Non-Threshold Genotoxic Carcinogens: WEL Changes Explained
From 1 December 2026, Australia's Workplace Exposure Limits (WEL) will replace the current Workplace Exposure Standards (WES). Most airborne contaminants are carrying across to the new list with a numerical limit. In some cases, these have changed while in most cases these chemicals remain unchanged. A specific group of substances is the exception: non-threshold genotoxic carcinogens (NTGCs). These substances will have no WEL at all.
Safe Work Australia's review of the WES identified 33 airborne contaminants as NTGCs. This article covers what that classification means, why these substances are being treated differently, which chemicals are on the list, and what continues to apply to workplaces where they're present.
What is a non-threshold genotoxic carcinogen?
Genotoxic substances can cause damage to genetic material, which can lead to cancer. For most airborne contaminants, it's possible to identify an exposure level below which adverse health effects are considered unlikely and this is the basis for setting a WEL. For NTGCs however, that isn't the case. Safe Work Australia states that ‘a practical, protective exposure level cannot be assigned for NTGCs due to limited data and the nature of their effects.’ In other words, there's no scientifically defensible concentration at which exposure to these substances can be considered safe.
This is a different situation to substances that simply have a low exposure limit. A low WEL still represents a level regulator consider protective when not exceeded. An NTGC has no such level.
Why are WELs being removed for NTGCs?
Because a protective airborne concentration can't be defined for NTGCs, Safe Work Australia's WEL list does not assign them a TWA, STEL or peak limitation. From 1 December 2026, there will no longer be exposure limits for NTGCs.
This does not mean NTGCs fall outside regulation, or that the risk they pose is considered less serious. The opposite is true. Where an NTGC is present, PCBUs must eliminate it from the workplace, substitute it with a safer alternative where possible, or otherwise reduce the risk so far as is reasonably practicable.
1 December 2026: The 33 Non-Threshold Genotoxic Carcinogens
There are 33 substances Safe Work Australia has identified as NTGCs in the November 2025 WEL. Some examples of NTGCs and the kinds of workplaces they can be found include:
Hexavalent chromium compounds – found in welding and hot-working of stainless steel and high-chromium alloys, during shutdowns and turnarounds when boilers, ducting and exhaust systems are opened, and in engine rooms and other machinery spaces where chromium alloys are common.
Coal tar – now largely a legacy contaminant, encountered by workers remediating or excavating former gasworks and coal gas production sites, many of which sit on old waterside or inner-city land once used for water and gas utilities.
Ethylene oxide – Not commonly used anymore as on-site hospital sterilising and central sterilisation units have declined in favour of newer methods with most current exposure occurring in the manufacture of other chemicals including glycol and polyester.
Lead chromate – historically used in anti-corrosive primer paints, so exposure now mainly arises during maintenance, blasting or repainting of aged infrastructure such as defence assets and oil and gas rigs, or where old coatings are flaking into surrounding water.
Polycyclic aromatic hydrocarbon (PAH) mixture containing benzo[a]pyrene – generated by combustion of carbon-based materials, occurring in aluminium smelting, historic gas works, and petroleum refining and coking operations.
The full list is available in Appendix B of the WEL. It’s essential that PCBUs check the list to determine whether they must eliminate or minimise the risk of exposure to these substances in the workplace.
What this means for workplaces where NTGCs are present
For workplaces that use, handle, generate or store any of the 33 listed substances, the practical shift is away from managing exposure against a target concentration and towards applying the hierarchy of controls. This means understanding where the substance is used or generated, considering elimination and substitution first, and minimising exposure where these options are not reasonably practicable.
The absence of a WEL does not remove the value of air quality monitoring. Instead, it changes how monitoring is used. Rather than comparing measured concentrations against a fixed exposure limit, monitoring can help characterise where and how an NTGC is present, establish baseline exposure conditions, and assess whether control measures such as engineering controls, ventilation, PPE and process changes are effectively reducing exposure over time.
For NTGCs that also have a health monitoring requirement under Schedule 14 to the Model Work Health and Safety Regulations, involvement from a registered medical practitioner is a separate obligation and should be considered alongside workplace exposure controls.
Given the serious implications of a genotoxic carcinogen classification, and the additional requirements that may apply to some substances, including restricted or prohibited carcinogen status and mandatory health monitoring, workplaces should consider seeking advice from an occupational hygienist or other appropriately qualified professional to assess exposure risks and determine appropriate control measures.
