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Cyanide

Overview
 
CAS Number: 74-90-8
Synonyms: Hydrocyanic acid, Hydrogen cyanide, Prussic acid
Contaminant Type: Chemical

Cyanide refers to the –CΞN anion radical (CN-). Cyanide compounds can be inorganic or organic. Inorganic compounds may be simple (e.g., HCN, KCN) or complex (e.g., Cu[CN]2-). [1368] Free cyanide is defined as the sum of the cyanide present as either hydrogen cyanide (HCN) or CN-. [1368] Cyanide in this database focuses on free cyanide, as it is the most toxic form.

Cyanide naturally occurs in many foods. For example, hydrogen cyanide is released from glycoside by hydrolysis catalyzed by various enzymes in at least 2000 plants. [1356] Cyanide is widely used in industry and five processes account for most of cyanide wastes causing stream pollution, including metal plating, case hardening of steel, neutralizing of acid “pickle scum”, refining of gold and silver ores, and scrubbing of stack gases from blast and producer gas furnaces. [1364] Roughly 5 billion pounds of common cyanides were produced each year in the late 1980s and early 1990s. [1320]

USEPA established a maximum contaminant level (MCL) of 0.2 mg/L and a maximum contaminant level goal (MCLG) of 0.2 mg/L as free cyanide. [1320] Best Available Technologies for control of cyanide are: oxidation by chlorine, ion exchange and reverse osmosis. [1320] 

Cyanide is toxic and the lethal oral doses of cyanide compounds generally range from 50 to 200 mg CN (0.7 to 2.9 mg/Kg). [1322] Short-term exposure to cyanide above the MCL can cause rapid breathing, tremors and other neurological effects. [1320] Long-term exposure (e.g., lifetime) at levels above the MCL can cause weight loss, thyroid effects and nerve damage. [1320] At present, no adequate evidence that cyanide compounds have the potential to cause cancer from lifetime exposure in drinking water. [1321]

Cyanide can enter surface water through releases from industries using cyanides (e.g., metal finishing industries, iron and steel mills), runoff from disposal of cyanide wastes in landfills, pesticides and the use of cyanide-containing road salts. [1357] Cyanide is usually found at very low concentrations in drinking water sources. [1356] According to USEPA STORNET database, the mean cyanide concentration in most surface waters in the U.S. is less than 3.5 µg/L. [1356] In 1978, a USEPA survey showed that approximately 7% of drinking water sources had cyanide at levels greater than 10 µg/L. [1356]

Soluble cyanide compounds (e.g. HCN, KCN) are mobile in soils and have low adsorption to soils with high pH, high carbonate and low clay content. [1321] Cyanide may leach to groundwater. [1320] Under typical conditions in natural waters (pH less than 9.2), most free cyanide is expected to convert to hydrogen cyanide that is highly volatile. [1321] Thus, volatilization from water surfaces is expected to be an important fate process. Cyanide is not likely to accumulate in aquatic life. [1320]

Date of Literature Search: August 2009



1320 USEPA; 2009; Consumer Factsheet on: Cyanide; http://www.epa.gov/OGWDW/contaminants/dw_contamfs/cyanide.html; As posted on August 19, 2009. USEPA Office of Ground Water and Drinking Water, Washington, DC.
1321 USEPA; 2009; Technical Factsheet on: Cyanide; http://www.epa.gov/ogwdw/pdfs/factsheets/ioc/tech/cyanide.pdf; As posted on August 19, 2009. USEPA Office of Ground Water and Drinking Water, Washington, DC.
1322 USEPA; 1985; Health Effects Criteria Document for Cyanide; Health Effects Criteria Document for Cyanide; Available: Canadian Federal-Provincial-Territorial Committee on Drinking Water. Cyanide. <http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/cyanide-cyanure/index-eng.php> [cited August 19, 2009]
1356 WHO; 2007; Cyanide in Drinking-Water, Background Document for Development of WHO Guidelines for Drinking-water Quality; Cyanide in Drinking-Water, Background Document for Development of WHO Guidelines for Drinking-water Quality; WHO/SDE/WSH/07.01/2. pp 1-5 and 10-12. World Health Organization, Geneva, Switzerland.
1357 U.S. Department of the Interior, Bureau of Reclamation; 2001; Cyanide Fact Sheet; Cyanide Fact Sheet; Bureau of Reclamation, Technical Service Center, Water Treatment Engineering and Research Group, D-8230, Denver, CO.
1364 White, G.C. (Ed.); 1999; Chlorination of Wastwater; Handbook of Chlorination and Alternative Disinfectants (4th Ed.); Chapter 7, pp. 601-606. White, G.C. (Ed.) John Wiley & Sons, New York.
1368 Canadian Federal-Provincial-Territorial Committee on Drinking Water; 1991; Cyanide; Guidelines for Canadian Drinking Water Quality - Technical Documents; pp. 1-4



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