OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: 126-98-7; Chemical Formula: CH2=C(CH3)C=N
OSHA previously had no standard for methylacrylonitrile. The ACGIH recommends a 1-ppm TLV-TWA with a skin notation to protect workers who are occupationally exposed to methyl acrylonitrile. The Agency proposed, and the final rule establishes, a permissible 8-hour TWA exposure limit of 1 ppm, with a skin notation, for methylacrylonitrile, which is a colorless liquid. NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate.
Methylacrylonitrile has been shown to be extremely toxic in animals, both by inhalation and dermal absorption. The dermal LD(50) in rabbits is 0.35 ml/kg (280 mg/kg) (ACGIH 1986/Ex. 1-3, p. 370). Beagles exposed for 90 days to 13.5 ppm convulsed and lost motor control in their hind limbs. Microscopic brain lesions were detected in one of the dogs. The level at which no effects were detected was determined to be between 3.2 and 8.8 ppm (ACGIH 1986/Ex. 1-3, p. 370) No comments (other than NIOSH’s) on the health effects of methyl acrylonitrile were submitted to the rulemaking record.
OSHA is establishing a 1-ppm 8-hour TWA PEL and a skin notation for this substance. The Agency concludes this limit will substantially reduce the significant risk of neurological damage (which constitutes a material health impairment) that formerly existed in the absence of an OSHA exposure limit for this substance.