The practice is currently a regulatory requirement for exposure to other hazardous substances including respirable coal dust, respirable crystalline silica and carbon monoxide.
The QMI does not specify which to use but the method selected should consider factors such as toxicity of the agent, the target organ and time for action (whether acute or chronic).
Several recognised methods are currently used for shift adjustment of occupational exposure limits.
“Adjustment models must be selected by someone appropriately qualified, such as an occupational hygienist, who has a sound understanding of the toxicology and pharmacokinetics of the substance as well as the rationale for setting the exposure standard,” the QMI said.
The International Agency for Research on Cancer declared diesel engine exhaust to be carcinogenic to humans (a group 1 carcinogen) in June 2012.
The IARC working group found sufficient evidence linking exposure to diesel exhaust to increased risk of lung cancer.
Diesel exhaust contains both a gaseous and particulate fraction.
The particulate fraction contains elemental carbon which can be accurately measured to determine the amount of diesel particulate matter present.
This in turn can be used to provide a reliable indication of the amount of diesel exhaust present in the working environment.
Queensland mining legislation does not specify an occupational exposure limit for DPM.
However, the QMI recommends adopting the limit used in New South Wales machine design guideline MDG 29.
The DPM limit specified in MDG 29 is 0.1 milligram per cubic metre (measured as sub-micron EC). This limit is based on preventing irritant health effects, not protecting against the risk of lung cancer.
IARC’s declaration linking diesel exhaust exposure to lung cancer is likely to result in the limit being reviewed.
“The Mines Inspectorate believes that in line with best practice all exposures should be reduced to as low as reasonably achievable,” it said.