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Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 2
Zwart, A. et al. 1990. Determination of concentration-time-mortality relationships to replace LC50 values. Inhalation Toxicol. 2:105–117.
Test species/Strain/Sex/Number: Wistar rats/5 males and 5 females
Exposure route/Concentrations/Durations: Rats/Inhalation: 12, 15, 16, 17, or 24 ppm for 30 min (the highest concentration causing no mortality in the rat after a 30-min exposure of 15 ppm was determinant for AEGL-3)
End point/Concentration/Rationale: The highest concentration causing no mortality in the rat after a 30-min exposure 30-min experimental no-effect-level for death (15 ppm) was used as a threshold for death in rats for the 30-min, 1-, 4-, and 8-h values. The highest concentration causing no mortality in the rat after a 10-min exposure (36 ppm) was utilized for the 10-min value.
Total uncertainty factor: 10
Interspecies: 3—little species variability is observed with both lethal and nonlethal end points in many studies after exposure to phosgene
Intraspecies: 3—due to the steep concentration-response curve and effects appear to be due to irritation and binding to macromolecules are not expected to differ greatly among individuals .
Modifying factor: Not applicable
Animal to human dosimetric adjustment: Insufficient data
Time scaling: Cn×t=k where n=1. Haber’s Law (C×t=k) has been shown to be valid for phosgene within certain limits (EPA 1986). Haber’s Law was originally derived from phosgene data (Haber 1924). Reported 30-min data point used to determine the 30-min AEGL value. AEGL-3 values for 1-, 4-, and 8-h were based on extrapolation from the 30 min value. The 10-min value was based on a reported 10-min data point.
Data adequacy: The AEGL-3 values are based on a well-conducted study in rats and the database is rich.