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Acute Exposure Guideline Levels for Selected Airborne Chemicals, Volume 5
400 ppm:
4/4
1 h LC50 is 230 ppm (provided in reference)
1 h LC01 could not be calculated
End point/Concentration/Rationale: 127 ppm for 1 h, the highest non-lethal value in the monkey, was considered the threshold for lethality, the defined end point for the AEGL-3.
Uncertainty Factors/Rationale:
Total uncertainty factor: 6
Interspecies: 2—Based on the similarity in respiratory parameters among primates. In addition, effects were similar among species and LC50 values varied by less than a factor of two for the monkey, rat, and mouse (indicating similar species sensitivity).
Intraspecies: 3—The concentration at which extreme irritation and pulmonary damage may lead to lethality should not differ by more than a factor of 3 among the general population.
Modifying Factor: Not applicable.
Animal to Human Dosimetric Adjustment: Insufficient data.
Time Scaling: Cn × t = k where n = 1.3; based on the time-concentration relationship for LC50 values in monkeys, rats, and mice for exposure durations of 13.5-222 min (Horn and Weir 1955; MacEwen and Vernot 1970; Dost et al. 1974).
Data Adequacy: The key study was well conducted and documented. LC50 values from several additional studies were within a factor of two for all tested species. Similar values can be derived using the rat data (MacEwen and Vernot 1970; Dost et al. 1974) and a total uncertainty factor of 10.
