BMC01: 170 ppm for males and females; 223 ppm for males; 394 ppm for females
BMLC05 144 ppm for males and females; 131 ppm for males; 258 ppm for females
End point/Concentration/Rationale: Threshold for death; BMCL05 for male rats of 131 ppm
Uncertainty factors/Rationale:
Total uncertainty factor: 10
Interspecies: 3, available information suggests that the primary effects of chloroacetone via inhalation are due to direct-acting irritation; this type of port-ofentry effect does not exhibit toxicokinetic variability and, thus, is not expected to vary greatly between species. Factor is also supported by data suggesting little species variability in lethality from oral and dermal exposure to chloroacetone (rat oral LD50 values: 100-141 mg/kg; mouse oral LD50 values: 127-141 mg/kg; rabbit dermal LD50 = 141 mg/kg), and the 1-h LC50 of 500 ppm for male and female rats is approximately a dose of 114 mg/kg, which corresponds to the oral LD50 values (assuming 100% retention, 245 mL minute volume, and a rat body weight of 250 g).
Intraspecies: 3, available information suggests that the primary effects of chloroacetone via inhalation are due to direct-acting irritation; this type of port-ofentry effect does not exhibit toxicokinetic variability and, thus, is not expected to vary greatly among individuals. A factor of 3 is also considered sufficient because the point-of-departure was from more sensitive male rats.
Modifying factor: Not applicable
Animal-to-human dosimetric adjustment: Not applicable
Time scaling: Cn × t = k, where an n of 3 was applied to extrapolate to the 10- and 30-min durations and an n of 1 was applied to extrapolate to the 4- and 8-h durations (NRC 2001).


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