Inspector, (Occupational Hygiene), Department of Natural Resources, Mines and Energy
Inhalable dust refers to all dust that may enter the mouth and nose during normal breathing. Inhalable dust may be divided into ‘respirable’ and ‘non- respirable’ fractions. The dust particle size will ultimately determine the site of deposition within the respiratory system. Respirable dust particles (<10 micron) may penetrate deep into the gas exchange regions of the lung. The ‘non respirable’ faction includes both ‘extra thoracic dust particles (<100 micron)’ and ‘thoracic dust particles (<25 micron)’.
The re-identification of CWP among Queensland coal mine workers and, more recently, the increase in cases of silicosis among engineered stone workers is a stark reminder of the hazards associated with exposure to respirable dust. Recent reforms to the respiratory component of the existing coal mine workers health scheme have resulted in major improvements with respect to the early detection and diagnosis of mine dust lung disease (MDLD). These improvements have led to a number of other forms of MDLD being detected among Queensland mine workers that are not associated with pneumoconiosis. A growing number of these cases fall into the broad category of chronic obstructive pulmonary disease (COPD). There is an increasing body of evidence implicating exposure to larger dust particles (outside the respirable fraction) and an inflammatory response in the lung, resulting in COPD.
Unlike the Queensland metalliferous mining and quarrying legislation, there is currently no prescribed regulatory limit for inhalable dust in Queensland coal mining legislation. Despite this, the majority of coal mines have recognised this as a potential health hazard as part of their site health risk assessments (HRA).
This paper reviews available inhalable dust exposure data that has been provided to the Mines Inspectorate for Queensland coal mines since the introduction of risk based legislation in 1999. The paper considers the evidence basis for regulatory amendment to ensure risk is at an acceptable level and as low as reasonably achievable.