agent, specialty solvent, and heat transfer medium. It is a volatile liquid with a slight ethereal odor. No information on production was located.

Except for a single monitoring study conducted by 3M Company and reported by AIHA (1999) in which exposures were noted to be below 50 ppm, no information was located on human exposure. Animal data using the rat as the model addressed anesthetic properties, acute oral, dermal, and inhalation toxicity; neurotoxicity, and genotoxicity. A study with the beagle dog addressed cardiac sensitization. HFE-7100 is of low acute oral and inhalation toxicity. It does not have anesthetic properties, is not neurotoxic or genotoxic, and is not a cardiac sensitizer. In developmental studies with the rat, the fetal effect of an increase in supernumerary ribs was observed only in conjunction with slight maternal toxicity. No information useful for time scaling across the AEGL exposure durations was available.

The AEGL-1 value is based on a subchronic study with the rat (Coombs et al. 1996a). In this study, groups of 20 male and female rats were exposed to concentrations up to 15,159 ppm for 6 h/day, 5 days/week for 13 weeks. This concentration was not neurotoxic. Reversible increases in weight of the liver, kidney, and spleen were observed, and these were considered a natural adaptation to chemical treatment. An interspecies uncertainty factor of 1 was applied because the concentration was basically a NOAEL, the exposures were repeated, and uptake is greater in the rodent than in primates (based on the higher respiratory rate and cardiac output of rodents compared with primates). Studies addressing neurotoxicity and cardiac sensitization and studies with pregnant rats failed to identify significant toxicological end points. Therefore, an intraspecies uncertainty factor of 3 was applied. A modifying factor of 2 was applied because human data are very limited and because some of the key studies used limited numbers of animals. The resultant value is 2,500 ppm. Time scaling may not be relevant for halogenated hydrocarbons as blood concentrations of these chemicals rapidly reach equilibrium and do not greatly increase as exposure duration is increased. The presence of the perfluoro group of HFE-7100 limits its solubility in biological fluids. Furthermore, the repeated number of the exposures in the key study supports the use of the same value across all time points. Therefore, the 2,500 ppm concentration is applicable for all AEGL-1 time points.

The AEGL-2 value is based on a 5-min no-adverse-effect exposure prior to a cardiac sensitization test with beagles (Kenny et al. 1996) and is supported by a 4-week repeat exposure study with the rat (Coombs et

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