Cyanide | ToxFAQs™ | ATSDR (2024)

ToxFAQs™ for Cyanide for Cyanide

Spanish: Cianuro

CAS#: 74-90-8; 143-33-9; 151-50-8; 592-01-8; 544-92-3; 506-61-6; 460-19-5; 506-77-4

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This fact sheet answers the most frequently asked health questions about cyanide. For more information, you may call the ATSDR Information Center at 1-888-422-8737. This fact sheet is one in a series of summaries about hazardous substances and their health effects. This information is important because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present.

Highlights

Exposure to high levels of cyanide harms the brain and heart, and may cause coma and death. Exposure to lower levels may result in breathing difficulties, heart pains, vomiting, blood changes, headaches, andenlargement of the thyroid gland. Cyanide has been found in at least 471 of the 1,662 National Priorities List sites identified by the Environmental ProtectionAgency (EPA).

What is cyanide?

Cyanide is usually found joined with other chemicals to form compounds. Examples of simple cyanide compounds arehydrogen cyanide, sodium cyanide and potassium cyanide.Certain bacteria, fungi, and algae can produce cyanide, andcyanide is found in a number of foods and plants. In certainplant foods, including almonds, millet sprouts, lima beans, soy, spinach, bamboo shoots, and cassava roots (which are a major source of food in tropical countries), cyanides occur naturally as part of sugars or other naturally-occurring compounds. However, the edible parts of plants that are eaten in the United States, including tapioca which is made from cassava roots, contain relatively low amounts of cyanide.

Hydrogen cyanide is a colorless gas with a faint, bitter, almond-likeodor. Sodium cyanide and potassium cyanide are both whitesolids with a bitter, almond-like odor in damp air. Cyanide andhydrogen cyanide are used in electroplating, metallurgy, organicchemicals production, photographic developing, manufactureof plastics, fumigation of ships, and some mining processes.

What happens to cyanide when it enters the environment?

• Cyanide enters air, water, and soil from both natural processesand industrial activities.
• In air, cyanide is mainly found as gaseous hydrogen cyanide;a small amount is present as fine dust particles.
• The half-life (the time needed for half of the material to beremoved) of hydrogen cyanide in the atmosphere is about 1–3 years.
• Most cyanide in surface water will form hydrogen cyanideand evaporate.
• Cyanide in water does not build up in the bodies of fish.
• Cyanides are fairly mobile in soil. Once in soil, cyanide canbe removed through several processes. Some cyanidecompounds in soil can form hydrogen cyanide and evaporate,whereas some cyanide compounds will be transformed into otherchemical forms by microorganisms in soil. At the highconcentrations, cyanide becomes toxic to soil microorganisms.Because these microorganisms can no longer change cyanideto other chemical forms, cyanide is able to passes through soilinto underground water.

How might I be exposed to cyanide?

• Breathing air, drinking water, touching soil, or eating foodsthat contain cyanide.
• Smoking cigarettes and breathing smoke-filled air during firesare major sources of cyanide exposure.
• Breathing air near a hazardous waste site containing cyanide.
• Eating foods naturally containing cyanide compounds, suchas tapioca (made from cassava roots), lima beans, and almonds.However, the portions of these plants that are eaten in the UnitedStates contain relatively low amounts of cyanide.

How can cyanide affect my health?

You are not likely to be exposed to large enough amounts ofcyanide in the environment to cause adverse health effects. Theseverity of the harmful effects following cyanide exposure depends in part on the form of cyanide, such as hydrogen cyanidegas or cyanide salts. Exposure to high levels of cyanide for ashort time harms the brain and heart and can even cause comaand death. Workers who inhaled low levels of hydrogen cyanideover a period of years had breathing difficulties, chest pain,vomiting, blood changes, headaches, and enlargement of thethyroid gland.

Some of the first indications of cyanide poisoning are rapid, deepbreathing and shortness of breath, followed by convulsions(seizures) and loss of consciousness. These symptoms can occurrapidly, depending on the amount eaten. The health effects oflarge amounts of cyanide are similar, whether you eat, drink, orbreathe it; cyanide uptake into the body through the skin isslower than these other means of exposure. Skin contact withhydrogen cyanide or cyanide salts can irritate and produce sores.

How likely is cyanide to cause cancer?

There are no reports that cyanide can cause cancer in people oranimals. EPA has determined that cyanide is not classifiable asto its human carcinogenicity.

How can cyanide affect children?

Effects reported in exposed children are like those seen in exposedadults. Children who ate large quantities of apricot pits, whichnaturally contain cyanide as part of complex sugars, had rapidbreathing, low blood pressure, headaches, and coma, and somedied. Cyanide has not been reported to directly cause birthdefects in people. However, among people in the tropics whoeat cassava root, children have been born with thyroid diseasebecause of the mothers' exposure to cyanide and thiocyanateduring pregnancy. Birth defects occurred in rats that ate cassavaroot diets, and harmful effects on the reproductive systemoccurred in rats and mice that drank water containing sodiumcyanide.

How can families reduce the risk of exposure to cyanide?

Families can reduce their exposure to cyanide by not breathingin tobacco smoke, which is the most common source of cyanideexposure for the general population. In the event of a buildingfire, families should evacuate the building immediately, because smoke from burning plastics contains cyanide (and carbonmonoxide). Breathing this smoke can lead to unconsciousnessor death. Cyanide in smoke can arise from the combustion ofcertain plastics (e.g., polyacrylamines, polyacrylics,polyurethane, etc.).

Compounds that release cyanide are naturally present in plants.The amounts are usually low in the edible portion but are higherin cassava. Pits and seeds of common fruits, such as apricots,apples, and peaches, may have substantial amounts of cyanidereleasingchemicals, so people should avoid eating these pitsand seeds to prevent accidental cyanide poisoning.

Is there a medical test to show whether I've been exposed to cyanide?

There are medical tests to measure blood and urine levels ofcyanide; however, small amounts of cyanide are always detectablein blood and urine. Tissue levels of cyanide can be measuredif cyanide poisoning is suspected, but cyanide is rapidly clearedfrom the body, so the tests must be done soon after the exposure.An almond-like odor in the breath may alert a physician that aperson was exposed to cyanide.

Has the federal government made recommendations to protect human health?

EPA regulates the levels of cyanide that are allowable in drinkingwater. The highest level of cyanide allowed in drinking water is0.2 parts cyanide per 1 million parts of water (0.2 ppm).The Occupational Safety and Health Administration (OSHA) hasset a limit for hydrogen cyanide and most cyanide salts of 10parts cyanide per 1 million parts of air (10 ppm) in the workplace.

References

Agency for Toxic Substances and Disease Registry (ATSDR). 2006. Toxicological Profile for Cyanide. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.

Where can I get more information?

If you have questions or concerns, please contact your community or state health or environmental quality department or:

For more information, contact:
Agency for Toxic Substances and Disease Registry
Office of Innovation and Analytics, Toxicology Section
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO

ATSDR can also tell you the location of occupational and environmental health clinics. These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances.