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Heavy Equipment Operator Certification Exam Prep · Question

An aggregate plant is experiencing high levels of crystalline silica dust. What is the occupational exposure limit (OEL) for respirable crystalline silica in Ontario?

Ontario Regulation 490/09, Designated Substances – Silica, sets the occupational exposure limit for respirable crystalline silica at 0.05 mg/m³ TWA, reflecting

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Question: An aggregate plant is experiencing high levels of crystalline silica dust. What is the occupational exposure limit (OEL) for respirable crystalline silica in Ontario?

Answer options: ✅ 0.05 mg/m³ TWA (Time-Weighted Average)

  • 0.5 mg/m³ STEL (Short-Term Exposure Limit)
  • 5.0 mg/m³ TWA
  • 10.0 mg/m³ Ceiling Limit

Correct answer: 0.05 mg/m³ TWA (Time-Weighted Average)

Explanation: Ontario Regulation 490/09, Designated Substances – Silica, sets the occupational exposure limit for respirable crystalline silica at 0.05 mg/m³ TWA, reflecting the severe health risks associated with prolonged exposure.

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