| Abstract |
Overview of the IDLH Value for Methacrylonitrile IDLH value: 4.0 ppm (11 mg/m3). Basis for IDLH value: Among the acute lethality studies, mice and rabbits appear to be the most sensitive species. The LC50 values in mice and rabbits were 36 and 37 ppm, respectively for a 4-hour exposure [Pozzani et al. 1968]. In the same study, no deaths or clinical signs were reported in mice or rabbits exposed to 19.7 ppm for 4-hours, indicating a steep concentration-response curve. The NOAEL of 19.7 ppm after duration adjustment yields a 30-minute equivalent concentration of 39 ppm. An uncertainty factor of 10 was applied to account for a steep-dose response relationship, animal to human differences, and human variability resulting in an IDLH value of 4.0 ppm. 1.2 Purpose: This IDLH Value Profile presents (1) a brief summary of technical data associated with acute inhalation exposures to methacrylonitrile and (2) the rationale behind the immediately dangerous to life or health (IDLH) value for methacrylonitrile. IDLH values are developed on the basis of the 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 methacrylonitrile, the in-depth literature search was conducted through July 2017. |
