Immediately Dangerous to Life or Health (IDLH) Value Profile, Methyl Isocyanate [CAS® No. 624-83-9]
DHHS (NIOSH) Publication Number 2017-105 [CAS® No. 624-83-9]
Basis for IDLH value: The IDLH value for methyl isocyanate is based on the LOAEL for severe reproductive and developmental effects. Varma  reported a LOAEL of 2 ppm for these developmental and reproductive effects in dams exposed for 3 hours on gestation day (GD) 8. This represents a one-time acute exposure at a critical developmental time of the dam and fetuses. The LOAEL was adjusted to a 30-minute equivalent duration concentration of 3.6 ppm. A composite uncertainty factor of 30 was applied to account for extrapolation from a concentration that causes severe effects in animals, animal to human differences, human variability, and uncertainty about the threshold for escape-impairing effects, yielding an IDLH value of 0.12 ppm.
NIOSH . Immediately dangerous to life or health (IDLH) value profile: methyl isocyanate. By Dotson GS, Maier A, Parker A, Haber L. Cincinnati, OH: US Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2017-105.