Dotson, GS; Maier, A; Parker, A; Haber, L
Overview of the IDLH Value for Chloroacetonitrile: IDLH value: 14 ppm (23 mg/m3). Basis for IDLH value: No inhalation exposure data were located for chloroacetonitrile. Therefore, acetonitrile is used as a surrogate, as the effects and mode of action are similar; however, acetonitrile is less potent. The mouse LC50 value of 2,693 ppm for a 60 minute exposure to acetonitrile (Willhite 1981) was selected as the basis for the IDLH value. Duration adjustment resulted in the calculation of a 30-minute equivalent LC50 value of 4,120 ppm. An uncertainty factor of 30 was applied to account for extrapolation from a concentration that is lethal to animals, animal to human differences, and human variability, resulting in an IDLH value for acetonitrile of 137 ppm. Available data (Lewis 1996; NAS 2014) indicate that chloroacetonitrile is 10 times more toxic than acetonitrile. A modifying factor of 10 is applied to the IDLH value to account for the greater potency of chloroacetonitrile compared to the potency of the surrogate, acetonitrile, resulting in an IDLH value of 14 ppm. This IDLH Value Profile presents (1) a brief summary of technical data associated with acute inhalation exposures to chloroacetonitrile and (2) the rationale behind the immediately dangerous to life or health (IDLH) value for chloroacetonitrile. IDLH values are developed on the basis of scientific rationale and logic outlined in the NIOSH Current Intelligence Bulletin (CIB) 66: Derivation of Immediately Dangerous to Life or Health (IDLH) Values [NIOSH 2013]. As described in CIB 66, NIOSH performs in-depth literature searches to ensure that all relevant data from human and animal studies with acute exposures to the substance are identified. Information included in CIB 66 on the literature search includes pertinent databases, key terms, and guides for evaluating data quality and relevance for the establishment of an IDLH value. The information that is identified in the in-depth literature search is evaluated with general considerations that include description of studies (i.e., species, study protocol, exposure concentration and duration), health endpoint evaluated, and critical effect levels (e.g., NOAELs, LOAELs, and LC50 values). For chloroacetonitrile, the in-depth literature search was conducted through July 2017.