**Diesel particulate matter (DPM)** enters Australia’s Workplace Exposure Limits list as a **new** airborne contaminant with an 8-hour TWA of **0.01 mg/m³** as **respirable elemental carbon (EC)**. There was **no previous SWA WES** for this listing. Until **30 November 2026**, apply the current WES regime and manage risk SFARP. From **1 December 2026**, apply the WEL once implemented in the jurisdiction — **confirm with the WHS regulator**.
This note stays inside published values: **0.01 mg/m³** respirable EC only. Do not invent ppm conversions or STELs for DPM in client communications unless Safe Work Australia publishes them for this listing.
## Characterise the aerosol before choosing a method
DPM exposure profiles in tunnelling typically split into:
1. **Production plant at the face** — loaders, dump trucks, roadheaders, temporary generators → near-field EC under limited dilution
2. **Staging and niches** — idling, congestion, plant waiting for muck or materials
3. **Cold start and maintenance** — aftertreatment not at temperature; DPF faults; filter service
4. **Cabin vs non-cabin** — enclosed filtered operators versus workers sharing the same air without enclosure
5. **Surface / portal plant** that still loads the same ventilation circuit
Your monitoring plan should state which profile you are characterising. Opacity, CO, or “nuisance dust” habits without EC speciation are a weak basis for claiming DPM compliance against **0.01 mg/m³**.
Agree with the laboratory:
– Analyte **elemental carbon** (and organic carbon where the method package reports both)
– Reporting units **mg/m³**
– Collection media and size selection matching **respirable** elemental carbon for WEL comparison
– Recovery, storage, blank discipline and reporting limits relative to **0.01 mg/m³**
– Whether NIOSH 5040-style carbon speciation (or an equivalent defended method) is being used
If SWA documentation for the listing specifies a fraction or notation in the full WEL text, follow that text over informal practice. The listing text used for planning is **respirable elemental carbon**.
## Why legacy 0.1 practice numbers mislead December reports
AIOH’s **August 2017** DPM paper framed **0.1 mg/m³** submicron EC as guidance with **0.05 mg/m³** as an action level — useful ALARP thinking, **not** the WEL. Many sites still carry 0.1-era narratives in risk files.
For client interpretation:
| Reference | Role |
|—|—|
| AIOH ~0.1 / action 0.05 (2017 guidance) | Explains why you investigate early; not the Dec compliance ceiling |
| WEL **0.01 mg/m³** respirable EC | Planning benchmark now; legal ceiling from **1 Dec 2026** once in force |
A campaign that “cleared” 0.1 does not clear **0.01**. Re-baseline SEGs and LOQ expectations before you write transition language.
## SEG walkthrough for a heading
Example: mixed diesel fleet, 12-hour shifts, filtered cabins on some plant only.
1. **SEG — cabin operators (production)** — full-shift personal EC on representative production days; note cabin filter status.
2. **SEG — non-cabin face / support** — often higher potential; do not bury inside cabin averages.
3. **SEG — staging / traffic control** — capture idle and congestion, not only continuous mucking.
4. **SEG — maintainers / DPF service** — short task samples; brief but intense.
5. **SEG — portal / temporary generation** — include if the air path is shared.
Pre-write decision rules: e.g. results approaching **0.01 mg/m³** on non-cabin SEGs → plant mix / ventilation redesign before arguing RPE is the long-term answer. Map **task + plant + ventilation state**, not the org chart. Contractors and labour-hire sit in the same logic.
## Monitoring strategy that survives audit
Recommended structure for tunnelling DPM SEGs:
– **SEG map** by cabin status, plant proximity, and idle/congestion potential
– **Full-shift personal samples** on high-likelihood SEGs, supplemented with **task samples** during start-up, staging peaks, and fan outages
– **Static samples** only as diagnostics (ventilation performance, niche background) — not substitutes for personal TWA comparison
– **Enough replicates** across days to see plant-mix variability; a single quiet afternoon misleads
– **Field blanks** and chain-of-custody disciplined enough for contested results
– **Covariates logged** — plant count and type, idle time, fan status, DPF fault codes, cabin filter condition, shift length
### Method cues that prevent rework
– Do not treat CO or opacity as a surrogate for respirable EC at **0.01 mg/m³**
– Match LOQ to decisions near **0.01 mg/m³**; an LOQ that is a large fraction of the WEL weakens ND narratives
– Record whether workers wore RPE during sampling (context for “as worked” vs unprotected potential)
– State shift duration and any 8-hour adjustment explicitly when shifts exceed 8 hours
– Keep DPM result tables separate from RCS / welding fume tables even when SEGs overlap geographically
## Interpretation against 0.01 mg/m³
– Use **0.01 mg/m³** as the planning benchmark now; as the WEL compliance limit from **1 Dec 2026** once implemented
– Report 8-hour TWAs with clear shift duration and any extrapolation
– Place LOD/LOQ in context: non-detects must be capable of informing decisions relative to the WEL, not merely “ND”
– Present task peaks and staging events as control diagnostics even when the shift TWA is the compliance comparator
– Translate numbers near the WEL into hierarchy-ordered actions the PCBU can fund (plant selection, DPF integrity, ventilation verification, traffic management) — RPE last
Recommend a verification sample set after engineering changes — same SEGs, same fraction, comparable plant intensity — so “we fixed it” is evidenced against **0.01 mg/m³**, not asserted.
## Transition communication to clients
Make the timeline explicit in every report covering DPM:
| Period | Reference |
|—|—|
| To 30 Nov 2026 | WES list (DPM had no previous WES — manage risk SFARP; use **0.01 mg/m³** as foresight) |
| From 1 Dec 2026 | WEL **0.01 mg/m³** respirable EC once jurisdictionally in force |
Never invent early adoption claims for a state or territory. Never present AIOH 0.1 guidance as if it were the WEL.
## Common failure modes
– Filing non-EC results as if they answered DPM at **0.01 mg/m³**
– Sampling only cabin operators when non-cabin and staging dominate
– Ignoring start-up and fan-outage windows
– Omitting fraction and method rationale from the method section
– Treating legacy “under 0.1” statements as December-ready evidence
– Merging DPM and RCS conclusions because both are “dusty underground” stories
## FAQ — technical
### Can static samples show WEL compliance?
No. They can support ventilation diagnosis and niche characterisation. Personal 8-h TWAs answer the WEL comparison.
### Is one production week enough?
Only if it represents the plant mix and ventilation states you claim to characterise. Congestion weeks and maintenance weeks often need explicit inclusion.
### How should we discuss IARC Group 1 classification in an air monitoring report?
Briefly, as context for why ALARP/SFARP matters — without expanding into a toxicology monograph the WEL framework does not require.
### What belongs in the executive summary?
Analyte (respirable EC), n of personal TWAs, range vs **0.01 mg/m³**, dominant tasks/plant states, and whether controls need work before **1 December 2026** (subject to jurisdictional implementation).
## Sources
– Safe Work Australia WEL changes: Diesel particulate matter (as respirable elemental carbon) — new — WEL **0.01 mg/m³**
– AIOH, *Diesel Particulate Matter and Occupational Health Issues* (August 2017) — hygiene framing only
– 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
## Technical support
For EC method selection, SEG design in headings, or interpretation against the incoming DPM WEL, see [occhygiene.com.au](https://occhygiene.com.au).
