Relationship between physical and chemical characteristics of coal dust particulates and incidence of coal workers’ pneumoconiosis

Coal workers' pneumoconiosis (CWP) has been related to the presence of reactive iron minerals (e.g. pyrite) in coal dust which, purportedly, results in the production of harmful reactive oxygen species (ROS) on exposure to air. The link between ROS and coal dust properties stems from studies in the United States where a link was identified between CWP prevalence and coal bioavailable iron content. While the ROS production mechanism from reduced iron minerals is without dispute, questions remain concerning the contribution towards CWP incidence.

The key objectives of this project were to:

• quantify the toxicity of Australian coal dust to human lung epithelial cells and to determine whether any relationship exists between the toxicity and elemental composition,
• quantify ROS production and determine whether a relationship exists between the oxidant generating capacity and the elemental composition,
• develop a screening protocol for particles with regard to potential toxicity and recommend management approaches; and
• develop guidelines relating to best practice dust management for Australian coals considered particularly problematic with regard to CWP risk.

A total of 59 coal mine samples (comprising both coal seams and waste bands) were supplied for detailed characterisation and to establish possible links to ROS production and lung cell toxicity.The samples were ground to suitable sized dusts in a standardised fashion to an appropriate size range, in order to standardise any impacts that variable mining techniques / equipment, particle storage and ageing were likely to impart upon results. As such, the dust samples produced in our scientific study may not necessarily represent the dust present in individual coal mines due to the differing impacts of dust production and mitigation technologies present.

The production of ROS and consequential impacts were investigated using i) abiotic studies involving simulated lung fluids, ii) the human epithelial lung cell line A549, and iii) the human bronchial cell line Calu-3.

The results of both studies are described in detail in the final report.

While these findings provide a certain degree of insight towards quantifying the toxicity and ROS-generating capacity of Australian coal dusts in relation to elemental composition the link was far from conclusive. Given the inconsistent links, establishing suitable screening protocols and developing guidelines for identifying and managing exposure to particles of most concern was not possible.