Some work processes create harmful dusts, mists, vapours, gases, fumes and fibres that contaminate the air and are hazardous to health. Breathing these airborne contaminants and substances can damage organs and cause diseases such as occupational asthma, bronchitis, silicosis and cancers. Workers may also be exposed to harm through skin absorption, ingestion, and injection.

WES and BEI are tools that can be used to better understand exposure to these hazards.

We publish WES values which represent airborne concentrations of substances in a worker’s breathing zone (the area immediately surrounding their nose and mouth). These values represent a level of exposure that most healthy adult workers can be exposed to without adverse health effects – either in the short-term, or during a standardised working lifetime.

WES are usually set for single substances but may also be produced for common mixtures in the workplace such as solvent mixes, oil mists, and fumes from welding or diesel fuel.

WES may be set for different levels of exposure. We provide information with a WES to aid understanding of how the WES should be applied.

WES are measured using procedures that gather air samples in the worker’s breathing zone. Assessment of work-related exposure and interpretation of results should be performed by a competent person, such as a suitably qualified and experienced occupational hygienist.

Exposure to a substance can also be estimated by biological exposure monitoring. BEI represent concentrations of substances (or their breakdown products) in biological samples (such as blood or urine) below which most workers should not experience adverse health effects from exposure.

A BEI value is intended to complement the WES value for airborne concentration of a substance.

BEI are measured using biological monitoring through urine or blood sampling of a worker.

WES and BEI values serve four important roles in the health and safety system:

• they provide information for PCBUs and other duty holders about work-related airborne contaminants and substances hazardous to health that need to be eliminated or minimised in the workplace
• they play an important role in the upstream management of exposure risks through manufacturer and engineering design
• they’re a tool for occupational hygiene or occupational health professionals when carrying out exposure assessments, assessing health risks, or assessing the need for or effectiveness of controls in a workplace, and
• they’re a benchmark to assess how well New Zealand workplaces are protecting workers.

WES and BEI aren’t:

• mandatory legal limits that must not be exceeded
• a ‘target’ to be met
• a dividing line between safe and unsafe levels of exposure
• a way to protect workers from exposure, or a way of eliminating or minimising exposure.

PCBUs should aim to achieve a level as far below a WES or BEI as is reasonably practicable.

We intermittently review and maintain our Workplace Exposure Standards and Biological Exposure Indices. We may update a substance’s WES and BEI values, add WES or BEI values for a substance, or remove the WES or BEI values for a substance.

We identify and prioritise substances for review based on the following:

• absence of a New Zealand WES or BEI for a substance, for which values have been set by Australia
• existence of New Zealand WES and BEI values that appear to be significantly out of alignment with recently updated values set by Australia, and
• existence of relevant new information or data which significantly affects the application of the substance in the New Zealand context.

Individuals, businesses and organisations can also request that we consider initiating a WES or BEI review.

Once we’ve decided to review or set a new value, we need to determine whether we should use the Australian WEL value as a WES or set an independent value.

The triage isn’t a full review of scientific data. To help us decide whether setting an independent value is appropriate, we assess whether:

• the New Zealand data indicates a materially different risk to Australia (such as surveillance signals or industry clusters)
• the New Zealand control environment differs materially from Australian assumptions (such as a substance which is banned in Australia and not in New Zealand)
• the prescribed nature of the Australian value would be significantly unsuited to a recommended value in New Zealand
• the substance doesn’t have an Australian WEL, but there’s good reason to set a WES or BEI for New Zealand
• the substance is a candidate for a prescribed exposure standard (there is clear high harm potential and need for enforceability).

We also consider the following:

• We only set an independent value in exceptional cases
• We only set a lower (more stringent) value than an Australian WEL value when there is an overwhelming case for doing so.

Once the review is complete, a recommendation is put to the relevant tier three decision maker to decide either:

• to adopt the Australian WEL value (the WES and BEI indices will be updated with the WEL value and any necessary supporting information), or
• that we’ll set an independent value.

When developing and updating WES and BEI values our staff with expertise relevant to exposure standard data will evaluate each substance using the latest available scientific data. We do this by conducting a literature review of credible sources that have derived a healthbased occupational exposure limit for a substance.

Our staff with policy expertise will also conduct a feasibility assessment which takes into account factors outside the scientific data, such as impact on small businesses.

A recommendation will be prepared based on the literature review and feasibility assessment which will include recommended WES and BEI values (and any notations for a substance) for New Zealand.

If we propose to adopt an Australian WEL value, we publish a report on the WES review for public consultation when there is reason to believe the value setting will attract increased public interest (for example, when industry stakeholders have publicly criticised the WEL value or when the WEL value is significantly lower than the previous WES value).

If we decide to set an independent value for a substance we produce a report on the recommended value for public consultation. We then review public submissions, select the final independent value, and submit their recommendation for the value to the relevant tier three decision maker for approval.

Following public consultation, we publish a WES Summary document which includes:

• an explanation of how stakeholder input was considered
• analysis on how technical evidence informed the value that was set
• analysis of any additional factors which informed the value that was set.