study in which only mild effects were induced; (4) rats exposed at 50 ppm for 6 h/d, 5 d/wk for 90 d (Toxigenics 1984) exhibited mild rhinitis. This level is already 2 times that of the AEGL-3 value for death. Thus, the total uncertainty factor is 10.

Modifying factor: Not applicable

Animal to human dosimetric adjustment: Insufficient data

Time scaling: Cn×t=k where n=1, based on regression analysis of rat and mouse mortality data (1 min to 100 min) reported by ten Berge et al. (1986). Reported 1-h data point was used to derive AEGL-3 values. AEGL-3 values for 10-min, 30-min, and 4-h were based on extrapolation from the 1-h value. The 4-h value was adopted as the 8-h value.

Data quality and research needs: Study is considered appropriate for AEGL-3 derivation because exposures are over a wide range of HCl concentrations and utilize a sufficient number of animals. Data were insufficient to derive a no-effect level for death. One-third of the LC50 has been utilized previously for chemicals with steep concentration-response curves. Also, in the key study, no deaths were observed in rats exposed at 1,813 ppm.

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