[Silicon carbide, occupational exposure, proposed MAC values]

Area of Science:

• Industrial Hygiene
• Materials Science
• Occupational Health

Background:

• Occupational exposure to silicon carbide (SiC) dust is a concern in its production and use.
• Understanding dust composition and concentration is crucial for risk assessment.

Purpose of the Study:

• To evaluate occupational exposure levels to silicon carbide dust.
• To characterize the mineral composition and morphology of workplace dust.
• To propose a Maximum Allowable Concentration (MAC) value for SiC dust.

Main Methods:

• Individual dosimetry for total and respirable dust.
• Light microscopy for respirable mineral fibers.
• Laser analysis for fiber length distribution.
• Electron microscopy for dust morphology.
• X-ray diffraction and infrared spectrometry for mineral identification.

Main Results:

• SiC production sites showed higher mean concentrations: total dust (10.3 mg/m³), respirable dust (1.1 mg/m³), and respirable mineral fibers (0.64 f/cm³).
• SiC product use sites had approximately half the dust and fiber concentrations compared to production sites.
• Detected minerals included carborundum, mullite, and cristobalite.

Conclusions:

• Workplace air in SiC production and use contains various mineral dusts, including SiC, mullite, and cristobalite.
• Exposure levels are significantly higher in SiC production compared to its use.
• A proposed MAC value for nonfibrous SiC dust (with <2% free crystalline silica) is 10 mg/m³ for total dust.