Manganese — Workplace Exposure Limit Change

CAS: 7439-96-5 | Notation: Inhalable fraction

Current WES

mg/m³

New WEL (Dec 2026)

0.02

mg/m³

Change

-98%

reduction

Health Effects

Chronic manganese exposure causes manganism, a progressive neurological condition with symptoms resembling Parkinson's disease including tremors, difficulty walking, facial muscle rigidity, and cognitive impairment. Early symptoms include fatigue, headache, muscle cramps, and mood changes that are frequently misdiagnosed. Manganese accumulates in the brain's basal ganglia, and neurological damage is largely irreversible once established. Reproductive toxicity has also been demonstrated, with reduced fertility observed in exposed workers. Respiratory effects include chemical pneumonitis from acute inhalation of manganese fume and chronic inflammatory changes in the lungs from prolonged exposure to manganese dust.

Where Exposure Occurs

MIG and stick welding of carbon steel and manganese-steel alloysSteel manufacturing and foundry operationsBattery manufacturing (alkaline and lithium-ion)Mining and processing of manganese oreDemolition of structures containing manganese-bearing alloysProduction of ferromanganese and silicomanganese

What to Do Now

01Conduct baseline air monitoring at all workstations where manganese exposure is possible to establish current exposure levels against the incoming 0.02 mg/m³ limit. Most welding operations that were compliant under the 1 mg/m³ WES will exceed the new WEL by a factor of 10 or more, requiring fundamental changes to exposure control strategies.

02Upgrade local exhaust ventilation systems on all welding bays and grinding stations. The 98 per cent reduction in the permissible limit means that general dilution ventilation is no longer adequate — source capture extraction positioned within 150mm of the emission point is required to achieve the necessary reduction in airborne manganese concentrations.

03Review and upgrade respiratory protective equipment programs. RPE selection must be based on the assigned protection factor required to reduce exposure below the new WEL. For many welding operations, this will require powered air-purifying respirators rather than disposable P2 masks, along with mandatory fit-testing and RPE maintenance programs.

04Implement biological exposure monitoring for workers with regular manganese exposure. Urinary manganese and blood manganese levels provide complementary data to air monitoring and can identify workers who are absorbing manganese through routes not captured by personal air sampling.

05Evaluate substitution opportunities including low-manganese welding consumables, alternative joining methods such as friction stir welding for suitable applications, and engineering redesigns that reduce the number of welding operations required. The magnitude of the limit reduction makes elimination and substitution controls economically attractive compared to the ongoing cost of extraction and RPE programs.

Monitoring Method

Personal air sampling using a calibrated sampling pump with IOM inhalable sampler and mixed cellulose ester filter. Analysis by ICP-MS or ICP-OES after acid digestion. Sampling duration should cover a full shift to capture time-weighted average exposure. Static monitoring may supplement personal sampling to characterise spatial exposure patterns.

Affected Industries

Metal Fabrication →Construction →

Measure exposure against the right limit

OH Consultant designs and runs personal exposure monitoring for manganese and inorganic manganese compounds, reviewed by a Certified Industrial Hygienist, and reports results against the limit that applies to your site, whether the 1 December 2026 WHS WEL or a mine-specific limit.

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