OSHA previously had a 250-ppm 8-hour TWA limit for isopropyl acetate. The Agency proposed supplementing this limit with a 15-minute STEL of 310 ppm, based on the ACGIH (1986/Ex. 1-3) recommendation. OSHA is establishing these limits for this substance in the final rule. Isopropyl acetate is a colorless liquid and has a fruity odor.
The oral LD(50) for rats is reported to be 6.75 g/kg; five of six rats died after a four-hour exposure to 32,000 ppm, and one of six rats died after a four-hour exposure to 16,000 ppm (Smyth, Carpenter, Weil, and Pozzani 1954/Ex. 1-440).
The primary problems in occupational exposures to isopropyl acetate are eye and mucous membrane irritation. In humans, exposure to 200 ppm isopropyl acetate for 15 minutes caused eye irritation, with nose and throat irritation occurring at higher concentrations (Silverman, Schulte, and First 1946/Ex. 1-142). NIOSH (Ex. 8-47, Table N2) notes that the majority of subjects exposed to 200 ppm in the Silverman, Schulte, and First (1946/ Ex. 1-142) study experienced eye irritation and that the authors of this study recommended an 8-hour TWA of 100 ppm to prevent sensory irritation. OSHA agrees with NIOSH that this substance presents a hazard at elevated short-term levels and has accordingly added a STEL to ensure that worker exposures are maintained under good industrial hygiene control.
OSHA concludes that, in the absence of a short-term limit on exposure, the 250-ppm TWA limit alone will not protect employees from experiencing the irritant effects associated with elevated short-term exposures to isporopyl acetate. OSHA has determined that the irritant effects related to exposure to isopropyl acetate are material impairments of health. Therefore, to reduce the risk of irritation among exposed employees, the Agency is establishing a 250-ppm 8-hour TWA limit and a 310 ppm STEL for this substance.