The New Straits Times, February 12, 1996
Q: I read a statement recently which sated that if a person swallows "between one and 300 milligrammes per kilogramme of body weight of cyanide, he may die." Can you please clarify how dangerous is cyanide?
A: Cyanide is an extremely dangerous chemical substance and all exposures are treated as potentially lethal. In the body, it is capable of blocking the use of oxygen resulting in fatal respiratory depression.
Depending on the amount exposed, victims may develop headache, nausea, dyspnea (breathing difficulty) and confusion, while others may even progress to seizures, coma and cardiovascular collapse. In some cases, a brief delay may occur if the cyanide is ingested as a salt, especially if there is food in the stomach.
Cyanide can be found in a variety of sources (see below). It can also exist in many forms, notably as salts such as sodium or potassium cyanide, and as hydrogen cyanide gas. The gas is easily generated when acid is mixed with the cyanide salts.
The toxicity level varies with the chemical forms. For example, in the salt form, ingesting as little as 3mg has been shown to be fatal.
Similarly, exposure to hydrogen cyanide gas at levels as low as 130 ppm (part per million is fatal in about an hour. The Occupational Safety and Health permissible exposure limit (PEL) for the gas is 10ppm as an eight-hour time-weighted average, that is the concentration in air to which an individual may be exposed repeatedly day after day for an eight-hour workday and 40-hour workweek without adverse effects.
Types of cyanide sources
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Gaseous: Cyanide gas from fumigation of insects and rodents; cigarette smoking; production of combustion of petrochemicals; products of combustion in fires, especially involving plastics, wool, silk, synthetic rubber, polyurethane and asphalt.
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Liquid and solid form: Cyanide salts and solutions containing these salts. By-products of industries such as petroleum-refining, ore extraction, electroplating, metal heat treating.
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Medicines: There are medicines that can release cyanide. Some examples include:
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Nitroprussid used in the management of hypertensive emergencies.
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Laetrile contains amygladin that is converted to cyanide in the GI tract. One example is succinonitrile, which is an antidepressant.
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Nitrile that liberates cyanide when metabolised in vivo.
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Plants:
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Prunus species - Peach, plum apricot, bitter almond. Amygladin is present in the leaves, flowers barks and seeds.
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Sorghum species - Johnson grass, sorghum, sudan grass, arrow grass.
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Linum species - Flax, yellow pine fax.
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Pear, apple, crabapple seeds, bamboo, cassava (tapioca), linseed.
