Manganese (dust / fume / compounds, as Mn) is a **WES_reduced** listing. Previous WES expressions in the CSV extract sit at **TWA 1 (dust); 1/3 (fume)** mg/m³. From **1 December 2026**, the Workplace Exposure Limit is **Inhalable 0.1; respirable 0.02** mg/m³ **as Mn** (per Safe Work Australia’s published changes and our CSV extract). That is a **dual-fraction** WEL — one metal, two method decisions.
Until **30 November 2026**, the current WES list still governs airborne contaminant compliance. From **1 December 2026**, WEL applies once given effect in your jurisdiction. **Check your WHS regulator** for adoption and any local commencement detail — national policy documents are not a substitute for jurisdictional law.
## Why this matters for PCBUs
Mining, mineral processing, welding and foundry sites often still talk about “manganese fume at 1” or “dust at 1” as if a single sampler answers the December question. It does not. You must know whether you are defending **inhalable 0.1** or **respirable 0.02** (as Mn) — and your lab report must say which fraction was collected.
If the register still quotes the old dust/fume pair without fraction language, fix the register before you argue about results.
## Where manganese shows up
Typical Australian settings:
– Mining and mineral processing — ore handling, milling, concentrate transfer
– Welding and fabrication — Mn-bearing consumables, stainless and high-Mn wires, confined repair
– Foundries — melting, pouring, shake-out, grinding of Mn steels
– Smelting and refining support tasks
– Battery materials and specialty alloy powder handling (where Mn compounds are present)
– Maintenance on dust collectors, baghouses and ventilation serving Mn processes
– Contract grinders and mobile welders who inherit plant dust histories
Fume-dominant welding SEGs and dust-dominant milling SEGs are not interchangeable — even when both are “manganese as Mn” on the WEL list.
## SEG walkthrough (fabrication + foundry colour)
Imagine a site with a weld bay using Mn-bearing wire and a small foundry grind booth finishing Mn steel castings.
**SEG candidates**
1. **Welders — production bay** — continuous MIG/FCAW on Mn consumables
2. **Welders — confined repair** — short duration, poor dilution, different profile
3. **Grinders / finishers** — respirable-rich aerosol from powered tools
4. **Furnace / pour crew** — fume and dust mix at melt and pour
5. **Baghouse / maintenance** — filter change and duct cleaning
6. **Mobile contractors** — inherit both weld and grind exposures without appearing on the roster map
**Walkthrough questions with ops**
– Which consumables actually contain Mn — and are they named on the register?
– Do you sample **inhalable**, **respirable**, or both — and why?
– Who grinds after welding — same SEG or a new aerosol profile?
– Are night maintenance crews who open collectors in the SEG map?
– Does anyone still cite **TWA 1** as if it remains the WEL comparator?
Build SEGs from tasks and aerosol generation, not from “metal trades” as a single bucket.
## Register and SEG questions for HSE / ops
1. **Are manganese dust, fume and compounds named as Mn** on the hazardous chemical / airborne contaminants register?
2. **Which SEGs** could inhale Mn — weld, grind, mill, pour, baghouse, contractors?
3. **Does paperwork still cite WES dust 1 / fume 1/3** without the incoming dual WEL?
4. **Have you recorded fraction decisions** — inhalable **0.1** vs respirable **0.02** — per SEG objective?
5. **Is there historical monitoring** that states fraction and “as Mn” reporting basis?
6. **Who owns eliminate / substitute / LEV** before RPE becomes the default on grind and weld?
7. **Are SDS and emergency procedures** current for Mn-bearing consumables and powders?
8. **Do contractors** appear in the SEG map with Mn named?
If welding procedures specify Mn wire but the register is silent, fix the register first.
## Controls that actually move the dial
### Eliminate / substitute
– Can consumables move to lower-Mn alternatives where process allows?
– Can grind move to wet methods or enclosed booths?
– Can powder handling move to closed transfer?
Document residual risk — substitution is a decision record.
### Engineering
– On-torch extraction and booth LEV for weld; verified capture on grind booths
– Enclosed transfer and maintained filtration on mineral-processing dust paths
– Treat baghouse pulse and duct cleaning as engineered events with written isolation
– Design filter change for settle / break sequences that cut open volume
### Administrative
– Separate weld, grind and mill SEGs in training and monitoring plans
– Written methods for confined weld repair; restrict non-essential people
– Consumable control — issue Mn wire deliberately, not from an unmarked rack
– Stop-work triggers for LEV failure or visible fume escape — without treating smell as a calibrated instrument
### PPE
– RPE selected for fume / dust and expected concentration, with fit testing and change rules
– Eye / face / skin protection aligned with grind and weld tasks
– PPE last — never the only control on a grind booth that can be enclosed
## Monitoring and readiness without jumping the gun
– Confirm presence and SEGs, including contractors and maintenance
– Get baseline data against **inhalable 0.1** and/or **respirable 0.02** mg/m³ as Mn — matching the fraction to the SEG objective
– Include weld, grind and baghouse tasks — full-shift only on a light fabrication day understates risk
– Close obvious engineering and admin gaps now
– Align training with **manganese as Mn** and the dual WEL numbers
– Ask your OH provider to state fraction, sampler type and “as Mn” basis on every report
Do **not** invent additional mg/m³ figures beyond the published WEL pair. Do **not** treat old dust **1** / fume **1/3** as the December WEL comparators. Do **not** claim early jurisdictional adoption without regulator confirmation. Method colour (which Australian / ISO sampler conventions apply) should be confirmed with your hygienist and lab before you lock a programme — cite method IDs in reports, not in marketing copy.
## Common mistakes
– One “Mn sample” filed against both WEL fractions
– Still quoting WES **1** / **1/3** in Dec readiness packs
– Welding SEG only — skipping grind and baghouse
– RPE without fit testing on multi-hour grind days
– Contractors invisible on the SEG map
– Mixing cobalt / cadmium / beryllium messaging into the same primary without separate listings
## FAQ — HSE and operations
### Which number do we manage to — 0.1 or 0.02?
Both are published WEL expressions for manganese as Mn: **inhalable 0.1** and **respirable 0.02** mg/m³. Your SEG objective and sampler fraction decide which comparison is valid for a given result.
### Is the old fume 1/3 still the WEL?
No. Plan to the published WEL pair: **Inhalable 0.1; respirable 0.02** mg/m³ as Mn.
### Do we need two samplers on every person?
Not always — but you need a written fraction decision per SEG. Some programmes run both fractions on priority SEGs until controls are understood.
### When does WEL “count”?
WES until **30 November 2026**; WEL from **1 December 2026** once implemented — **verify with your WHS regulator**.
## Sources
– Safe Work Australia, *Changes to Workplace Exposure Limits – May 2025* (PDF): https://www.safeworkaustralia.gov.au/sites/default/files/2025-05/changes_to_workplace_exposure_limits_-_may_2025.pdf
– SWA WEL / WES changes page: https://www.safeworkaustralia.gov.au/safety-topic/managing-health-and-safety/workplace-exposure-limits-airborne-contaminants/changes-between-wes-and-wel
– `/workspace/wel/wes-to-wel-changes-2026.csv` — Manganese WES_reduced; WEL Inhalable 0.1; respirable 0.02 as Mn
– Nov-pack FINAL ideas: `/workspace/anitech-social/nov-pack-research-2026-09-16/FINAL-25-30-IDEAS.md` (idea 3)
## Next step
If manganese dust, fume or compounds are present in weld, grind, mill or foundry tasks on your site, book a consult to lock fraction decisions, SEGs and a monitoring plan before the WEL date.
**Book a consult:** [anitechgroup.com](https://anitechgroup.com) · **sales@anitechgroup.com**
Recent Comments