Immediately Dangerous to Life and Health (IDLH) values have been established by the National Institute for Occupational Safety and Health (NIOSH) to protect workers against exposure conditions that may cause severe irreversible health effects or impair escape from exposure environments. Original assessments were used primarily as a tool to recommend respiratory protection and IDLH values were often based on limited scientific data, secondary source reported data, or safety considerations. In 1994, NIOSH reevaluated the IDLH values and developed more formal criteria for determining IDLH values. A review of the toxicological basis for 35 of a. total 398 of the current IDLH values was conducted to determine if the existing IDLH recommendations were consistent with current toxicological data. For this critical analysis, a qualitative rating method was developed as a tool for conducting the evaluation. Technical guidelines were established for selection of experimental studies, evaluation of each study, and evaluation of the database for each substance. Experimental study protocol and methods were recorded into a customized database designed for tracking and sorting scientific data specific to acute exposures to hazardous substances. Two overall evaluations were made for each substance. The first evaluation rated the adequacy of the database to support the development of an IDLH value and classified each as adequate, marginally adequate, or inadequate. Out of a total 35 substance databases, approximately 50% were considered marginally adequate and 50% adequate. The second evaluation rated the degree to which the current IDLH value was likely to be protective against dangerous levels of exposure. Of the current 35 IDLH values reviewed, approximately 20% were considered more than adequately protective, 63% were considered protective, and 17% were considered inadequately protective.
The Toxicologist. Society of Toxicology 42nd Annual Meeting and ToxExpo, Cutting-Edge Science, Networking, New Perspectives, March 9-13, 2003, Salt Lake City, Utah
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