Assessment of Pyrite Coal Dust Induced Pneumoconiosis

There have been recent concerns regarding the re-identification of Coal Workers' Pneumoconiosis (CWP), or 'Black Lung', in Australian coal miners. Based on research from the United States, it has been suggested that a key contributor to the CWP respirable dust hazard is the pyrite content of inhaled coal dust. However, this has never been tested using Australian coals and the limited experimental studies that do exist have design flaws. To address this issue, laboratory experiments were conducted using Australian coals to replicate previously published studies from the United States and extend on these studies using a broader range of mined coal samples.

In the first set of laboratory experiments lung cells were exposed to coal dust with artificially added crystalline pyrite dust at a range of concentrations from 0.15% to 4.40% pyrite. Contrary to previous reports, the addition of increasing concentrations of crystalline pyrite to Australian coal dust decreased the lung cell response.

In a second set of experiments, which formed the main body of this work, three different lung cell types with varying roles in CWP were exposed to coal dust with a range of natural pyrite concentrations from 0.37% to 49.70% pyrite. Based on the data from these experiments, there was a variable association between the pyrite content of the coal dust and the bioavailable iron released which argues against the release of bioavailable iron as the primary determinant of CWP respirable dust hazard as proposed in previous studies. Exposure to the different pyritic coal samples caused variable levels of toxicity and inflammation in the lung cells. However, the relationship between pyrite content and/or the bioavailable iron and the magnitude of the cell response was not consistent. There was no association between the pyrite content of the coal dust and detrimental cell responses. In some instances there was a positive association between the bioavailable iron and the cell response, however, this was not consistently observed across all cell types under all conditions.

On the basis of these data, in the Australian context, there does not appear to be a direct causal relationship between the pyrite content of coal dust and the CWP respirable dust hazard.