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INTRODUCTION TO OCCUPATIONAL HEALTH |
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Short-Term Exposure Limit (TLV-STEL) |
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Short-Term Exposure Limit (TLV-STEL) is the maximum concentration to which
workers can be exposed continuously for a short period of time without suffering from
irritation, chronic or irreversible tissue change, or narcosis
of sufficient degree to increase accident proneness, impair self-rescue, or materially
reduce work efficiency. The STEL is a 15-minute time-weighted average (TWA) exposure which should not be exceeded at any time during a work day, even if the 8-hour time-weighted average is within the TLV-TWA. Exposures above the TLV-TWA up to the STEL should not occur more than four times per day. There should be at least 60 minutes between successive exposures in this range. The STEL is not a separate exposure limit, rather it supplements the TWA limit where there are recognized acute effects from a substance whose toxic effects are primarily of a chronic nature. STELs are recommended only where toxic effects have been reported from high short-term exposures in either humans or animals. |
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