This year we are consulting on Workplace Exposure Standards (WES) and Biological Exposure Indices (BEI). We’re proposing changes to the WES of 34 substances and the BEI of one substance. 

You may know about WES and BEI or heard other people talk about them – here is a brief explanation of what they are and why they are so important.

WES are levels of airborne substances it is expected most workers can tolerate repeated exposure to without coming to harm. We say ‘most’, not ’all’ workers as differences between people, such as genetic variation, may mean some are more at risk from exposure. In addition toxicology data on the risk of certain chemicals is often limited, so setting a suitable WES value can be difficult.

Prescribed exposure standards (PES) are an upper limit above which no worker should be exposed. These are prescribed in legislation or a safe work instrument. Currently there are no WES prescribed in regulation, no Safe Work Instrument for WES/BEI, and no WES set in current Group Standards. There are some PES set in controls under section 77 or 77A and under section 77B of the HSNO Act 1996 including methyl bromide and 1080. These are in our WES book.

The rest of the WES in the book are guideline values for people qualified in occupational health practice and are for use in risk assessment. A good sampling strategy is critical when applying WES to ensure a good understanding of exposure variants, which always occur. The PCBU should take advice from a competent person on how exposure will be monitored in the workplace. It is not good practice to compare one or two samples to a WES and determine if risk is managed based on that simple comparison.

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.

Biological monitoring measures the concentration of a substance - or its breakdown products - in blood or urine. The monitoring result is compared to a standard established for the specific substance – known as its biological exposure index (BEI).

For substances that can be readily absorbed through skin as well as inhaled, biological monitoring may be the preferred exposure monitoring tool, as measuring air levels alone may not give the full exposure picture. However, options on biological monitoring are limited as there are only about 20 biological exposure indices, compared with over 700 exposure standards for airborne monitoring.

Biological monitoring should not be confused with health monitoring, which determines any negative changes in the worker’s health. Health monitoring should ideally show no changes occurring, meaning control measures are effective and risk is being managed.

PCBUs must minimise exposure and monitor the conditions of the workplace where the exposure cannot be eliminated. Monitoring conditions of the workplace for the purpose of preventing illness is about assessing the worker exposure to hazardous or toxic substances. WES are an important tool 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.

This is because professional judgement is required in making decisions regarding safety levels of exposure to chemical and physical agents at work.

Last year’s WES consultation highlighted that:

• some PCBUs do not have a good understanding of how WES are applied, nor of the importance of good exposure monitoring in health risk assessment 
• there is misunderstanding about the difference between WES values and the regulatory ‘prescribed exposure standards’.

Other feedback related more specifically to proposed changes to hydrogen sulphide, nitrogen dioxide and synthetic mineral fibres. 

As a result we engaged with industry to better understand their point of view, explain our position and discuss good practice in health risk assessment and exposure monitoring.

Following the consultation many participating PCBUs indicated they will review their health risk management / exposure monitoring programmes with a view to lowering exposures to these substances. 

We are also going to support some specific industries on health risk management, including hydrogen sulphide in fellmongers’ and geothermal energy production.

The new WES and BEI values were published in the 2018 WES/BEI book in late November. 11 WES values were reduced at that time.

It is noted that Safe Work Australia has recently commenced consultation in relation to their WES for respirable crystalline silica and for respirable coal dust. Safe Work Australia are proposing an 8-hour time-weighted average concentration of 0.02 mg/m³ for respirable crystalline silica.

We will be carefully considering the outcome of Safe Work Australia’s review.