Media Release - MinEx produces guidance on Worker Exposure Standards

Posted on 6 May 2021

MinEx produces guidance on Worker Exposure Standards

A short guidance document to assist quarries and mines to deal with the complex issues of Worker Exposure Standards (WES) has been produced and is now available from MinEx, the organisation responsible for health and safety in NZ’s extractives sector.

MinEx CEO Wayne Scott says he’s produced the 8-page document to assist quarry and mine operators to work through sometimes confusing advice on WES involving hazardous substances such as Respirable Crystalline Silica (RCS), Nitrogen Oxides, Arsenic, Chromium VI compounds, and Sulphur Dioxide.  Further substances will be added to the guidance as issues are identified.

“WorkSafe updated the 12th annual Worker Exposure Standard Guidance document in late 2020 which runs to more than 90 pages including advice on Biological Exposure Indices, some of which impact on the extractives sector but generally are less relevant to our sector.

“The WorkSafe document includes the WES for the quarrying industry’s biggest occupational health risk – Respirable Crystalline Silica (RCS) at 0.05 milligrams in three square metres of air space.

“That’s an aspirational target that’s twice, for instance, the 0.1mg/m3 which the Australian Institute of Occupational Hygienists recommends for extractive sites across 8 hours of work.

“RCS at 0.05mg/m3 is difficult to measure with any degree of accuracy unless multiple samples over a number of shifts are taken and WorkSafe is making clear this level and others within its document are not prescribed or enforceable standards.”

The WorkSafe document says:The values proposed are also considered to be health-based WES which means they are based on minimising health risk and don't take into consideration practicability of achieving or measuring the value.

“We are on the same page with WorkSafe in saying operators need to do all they can to minimise worker exposure to RCS and any exposures to hazardous substances in the workplace,” says Wayne Scott.

“Given that some of the WorkSafe WES and BEI cannot be measured and/or achieved, our MinEx document gives guidance on international best practice and what operators should be doing to reduce worker exposure to a number of hazardous substances.”

While WorkSafe’s WES and BEI are not enforceable, quarries and mines should be reducing exposure to as low as reasonably practicable and, as technology improves, working toward the WorkSafe standards, says Wayne Scott.

The MinEx Guidance on Worker Exposure to Hazardous Substance in the Extractives sector can be found at