Agent Name


Alternative Name


Major Category

Toxic Gases & Vapors


CLASSES; Hydrogen cyanide; Sodium cyanide; Potassium cyanide; Calcium cyanide; Ammonium cyanide; Silver cyanide; Barium cyanide; Gold cyanide; Cadmium cyanide; Zinc cyanide; Mercury II cyanide; Cuprous cyanide; Tetrabutylammonium cyanide; Potassium silver cyanide; Potassium gold cyanide; Lithium cyanide; Copper II cyanide; Copper I potassium cyanide; Cobaltous cyanide; Mercuric potassium cyanide; Nickel potassium cyanide; Nickel II cyanide; Mercury II oxycyanide;




Varies; See specific cyanide salt;


Used in electroplating, silver and gold extraction, metal cleaning, metal nitriding, ship fumigating, mining processes, cement stabilizing, photo developing, and organic synthesis; Used in the past to fumigate fruit trees, railroad cars, ships, warehouses, rabbit and rat burrows, and termite nests; In tropical countries where the potato-like tubers of the cassava plant are grown, cyanide poisonings due to ingestion of the cassava root have been reported. [ATSDR ToxProfiles] In the past, occupational cyanide poisoning was most common in metal extraction, electroplating, metal hardening, and fumigation; [Sullivan, p. 706] The cyanides of mercury, lead, cobalt, and nickel do not have any major industrial importance." [Ullmann]


A fatal inhalation dose of hydrogen cyanide is 600 to 700 ppm for 5 minutes or 200 ppm for 30 minutes. In victims overcome by smoke inhalation, hypoxia from carbon monoxide is initially indistinguishable from that caused by cyanide. Smokers have elevated whole blood cyanide levels up to 0.4 ug/ml. In poisoning cases, victims are agitated at levels above 1.0 ug/ml and comatose at levels above 2.5 ug/ml. Acrylonitrile, acetonitrile, and other aliphatic nitriles can cause cyanide poisoning after absorption and hepatic transformation. [ATSDR Case Studies # 15] "Symptoms of cyanide toxicity can occur within seconds of inhalation of hydrogen cyanide or within minutes of ingestion of cyanide salts. Onset may be delayed up to 12 h after ingestion of cyanogenic glycosides, nitriles, or thiocyanates." [INCHEM: CICAD 61] Cyanide is detoxified in the body when it is combined with sulfur to form thiocyanate. [Ford, p. 705] Urine thiocyanate levels are <0.11 mg/24h without occupational exposure. The no-adverse-effect-level is 6.5 mg/24h. Smokers have higher levels. [LaDou, 4th edition, p. 633] In nitroprusside poisoning cases, the half-life of thiocyanate is 2.7 days (normal renal function). [Ford, p. 410] Thiocyanate levels correlate with thiocyanate toxicity, not with degree of cyanide poisoning. Thiocyanate toxicity occurs when thiocyanate levels exceed 100 mg/L. [Haddad, p. 985] Chronic exposure to cyanide causes tobacco amblyopia (from cigarette smoking) and tropical ataxic neuropathy (from eating improperly processed cassava). Both conditions are associated with low B12 levels. Thiocyanate can competitively inhibit the entry of iodide into the thyroid gland and cause hypothyroidism and goiters. [Goldfrank, p. 1680] Handle all cyanide compounds with care. HCN may be released from relatively stable compounds like ferro- and ferricyanides in the presence of strong acids. Even weak acids can cause a slow release of cyanide. [Ullmann] Workers exposed to HCN for seven years at 4.2 to 12.4 ppm in breathing zone air had increased headache, weakness, and thyroid gland enlargement. [ACGIH: HCN] See "Hydrogen cyanide." See "NITRILES."

Exposure Assessment
Ceiling (ACGIH)

5 mg/m3, as CN(calcium,hydrogen,sodium,and potassium cyanide)


5 mg/m3,as CN(calcium,sodium,and potassium cyanide), 11 mg/m3(hydrogen cyanide)


2 mg/m3,as CN,inhalable fraction(calcium cyanide), 2.1 mg/m3(hydrogen cyanide), 5 mg/kg, as CN, inhalable fraction(potassium cyanide), 3.8 mg/m3, as CN, inhalable fraction(sodium cyanide)


25 mg/m3, as CN(sodium and potassium cyanide), 50 ppm(hydrogen cyanide)

Excerpts from Documentation for IDLHs

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]. . . . 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.]

Half Life

Whole body: 19 hours; [TDR, p. 422]

Reference Link

ATSDR - ToxFAQs - Cyanide

Adverse Effects
Other Poison

Chemical Asphyxiant

Links to Other NLM Databases
Toxicity Information


Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure:


Activities with risk of exposure: