Are you sure you haven't missed a couple of zeros for the rest of world figures? Seems like most are at 0.005mg/m³, or maybe confusing between hexavalent and trivalent/divalent chromates which still have a TWA limit of 0.5mg/m³. With a lot of government advisory groups recommending the 0.00002mg/m³ TWA limit that WorkSafe have adopted.

If you type into Google "chromium wes nz". You will be taken to a document Workplace Exposure Standard review. It goes into great detail on why the proposed standard is for chromium VI or chromium six. Some key points.

It

• is a based on research and risk to health.
• The standard set 0.02 µg/m3 or 0.00002 mg/m3 is based on human heath effects, (human data)
• Chromium VI is a Genotoxic compound, that is any concentration has potential to cause health effects.
  
  They do look at other countries and organizations what their assessments are of risks to health.
  
  In a workplace if you have potential exposure to chromium six you really must do all you can to eliminate this exposure. Or make it low as possible. You must not be driven by exposure standards you must be driven by reducing exposure to minimize health effects.
  
  In years gone by if you were stressed a doctor would prescribe smoking. We are learning always about what the health effects are of compounds. Just because it was ok yesterday does not it mean it is ok today.

A timeline of WorkSafe WES-TWA values for Cr(VI)

• 2017 - 0.05 mg/m3
• 2018 - WES Review for Cr(VI) recommended 0.0002 mg/m3
• 2018 - 0.01 mg/m3 (adopted 0.01 mg/m3 with a view to review again)
• 2019 - 0.01 mg/m3 (Interim)
• 2020 - WES Review for Cr(VI) recommended 0.00002 mg/m3
• 2020 - 0.00002 mg/m3

A brief rationale of why Cr(VI) was set to 0.00002 mg/m3

• The WES-TWA corresponds to 1 extra lung cancer case per 10,000 exposed workers.
• The WES-STEL is set to minimise transient peak exposures that could trigger asthmatic responses.
• Introduction of dsen and rsen notations based on association with contact and rarely
  occupational asthma.
• Introduction of skin notation based on the systemic absorption of chromium following dermal exposures to water-soluble Cr(VI) compounds.
• Removal of individual WES for Cr(VI) compounds based on the ACGIH®, SCOEL, DECOS and NIOSH recommendations that concluded that all hexavalent chromium compounds should be considered as carcinogens, that underlying processes include a stochastic genotoxic mechanism [that is, no threshold], and that in the health-based cancer risk calculation no distinction should be made between soluble and poorly soluble hexavalent chromium compounds.

Other countries WES-TWA for Cr(VI) (non-exhaustive)

• 0.001 mg/m3 - France, Germany, USA NIOSH
• 0.005 mg/m3 - Denmark, EU, Finland, Sweden, Switzerland

WES vs PES

• The WES and BEIs are guidance values – not prescribed exposure standards.
• The values are considered to be health-based WES.
• This means they are based on minimising health risk and don't take into consideration practicability of achieving or measuring the value.
• More information can be found here: https://www.worksafe.govt.nz/topic-and-industry/monitoring/exposure-standards-and-biological-exposure-indices