observed. The only long-term effect was increased fluoride deposition in the bone and urine. Therefore, 24 ppm was considered a no-effect level for an 8-h exposure, and was selected as the point of departure. That value was divided by a total uncertainty factor of 30 (3 for interspecies differences and 10 for intraspecies variability). An interspecies uncertainty factor of 3 was selected because lethality values for dogs, rats, and mice differed by less than a factor of 3. An intraspecies uncertainty factor of 10 was considered appropriate because infants are considerably more susceptible to methemoglobinemia than healthy adults. In the absence of time-scaling information, the 6-h value was scaled using the equation Cn × t = k, using the default values of n = 3 and n = 1 to extrapolate to shorter or longer exposure durations, respectively. Because of the uncertainty associated with scaling a 6-h exposure to 10 min, the 10-min AEGL value was set equal to the 30-min AEGL value.

No acute studies were available that addressed relevant AEGL-2 effects. In the absence of appropriate chemical-specific data, AEGL 2 values were set at one-third of the AEGL-3 values (NRC 2001). This approach is supported by the apparent steep-concentration response curve for perchloryl fluoride. Two of two dogs exposed to perchloryl fluoride at 425 ppm survived a 4-h exposure, but one of two dogs was found moribund after a 4-h exposure at a slightly higher concentration of 451 ppm (Green et al. 1960).

AEGL-3 values were based on moderate cyanosis and hyperpnea observed in dogs exposed to perchloryl fluoride at 224 ppm for 4-h. No dogs died at the next highest concentration of 451 ppm, but that concentration is greater than the rat 4-h LC50 of 385 ppm in the same study. A total uncertainty factor of 30 was applied (3 for interspecies differences and 10 for intraspecies variability). An interspecies uncertainty factor of 3 was selected because lethality values among dogs, rats, and mice differed by less than a factor of 3, and lethal values for the rat were considered in selecting the point of departure. An intraspecies uncertainty factor of 10 was considered appropriate because infants are considerably more susceptible to methemoglobinemia than healthy adults. In the absence of time-scaling information, the 4-h value was scaled to the shorter- and longer-exposure durations using the same approach as that for the AEGL-1 values. Because of uncertainty in time scaling from a 4-h exposure to 10 min, the 10-min value was set equal to the 30-min AEGL value.

AEGL values for perchloryl fluoride are presented in the Table 5-1.

1. INTRODUCTION

Perchloryl fluoride is a colorless gas with a characteristic sweet odor. Chemically, it is the acyl fluoride of perchloric acid, and is prepared by electrolysis of a saturated solution of sodium perchlorate in anhydrous hydrofluoric acid. It is a very stable compound. Perchloryl fluoride is used as a fluorinating agent, an oxidant in rocket fuels, and a gaseous dielectric for transformers (Mendiratta et al. 2005). It is a strong oxidizer, and acts as a strong irritant of the



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