10 min

30 min

1 h

4 h

8 h

27 ppm

21 ppm

15 ppm

8.6 ppm

6.6 ppm

Reference: The AEGL-3 values for acetone cyanohydrin are set at the same values (on a ppm basis) as the AEGL-3 values for HCN.

NRC (National Research Council). 2002. Hydrogen cyanide. Pp. 211-276 in Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol. 2. National Academy Press, Washington, DC.

Test Species/Strain/Sex/Number: Not applicable.

Exposure Route/Concentrations/Durations: Not applicable.

Effects: Not applicable.

End Point/Concentration/Rationale: The derivation of AEGL-3 values was based upon the facts that acetone cyanohydrin decomposes spontaneously to HCN and acetone and that the systemic toxicity of acetone cyanohydrin is due to free cyanide. Once absorbed, a dose of acetone cyanohydrin behaves in a manner identical to that of its molar equivalent in absorbed free cyanide. It is appropriate to apply the AEGL-3 values (on a ppm basis) derived for HCN (NRC 2002) to acetone cyanohydrin.

Uncertainty Factors/Rationale: Not applicable.

Modifying Factor: Not applicable.

Animal to Human Dosimetric Adjustment: Not applicable.

Time Scaling: Not applicable.

Data Quality and Support for the AEGLs: Support comes from the close similarity of acetone cyanohydrin and HCN regarding death in rats: Blank (1983) reported that 3 of 10 rats died after the first exposure to HCN at 68 ppm, but the subsequent two exposures on the following days caused no additional deaths. This finding closely resembles that of Monsanto (1986a) reporting death of 3 of 20 animals after the first exposure to acetone cyanohydrin at 60 ppm (the actual exposure concentration on the first day might have been slightly higher than the average 59.6 ppm), and no additional deaths were found in the 19 subsequent exposures.

aAcetone cyanohydrin decomposes spontaneously in the presence of water to yield HCN and acetone. Therefore, both acetone cyanohydrin and HCN concentrations should be considered.

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