Exposure values
| CAS number | 78-93-3 |
|---|---|
| Current WES (to 30 Nov 2026) | 150 ppm (445 mg/m³) TWA; 300 ppm (890 mg/m³) STEL |
| WEL (from 1 Dec 2026) | 200 ppm (590 mg/m³) TWA; 300 ppm (885 mg/m³) STEL [Sk] |
| Change | Limit increased |
| Notations, WES (to 30 Nov 2026) | none |
| Notations, WEL (from 1 Dec 2026) | Sk: skin absorption may be a significant source of exposure |
| Notation change | added Sk |
| Other names | Methyl ethyl ketone (MEK); MEK; 2-Butanone |
TWA: 8-hour time-weighted average. STEL: 15-minute short-term exposure limit. ppm values apply to vapours and gases; mg/m³ to all forms.
What to do in your register
- Record the new WEL against this substance, to apply from 1 December 2026.
- A higher limit doesn't mean existing controls can be removed. Review them through your normal risk management process first.
- Update the notations: add Sk.
- Match your register row by CAS number (78-93-3) from section 3 of the safety data sheet (SDS), not by trade name.
Information only, not WHS or occupational hygiene advice. If you need to know actual exposures, talk to an occupational hygienist.
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Source
Values for this substance: Safe Work Australia, Changes to Workplace Exposure Limits, effective from 1 December 2026 (comparison table last updated 29 May 2025). Full lists: Safe Work Australia WEL list, WES list and WES-to-WEL comparison table.
© Commonwealth of Australia (Safe Work Australia), licensed under CC BY 4.0. Changes: values machine-read from SWA's files, reformatted and combined into one WES-to-WEL comparison per substance. This site isn't affiliated with or endorsed by Safe Work Australia.
Dataset swa-2026-10-11, every value cross-checked against the PDF lists. Page generated 2026-10-12.