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: 75-31-0; Chemical Formula: (CH3)2CHNH2
OSHA’s previous limit for n-isopropylamine was 5 ppm as an 8-hour TWA. The Agency proposed retaining this TWA limit and adding a 10-ppm 15-minute STEL, based on the ACGIH recommendation. NIOSH (Ex. 8-47, Table N1; Tr. p. 3-86) concurred with this proposal, and these limits are established in the final rule. This substance is a flammable, volatile, colorless liquid that has an odor similar to that of ammonia.
The most serious effect of n-isopropylamine in laboratory animals is respiratory tract irritation, which can be severe enough to cause lung edema (Smyth 1956/Ex. 1-759). Rats survived a four-hour inhalation at 4000 ppm, but an 8000-ppm exposure resulted in fatalities (Smyth, Carpenter, and Weil 1951/Ex. 1-439). Proctor and Hughes (1978/Ex. 1-1136) have reported that the odor of n-isopropylamine becomes strong and unpleasant at the 10- to 20-ppm level; nose and throat irritation is experienced even as a result of brief exposures.
Except for NIOSH, no rulemaking participants commented on OSHA’s proposal to issue a 5-ppm TWA and 15-minute STEL of 10 ppm for this substance. The Agency concludes that both a TWA and STEL are required to protect exposed workers from the significant risk of upper respiratory tract irritation that is known to occur even at brief excursions above the 8-hour PEL. The Agency considers upper respiratory tract irritation resulting from exposure to this substance to be a material impairment of health. Therefore, OSHA is revising the PEL for n-isopropylamine to 5 ppm as an 8-hour TWA and 10 ppm as a 15-minute STEL; these limits are established in the final rule.