Workplace exposure standards (WES), or workplace exposure limits (WEL), are the maximum level of an airborne contaminant that most people can be exposed to without harm to their health.
There are over 600 substances and mixtures with an established workplace exposure standard or workplace exposure limit, however, there are others that are hazardous to human health that do not have a mandatory exposure limit.
Background
Australia first adopted the WES list in 1995. Since the last comprehensive review in 2003, more evidence has emerged in relation to the harmful effects, and the thresholds below which no adverse effects are observed, for many chemicals.
Following the WES review, work health and safety (WHS) ministers have agreed to the WES list becoming the WEL list and changes to the exposure limits of some chemicals.
Controlling risks from airborne contaminants
An airborne contaminant is a fume, mist, gas, vapour or dust that can be harmful to health when breathed in.
They may not be visible to the naked eye nor detected by odour. They may arise from chemicals or materials used in the workplace or be generated by work processes.
The risks from airborne contaminants in the workplace must be managed by employers and other duty holders, as a person conducting a business or undertaking (PCBU) by eliminating the airborne contaminants if it is reasonably practicable to do so.
If it isn’t reasonably practicable to eliminate exposure, PCBUs must minimise exposure to the airborne contaminant so far as is reasonably practicable.
PCBUs must ensure that no person at the workplace is exposed to a substance or mixture in an airborne concentration that exceeds the exposure limit for that substance or mixture.
The hierarchy of control measures should be used to control risks and reduce exposure to airborne contaminants. Protection provided by respiratory protective equipment (RPE) can be considered when determining compliance with the WEL only when all reasonably practicable higher order controls have been implemented, and the RPE is necessary to control any remaining risk, and it is worn correctly.
Air monitoring must be carried out to determine the concentration of a substance or mixture in the air where the PCBU is not certain on reasonable grounds whether the concentration of the substance exceeds the exposure standard (or exposure limit), or where it is necessary to determine if there is a risk to health.
Managing risk where there is no WEL or where exposures are too low to effectively measure
For 33 chemicals classified as non-threshold genotoxic carcinogens (NTCGs) there will no longer be a WES/WEL from 1 December 2026. The list of these substances is provided by Safe Work Australia, and examples include Chromium VI compounds, dimethyl sulfate, ethylene oxide, MOCA, and vinyl chloride monomer.
There are other chemicals where the revised WEL is very low and may be below the limits to which current sampling and analysis can measure.
In these cases, a competent person should conduct a review of the control measures in place to minimise exposure, to check that suitable controls have been implemented and are being effectively maintained. A review schedule for checking the controls should be implemented.
Where suitable methods and standards are available, biological exposure may be assessed. An occupational physician can advise on the use of biological exposure assessments.
Air monitoring may still be conducted as part of the risk assessment for these substances and to check that controls are working, to the extent possible using the available technology.
Preparing for the change to WEL
The WEL is not the dividing line between a healthy and unhealthy work environment. Natural human biological variations and individual susceptibilities (such as a pre-existing medical condition) mean a small number of people may still experience adverse health effects from exposure to levels below the WEL. As such, you must always eliminate the risk of exposure to airborne contaminants so far as is reasonably practicable. If it is not reasonably practicable to eliminate the risk, minimise the risk so far as is reasonably practicable.
In preparing for the change to WELs, identify which WELs have changed at your workplace using Safe Work Australia’s Changes to workplace exposure limits guidance. Review your risk assessments to check exposure monitoring results, where available. Update the risk assessments in consultation with workers. Identify work activities where there may be a health risk or where you are uncertain whether the revised WEL will be exceeded and consult an occupational hygienist if further assessment monitoring may be required. An occupational hygienist can assist with reviewing your risk assessment, and where required can establish a plan for exposure monitoring, conduct the monitoring and report on the results.