Australia is introducing a new set of mandatory Workplace Exposure Limits (WELs) for airborne contaminants, which will come into effect on 1 December 2026. These will replace the current Workplace Exposure Standards (WES) with updated, and in many cases stricter, limits.
For diesel engine emissions, the incoming WELs are substantially lower than current recommended limits.
Managing diesel emissions is not new in industries like mining and tunnelling, where diesel equipment is widely used in underground environments with limited ventilation. However, stricter national exposure limits mean the issue may soon extend well beyond these sectors.
At a recent AIOH South Australia Chapter meeting, GCG Senior Occupational Hygienist Hamish Rae presented alongside Logan Tibbetts, Occupational Hygienist on the Torrens to Darlington (T2D) project, to unpack what’s coming and what it could mean in practice.
Diesel engine exhaust (DEE) is classified as a Group 1 carcinogen, meaning there is clear evidence it causes cancer. Because the full exhaust mixture is difficult to measure, exposure is typically measured using diesel particulate matter (DPM) as a surrogate indicator.
The Australian Institute of Occupational Hygienists (AIOH) recommends a worker’s exposure to DPM be kept below 0.1 mg/m³ (as sub-micron elemental carbon).
While employers have a duty of care to ensure the health and safety of workers, Australia does not currently have a national Workplace Exposure Standard (WES) for DPM. Specific exposure limits apply in the mining industry under State legislation, including:
In addition to the shift from Workplace Exposure Standards (WES) to Workplace Exposure Limits (WEL), there will also be a change in how exposure is typically measured for DPM. Monitoring will move from sub-micron elemental carbon to respirable elemental carbon, capturing a wider range of particle sizes.
The new national WEL being introduced by Safe Work Australia will be 0.01 mg/m³ as respirable elemental carbon – around ten times lower than the current recommended limit. The new limit will apply to all Australian workplaces, not just mining operations.
While sectors like mining and tunnelling are used to monitoring diesel emissions, for many organisations, diesel emissions simply haven’t been on the radar.
With the new lower WEL applying to all workplaces, it’s likely that more industries and workplaces will need to assess and control exposures. This may include distribution centres, freight depots, warehouses, workshops, and construction sites (especially where diesel vehicles operate indoors or in poorly ventilated areas).
Lower exposure limits make managing diesel emissions more critical and more complex. Operations may need to consider a broad range of controls, including:
However, WELs were set as “health-based” with limited consideration of whether current technology can achieve these levels, and a key question remains: how practical are these controls in real-world conditions?
For example, electrification is often positioned as a key control, but in some environments, fire loading and current battery-powered equipment may not yet meet safety or operational requirements. Limitations such as run time, charging infrastructure, and overall capability can affect whether it is a viable option.
It is not yet clear how the new limits will be adopted across all different states and industries.
There are also questions around DPM measurement, the capability and availability of equipment and current technology to meet lower limits, and how compliance will be enforced — particularly in industries where diesel exposure has not historically been assessed.
For industries already managing diesel emissions, the introduction of a significantly lower limit means reassessing whether existing controls are sufficient.
For others, it may mean identifying diesel exposure as a risk for the first time and introducing monitoring and control measures.
The implications for operations (particularly in mining and tunnelling) may be significant, requiring forward planning to avoid disruption.
Potential impacts include:
Operational upgrades
Regulatory and compliance risks
Changes in operational practices
Financial impact
Organisations should begin assessing their DPM exposure and planning for these changes now. Understanding where diesel emissions exist in your operations, how exposures are currently identified and managed, and where gaps may exist is critical to responding as these changes come into effect.
The key takeaway here is to understand your exposures now, before these limits become law, to ensure workers’ health is protected and to prevent legislative non-compliance.