The Threshold Limit Value-Short Term Exposure Limit (TLV-STEL) is defined as:
- A The maximum airborne concentration of a substance to which workers may be exposed for an 8-hour workday without adverse effects
- B The concentration that should not be exceeded even for an instant
- C The 15-minute time-weighted average concentration that should not be exceeded at any time during the workday, even if the 8-hour TWA is within limits ✓
- D The lowest concentration detectable by standard industrial hygiene sampling equipment
Correct answer: C. The 15-minute time-weighted average concentration that should not be exceeded at any time during the workday, even if the 8-hour TWA is within limits
Explanation
TLV-STEL is a 15-minute time-weighted average concentration that should not be exceeded at any time during the workday, with no more than four such excursions per day, each separated by 60 minutes. It is designed to protect against acute effects from peak short-term exposures, supplementing the 8-hour TLV-TWA. TLV-TWA (option A) is the 8-hour standard. TLV-C (ceiling value) is the concentration that should not be exceeded even momentarily. Option D describes a detection limit, not a health standard.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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