In evaluating an occupational health hazard, the Threshold Limit Value–Short Term Exposure Limit (TLV-STEL) is defined as:
- A The concentration a worker can be exposed to for 15 minutes, no more than 4 times per day, with at least 60 minutes between exposures ✓
- B The maximum concentration to which workers can be exposed continuously for 8 hours a day, 5 days a week, without adverse health effects
- C The absolute ceiling concentration that should never be exceeded at any time
- D The airborne concentration that represents a danger to life or health after 30 minutes of exposure
Correct answer: A. The concentration a worker can be exposed to for 15 minutes, no more than 4 times per day, with at least 60 minutes between exposures
Explanation
TLV-STEL (ACGIH definition) is the concentration to which workers can be exposed continuously for a short period (15 minutes) up to 4 times per day, with at least 60 minutes between exposures, provided the TLV-TWA is not exceeded. TLV-TWA (Time Weighted Average) applies to an 8-hour day/40-hour week. TLV-C (Ceiling) is the concentration never to be exceeded instantaneously. IDLH (Immediately Dangerous to Life and Health) is a 30-minute threshold used for respirator selection purposes.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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