While the industry has made progress in the control of respirable dust and its harmful effects on lung and throat disease, it is yet to fully comprehend and analyse the growing data which documents the exceedence of inhalable dust levels on the digestive system.

A recent report by the director of mine safety operations branch of Industry & Investment NSW Rob Regan found that the Hunter Valley and Newcastle in particular had high incidences of exceedences of dust in longwall mine operations.

In its review of inhalable dust monitoring between February 2008 and September 2009, the mine safety operations branch found there were 44 exceedences in Newcastle, 50 in the Hunter Valley, and 19 in the Southern zone.

Overall there was a 37.3% exceedence level in NSW longwall mines.

The Coal Mine Health and Safety Act 2002 imposed a limit of 10 milligrams per cubic metre inhalable dust on all coal mine operations in NSW and measurement of the inhalable dust component of airborne dust was included in the monitoring requirements of the NSW coal mining industry by the same notice.

The mine safety operations branch report found continuous miner units fared better but results overall tend to compare unfavourably with those achieved by respirable dust monitoring.

While different geology accounts for most of regional discrepancies, with Hunter Valley and Newcastle coals being generally harder and drier, the issue of higher inhalable dust levels has not escaped the notice of the CFMEU and other health specialists.

“It’s a problem,” a CFMEU spokesperson in Cessnock told International Longwall News.

“We continue to remind them that constant testing of coal dust is important. When there is a failure we need to know what is being done to rectify the problem.”

The mine safety operations branch attributes the high dust levels to inadequate ventilation, water or dust control, poor operator positioning, damaged equipment and poor work practices.

The Coal Mine Health & Safety Act Regulation 2006 defines airborne dust to include both respirable dust and inhalable dust, it is also known as airborne particulate matter or airborne particulates.

There was a change in the report requirements in December 2007. Prior to this there was no routine monitoring of inhalable dust (large dust, greater than 100 microns).

Only respirable dust (small dust, greater than 5 microns) was measured. This strategy has successfully controlled incidence of lung diseases.

In order to provide even greater protection the Legislator included inhalable dust monitoring as part of routine dust sampling.

“Dust control strategies which have been successful for respirable dust have not readily transferred to the control of inhalable dust,” Coal Services mines rescue regulation and compliance general manager Paul Healey said.

“The overall level of dust is still low and this is borne out in incidence of lung diseases which is the lowest in the world. Mines are continuing to develop improved controls.”

At this stage there is not enough research to indicate that inhalable dust is a contributor to chronic obstructive pulmonary disease (COPD) and insufficient evidence to classify coal dust as a carcinogen.

Occupational hygienists Martin Jennings and Martyn Flahive prepared a landmark report calling for the monitoring of the correlation between the incidence and prevalence of COPD and upper airways disorders in NSW coal miners and inhalable dust levels.

They also ask for further sampling of inhalable dust to be carried out and particle size distributions to be characterised.

Improved dust control measures will be required in the underground coal mines of NSW, especially longwall mines in the Newcastle and Hunter Valley districts, according to Regan’s report.

Read Tuesday’s report in ILN for recommendations for dealing with the problem of inhalable dust.