ACUTE INHALATION TOXICITY STUDIES OF n -BUTYL ACETATE

Abstract

Aerosolized n -butyl acetate (n -BA) was reported to have an LC50 value of approximately 160 ppm in a study conducted by 3M at NOTOX. Six follow-up studies at three laboratories (BASF, BRRC, NOTOX) were conducted in an attempt to reproduce this value. Two other LC50 values for aerosolized n -BA were generated (390 and 1096 ppm). However, 4 studies did not result in any lethalities from aerosolized n -BA at concentrations of 415.5, 798, 1033.5, 1411, 1442, 1517, 1575, 4429.2, 5082, and 9312 ppm. Thus, no consistent LC50 value for aerosolized n -BA was determined. Statically saturated and dynamically evaporated n -BA studies were conducted to investigate whether the aerosolization process of n -BA had an impact on the toxicity. No deaths were observed from animals exposed to statically generated n -BA vapor at a concentration of 6867 ppm and dynamically evaporated n -BA vapor at concentrations of 2027, 3013, 4429.2, and 6335 ppm. Exposures of aerosolized n-BA from old and current productions of n -BA were monitored for small particles (minimum size 0.01 m) to determine any effect the presence of these particles might have on toxicity. No differences in the particle concentrations between the old and current productions of n -BA were noted, and particle size/concentration appeared unrelated to toxicity. Two other parameters were investigated: Relative humidity was elevated (100%), and different atomizers were used to investigate the particle effect on the toxicity of aerosolized n -BA. No lethalities were observed using the different productions of n -BA, elevated relative humidity, different atomizers, or different air sources for the aerosolization of n -BA. Findings in the 3M/NOTOX study not observed in any other studies were (1) low chamber relative humidity, (2) brief times to death of the animals, and (3) histopathological finding of vesicular emphysema. Occupational exposure to n BA does not result from the usage of aerosolized pure n -BA, but rather mixtures con- taining n -BA in which n -BA is released as a vapor. Aerosolized n -BA was not found at the workers' breathing zone in a furniture paint spray study. The animal vapor data suggest only low to moderate toxicity at high concentrations. Thus, this anomaly of low and variable LC50 values of aerosolized pure n -BA does not appear to be of great concern in occupational settings. Consequently, the American Conference of Governmental Industrial Hygienists (ACGIH) in 1996 maintained a threshold limit value (TLV) value of 150 ppm.