AEGL-3 VALUES

10 min 30 min 1 h 4 h 8 h
110 mg/m3 110 mg/m3 88 mg/m3 55 mg/m3 28 mg/m3
Key reference: Rusch, G.M., G.M. Hoffman, R.F. McConnell, and W.E. Rinehart. 1986. Inhalation toxicity studies with boron trifluoride. Toxicol. Appl. Pharmacol. 83(1):69-78.
Test species/Strain/Number: Rat, F344, 5 male and 5 female per group
Exposure route/Concentrations/Durations: Inhalation; 0, 1,010, 1,220, 1,320, or 1,540 mg/m3 for 4 h
Effects:
Concentration (mg/m3) Mortality
0 0/10
1,010 3/10
1,220 2/10
1,320 8/10
1,540 9/10
LC50: 1,210 mg/m3
LC01: 736 mg/m3
BMCL05 = 554 mg/m3
End point/Concentration/Rationale: 4-h BMCL05 was chosen as point of departure for AEGL-3 to represent the threshold for lethality.
Uncertainty factors/Rationale:
Total uncertainty factor: 10
Intraspecies: 3, because boron trifluoride is a corrosive irritant and the mechanism of action is not expected to vary greatly among species.
Intraspecies: 3, because the mechanism of irritation is not expected to vary greatly among subpopulations; an uncertainty factor of 3 is also supported by the steep doseresponse curve for lethality (3/10 rats died at 1,010 mg/m3, while 9/10 rats died at 1,540 mg/m3), which indicates there is not much variability in the response within a population.
Modifying factor: Not applicable
Animal-to-human dosimetric adjustment: Not applicable
Time scaling: Extrapolation to different exposure durations was performed using the equation Cn × t = k (ten Berge et al. 1986), where n = 3 for extrapolation to durations of 30-min and 1 h, and n = 1 for extrapolation to 8 h. The 30-min value was adopted as the 10-min value because of the uncertainty with extrapolating from a 4-h exposure to 10 min.
Data adequacy: AEGL-3 values based on a calculated BMCL05 from a study with measured concentrations of boron trifluoride. A limitation of the study was that mortality was observed at all exposure concentrations. Another limiting factor is that other studies addressing mortality after acute exposure did not provide analytic exposure concentrations; therefore, there are no other studies using the same or other species to support the values. Nonetheless, a study by Kasparov and Kiri. (1972) provide some supporting evidence with a 4-h LC50 of 1,180 mg/m3 in rats.


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