Australia is moving from workplace exposure standards to a workplace exposure limits list. Safe Work Australia states the duty plainly: from 1 December 2026, employers must ensure that no person at their workplace is exposed to an airborne contaminant at a level above the exposure limit in the WEL list.

Diesel particulate matter is on that list at 0.01 mg/m3. Safe Work Australia describes it as the measure used for exposure to diesel engine emissions, and is direct about why it matters: exposure can have serious health impacts “including lung disease and cancer”.

Who this actually lands on

The regulator names the settings: mining, quarrying, tunnelling, construction, agriculture, transport and logistics, oil and gas, and vehicle maintenance.

Read that list and the common feature is not diesel as such, it is diesel running where the exhaust cannot disperse. An excavator in open air and the same machine in a decline or a tunnel are different exposure problems, and the industries named are the ones where the second case is routine. For anyone running underground plant, this is the number the next four months are about.

Why this one proceeded and nine others did not

We reported in July that WHS ministers could not agree to tighter limits for silica, benzene and seven other chemicals, so those older numbers carry over into the new list on the same 1 December date. Diesel particulate matter is not among them; it appears in the material as a limit that applies from that date.

Our view, labelled as such: a transition that carries over nine contested numbers while introducing a new one for diesel is not a contradiction, it is what a limits list looks like when each entry has its own evidence base and its own opposition. But it does mean 1 December is doing two different jobs, and a duty holder reading only the headline about the nine chemicals could reasonably conclude nothing changed on that date. Something did.

The three guides

All published 30 July 2026.

  • Guide for PCBUs: Air monitoring and the workplace exposure limits for airborne contaminants. Aimed at employers. Covers when air monitoring may be required, how to engage a competent person to undertake it, how to interpret and respond to results, and common questions. Safe Work Australia restates the hierarchy here: eliminate the risk where reasonably practicable, and where elimination is not possible, minimise it so far as is reasonably practicable.
  • Technical guide: Air monitoring and the workplace exposure limits for airborne contaminants. For occupational hygienists and technical professionals assessing exposure and determining compliance. Covers assessing exposure, planning and conducting monitoring, interpreting results, and reporting findings and advising employers. Its stated aim is consistent, high-quality monitoring and decision-making across Australian workplaces.
  • Managing the risks of exposure to diesel engine emissions in the workplace. The one carrying the 0.01 mg/m3 limit, aimed at anyone working where diesel engine emissions may be present.

The split between the first two is worth noticing. Air monitoring against a numeric limit is not something most employers can do themselves, and the PCBU guide covers engaging a competent person rather than pretending otherwise. If your workplace has diesel plant in an enclosed space and no monitoring history, the practical reading of these documents is that four months is not a lot of time to find a hygienist, get a baseline and fix what it shows.

What the number actually is, and what it does not cover

We have now read the exposure-limit list itself and the diesel guide behind the announcement, and both add precision the announcement does not carry. Two details change how you comply.

It is an 8-hour time weighted average, and it is measured as respirable elemental carbon. The list entry reads “Diesel particulate matter (as respirable elemental carbon)” with 0.01 in the TWA column, and the guide states the same thing in full: a health-based 8-hour TWA workplace exposure limit for diesel particulate matter, as an indicator for diesel engine emissions, of 0.01 mg/m3 measured as respirable elemental carbon. That measurand is the practical half of the rule. Elemental carbon is the soot fraction, and an air monitoring result for total particulate is not the same measurement and will not tell you whether you comply.

There is no short-term or peak limit. Some contaminants in the list carry a short term exposure limit or a peak limit as well as a TWA. Diesel particulate matter has neither, so the whole obligation runs on the eight-hour average.

And the limit is an indicator, not a boundary around the hazard. The guide is explicit that there is no single exposure limit for diesel engine emissions as a whole, because the composition varies with engine type, fuel type and operating conditions. It says you may also need to measure other hazardous chemicals in the mixture, naming nitrogen dioxide and carbon monoxide. So a workplace sitting under 0.01 has met this limit, which is not the same as having controlled the exposure.

Why a hard number for this one

The guide sets out the health basis, and it is blunter than the announcement. Diesel engine emissions are carcinogenic: exposure can cause lung cancer and presents an increased risk of bladder cancer, citing the IARC monograph. Polycyclic aromatic hydrocarbons, a trace contaminant, are separately carcinogenic. Around 130 Australians are diagnosed each year with lung cancer caused by work-related exposure to diesel engine emissions. Long-term exposure can also worsen asthma and allergies and raise the risk of heart and lung disease including chronic obstructive pulmonary disease. Short-term, high concentrations range from eye, nose, throat and lung irritation through to asphyxiation from carbon monoxide poisoning.

The guide names the industries where exposure is most likely: mining and quarrying, oil and gas, tunnelling, construction, agriculture, transport and logistics, and vehicle maintenance. It notes that levels are higher in enclosed, poorly ventilated areas where exhaust builds up, and that the source is not only vehicles but stationary plant such as generators and winch motors.

How we sourced this

The 1 December 2026 commencement and the duty as stated, the transition to the workplace exposure limits list, the 0.01 mg/m3 limit for diesel particulate matter, the description of diesel particulate matter as the measure of exposure to diesel engine emissions, the health impacts named, the list of affected industries, the publication of three guides on 30 July 2026 and the described contents of each are from Safe Work Australia's news item “New guidance on managing workplace exposure to airborne contaminants”, read on 31 July 2026.

We have not opened the three guides themselves, only the regulator's summary of what each contains, so their detail is described at second hand and any figure inside them beyond the limit quoted here is unverified by us. The observation about diesel running in enclosed spaces, and the paragraph beginning “Our view”, are ours and are built on the sourced facts above. The comparison with the nine chemicals draws on our earlier reporting, linked above; diesel particulate matter does not appear in that story.

Sources

  1. Safe Work Australia, Workplace exposure limits for airborne contaminants (amended November 2025; downloaded and read 1 August 2026): the list entry “Diesel particulate matter (as respirable elemental carbon)” carrying 0.01 mg/m3 in the 8-hour TWA column and no short term or peak limit, and the definitions of TWA, STEL and peak limit.
  2. Safe Work Australia, Guide to managing the risks of exposure to diesel engine emissions in the workplace (June 2026; downloaded and read 1 August 2026): that there is no single workplace exposure limit for diesel engine emissions as a whole and why, the 8-hour TWA of 0.01 mg/m3 measured as respirable elemental carbon as an indicator, the statement that other contaminants including nitrogen dioxide and carbon monoxide may also need measuring, the carcinogenicity findings and the figure of around 130 Australians diagnosed each year with work-related lung cancer from these emissions, and the list of most-exposed industries.
  3. Safe Work Australia, New guidance on managing workplace exposure to airborne contaminants (30 July 2026, read 31 July 2026): the transition to the workplace exposure limits list, the duty from 1 December 2026, the 0.01 mg/m3 limit for diesel particulate matter, the health impacts and named industries, and the three published guides with their described contents.
  4. The Duty Holder, Ministers could not agree to tighter limits for silica, benzene and seven other chemicals: our earlier reporting on the nine chemicals whose older numbers carry over on the same date.

Updated 1 August 2026. The original was written from Safe Work Australia's announcement. We have since read the exposure-limit list and the June 2026 diesel guide, and added what they specify and it does not: that 0.01 mg/m3 is an 8-hour time weighted average measured as respirable elemental carbon, that there is no short term or peak limit, that no single limit covers diesel engine emissions as a whole so other contaminants may still need measuring, and the health basis including the roughly 130 work-related lung cancer diagnoses a year. The 0.01 figure and the 1 December 2026 date are unchanged.

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