The Manganese Exposure Crisis: What Fabricators Must Do

The incoming workplace exposure limit for manganese (inhalable fraction) is 0.02 mg/m³, replacing the current workplace exposure standard of 1 mg/m³. This is a 98 per cent reduction and represents the single largest proportional decrease in the entire WEL schedule. Manganese is not a niche substance confined to specialist operations. It is present in virtually all carbon steel and structural steel welding consumables, making it the most widely encountered metal fume constituent in Australian metal fabrication. Every MIG welding wire, every stick electrode, and every flux-cored wire used on carbon steel contains manganese as an alloying element and deoxidiser. When these consumables are melted by the welding arc, manganese vaporises and condenses into fine particulate fume that is readily inhaled deep into the lungs. The health effects of chronic manganese exposure include manganism, a progressive neurological condition similar to Parkinson's disease, characterised by tremor, difficulty walking, slurred speech, and cognitive impairment. There is no cure, and the damage is irreversible once it occurs.

Occupational hygiene monitoring data from Australian fabrication workshops consistently shows that manganese exposure during routine MIG welding of carbon steel with standard workshop ventilation ranges from 0.05 to 0.3 mg/m³. These levels are well within the current WES of 1 mg/m³ but are two to fifteen times above the incoming WEL of 0.02 mg/m³. Even fabrication shops with extraction arms at every welding station typically achieve manganese levels in the range of 0.03 to 0.1 mg/m³, which means they will also exceed the incoming limit unless those systems are upgraded or supplemented with additional controls. Stick welding generates higher fume rates than MIG welding, and manganese levels during stick welding with E7018 electrodes can reach 0.5 mg/m³ or higher, which is 25 times the incoming WEL. Flux-cored arc welding, particularly with self-shielded wires, generates the highest fume rates of any common arc welding process and produces correspondingly high manganese levels. The scale of the challenge is significant, but it is not insurmountable if fabrication businesses begin taking action now.

The scientific evidence supporting the reduction in the manganese WEL has strengthened considerably over the past decade. Studies of welders with long-term exposure to manganese at levels below the current WES of 1 mg/m³ have found measurable neurological effects including reduced motor function, impaired cognitive performance, and mood disturbances. These effects occur at exposure levels as low as 0.05 mg/m³ when sustained over periods of ten years or more. The new WEL of 0.02 mg/m³ is based on the no-observed-adverse-effect level identified in the most robust epidemiological studies, with appropriate uncertainty factors applied. Manganism, the severe form of manganese neurotoxicity, was historically associated with mining and ore processing, but occupational physicians now recognise that welders represent the largest occupationally exposed group in developed countries. Early symptoms of manganese overexposure are subtle and easily attributed to ageing or fatigue, which means the condition is often not diagnosed until significant irreversible damage has occurred. Health surveillance with neurological assessment is essential for early detection.

Achieving compliance with the incoming manganese WEL requires a layered approach that combines engineering controls, administrative controls, and respiratory protection. The first priority is upgrading local exhaust ventilation to achieve capture velocities of at least 0.5 m/s within 300 mm of every weld zone. For workshops where extraction arms cannot be positioned effectively due to component size, enclosed welding cells or downdraft benches should be installed. The second priority is substitution of welding consumables — some wire manufacturers now offer lower-manganese MIG wire formulations that achieve the same mechanical properties with reduced fume manganese content. While substitution alone will not achieve compliance, it reduces the exposure baseline that LEV and RPE must address. The third priority is a robust RPE program with powered air-purifying respirators as the minimum standard for all welding operations until engineering controls are verified to achieve compliance through personal exposure monitoring. The fourth priority is administrative controls including welding process selection, reducing arc-on time where practicable, and positioning workers upwind of fume during outdoor operations.

The WHS Regulation 2025 requires PCBUs to conduct air monitoring where there is uncertainty about whether worker exposure exceeds the applicable WEL. Given that virtually all fabrication workshops will need to demonstrate compliance with the new manganese limit, air monitoring should be treated as mandatory. Personal exposure monitoring using calibrated sampling pumps and filter cassettes worn in the welder's breathing zone is the standard method. Samples must be analysed by a NATA-accredited laboratory for manganese content. Static monitoring using area samplers does not measure the worker's actual exposure and should only be used to supplement personal monitoring, not replace it. Monitoring should be conducted for each welding process, base metal, and consumable combination in use, as manganese fume generation varies significantly between processes. Health surveillance for manganese-exposed workers should include baseline and periodic neurological assessment, blood manganese levels, and respiratory function testing. All monitoring and surveillance results must be recorded, retained, and reported to workers. EHS Atlas stores all monitoring results, tracks trends over time, and alerts management when results approach or exceed the WEL.