OSHA previously had no limit for n-butyl lactate but proposed a 5-ppm 8-hour TWA limit, based on the ACGIH recommendation. NIOSH (Ex. 8-47, Table N1) concurred with the proposed 5-ppm TWA limit, and this limit is established in the final rule. Butyl lactate is a colorless liquid ester of lactic acid.
In humans, prolonged exposures to n-butyl lactate at approximately 7 ppm, with brief peak excursions to 11 ppm, caused headache, irritation of the pharyngeal and laryngeal mucosa, and coughing in all workers, and occasional nausea, vomiting, and sleepiness in some (Zuidema and Pel 1969, as cited in ACGIH 1986/Ex. 1-3, p. 82). Headache, coughing, and irritation of the pharynx were sometimes related to n-butyl lactate concentrations of 4 ppm; however, no adverse effects were observed at a concentration of 1.4 ppm. Studies employing improved sampling and analytic methods have subsequently concluded that, although the odor of n-butyl lactate is discernible at the 7-ppm level, this concentration does not produce objectionable or injurious effects (Turner 1972/as cited in ACGIH 1986/Ex. 1-3, p. 82).
In the preamble discussion of the proposed limit for this substance, OSHA noted that some studies reported acute adverse effects associated with exposure levels below the proposed 5-ppm TWA limit. This was also pointed out by Dr. Grace Ziem, an independent physician (Ex. 46). Based on the study by Turner (1972, as cited in ACGIH 1986/Ex. 1-3, p. 82), which employed improved sampling and analytical techniques as compared to earlier studies, OSHA judges that promulgation of a 5-ppm 8-hour TWA limit will effectively protect workers from the significant risks of irritation, headache, and nausea caused by exposure to higher concentrations of n-butyl lactate. OSHA considers these adverse effects to represent material impairments of health. Therefore, OSHA is establishing a 5-ppm 8-hour TWA limit for n-butyl lactate.