposure concentrations for respirable dust and quartz were ranked and categorized in quartiles and the highest decile, with the first quartile as the reference group. Logistic regression models were used to determine odds ratios for FEV(1)/FVC < 0.7 and FEV(1)% < 80 for categories of cumulative dust or quartz exposure. The prevalence of FEV(1)/FVC < 0.7 among the workers was 17.3%. Workers in the development team (20.5%) had the highest prevalence of FEV(1)% < 80%. The estimates of the effects of cumulative exposure on FEV(1)/FVC were -0.015% per mg years m(-3) for respirable dust and -0.3% per mg years m(-3) for respirable quartz. In logistic regression models, the odds ratios for airway limitation (FEV(1)/FVC < 0.7) for the workers in the highest decile of cumulative dust and quartz exposure versus the referents were 4.36 (95% confidence interval: 1.06, 17.96) and 3.49 (0.92, 13.21), respectively. The upper 10% of workers by cumulative dust and quartz exposure also had higher odds ratios for predicted FEV(1)% < 80% than the reference group odds ratio: 10.38 (1.38, 78.13) and 14.18 (1.72, 116.59), respectively. The results must be interpreted with caution due to a possible healthy worker effect and selection bias. Exposure to respirable coal mine dust was associated with airway limitation as measured by FEV(1)/FVC and predicted FEV(1)%.

Dust related risks of clinically relevant lung functional deficits

Aim: To quantify the risks of clinically important deficits of FEV1 in coal miners in relation to cumulative and average concentrations of respirable dust. Methods: Data were studied from over...

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 FEV(1) and FVC, controlling for smoking, past history of TB and employment status. A statistically significant decline in FEV(1) of 1.1 and 2.2 ml/mg-year/m(3) 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 FEV(1) 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.

Risk of silicosis in cohorts of Chinese tin and tungsten miners, and pottery workers (I): An epidemiological study

Epidemiological evaluations of the risk of silicosis in relation to exposure to crystalline silica have raised the question of whether different types of silica dust exposures vary with respect to their ability to cause silicosis. The aim of this study is to compare the risk of silicosis among cohorts of silica dust-exposed Chinese tin miners, tungsten miners, and pottery workers and to assess whether gravimetric measurements of respirable silica dust sufficiently determine the risk of silicosis or whether other factors of exposure may play a significant role. Cohorts were selected from 20 Chinese mines and potteries. Inclusion criteria were starting employment after January 1, 1950 and being employed for at least 1 year during 1960-1974 in one of the selected workplaces. Radiological follow-up for silicosis onset was from January 1, 1950 through December 31, 1994. Silicosis was assessed according to the Chinese radiological criteria for diagnosis of pneumoconiosis (as suspect, Stage I, II, or III). Exposure-response relationships were estimated for silicosis of Stage I or higher. Silica dust exposure was estimated in terms of cumulative total dust exposure, calculated from a workplace, job title, and calendar year exposure matrix, and individual occupational histories. Cumulative total dust exposure was converted in two steps into cumulative respirable dust exposure and cumulative respirable silica dust exposure using conversion factors estimated from side-by-side measurements conducted in 1988-89. The male cohorts included 4,028 tin miners, 14,427 tungsten miners, and 4,547 pottery workers who had similar onset of employment and duration of follow-up. For a given exposure level, the risk of silicosis was higher for the tin and tungsten than the pottery workers. The observed differences in the risk of silicosis among the three cohorts suggest that silica dust characteristics, in addition to cumulative respirable silica dust exposure, may affect the risk of silicosis.

Radiographic outcomes among South African coal miners

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. 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. kappa-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. The overall prevalence of pneumoconiosis was low (2%-4%). The degree of agreement between the two readers for profusion was moderate to high (kappa=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. 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.

Indirect validation of a retrospective method of exposure assessment used in a nested case-control study of lung cancer and silica exposure.

Validations of retrospective methods of assessment used in occupational epidemiological studies have rarely been published. This study is an indirect validation of a quantitative retrospective assessment of exposure to silica used in a nested case-control study of lung cancer among workers at 29 metal mines and pottery factories in China. Indices of cumulative total dust and cumulative respirable dust were calculated by merging work histories with the historical exposure profile for each subject. To validate indirectly the methods of exposure assessment used in the study of lung cancer, trends for exposure response relation between the two indices of exposure to silica and risk of silicosis were evaluated with 376 patients with silicosis from the study population as the cases, and 1262 controls without silicosis for comparison. Age adjusted odds ratios (ORs) as a measure of risk of silicosis showed striking trends with both indices of exposure to silica. For cumulative respirable dust, the OR (95% confidence interval) rose from 7.6 (5.1-11.4) for low exposure to 20.0 (13.2-30.6) for medium exposure, and to 51.7 (31.0-86.8) for high exposure. The strength of the association between exposure to silica and risk of silicosis suggests that the retrospective assessment of exposure used in the case-control study of lung cancer would accurately reflect an exposure response relation between silica and lung cancer, if it existed.

Occupational Dust Exposure and Chronic Obstructive Pulmonary Disease: A Systematic Overview of the Evidence

The object of this study was to assess the relationship between occupational dust exposure and chronic obstructive pulmonary disease (COPD). Studies were identified using MEDLINE (January 1966 to July 1991), SCISEARCH, manual review of reference lists, and personal contact with more than 30 international experts. Studies of COPD, lung function, emphysema, chronic bronchitis, or mortality in workers exposed to nonorganic dust were retrieved. Studies were included if dust exposure was measured quantitatively, and a quantitative relationship between dust exposure and one of the outcomes of interest was calculated while controlling at least for smoking and age. Methodological rigor was assessed, and data regarding the study populations, prognostic factors, and outcomes were extracted independently by two reviewers. Thirteen reports derived from four cohorts of workers met our inclusion criteria. Three of the cohorts were of coal miners and one was of gold miners. All of the studies found a statistically significant association between loss of lung function and cumulative respirable dust exposure. It was estimated that 80 (95% CI, 34 to 137) of 1,000 nonsmoking coal miners with a cumulative respirable dust exposure of 122.5 gh/m3 (considered equivalent to 35 years of work with a mean respirable dust level of 2 mg/m3) could be expected to develop a clinically important (> 20%) loss of FEV1 attributable to dust. Among 1,000 smoking miners the comparable estimate was 66 (95% CI, 49 to 84). The risk of a clinically important loss of lung function attributable to dust among nonsmoking gold miners was estimated to be three times as large as for coal miners at less than one fifth of the cumulative respirable dust exposure (21.3 gh/m3), the maximal exposure observed among the cohort of gold miners. We conclude that occupational dust is an important cause of COPD, and the risk appears to be greater for gold miners than for coal miners. One possible explanation of the greater risk among gold miners is the higher silica content in gold mine dust.

Work related decrement in pulmonary function in silicon carbide production workers.

The relation between pulmonary function, cigarette smoking, and exposure to mixed respirable dust containing silicon carbide (SiC), hydrocarbons, and small quantities of quartz, cristobalite, and graphite was evaluated in 156SiC production workers using linear regression models on the difference between measured and predicted FEV1 and FVC. Workers had an average of 16 (range 2-41) years of employment and 9.5 (range 0.6-39.7) mg-year/m3 cumulative respirable dust exposure; average dust exposure while employed was 0.63 (range 0.18-1.42) mg/m3. Occasional, low level (less than or equal to 1.5 ppm) sulphur dioxide (SO2) exposure also occurred. Significant decrements in FEV1 (8.2 ml; p less than 0.03) and FVC (9.4 ml; p less than 0.01) were related to each year of employment for the entire group. Never smokers lost 17.8 ml (p less than 0.02) of FEV1 and 17.0 (p less than 0.05) of FVC a year, whereas corresponding decrements of 9.1 ml (p = 0.12) in FEV1 and 14.4 ml (p less than 0.02) in FVC were found in current smokers. Similar losses in FEV1 and FVC were related to each mg-year/m3 of cumulative dust exposure for 138 workers with complete exposure information; these findings, however, were generally not significant owing to the smaller cohort and greater variability in this exposure measure. Never smokers had large decrements in FEV1 (40.7 ml; p less than 0.02) and FVC (32.9 ml; p = 0.08) per mg-year/m3 of cumulative dust exposure and non-significant decrements were found in current smokers (FEV1: -7.1 ml; FVC: -11.7 ml). A non-significant decrement in lung function was also related to average dust exposure while employed. No changes were associated with SO(2) exposure or and SO(2) dust interaction. These findings suggest that employment in SiC production is associated with an excessive decrement in pulmonary function and that current permissible exposure limits for dusts occurring in this industry may not adequately protect workers from developing chronic pulmonary disease.

Pneumoconiosis in iron ore surface mining in Labrador.

A cross-sectional survey of the work force at an iron ore surface mine and beneficiation plant in Labrador identified cases with a radiologic diagnosis compatible with simple pneumoconiosis by the International Labour Organization (ILO) classification (1980). Their distribution by ILO categories 1, 2, and 3, after excluding those with confounding diagnoses for pneumoconiosis, was 30, 10, and 2 cases, respectively. ILO category was related to age, duration of current employment, and cumulative respirable dust and quartz levels, as well as to decrement in ventilatory function.

Pulmonary Function in Silicosis

Abstract The relationship between ILO Category for pneumoconiosis, spirometry and four indices of accumulated dust exposure was studied in the work force of an iron ore surface mining and beneficiation plant in Labrador. A significant difference ( p 1 , and %PFVC was found between Categories 2, 3 compared with controls (Category 0) matched for all four indices: cumulative respirable dust (CD), peak respirable dust (PD), cumulative respirable quartz (CQ) and peak respirable quartz (PQ). There was no difference between ILO Categories 0 and 1 except for % PFEV 1 in PD. These findings support the view that simple silicosis is associated with decrements in lung function in addition to that which can be attributed to dust exposure.