The fox guarding the chicken coop: monitoring exposure to respirable coal mine dust, 1969-2000

Thin seams and small mines are associated with higher exposures to respirable crystalline silica in US underground coal mines

OBJECTIVES

Previous radiologic and histopathologic studies suggest respirable crystalline silica (RCS) overexposure has been driving the resurgence of pneumoconiosis among contemporary US coal miners, with a higher prevalence of severe disease in Central Appalachia. We sought to better understand RCS exposure among US underground coal miners.

METHODS

We analysed RCS levels, as measured by respirable quartz, from coal mine dust compliance data from 1982 to 2021.

RESULTS

We analysed 322 919 respirable quartz samples from 5064 US underground coal mines. Mean mine-level respirable quartz percentage and mass concentrations were consistently higher for Central Appalachian mines than the rest of the USA. Mean mine-level respirable quartz mass concentrations decreased significantly over time, from 0.116 mg/m3 in 1982 to as low as 0.017 mg/m3 for Central Appalachian mines, and from 0.089 mg/m3 in 1983 to 0.015 mg/m3 in 2020 for the rest of the USA. Smaller mine size, location in Central Appalachia, lack of mine safety committee and thinner coal seams were predictive of higher respirable quartz mass concentrations.

CONCLUSIONS

These data substantially support the association between RCS overexposure and the resurgence of coal workers' pneumoconiosis in the USA, particularly in smaller mines in Central Appalachia.

Predicting coal workers' pneumoconiosis trends: Leveraging historical data with the GARCH model in a Chinese Miner Cohort

Coal workers' pneumoconiosis (CWP) is one of the most common and severe occupational diseases worldwide. The main risk factor of CWP is exposure to respirable mine dust. Prediction theory was widely applied in the prediction of the epidemic. Here, it was used to identify the characteristics of CWP today and the incidence trends of CWP in the future. Eight thousand nine hundred twenty-eight coal workers from a state-owned coal mine were included during the observation period from 1963 to 2014. In observations, the dust concentration gradually decreased over time, and the incidence of tunnels and mine, transportation, and assistance workers showed an overall downward trend. We choose a better prediction model by comparing the prediction effect of the Auto Regression Integrate Moving Average model and Generalized Autoregressive Conditional Heteroskedasticity model. Compared with the Auto Regression Integrate Moving Average model, the Generalized Autoregressive Conditional Heteroskedasticity model has a better prediction effect. Furthermore, the status quo and future trend of coal miners' CWP are still at a high level.

Coal mine dust lung disease in miners killed in the Upper Big Branch disaster: a review of lung pathology and contemporary respirable dust levels in underground US coal mines

OBJECTIVES

In 2010, 29 coal miners died due to an explosion at the Upper Big Branch (UBB) mine in West Virginia, USA. Autopsy examinations of 24 individuals with evaluable lung tissue identified 17 considered to have coal workers' pneumoconiosis (CWP). The objectives of this study were to characterise histopathological findings of lung tissue from a sample of UBB fatalities and better understand the respirable dust concentrations experienced by these miners at UBB relative to other US coal mines.

METHODS

Occupational pulmonary pathologists evaluated lung tissue specimens from UBB fatalities for the presence of features of pneumoconiosis. Respirable dust and quartz samples submitted for regulatory compliance from all US underground coal mines prior to the disaster were analysed.

RESULTS

Families of seven UBB fatalities provided consent for the study. Histopathologic evidence of CWP was found in all seven cases. For the USA, central Appalachia and UBB, compliance dust samples showed the geometric mean for respirable dust was 0.468, 0.420 and 0.518 mg/m³, respectively, and respirable quartz concentrations were 0.030, 0.038 and 0.061 mg/m³. After adjusting for quartz concentrations, UBB exceeded the US permissible exposure limit (PEL) for respirable dust in 28% of samples.

CONCLUSIONS

Although higher than average respirable dust and quartz levels were observed at UBB, over 200 US underground coal mines had higher dust concentrations than UBB and over 100 exceeded the PEL more frequently. Together with lung histopathological findings among UBB fatalities, these data suggest exposures leading to CWP in the USA are more prevalent than previously understood.

Progressive Massive Fibrosis Resurgence Identified in U.S. Coal Miners Filing for Black Lung Benefits, 1970-2016

RATIONALE

There has been a resurgence of progressive massive fibrosis (PMF) in the United States, particularly among central Appalachian miners.

OBJECTIVES

We characterized the proportion of PMF among former U.S. coal miners applying for Federal Black Lung Program benefits, 1970-2016.

METHODS

Data from the U.S. Department of Labor were used to characterize trends in proportion of PMF cases, defined as an approved black lung claim with a determination of PMF, among all miners who filed for federal benefits between January 1, 1970, and December 31, 2016. Joinpoint, logistic, and linear regression models were used to identify changes in the proportion of claimants with PMF over time.

RESULTS

There were 4,679 unique PMF cases among claimants for federal black lung benefits between 1970 and 2016, with 2,474 miners determined to have PMF since 1996. The number of PMF cases among Federal Black Lung Program claimants fell from 404 (0.5% of claimants) in 1978 to a low of 18 cases (0.6%) in 1988, and then increased to 353 cases (8.3%) in 2014. The proportion of federal black lung benefits claimants with PMF has been increasing since 1978 (0.06% annual percent change [APC]; 95% confidence interval [CI], 0.05-0.07%; P < 0.0001), and began increasing at a significantly increased rate after 1996 (0.26% APC; 95% CI, 0.25-0.28%; P < 0.0001). Most miners with PMF (84%) last mined in West Virginia, Kentucky, Pennsylvania, or Virginia. Since 1970, the proportion of claimants with PMF has increased significantly among miners who last worked in Kentucky (16.6% APC; 95% CI, 16.5-16.7%), Pennsylvania (4.7% APC; 95% CI, 4.6-4.8%), Tennessee (16.1% APC; 95% CI, 15.7-16.4%), West Virginia (16.8% APC; 95% CI, 16.6-16.9%), and most sharply among miners last working in Virginia (31.5% APC; 95% CI, 31.2-31.7%), where in 2009, more than 17% of claimants received a PMF determination. The proportion of PMF determinations for the rest of the United States has not exceeded 4%.

CONCLUSIONS

There has been a resurgence of PMF, particularly in central Appalachian miners. The resurgence of this preventable disease points to the need for improved primary and secondary prevention of dust-related lung disease in U.S. coal miners.

Risk identification and prediction of coal workers' pneumoconiosis in Kailuan Colliery Group in China: a historical cohort study

BACKGROUND

Prior to 1970, coal mining technology and prevention measures in China were poor. Mechanized coal mining equipment and advanced protection measures were continuously installed in the mines after 1970. All these improvements may have resulted in a change in the incidence of coal workers' pneumoconiosis (CWP). Therefore, it is important to identify the characteristics of CWP today and trends for the incidence of CWP in the future.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 17,023 coal workers from the Kailuan Colliery Group were studied. A life-table method was used to calculate the cumulative incidence rate of CWP and predict the number of new CWP patients in the future. The probability of developing CWP was estimated by a multilayer perceptron artificial neural network for each coal worker without CWP. The results showed that the cumulative incidence rates of CWP for tunneling, mining, combining, and helping workers were 31.8%, 27.5%, 24.2%, and 2.6%, respectively, during the same observation period of 40 years. It was estimated that there would be 844 new CWP cases among 16,185 coal workers without CWP within their life expectancy. There would be 273.1, 273.1, 227.6, and 69.9 new CWP patients in the next <10, 10-, 20-, and 30- years respectively in the study cohort within their life expectancy. It was identified that coal workers whose risk probabilities were over 0.2 were at high risk for CWP, and whose risk probabilities were under 0.1 were at low risk.

CONCLUSION/SIGNIFICANCE

The present and future incidence trends of CWP remain high among coal workers. We suggest that coal workers at high risk of CWP undergo a physical examination for pneumoconiosis every year, and the coal workers at low risk of CWP be examined every 5 years.

The classic pneumoconioses: new epidemiological and laboratory observations

The purpose of this article is to provide an update on selected issues of current interest and recent developments related to 3 types of inorganic mineral dust exposures causing classic forms of pneumoconiosis: coal mine dust, crystalline silica, and asbestos. Common themes include new imaging modalities, emerging exposures, and evolving appreciation of additional adverse health effects associated with exposure to these inorganic mineral dusts.

Severe occupational pneumoconiosis among West Virginian coal miners: one hundred thirty-eight cases of progressive massive fibrosis compensated between 2000 and 2009

BACKGROUND

Miners inhale dust at work and are at a risk for coal workers pneumoconiosis (CWP), a preventable and potentially fatal lung disease. After regulations were implemented in the 1970s, declines were reported in both dust levels and the prevalence of simple and advanced CWP until about 2001, when despite stable reported dust levels, disease levels sharply increased.

METHODS

A structured, retrospective chart review was performed to describe the demographics and disease progression for 138 coal miners with progressive massive fibrosis (PMF) whose claims were approved by the West Virginia State Occupational Pneumoconiosis Board between January 2000 and December 2009.

RESULTS

PMF, a complication of CWP, developed in 138 West Virginian coal miners at a mean age of 52.6 years after an average of 30 years work tenure. The time of progression averaged 12.2 years from the last normal chest radiograph until PMF was detected. Lung function declined sharply in both smokers and nonsmokers, averaging 87 mL/y for FEV(1) and 74 mL/y for FVC. The board has confirmed 21 deaths in this group. The most common job activities were operating continuous-mining machines (41%) and roof bolting (19%). Virtually all of these miners' dust exposures occurred after the implementation of current federal dust regulations.

CONCLUSIONS

Contemporary occupational dust exposures have resulted over the past decade in rapidly progressive pneumoconiosis and massive fibrosis in relatively young West Virginian coal miners, leading to important lung dysfunction and premature death.

Prevalence characteristics and prediction of coal workers' pneumoconiosis in the Tiefa Colliery in China

To explore characteristics of the development of coal workers' pneumoconiosis (CWP) at present and trend in the future, we investigated 16,154 coal miners exposed to dust for at least 1 yr in the Tiefa Colliery in China. Occupational categories were divided into tunneling, mining, combining and helping. Four cohorts (before 1958, 1958-, 1968-, and after 1978) were created according to years of first exposure. Life-Table Method was used to calculate cumulative incidence rates of CWP adjusted by duration of dust exposure and predict the number of the new CWP patients. Results indicated that cumulative incidence rates of CWP in four cohorts were 26.65%, 18.94%, 1.15%, and 0.06%, respectively (Chi(2)=493.57, p<0.0001). The 55-yr cumulative rate of CWP of tunneling miners (25.90%) or that of combining miners (14.53%) was statistically higher than that of mining miners (7.26%) or that of helping miners (0.89%). The number of new CWP patients predicted in future was approximately 77. New CWP patients predicted would mainly occur among coal miners with first dust exposure in 1958-1967 and those working at tunneling. Most of them could be diagnosed in the age group from 45 to 75 and in the period of the next 20 yr from 2008 to 2028.

Metal and non-metal miners' exposure to crystalline silica, 1998-2002

BACKGROUND

Crystalline silica is well known to cause silicosis and other diseases. Exposure is common in the mining industry and consequently, the US Mine Safety and Health Administration (MSHA) evaluates miners exposure to silica to determine compliance with its exposure limit.

METHODS

MSHA exposure measurements were obtained for the 5-year period from 1998 to 2002 and average exposure was calculated classified by occupation and by mine. Evaluation criteria were whether average values exceeded MSHA's permissible exposure limit or the limit recommended by the National Institute for Occupational Safety and Health (NIOSH), whether there was a risk of exposure to freshly fractured silica, and whether there was a risk of a high rate of exposure to silica.

RESULTS

Miners in certain jobs are exposed to silica above permissible and recommended exposure limits. Some miners may also be exposed at a high rate or to freshly fractured silica.

CONCLUSIONS

Known dust control methods should be implemented and regular medical surveillance should be provided.

The Mine Safety and Health Administration's criterion threshold value policy increases miners' risk of pneumoconiosis

BACKGROUND

The Mine Safety and Health Administration (MSHA) proposes to issue citations for non-compliance with the exposure limit for respirable coal mine dust when measured exposure exceeds the exposure limit with a "high degree of confidence." This criterion threshold value (CTV) is derived from the sampling and analytical error of the measurement method.

CONCEPTUAL FRAMEWORK

This policy is based on a combination of statistical and legal reasoning: the one-tailed 95% confidence limit of the sampling method, the apparent principle of due process and a standard of proof analogous to "beyond a reasonable doubt."

CRITIQUE

This policy raises the effective exposure limit, it is contrary to the precautionary principle, it is not a fair sharing of the burden of uncertainty, and it employs an inappropriate standard of proof. Its own advisory committee and NIOSH have advised against this policy. For longwall mining sections, it results in a failure to issue citations for approximately 36% of the measured values that exceed the statutory exposure limit.

DISCUSSION

Citations for non-compliance with the respirable dust standard should be issued for any measure exposure that exceeds the exposure limit.

Occupational medicine: the case for reform

The specialty of occupational medicine is in peril, in large part because of its reliance on financing by industry, which has powerful incentives to limit costs and to favor physicians who are useful to their employers. Occupational physicians generally practice within the framework of the workers' compensation system. Serious flaws in the incentive structure of workers' compensation constrain objectivity in their practice. Under present law they are unavoidably subject to perverse influences from employers and insurance companies. A fundamental reform of workers' compensation law and practice is urgently needed to separate occupational physicians from the control of employers and workers' compensation insurers, whose interests should not be allowed to override the physicians' integrity or to compromise the specialty.