10 min 30 min 1 h 4 h 8 h
See belowa See belowa See belowa See belowa See belowa

Key reference: Shugaev, B.B. 1969. Concentrations of hydrocarbons in tissues as a measure of toxicity. Arch. Environ. Health 18(6):878-882.
Test species/Strain/Number: Mice, strain and number not specified.
Exposure route/Concentrations/Durations: Inhalation for 2 h, butane concentrations not specified.
Effects: LC16 = 224,000 ppm; LC50 = 287,000 ppm; LC84 = 363,000 ppm A 2-h LC01 was calculated to be 160,000 ppm.
End point/Concentration/Rationale: Lethal concentration, 1% lethality
Uncertainty factors/Rationale:
Total uncertainty factor: A total uncertainty factor of 3 is considered sufficient because the effects are attributed to butane itself, and no relevant differences in kinetics are assumed. A species with a relatively high susceptibility is used. The concentration-response curve appears to be very steep indicating that a large factor s unnecessary. Further, a larger uncertainty factor would lead to unrealistically low values for AEGL-3, which would be similar to the AEGL-2 values.
Modifying factor: Not applicable
Animal-to-human dosimetric adjustment: Not applicable
Time scaling: A steady state is reached within 30 min, and the effects are considered to be concentration dependent. Therefore, the starting point for the 30-min and the 1-, 4-, and 8-h values were the 2-h steady-state value of 160,000 ppm. For extrapolation from 30 to 10 min, n = 3.
Data adequacy: The results of the key study in mice are comparable with the results from a second study in mice. The 10-min value is supported by human data. Exposure to slowly increasing concentrations of butane up to 50,000 ppm (total exposure duration at least 10 min) and a short exposure (exact duration unknown) at 100,000 ppm on the same day did not result in serious complaints.

a The 10-min AEGL-3 values is 77,000 ppm (180,000 mg/m3), and the AEGL-3 value for 30 min and 1, 4, and 8 h is 53,000 ppm (130,000 mg/m3). All of the AEGL-3 values are greater than the lower explosive limit for butane in air of 19,000 ppm. Therefore, extreme safety considerations against the hazard of explosion must be taken into account.

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