Annex III: Revised Workplace Exposure Standard

As part of eliminating risks or minimising risks to workers from RCS so far as is reasonably practicable, PBCUs can consider and use Workplace Exposure Standards (WES).

A WES refers to the airborne concentration of a substance, at which it is found that nearly all workers can be repeatedly exposed to, day after day, without coming to harm. The values are normally calculated on work schedules of five shifts of eight hours duration over a 40-hour week. A WES thus aims to avoid adverse health effects for most workers. These WESs are set by WorkSafe based on toxicological effects of the substance.[1]  

A WES is an advisory standard. It is not a mandatory occupational exposure level that must not be exceeded, unless it is prescribed as a “prescribed exposure standard” (PES)[2]in a safe work instrument made under the Health and Safety at Work (General Risk and Workplace Management) Regulations 2016 or by specific regulations. This contrasts with, for example, Australia, where all WESs are mandatory, and with the United States requirements referred to below.

The WorkSafe WES for RCS has been set at 0.025 mg/m3.[3] This is consistent with what has happened in most jurisdictions overseas, but not all. Some, such as the United Sates, have set a permissible exposure limit (PEL) at 0.05 mg/m3. A PEL set by the federal agency Occupational Safety and Health Administration is mandatory and had to be established as both measurable and achievable for businesses before it could be prescribed by regulation in 2016.


Footnotes

[1] See: https://www.worksafe.govt.nz/laws-and-regulations/operational-policy-framework/operational-policies/how-we-set-workplace-exposure-standards-and-biological-exposure-indices/.

[2] At present only one substance in New Zealand has a PES (a fumigation chemical).

[3] The WES for RCS was changed from 0.1 mg/m3 to 0.05 mg/m3 in November 2019. After consultation, WorkSafe changed it from 0.05 mg/m3 to 0.025 mg/m3 in November 2023.