Workplace Exposure Standards (WES) and Biological Exposure Indices (BEI) are health-based values. This means they are based on minimising health risk and don't take into consideration practicability of achieving or measuring the value.
We consider it critical to set health-based values as risk criteria, so that risk assessment is based on an actual understanding of health risk. Efforts need to be directed to the adequacy of controls rather than merely measuring a level of exposure.
What is a WES?
A WES is a guidance value that refers to the airborne concentration of a substance at which it is believed that nearly all workers can be repeatedly exposed day after day without coming to harm. WES are provided by WorkSafe as a tool in risk management. They are intended to be used as risk criteria for health risk assessment
What is a BEI?
A BEI is guidance value for assessing biological exposure monitoring results and is another tool that can be used in managing risks to health and safety associated with substances hazardous to health in the workplace.
What is a PES?
A prescribed exposure standard (PES) is a prescribed workplace exposure standard or biological exposure index that has the purpose of protecting persons in a workplace from harm to health. PES must be complied with (and is not a guidance value like WES). PES are prescribed in:
- regulations;
- a safe work instrument; or
- the Hazardous Substances and New Organisms Act 1996 as a control under section 77 or 77A, or an exposure limit under section 77B or a group standard approval issued under section 96B.
Currently there is only one PES which is for ethanedinitrile (EDN) prescribed in a safe work instrument. The WES and BEI values discussed in this consultation are not PES and are therefore guideline values. They are intended to be used by people with the appropriate knowledge, skills, and experience to apply them for health risk assessment.
WES and BEI sampling strategies
A robust sampling strategy is critical when applying WES to ensure a good understanding of exposure variations which always occur. Exposure levels are commonly variable even in work that is regular and consistent. Variation in worker exposure arises from variation in work activities, control methods, and environmental conditions. Due to this variation, exposure measured on a single day may not reflect exposure on other days. Multiple samples generally allow for better understanding of the variation in exposure, and thus provide more detailed information for the risk assessment. However, even samples from multiple days may not reflect the true variation in exposure that may occur over the long term. With this in mind, the PCBU should take advice from a competent person on how exposure should be monitored in the workplace, including the sampling strategy. The sampling strategy must be designed to provide sufficient measurements to reflect the risk to the worker from the variation in exposure.
Biological monitoring and health monitoring
BEI are guidance values for assessing biological monitoring results.
Biological and airborne exposure monitoring should not be confused with health monitoring. Exposure monitoring means the measurement and evaluation of exposure to a health hazard experienced by a person; and includes monitoring of the conditions at the workplace, and biological monitoring of the people. Health monitoring, in relation to an individual, means monitoring of the individual to identify any changes in his or her health status because of exposure to certain health hazards.
Health risk management must consider a number of aspects from identification, to assessment, to control, with exposure monitoring being just one part – not the only part that needs to be considered.
PCBUs must minimise exposure and monitor the conditions of the workplace if the exposure cannot be eliminated. WES and BEI are important tools for monitoring worker exposures.
While PCBUs must understand and manage the risks of hazardous or toxic substances at work, we do not recommend untrained people use WES to determine compliance. WES are guidance for qualified occupational health practitioners.