Manganese and Welding Fume: Manganism Risk for Australian Welders

Manganese in Welding Operations

Welding fume is a complex mixture of metal oxides, fluorides, and other compounds generated when the electrode, base metal, and coatings are volatilised by the welding arc. Manganese (Mn) is present in virtually all carbon steel and stainless steel base metals and in most welding consumables — it improves weld strength and deoxidises the weld pool. As a result, welding fume from the majority of steel welding processes contains measurable manganese.

The processes generating the highest Mn fume concentrations are:

• Flux-cored arc welding (FCAW): Generates the highest fume generation rates (FGR) of any common arc welding process and high Mn concentrations
• Shielded metal arc welding (SMAW/stick welding): High FGR; Mn content depends on consumable type
• Gas metal arc welding (GMAW/MIG welding): Lower FGR than FCAW/SMAW, but still significant Mn exposure without controls
• Submerged arc welding (SAW): Very low visible fume, but Mn-containing gases and vapours still generated

High-Mn consumables (used for hard-facing wear-resistant overlays and joining high-Mn steel) generate extremely high manganese fume concentrations and require stringent engineering controls.

Manganism: The Neurological Disease of Manganese Overexposure

Manganism is a progressive neurological disorder resulting from accumulation of manganese in the basal ganglia, particularly the globus pallidus. Symptoms closely resemble Parkinson’s disease but have distinct features:

• Early symptoms: fatigue, cognitive slowing, mood changes (irritability, apathy, hallucinations in severe cases), mild tremor
• Intermediate stage: increasingly prominent tremor, gait disturbance (“cock walk” — a characteristic high-stepping gait with tendency to fall backward), mask-like facies
• Advanced manganism: severe motor impairment, dysarthria (slurred speech), cognitive impairment

A critical distinction from Parkinson’s disease: manganism responds poorly to levodopa treatment, which is the cornerstone of Parkinson’s management. Early diagnosis (before significant neurological damage) is therefore critical — removing the worker from manganese exposure before severe damage occurs may arrest progression.

The latency between significant manganese exposure and the onset of manganism varies from months (extreme exposure) to years or decades (moderate occupational exposure). This long latency means that welders may accumulate significant neurological damage before symptoms are recognised.

Australian WES for Manganese

The current Safe Work Australia WES for manganese and its inorganic compounds is:

• Manganese (inhalable fraction): WES-TWA 0.2 mg/m³
• Manganese (respirable fraction): WES-TWA 0.1 mg/m³

These values were halved in 2013 from the previous 0.2 mg/m³ (respirable) and 0.5 mg/m³ (inhalable) standards, following new epidemiological evidence of subclinical neurological effects at lower exposure levels. The ACGIH TLV is 0.02 mg/m³ (inhalable) — an order of magnitude lower than the Australian WES — reflecting the evolving evidence that even moderate manganese exposure may cause subtle neurobehavioural changes.

This gap between Australian WES and ACGIH TLV is one of the most significant discrepancies in the WES/WEL framework, and Australian regulators are likely to review Mn standards as part of the 2026 WEL transition.

Monitoring and Health Surveillance

Air monitoring for manganese in welding fume uses personal sampling onto PVC membrane filters (25 mm, 5 µm pore size) at 2–4 L/min for 8-hour shift sampling, analysed by ICP-MS or ICP-OES at a NATA-accredited laboratory. Sampling must be conducted close to the breathing zone, with samples collected within the respirator (if worn) or outside it to assess actual inhaled dose.

Biological monitoring for manganese uses whole blood manganese (reference range typically <15 µg/L) or urinary manganese. Blood manganese reflects recent exposure and is the most commonly used biomarker. However, the relationship between blood Mn and neurotoxic risk is complex — Mn in the brain is not well reflected by blood levels, particularly in workers with long-term exposure histories.

Neurological health surveillance for high-exposure welders should include periodic neurobehavioural assessments using validated tools (cognitive testing, tremor assessment, gait assessment). Early detection of subclinical effects allows intervention before irreversible damage occurs.

Engineering Controls for Mn Fume Reduction

• LEV at welding arc: Capture hoods positioned within 100–200 mm of the arc, or fume extraction guns (on-gun LEV) that extract fume directly from the welding torch tip
• Welding process selection: Substituting FCAW with GMAW where technically feasible reduces FGR significantly
• Low-fume consumables: Some consumable formulations are designed to reduce overall fume generation rates
• Welding position: Flat position (downhand) welding generates less exposure to the welder’s breathing zone than vertical or overhead positions
• General dilution ventilation: As a supplement to LEV — not as a primary control for enclosed spaces
• Respiratory protection: P2 or P3 filter respirators (combined with organic vapour cartridges for stainless and coated material welding) where LEV is insufficient

Frequently Asked Questions

My welders have worked for 20+ years without obvious symptoms — do they still need manganese monitoring?

Yes. The absence of obvious symptoms does not exclude subclinical neurological changes that increase the risk of future manifest disease. Twenty-year welding careers can accumulate significant Mn in the basal ganglia even with moderate exposure. Neurological health surveillance using validated tools can detect early changes before they progress. Retrospective exposure reconstruction and medical assessment by an occupational physician are advisable for long-term welders concerned about their cumulative Mn exposure.