Cadmium exposures at three nonferrous foundries: an unexpected trace source

Area of Science:

• Occupational Health and Safety
• Environmental Science
• Metallurgy

Background:

• Trace substances are frequently overlooked sources of significant occupational exposure in industrial settings.
• An unexpected cadmium finding occurred during a lead exposure assessment at a brass foundry, despite its absence from material safety data sheets (MSDS).

Purpose of the Study:

• To investigate the source and extent of cadmium exposure in nonferrous foundries.
• To determine if trace cadmium in special high-grade (SHG) zinc used in brass and bronze alloying can lead to occupational overexposures.

Main Methods:

• Air sampling was conducted in three nonferrous foundries to measure cadmium levels.
• Analysis of air samples from the plume generated by adding SHG zinc to molten metal.
• Comparison of measured exposure levels with Occupational Safety and Health Administration (OSHA) action and permissible exposure limits.

Main Results:

• Cadmium was identified as a trace component (up to 0.003%) in SHG zinc used in brass and bronze alloys.
• Employee exposures, particularly for metal pourers (up to 7.2 µg/m³), exceeded OSHA limits (2.5 µg/m³ action level, 5 µg/m³ PEL).
• Air samples from the plume after zinc addition showed extremely high cadmium levels (up to 3070 µg/m³), confirming zinc as the cadmium source.

Conclusions:

• Trace cadmium present in SHG zinc can cause significant occupational overexposures in brass and bronze foundries.
• It is crucial to consider all trace components, not just listed ingredients, when assessing potential employee exposures.
• Foundries need to re-evaluate their material sourcing and exposure control strategies to mitigate risks from unexpected trace contaminants.