OSHA formerly had no limit for 2-N-dibutylaminoethanol (DBAE). The ACGIH has a TLV-TWA of 2 ppm, with a skin notation, for this colorless, combustible liquid, which has a faint, amine-like odor. The proposed PEL was 2 ppm as an 8-hour TWA. NIOSH (Ex. 8-47) concurred with this limit, and this is the limit established by the final rule. The proposed skin notation is not retained in the final rule.
In rats, 2-N-dibutylaminoethanol has a single-dose oral LD(50) of 1.7 g/kg and a corresponding intraperitoneal LD(50) of 0.14 g/kg; these values are approximately analogous to the oral and intraperitoneal LD(50)s for diethanolamine (Hartung and Cornish 1968/Ex. 1-328). The LD(50) for skin absorption in rabbits is 1.68 g/kg (Smyth, Carpenter, Weil, and Pozzani 1954/Ex. 1-440). In male rats, the lowest five-week drinking water dose tolerated without weight loss was 0.13 g/kg/day. Rats that ingested a dose of 0.43 g/kg/day showed elevated kidney-to-body-weight ratios but no histologic changes at autopsy (Cornish, Dambrauskas, and Beatty 1969/Ex. 1-411). In inhalation studies of rats, 6-hour exposures at 70 ppm for five days killed one rat; the surviving rats showed a 57-percent average body weight loss, as well as a doubling of kidney-to-body-weight ratios, a tenfold increase in serum bilirubin, a slight increase in clotting time,and an elevated hematocrit. Inhalation of 33 ppm for one week caused a 3-percent body weight loss and a slight increase in clotting time, but significant changes in the other variables observed. Twenty-seven weeks of exposure to 22 ppm resulted in no differences between exposed rats and controls in the variables measured (Cornish, Dambrauskas, and Beatty 1969/Ex. 1-411). 2-N-dibutylaminoethanol is a more potent inhibitor of acetylcholinesterase in vitro than is diethylamine (DEA) (Hartung and Cornish 1968/Ex. 1-328). NIOSH was the only commenter to the rulemaking record for DBAE.
In the final rule, OSHA is establishing an 8-hour TWA PEL of 2 ppm for 2-N-dibutylaminoethanol. The Agency concludes that this limit will protect workers from the significant risk of metabolic effects associated with inhalation exposure at the levels permitted in the absence of any OSHA limit. OSHA has determined that this substance does not present a significant risk of systemic toxicity via percutaneous absorption (2-N-dibutylaminoethanol's dermal LD(50) in rabbits is 1.68 g/kg) and therefore, that no skin notation is required. Accordingly, the skin notation proposed for DBAE is not retained in the final rule.