ISOPROPYL ETHER

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: 108-20-3; Chemical Formula: (CH₃)₂CHOCH(CH₃)₂

OSHA’s former limit of 500 ppm (8-hour TWA) is being retained for isopropyl ether, and NIOSH (Ex. 8-47, Table N1) concurs that this limit is appropriate. The ACGIH recommends a TLV-TWA of 250 ppm and a TLV-STEL of 310 ppm for this liquid, which has a sharp, sickly sweet odor similar to that of ether.

Animal studies have shown that exposures to high concentrations of isopropyl ether cause narcosis and death (Machle, Scott, and Treon 1939/Ex. 1-348). Twenty exposures at a 1-percent vapor concentration produced intoxication and depression but no significant blood or organ weight changes. In rabbits, the minimum lethal dose has been reported to be 5 to 6.5 g/kg. The liquid is an irritant to the skin and mucous membranes and causes dermatitis on repeated exposure (Machle, Scott, and Treon 1939/Ex. 1-348).

Humans exposed for 15 minutes to isopropyl ether concentrations of 300 ppm experienced no overt irritation but complained about the objectionable odor of isopropyl ether; however, eye and nose irritation did occur as a result of five-minute exposures to 800 ppm. A 15-minute exposure to 500 ppm was not reported by volunteers to be irritating (Silverman, Schulte, and First 1946/Ex. 1-142). NIOSH was the only commenter to the record on this substance.

The final rule retains OSHA’s former limit for isopropyl ether of 500 ppm as an 8-hour TWA. OSHA is retaining its former limit because the evidence suggests that, although some volunteers complained of the odor at 300 ppm, the concentration reached 800 ppm before volunteers experienced objectionable effects.