effect on the tissues; this type of port-of-entry effect does not exhibit toxicokinetic variability and, thus, is not expected to vary greatly between species or among individuals. The interspecies uncertainty factor of 3 also is 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 (Arts and Zwart 1987) 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). The intraspecies uncertainty factor of 3 also is considered sufficient because data from male rats, which are more sensitive than female rats, were used as the point-of-departure. Thus, the total uncertainty factor is 10. It has been shown that the concentration-exposure time relationship for many irritant and systemically acting vapors and gases may be described by the equation Cn × t = k, where the exponent n ranges from 0.8 to 3.5 (ten Berge et al. 1986). Data were unavailable for an empirical derivation of n for chloroacetone, so default values were applied (NRC 2001). An n of 3 was applied to extrapolate to the 10- and 30-min AEGL durations, and an n of 1 was applied to extrapolate to the 4- and 8-h durations (NRC 2001). The calculated values are presented Table 3-1.
Chloroacetone is a colorless to amber liquid at ambient temperature and pressure. It has a pungent, suffocating odor similar to hydrogen chloride (Sargent et al. 1986). It is toxic by inhalation, ingestion, and dermal contact, and causes immediate lacrimation at low concentrations. Other effects from exposure to chloroacetone include contact burns of the skin and eyes, nausea, bronchospasm, delayed pulmonary edema, and death (HSDB 2011).
TABLE 3-1 Summary of AEGL Values for Cloroacetone
|Classification||10 min||30 min||1 h||4 h||8 h||End Point (Reference)|
|AEGL-1 (nondisabling)||NRa||NRa||NRa||NRa||NRa||Insufficient data|
|AEGL-2 (disabling)||8.0 ppm (30 mg/m3)||5.5 ppm (21 mg/m3)||4.4 ppm (17 mg/m3)||1.1 ppm (4.2 mg/m3)||0.53 ppm (2.0 mg/m3)||One-third of AEGL-3 values|
|AEGL-3 (lethal)||24 ppm (91 mg/m3)||17 ppm (65 mg/m3)||13 ppm (49 mg/m3)||3.3 ppm (13 mg/m3)||1.6 ppm (6.1 mg/m3)||Estimated lethality threshold for male rats (BMD05) (Arts and Zwart 1987)|
aNot recommended. Absence of an AEGL-1 value does not imply that exposure below the AEGL-2 value is without adverse effects.