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.

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, 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.
  2. 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.

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