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Chronic disease agent occupational exposure limits: upper control limits for each single shift TWA or the long-term average exposure?

Hewett P
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 1997 May; :43-44
Introduction: The idea that the ACGIH TWA TLVs and OSHA's TWA PELs were intended to be used as upper control limits for each worker 's long-term average exposure continues to be advanced in the industrial hygiene literature. The corollary concept that compliance with a TWA TLV or PEL is best determined using "mean testing" is also advanced. The objective of this presentation is to address the question "Do the TWA TLVs and PELs represent upper control limits for exposures averaged across each single shift or averaged across months or years?" Discussion: The following literature was reviewed: the published transactions of the ACGIH since 1960, the documentation of the TLVs, publications of prominent members of the ACGIH and the ACGIH TLV committee, preambles to several OSHA 6(b) standards, and the publications of the proponents of the "long-term average" interpretation. The documentation of the TLVs and the writings of prominent ACGIH members clearly point toward the "single shift" interpretation. The publications of OSHA support the "single shift" interpretation and in several OSHA explicitly states that in controlled work environments the long-term mean will be well below the single shift limit. The notion that the TIVA TLVs and PELs represent limits on long-term average exposures appears to have little basis in fact. Conclusions: The weight of the evidence clearly points to a conclusion that ACGIH intended the majority of the time-weighted average TLVs to be interpreted as upper control limits for daily average exposures. Consequently, one can conclude that OSHA correctly interpreted the 1968 ACGIH TWA TLVs as upper control limits for each single shift TWA exposure.
Exposure-levels; Exposure-limits; Workers; Work-environment; Diseases; Industrial-hygiene; Threshold-limit-values; Time-weighted-average-exposure; Permissible-limits
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American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division