Coal Mine Dust Lung Disease Research Report 2019

The Wesley Dust Disease Research Centre’s Flagship Project, “A Clinical, Radiological and Occupational Review of Coal Mine Dust Lung Disease (CMDLD) in Queensland”, has recently been completed.

The Wesley Dust Disease Research Centre has been investigating Coal Mine Dust Lung Disease (CMDLD) in Queensland since 2016. This research work began shortly after the re-identification of CMDLD in the Queensland coal industry in 2015, after a lapse of 30 years. This research project was important as the health of coal miners had not been reviewed since 1984, meaning both the coal mining and medical communities were not up-to-date with the status of CMDLD in Queensland.

The project was a case series undertaken following the re-identification of CMDLD in Queensland in 2015. The aim of this project was to review recently diagnosed cases of CMDLD to understand the spectrum of diagnoses, the severity of disease and the occupational histories leading to diagnosis.

The study comprised a review of records and the collection of information via questionnaire. Medical information was collected to confirm the diagnosis of CMDLD. This included a review of medical charts, imaging and spirometry from the point of diagnosis. Questionnaires were used to collect in-depth information on the individual’s occupational history and their current respiratory health. The occupational history questionnaire utilised was developed specifically for this study while the respiratory questionnaires used internationally-validated questions. Seventy-nine current or former Queensland coal industry workers, with confirmed CMDLD, were included in the study. Of these 79 subjects, 36 (46%) participated in the questionnaire component. All subjects were male, with a mean age of 59 years (range: 35-90). The first and last year in which any subject was employed in the coal industry was 1955 and 2018, respectively. The majority (74%) of study subjects had worked only in the Queensland coal industry, without any interstate or overseas history of work. The mean tenure of the study subjects in the coal industry was 26 years (range: 6-45). In regards to mine-type, 44% of subjects had worked only in underground coal mining, compared to 27% who had never worked underground (including two subjects who had worked in coal ports only). The remaining 29% of subjects had both underground and open-cut mining experience. One-quarter of the workers reported starting work between 2000 and 2008.

The full spectrum of CMDLD diagnoses was identified in this study group. Diagnoses were coal workers’ pneumoconiosis (CWP, n= 27), silicosis (n= 11), mixed dust pneumoconiosis (MDP, n= 18), dust-related diffuse fibrosis (DDF, n= 5) and chronic obstructive pulmonary disease (COPD, n= 22). Four individuals had two diagnoses, with one of these being CWP, MDP or DDF, and the second being COPD. Disease severity, as assessed on medical imaging, ranged from the lower radiological disease stages to advanced disease. Radiologically advanced disease was observed in 30% of subjects and included six cases of progressive massive fibrosis. Unfortunately, due to the nature of this study, we are unable to report on the cause for the relatively high proportion of advanced radiological disease which was observed. However, the authors postulate that delayed medical diagnosis is the most likely cause, given the Coal Mine Worker’s Health Scheme in Queensland has been identified as being ineffective between 1984 and 2016. Furthermore, an over-estimation of severity may have occurred, as advanced forms of disease are more easily appreciated on imaging and are thus more likely to be detected.

Disease severity, as assessed on spirometry testing, also ranged from normal to severely abnormal. In the study group, 47% of subjects had normal spirometry, compared to 53% who had abnormal spirometry. In the vast majority of subjects, spirometry was performed after the radiological diagnosis of CMDLD, including seven subjects who had spirometry performed three (or more) years after the initial diagnosis. This limits the ability of the study to identify useful correlations between radiological and clinical features of CMDLD. In terms of clinical features, the majority of subjects who completed the respiratory questionnaires were symptomatic, with 26/36 subjects reporting breathlessness. It must be noted that a high proportion of the study group were current smokers (10%) or ex-smokers (70%) and this may have contributed to findings on spirometry and clinical symptoms.

Examination of the extent of relationships between various variables reviewed in this study did not identify any correlations. No relationship was observed in the study group between radiological severity, either on chest radiograph or HRCT, and spirometry, or occupational factors, including tenure in the coal industry and type of coal mine worked in (p >0.05 in all comparisons). Further, no relationship was observed in our study group between spirometry values and tenure or coal mine type (p >0.05). The low power of the study means the lack of identified correlations may not adequately represent the true relationships between at least some of these variables. Continued research, including re-analysis of these relationships would be of the utmost interest, as further CMDLD cases are identified and additional data points become available. There remains a need for additional, high-quality longitudinal research before it can be determined whether the findings of this study are reflective of workers within the Queensland coal industry as a whole.

This study provides evidence that CMDLD exists in the Queensland coal industry and provides the first medical insight into these diseases in Queensland in over three decades. The full spectrum of CMDLD diagnoses was observed in this study group, and the information presented on disease severity on radiological and spirometry testing provides valuable insights to the current status of these diseases in coal workers. It is hoped the findings of this study lead to an increased awareness of these diseases and their current status in Queensland; continued improvement in the monitoring and control of dust exposures; and high-quality disease surveillance.

For more information or to request a copy of the full report contact the Wesley Dust Disease Research Centre team via email at: research@ucmi.com.au