Safety Assessment of Lactate Esters

Lactate esters have an oral LD50 greater than 2000 mg/kg and the inhalation LC50 is generally above 5000 mg/m3 and they may be potential eye and skin irritants, but not skin sensitizers. No evidence of teratogenicity or maternal toxicity was observed in an inhalation (2-ethylhexyl-l-lactate) or dermal study (ethyl-l-lactate). Subacute inhalation studies have been conducted at concentration up to 600 mg/m3 or higher on four lactate esters (ethyl, n-butyl, isobutyl, and 2-ethylhexyl-l-lactate). Degenerative and regenerative changes in the nasal cavity were noted in all studies. The NOAEL in ethyl, n-butyl, and isobutyl-l-lactate vapor studies was 200 mg/m3. For aerosol exposure, 2-ethylhexyl-l-lactate, the most toxic of the lactates, minimal damage to the nasal epithelium was noted at 75 mg/m3 with vapor being slightly less toxic than the aerosol. Lactates do not appear to cause systemic toxicity, except at very high concentrations (1800 mg/m3 or higher). These systemic effects may be secondary to severe irritation seen at high doses. Sensory irritation tests suggest that a vapor exposure limit of 75 mg/m3 ( approximately 15 ppm) should prevent irritation in humans and therefore an occupational exposure level for vapor of 75 mg/m3 is recommended. However, aerosol exposure should be kept as low as possible. The low vapor pressure of the higher molecular weight esters would tend to keep vapor exposure low and the odor of lactate esters serves as a warning of exposure. These lactate esters are readily biodegradable, suggesting little concern from an environmental point of view.