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Cyanides (as CN)

May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: Varies

NIOSH REL: 5 mg/m3 (4.7 ppm) 10-minute CEILING

Current OSHA PEL: 5 mg/m3 TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 5 mg/m3 TWA [skin]

Description of Substance: Varies

Original (SCP) IDLH: 50 mg/m3 (as CN)

Basis for original (SCP) IDLH: No useful acute inhalation toxicity data are available on which to base the IDLH for cyanides. For this draft technical standard, therefore, the chosen IDLH is based on an analogy with hydrogen cyanide. According to ACGIH [1971], Patty [1963] reported that hydrogen cyanide at 110 to 135 ppm (120 to 150 mg/m3) might be fatal to man after 0.5 to 1 hour or later, or dangerous to life; 45 to 54 ppm (50 to 60 mg/m3) could be tolerated for 0.5 to 1 hour without immediate or late effects [Flury and Zernik 1931; Dudley et al. 1942].

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD(as CN) Derived value(as CN)
Burrows et al. 1978
Marhold 1972
Smyth et al. 1969
Sterner 1979
15 mg/m3
22 mg/m3
56 mg/m3
30 mg/m3
1.5 mg/m3
2.2 mg/m3
5.6 mg/m3
3.0 mg/m3
Barnes and Eltherington 1973
Gaines 1969
Lorke 1983
Sheehy and Way 1968
14 mg/m3
28 mg/m3
14 mg/m3
24 mg/m3
1.4 mg/m3
2.8 mg/m3
1.4 mg/m3
2.4 mg/m3
NRC 1953 i.p. —– 100 141 mg/m3 14 mg/m3


Human data: Absorption of the alkali cyanides in amounts as low as 50 to 100 mg from a single, instantaneous dose may be followed by immediate collapse and cessation of respiration [Clayton and Clayton 1982]. It has been stated that although the fatal oral dose will vary considerably, depending on whether or not food is present in the stomach, it is probably in the order of 1 to 2 mg/kg [Clayton and Clayton]. [Note: An oral dose of 50 to 100 mg or 1 to 2 mg/kg is equivalent to a 70-kg worker being exposed to about 50 mg/m3 (as CN) for 30 minutes, assuming a breathing rate of 50 liters per minute and 100% absorption.]

Revised IDLH: 25 mg/m3 (as CN)Basis for revised IDLH: No inhalation toxicity data are available on which to base an IDLH for hydrogen cyanide. Therefore, the revised IDLH for cyanides is 25 mg/m3 (as CN) based on acute oral toxicity data in humans [Clayton and Clayton 1982].



1. ACGIH [1971]. Hydrogen cyanide. In: Documentation of the Threshold Limit Values for Substances in Workroom Air, 3rd edition. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 130-131.

2. Barnes CD, Eltherington LG [1973]. Drug dosages in laboratory animals: a handbook. Berkeley, CA: University of California Press, p. 209.

3. Burrows GE, Williams CE, Way JL [1978]. Antagonism of cyanide toxicity in sheep. Toxicol Appl Pharmacol 45:359-360 (Abstract of paper for Seventeenth Annual Meeting of the Society of Toxicology, San Francisco, California, March 12-16, 1978).

4. Clayton GD, Clayton, FE eds. [1982]. Cyanides and nitriles. Patty’s industrial hygiene and toxicology. 3rd rev. ed. Vol. 2C. Toxicology. New York, NY: John Wiley & Sons, Inc., pp. 4845-4856.

5. Dudley HC, Sweeney TR, Miller JW [1942]. Toxicology of acrylonitrile (vinyl cyanide). II. Studies of effects of daily inhalation. J Ind Hyg Toxicol 24:255-258.

6. Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany: Verlag von Julius Springer, p. 404 (in German).

7. Gaines TB [1969]. Acute toxicity of pesticides. Toxicol Appl Pharmacol 14(3):515-534.

8. Lorke D [1983]. A new approach to practical acute toxicity testing. Arch Toxicol 54:275-287.

9. Marhold JV [1972]. Sbornik vysledku toxixologiekeho vysetreni latek a pripravku. Prague, Czechoslovakia: Institut Prumyclu, p. 13 (in Czechoslovakian).

10. NRC [1953]. Chemical-Biological Coordination Center: review. Vol. 5. Washington, DC: National Academy of Sciences, National Research Council, p. 27.

11. Patty FA, ed. [1963]. Industrial Hygiene and Toxicology, 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1998.

12. Sheehy M, Way JL [1968]. Effect of oxygen on cyanide intoxication. III. Mithridate. J Pharmacol Exp Ther 161(1):163-168.

13. Smyth HF Jr, Carpenter CP, Weil CS, Pozzani UC, Striegel JA, Nycum JS [1969]. Range-finding toxicity data: list VII. Am Ind Hyg Assoc J 30:470-476.

14. Sterner RT [1979]. Effects of sodium cyanide and diphacinone in coyotes (canis latrans): applications as predacides in livestock toxic collars. Bulletin Environ Contam Toxicol 23:211-217.