Technical Factsheet on: CYANIDE

List of Contaminants

As part of the Drinking Water and Health pages, this fact sheet is part of a larger publication:
National Primary Drinking Water Regulations

Drinking Water Standards

MCLG: 0.2 mg/l
MCL: 0.2 mg/l
HAL(child): 1- to 10-day: 0.2 mg/L; Longer-term: 0.2 mg/L

Health Effects Summary

Acute: EPA has found cyanide compounds to potentially cause the following health effects from acute exposures at levels above the MCL: rapid breathing, tremors and other neurological effects.

Short-term exposures in drinking water considered "safe" for a 10-kg (22 lb.) child consuming one liter of water per day: upto a 7-year exposure to 0.2 mg/L.

Chronic: Cyanide compounds have the potential to cause the following chronic health effects from long-term exposures at levels above the MCL: weight loss, thyroid effects, nerve damage.

Cancer: There is inadequate evidence to state whether or not cyanide compounds have the potential to cause cancer from lifetime exposures in drinking water.

Usage Patterns

The most commonly used form, hydrogen cyanide, is mainly used in manufacturing other cyanides, particularly adiponitrile which is used in nylon, and acrylonitrile - used in acrylic/modacrylic fibers and resins. Other cyanides such as dichlobenil, bromoxynil and bantrol, are used as herbicides. Tabun is used as a chemical warfare agent. Potassium cyanide is used for silver plating and for dyes and specialty products.

Available production data on cyanides: hydrogen cyanide, 1 billion lbs. in 1987; acrylonitrile-2.5 billion lbs. 1993; adiponitrile-1.4 billion lbs. in 1991; bromoxynil-2.6 million lbs in 1990; acetonitrile-35 million lb. in 1989.

Release Patterns

The major sources of cyanide releases to water are reported to be discharges from metal finishing industries, iron and steel mills, and organic chemical industries. Releases to soil appear to be primarily from disposal of cyanide wastes in landfills and the use of cyanide-containing road salts. Cyanide released to air from car exhaust is expected to exist almost entirely as hydrogen cyanide gas.

Some foods may also naturally contain cyanides, including lima beans and almonds.

Chlorination treatment of some wastewaters can produce chloroacetonitriles as a by-product. Cyanide has been found in drinking water at levels on the order of a few parts per billion.

From 1987 to 1993, according to the Toxics Release Inventory cyanide compound releases to land and water totalled about 1.5 million lbs., of which about 65 percent was to water. These releases were primarily from steel mills and metal heat treating industries. The largest releases occurred in California and Pennsylvania.

Environmental Fate

Nitriles are generally highly volatile and biodegradable when released to water, and are not expected to bioconcentrate in aquatic organisms. Nitriles have the potential to leach to ground water as they do not adsorb to soil. They tend to be resistant to hydrolysis in soil or water. Cyanide-containing herbicides have more moderate potential for leaching, but again are readily biodegraded so they are not expected to bioconcentrate.

Soluble cyanide compounds such as hydrogen and potassium cyanide have low adsorption to soils with high pH, high carbonate and low clay content. However, at pH less than 9.2, most free cyanide is expected to convert to hydrogen cyanide which is highly volatile. Soluble cyanides are not expected to bioconcentrate.

Insoluble cyanide compounds such as the copper and silver salts may adsorb to soils and sediments, and generally have the potential to bioconcentrate. Insoluble forms do not biodegrade to hydrogen cyanide.

Tabun is rapidly hydrolyzed in soil and water, and so is not expected to leach or bioconcentrate.

Chemical/Physical Properties

CAS Number: Hydrogen cyanide- 74-90-8

Color/ Form/Odor: Cyanide is a carbon-nitrogen chemical unit which may be combined with a variety of organic and inorganic components. The most common is hydrogen cyanide, a colorless, flammable liquid or gas.

Soil sorption coefficient: Kocs of 1 to 70 for most soluble forms, with the nitriles having highest mobility in soils. Insoluble forms are expected to adsorb to sediments.

Cyanide-containing compounds:

Organics: Nitriles like Acetonitrile, butanenitrile, etc; bromoxynil, cyanocobalamin, cyanogens, cyanohydrins, tabun

Inorganics: combined with hydrogen, calcium, barium, sodium, zinc, nickel, mercury, potassium, copper, silver

Bioconcentration Factor: BCFs of <1 to 50 for most soluble forms, which are not expected to bioconcentrate in aquatic organisms. Insoluble forms may bioconcentrate.

Solubilities:

nitriles low to moderate
cyanohydrin highly soluble
cyanogens moderate to high
tabun soluble
other organics slightly soluble
Hydrogen soluble
sodium 48% at 10 deg C
potassium 50% in cold water
mercuric 10% at 14 deg C
barium 80% at 14 deg C
calcium soluble
copper insoluble
nickel insoluble
silver insoluble
zinc insoluble

Other Regulatory Information

Monitoring:

-- For Ground Water Sources:

Initial Frequency-1 sample once every 3 years

Repeat Frequency-If no detections for 3 rounds, once every 9 years

-- For Surface Water Sources:

Initial Frequency-1 sample annually

Repeat Frequency-If no detections for 3 rounds, once every 9 years

-- Triggers - If detect at > 0.2 mg/L, sample quarterly.

Analysis

*- measure "free" or amenable cyanide; other methods screen for "total" cyanide.

Treatment/Best Available Technologies: Ion Exchange, Reverse Osmosis, Chlorine

Toxic Release Inventory - Releases to Water and Land, 1987 to 1993 (in pounds):

For Additional Information:

EPA can provide further regulatory and other general information:
EPA Safe Drinking Water Hotline - 800/426-4791
Other sources of toxicological and environmental fate data include:
Toxic Substance Control Act Information Line - 202/554-1404
Toxics Release Inventory, National Library of Medicine - 301/496-6531
Agency for Toxic Substances and Disease Registry - 404/639-6000

List of Contaminants

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