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Updating IDHL values: a work in progress.

Weinrich-A; Ahlers-H
American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia. Fairfax, VA: American Industrial Hygiene Association, 2004 May; :21
NIOSH developed the Immediately Dangerous to Life and Health (IDLH) values beginning in 1974. In 1994, NIOSH reviewed all IDLH values to insure they were adequately protective, adding 10% of the lower explosive limit as a new criterion. NIOSH currently recommends IDLHs for 398 of 620 substances for which it has recommended exposure limits. Although NIOSH introduced IDLHs as respirator selection criteria, their application has spread, including specific references in regulations and routine use by emergency responders. In 1998, NIOSH began reevaluating the IDLHs. Two NIOSH-funded studies reviewed 50 IDLHs. Based on available toxicity data, at least 14% were questionably protective and approximately 20% were over-protective. NIOSH has begun a process to revise IDLH documentations. This process includes developing standard protocols to assure IDLH documentations and resulting values are transparent. This presentation expands on results from the review studies and discusses progress to date, including draft protocols inferred below, for consistently applying various data. Issues surrounding concerns and roadblocks to protocol development are addressed, in part to elicit substantive responses to the following questions: Does low potential for significant airborne exposure make an IDLH value unnecessary? Is the exposure data hierarchy of inhalation > intraperitoneal > ingestion generally appropriate? Is the tenBerge, Cn * t, relationship best for time-scaling acute inhalation exposure data, even when inadequate data require using default values for "n"? How protective is the default relationship, human IDLH = (30-minute LC50, any species)* (0.1)? Are assumptions of 70-kg weight and 10 M3 inhaled air volume appropriate for IDLHs? Is an animal-to-human data uncertainty factor of 1 generally appropriate for IDLHs? Should limited data suggesting genotoxicity or carcinogenicity potential from acute exposures drive an IDLH value? What are the ramifications of basing future IDLHs on toxicity data alone?
Exposure-limits; Emergency-responders; Respirators; Airborne-particles; Occupational-exposure; Exposure-levels; Inhalation-studies; Animals; Animal-studies; Acute-exposure; Carcinogenicity
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American Industrial Hygiene Conference and Exposition, May 8-13, 2004, Atlanta, Georgia