Cumulative Dust Exposure Research Articles

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.

Cement Dust Exposure and Ventilatory Function Impairment: An Exposure–Response Study

We investigated cumulative total cement dust exposure and ventilatory function impairment at a Portland cement factory in Tanzania. All 126 production workers were exposed. The control group comprised all 88 maintenance workers and 32 randomly chosen office workers. Exposed workers had significantly lower forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF), FEV1/FVC, FVC%, FEV1% and PEF%, than controls adjusted for age, duration of employment, height, and pack-years. Cumulative total dust exposure was significantly associated with reduced FVC, forced expiratory volume in 1 second, and peak expiratory flow rate adjusted for age, height and pack-years. Cumulative total dust exposure more than 300 mg/m year versus lower than 100 mg/m years was significantly associated with increased risk of developing airflow limitation (odds ratio = 9.9). The current occupational exposure limit for total cement dust (10 mg/m) appears to be too high to prevent respiratory health effects among cement workers.

Lung Function Among Workers in the Soft Tissue Paper-Producing Industry

To describe lung function in correlation with information on exposure to dust and fibers in soft tissue paper-producing factories in Germany. Ambient monitoring was performed for inhalable, respirable dust and fibers in nine soft tissue paper-producing factories. In a study group of 1,047 workers (189 control subjects, 240 workers with moderate exposure, and 618 workers with high exposure), spirometry (FVC, FEV(1)) was performed. Information on occupational history, duration of exposure, workshop within the company, former occupational exposures, and smoking habits were collected. By employing multiple linear regression modeling, the potentially confounding effects of age, sex, body mass index, smoking habits, and factory were incorporated into the analysis of FVC, FEV(1), and FEV(1) in percent of FVC (FEV(1)%FVC). By employing a logistic regression model, odds ratios were calculated for FVC < 80% predicted in different exposure subgroups. The mean concentrations for inhalable, respirable, and fibrous dusts were 12.4 mg/m(3), 0.28 mg/m(3), and 420,000 fibers per cubic meter. With relation to cumulative dust and fiber exposure, a decrease of FVC from 105.4% predicted to 96.9% predicted (dust) and 97.1% predicted (fibers) in the subgroup with highest cumulative exposure was observed. For FEV(1), a decrease from 107.3% predicted to 103.0% predicted (dust) and 102.8% predicted (fibers) was found. The parameter estimates show dose-response relationships that are more pronounced for FVC compared to FEV(1). FEV(1)%FVC did not change significantly with increasing cumulative exposure, indicating a restrictive pattern of the findings. Due to high ambient dust concentrations and the observed adverse effects on lung function, a reduction of dust exposure and secondary preventive measures is advised.

Epidemiological adaptation of quartz exposure modeling in Swedish aluminum foundries: nested case-control study on lung cancer.

In a recent cohort study in aluminum foundries and remelting plants an unexpectedly high risk of lung cancer was found in workers in sand foundries. On the basis of present and historical measurement data, we developed a statistical model for exposure to total dust and crystalline quartz for different jobs and time periods. Cumulative dose estimates of total dust and crystalline quartz were calculated and used in a nested case-control study in the cohort. From the cohort of foundry workers (n = 5016), 46 cases of lung cancer were identified. The final analysis was performed on 31 cases and 233 controls with one year or more of employment. Historical measurement data from the 1960s and onward were collected, totaling 203 total dust and 103 crystalline quartz exposure observations. Regression models, using the determinants of job title, time period, type of foundry, and size of production, were developed for assessing historical total dust and crystalline quartz air concentrations. These estimates were used to calculate individual cumulative exposure in the case-control study. In the multiple linear regression analysis, the determinants explained much of the variations in dust level (r(2) = 0.58). The explained variation in crystalline quartz was much lower (r(2) = 0.13). The regression coefficients for the type of foundry, time period, and size of production were statistically significant for total dust. On the basis of the regression analysis, the final models were used to calculate individual cumulative exposures. The calculated cumulative dust and quartz exposures averaged 33 mg/m(3) * year and 0.42 mg/m(3) * year, respectively. The odds ratios (ORs) were not significant, but showed dose-response trends for both dust and crystalline quartz.

A triangulation approach to historical exposure assessment for the carbon black industry.

The determination of cumulative exposures for individual workers is necessary for research and practice of occupational health and hygiene. Reconstruction of exposures for a study of respiratory morbidity was needed to study the effects of exposure to carbon black production. Approximately 15,800 exposure estimates were needed. There were 22 plants, a 40-year time span, six job categories, and three types of dust-exposure metrics (respirable, inhalable, and "total" dust). Three information sources were used: 1) Industrial hygiene air level measurements where available (several industry-wide surveys had been conducted). 2) A formal process survey identifying specific dates and types of process and control changes. 3) An Historical Relative Exposure Rating Scale; plant health and safety personnel used this spreadsheet-based rating scheme to quantify exposures before and between years of actual measurement relative to a reference year in which measurements were available. A job-exposure matrix was calculated by integrating these three methods. Linear scaling factors were identified to interconvert geometric to arithmetic means and to interconvert total and inhalable dust. Individual worker cumulative exposures were then calculated based upon job histories linked with the job-exposure matrix. The nine-step process for integrating all available relevant data was effective in estimating the exposures for each of the cells of the job-exposure matrix. Among the 1680 workers participating, the mean cumulative inhalable dust exposure was 48.4 mg-years/m3. Early years contribute disproportionately to the cumulative exposures of individuals since levels have declined significantly over time. The use of multiple sources of information, including a relative exposure rating instrument, significantly facilitates reconstruction of historical exposures. Inadequate adjustment for temporal trends can lead to underestimation of cumulative exposures and significantly affect estimation of dose-effect relationships. These methods are applicable to other situations requiring estimation of cumulative exposure with sparse industrial hygiene data in early years.

Effect of TNF and LTA polymorphisms on biological markers of response to oxidative stimuli in coal miners: a model of gene-environment interaction

Introduction: Interaction between genetic background and oxidative environmental stimuli in the pathogenesis of human lung disease has been largely unexplored. Methods: A prospective epidemiological study was undertaken in 253 coal...

Respiratory symptoms and diseases among workers in the soft tissue producing industry

Aims: To correlate the prevalence of respiratory tract symptoms and diseases with dust and fibre exposure in the soft tissue industry in Germany. Methods: Ambient monitoring was performed for inhalable,...

Estimation of the Risk of Contracting Pneumoconiosis in the UK Coal Mining Industry

This paper discusses the impact that proposed new regulations for respirable dust in UK coal mines could have on the risk of contracting pneumoconiosis in the UK coal industry. The risk of contracting pneumoconiosis is primarily a function of cumulative exposure to coal mine dust. Since the current dust regulations were introduced in the 1970s the average concentrations of dust to which miners are exposed have decreased considerably. However, working hours have increased in the last few years, leading to concerns of a potential upturn in the risk of contracting pneumoconiosis. The new regulations under discussion address the problem of excessive hours through scaling the limit values when long hours are worked. Hence, by controlling cumulative dust exposures to values below those currently encountered, the proposed new regulations are shown to lead to lower lifetime pneumoconiosis risk when compared with current conditions.

Genetic polymorphisms of MnSOD, GSTM1, GSTT1, and OGG1 in coal workers' pneumoconiosis.

Little is known about the genetic susceptibility to coal workers' pneumoconiosis (CWP). We investigated the association between genetic polymorphisms of MnSOD, GSTM1, GSTT1, or OGG1 and susceptibility to CWP. The study population was composed of 259 Chinese retired coal miners who had similar dust exposure histories. Of these, there were 99 cases with International Labor Organization chest radiologic criteria for CWP and 160 controls (with no radiologic criteria for CWP). Individual dust exposure variables were estimated from work histories, and smoking information was obtained from interviews. Polymerase chain reaction-based techniques evaluated the genotypes of all study subjects. There were no differences in genotype frequency of MnSOD, GSTM1, GSTT1, and OGG1 between miners with CWP and miners without CWP, by logistic regression analysis. Cumulative dust exposures, but not genetic polymorphisms, were associated significantly with the presence of CWP. This study illustrates the complexity of factors that may contribute to the development of CWP.

Respiratory effects of exposure to low levels of concrete dust containing crystalline silica.

Dusts containing crystalline silica are generated in mining, construction, glass, granite and concrete production industries. The association between exposure to low levels of concrete dust containing crystalline silica and reduction in lung function, was evaluated in a cross-sectional study. The study was carried out among 144 concrete workers, from two factories, with exposure assessment of respirable dust and silica by personal samplers. Results of respiratory questionnaires and standardized measurements of lung function were compared with the results in a control population. Multiple linear regression analysis was used in selecting factors that predict (age and standing height standardized residual) lung function. The average concentration of respirable dust in both factories was 0.8 mg/m(3) and 0.06 mg/m(3) for respirable silica. The average silica content of the dust was 9%. The average cumulative dust exposure was 7.0 mg/m(3) year and cumulative silica exposure was 0.6 mg/m(3) year. Significant associations between exposure to concrete dust and a small lung function (FEV(1)/FVC ratio, MMEF) loss were found, independent of smoking habits and of a history of allergy. Our results indicate that, concrete workers with chronic obstructive pulmonary symptoms and/or work-related lower respiratory symptoms are at risk of having a reduction in lung function (FEV&(1)/FVC ratio) outside the 5th percentile of the external reference population, and therefore, of mild chronic obstructive pulmonary disease, at respirable concrete dust levels below 1 mg/m(3) with a respirable crystalline silica content of 10% (TWA, 8 hr).

The Effect of Silica Dust on Ventilatory Function of Foundry Workers

The Effect of Silica Dust on Ventilatory Function of Foundry Workers: Jung Wan Koo, et al. Department of Preventive Medicine, College of Medicine, The Catholic University of Korea—In order to study the exposure level of silica dust and the effects of silica dust on ventilatory function, respirable dust samples were collected with personal air samplers by means of NIOSH method 0500 in selected foundry operations, and ventilatory function tests were performed on 209 male foundry workers and 239 male control subjects. The average quartz concentrations of respirable dust were the highest in melting (0.079 mg/m3) and followed by molding (0.051 mg/m3), finishing (0.041 mg/m3) and coremaking (0.023 mg/m3) in descending order. No significant differences in mean values for all ventilatory indices expressed as a percentage of the predicted value were demonstrated between smokers and nonsmokers in foundry workers and control subjects. Mean values for all ventilatory indices except FVC in foundry workers were significantly lower than those in control subjects. Mean values for FEV1%, MMF, FEF25, FEF50 and FEF75 expressed as a percentage of the predicted value tended to decrease with increasing cumulative dust exposure. In foundry workers, proportions of workers with low MMF, FEF50 and FEF75 were noticeably higher than those for other indices, and were significantly increased with increasing cumulative dust exposure. With the above considerations in mind, it suggested that increasing exposure to silica dust be associated with progressive deterioration in ventilatory function of an obstructive nature and that MMF, FEF50 and FEF75 be sensitive indices in the detection of early obstructive changes in air flow of workers exposed to silica dust.

Respiratory symptoms and spirometry in experienced coal miners: effects of both distant and recent coal mine dust exposures.

The goal of this study was to determine whether respiratory symptoms were associated with the lower concentrations of respirable coal mine dust that were required by the U.S. Coal Mine Health and Safety Act (CMHSA) of 1969. The subjects were 1,866 male miners who had participated in the National Study of Coal Workers' Pneumoconiosis (NSCWP) and been tested at least twice, initially in either Round 1 (R1) (1969-71) or Round 2 (R2) (1972-75) and then finally in Round 4 (R4) (1985-88). Self-reported information elicited with a standardized questionnaire was used to determine the presence at the final round (i.e., R4) of chronic bronchitis, shortness of breath, and wheeze. Cumulative coal mine dust exposure was characterized for both the pre- and post-CMHSA periods. Controlling for age and other potential confounders, increased risks for the symptoms were associated with higher levels of both measurements of exposure. Moreover, the adverse effects of the lower, post-CMHSA exposure were evident for shortness of breath and wheeze especially among subjects who had little pre-CMHSA coal mining experience. These findings provide additional evidence of the limitations of the current 2.0 mg/m3 coal mine dust standard to prevent respiratory disease.

Surface composition of respirable silica particles in a set of U.S. anthracite and bituminous coal mine dusts

Respirable particles of high-percentage silica content from anthracite and bituminous coal mine dust samples were analyzed for aluminosilicate clay surface coating, by measuring silicon and aluminum X-ray spectra using scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS). Silicon and aluminum elemental ratios were determined with incident electron energies of 20 and 5 keV to reveal whether surface occlusion was present. Some 20 respirable-sized, non-agglomerated particles with silicon fraction of signal of 75% or more (for elements above sodium) were analyzed for each of 12 coal mine dust samples. Mine dust samples were from U.S. anthracite and bituminous coal mining regions involved in epidemiological studies of the U.S. National Study of Coal Workers' Pneumoconiosis. Some particles of high-percentage silica content exhibited a decrease in the ratio of silicon-to-aluminum K-alpha line intensities with decreasing electron beam accelerating voltage, consistent with aluminosilicate clay surface contamination or occlusion of a silica particle. Significantly lower frequencies of particles manifesting occluded behavior were found for anthracite dusts versus all bituminous dusts. It is suggested that such occlusion alters the biological availability of the surface of those particles. This may be a factor in the results of attempts to correlate disease prevalence with conventionally measured dust composition, as in the classical failure of coal workers' pneumoconiosis disease prevalence to correlate with silica exposure while being correlated with cumulative total respirable dust exposure and with coal rank.

Lung cancer in relation to exposure to silica dust, silicosis and uranium production in South African gold miners.

BACKGROUND: A nested case-control study for lung cancer was performed on a cohort of 2260 South African gold miners in whom an association between exposure to silica dust and risk...

Western red cedar dust exposure and lung function: a dose-response relationship.

The relationship between levels of cumulative red cedar dust exposure and decline in lung function was explored in an 11-yr follow-up study of 243 sawmill workers who participated in at least two occasions. We also studied 140 office workers in a similar manner as control subjects. Workers with asthma were excluded from the analysis. During the period of the study, 916 personal and 216 area samples of dust were collected from the sawmill. Cumulative wood dust exposure was calculated for each sawmill worker according to the duration and exposure in each job, based on the geometric mean of all dust measurements for that job. Average daily dust exposure was calculated by dividing the total cumulative exposure by the number of days of work. Workers were divided into low-, medium-, and high-exposure groups with mean daily level of exposure of < 0.2, 0.2 to 0.4, and > 0.4 mg/m3, respectively. Sawmill workers had significantly greater declines in FEV1 and FVC compared with office workers adjusted for age, smoking, and initial lung function. A dose-response relationship was observed between the level of exposure and the annual decline in FVC. We conclude that exposure to Western red cedar dust is associated with a greater decline in lung function which may lead to development of chronic airflow limitation.

The Need for Determining the Bioavailability of Quartz in Coal Mine Dust Samples

Abstract A 3-year project focusing on the depth profiling of particles and giving their elemental characterizations at various depths has suggested that the reaction of lung tissues to coal mine dust exposures may be dependent upon coal rank-related surface coating of the particles, and ultimately upon specific quartz bioavailability. Previous research clearly indicates a coal rank relationship for the incidence of coal workers' pneumoconiosis and a hypothesized inhibitory role of clays on quartz fibrogenicity. Specifically, epidemiological studies conducted in 1961 and 1963 showed a greater disease incidence for a given cumulative dust exposure among Pennsylvania coal miners who worked in higher rank coal seams. Workers in anthracite mines had a higher incidence of coal workers' pneumoconiosis and progressive massive fibrosis than miners who worked in lower rank coal at equal cumulative exposures. This rank effect in Pennsylvania extended to all ranks of coal seams, that is, the lower the rank, the lower...

Coal mine dust exposure and spirometry in experienced miners.

In a previous study of new miners from the National Study of Coal Workers' Pneumoconiosis (NSCWP), researchers examined changes in spirometry values associated with coal mine dust exposure (Br J Ind Med 1993; 50:929-937). An unusual pattern of dust-related effects was observed: initial sharp decrements in FVC and FEV1 were followed by partial recovery. In the current study, similar methods were used to analyze data from experienced miners. Each of 1,915 male subjects contributed data from two of the NSCWP field surveys: either Round 1 (1969-71) and Round 2 (1972-75) and Round 4 (1985-88). From the cross-sectional analysis at Round 1 or Round 2 (R1/R2), changes of +0.6 ml FVC and -0.5 ml FEV1 were associated with each mg/m3-yr of cumulative coal mine dust exposure, but were not statistically significant (p > 0.05). From the analysis of longitudinal change in spirometry from R1/R2 to Round 4 (R4), annual declines in FVC (-0.10 ml/yr per mg/m3-yr, p = 0.003) and FEV1 (-0.07 ml/yr per mg/m3-yr, p = 0.006) were associated with pre-R1/R2 exposure. Both the pattern and the magnitude of the exposure-response relationship were different for experienced versus new miners. Possible reasons for these contrasts include differences in cumulative exposure between the two groups and the healthy worker effect among experienced miners.

Mortality of white South African gold miners.

This two part study aimed to determine whether there was an excess mortality generally or for some diseases among middle aged white South African gold miners on the Witwatersrand and whether the underground dust exposure of these miners contributed to the development of lung cancer, chronic obstructive pulmonary disease (COPD), or ischaemic heart disease (IHD). A cohort of 4925 white miners in South Africa, born between 1 January 1916 and 31 December 1930 who were alive and working in the vicinity of Johannesburg on 1 January 1970, then aged between 39 and 54, was followed up for 20 years by which time 2032 had died. Most were gold miners (about 87% had worked 85% or more of their shifts in gold mines). Standardised mortality ratios (SMRs) were calculated as percentages of the number of deaths observed in the cohort for a condition as stated on the death certificate divided by the number expected on the basis of concurrent mortality in the reference population (the total age specific white male population of South Africa). A case-control analysis was performed for three diseases (lung cancer, COPD, and IHD), the results of which are presented for those miners in the cohort who had spent at least 85% of their service on gold mines and had worked at least 15% of their shifts underground. The SMR for all causes of death was 129.6%, raised because of excess mortality due to the following causes: lung cancer (SMR = 139.8%), IHD (124.1%), COPD (189%) and cirrhosis of the liver (155.3%). Smoking was confirmed to be the main risk factor for lung cancer and COPD although cumulative dust exposure was found to increase the risk of COPD in conjunction with smoking. No significant risk of lung cancer resulted from exposure to dust. High blood pressure and smoking were found to increase the risk of IHD, but no association between IHD and the quetelet index (weight/height2) was found. The most significant and unexpected finding was the 30% increase in the SMR for all causes. Very little of this increase could be attributed to mining and the main factor for this was probably the adoption of an unhealthy lifestyle by these men (compared with other South African white men) particularly smoking (86% were smokers) and alcohol consumption.

Oxidative DNA damage in peripheral blood lymphocytes of coal workers.

Reactive oxygen species are important mediators of both mineral dust-induced (malignant) lung disease and in vitro DNA damage. Therefore, we studied in vivo oxidative DNA damage in coal workers who had been chronically exposed to silica-containing dust. In peripheral blood lymphocytes of 38 retired coal miners (eight with coal workers pneumoconiosis, 30 references) and 24 age-matched, non-dust-exposed controls 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) was determined by reversed phase high-performance liquid chromatography with electrochemical detection. The ratio of 8-oxodG residues to deoxyguanosine (dG) was related to individual cumulative dust exposure estimates and pneumoconiotic stage as established by chest radiography. The ratio of 8-oxodG to dG(x 10(-5)) in lymphocytes did not differ between miners with coal workers' pneumoconiosis (2.61 +/- 0.44) and miners without coal workers' pneumoconiosis (2.96 +/- 1.86). However, oxidative DNA damage in all miners was higher than in the non-dust-exposed controls (1.67 +/- 1.31). 8-oxodG/dG ratio was not related to individual cumulative coal dust exposure, age or smoking (pack years) when evaluated by multiple linear regression. We suggest that oxidative damage to the DNA of peripheral blood lymphocytes may be introduced by increased oxidative stress responses in subjects chronically exposed to mineral dusts. Whether this is an important pathway in the suggested carcinogenicity of silica is still an open question.

Byssinosis in Guangzhou, China.

To study the prevalence of byssinosis and other respiratory abnormalities in workers exposed to cotton dust in Guangzhou in two factories that processed purely cotton. All the 1320 workers exposed were included. The controls were 1306 workers with no history of occupational dust exposure. Total dust and inhalable dust were measured by Chinese total dust sampler and American vertical elutriator respectively. A World Health Organisation questionnaire was used. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by a Vitalograph spirometer. The median inhalable dust concentrations ranged from 0.41 to 1.51 mg/m3 and median total dust concentrations from 3.04 to 12.32 mg/m3. The prevalence of respiratory abnormalities in the cotton workers were (a) typical Monday symptoms 9.0%; (b) FEV1 fall by > or = 5% after a shift 16.8%; (c) FEV1 fall by > or = 10% after a shift 4.2%; (d) FEV1 < 80% predicted 6.1%; (e) FEV1/FVC < 75% 4.0%; (f) cough or phlegm 18.2%; (g) chronic bronchitis 10.9%; and (h) byssinosis, defined by (a) plus (b) 1.7%. With the exception of (d), most of the prevalences increased with increasing age, duration of exposure, and cumulative inhalable dust exposure. No increasing trends of respiratory abnormalities were found for current total dust, inhalable dust, and cumulative total dust concentrations. Compared with controls, after adjustment for sex and smoking, with the exception of (d), all the pooled relative risks of respiratory abnormalities were raised for cotton exposure. It is concluded that cumulative inhalable cotton is likely to be the cause of byssinotic symptoms, acute lung function decrements, cough, or phlegm, and chronic bronchitis.