400 ppm:





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.

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