adminWhat is cyanide?
Cyanide is a highly toxic element that is found both naturally and as an introduced contaminant in the environment. Cyanides are naturally occurring substances found in a number of foods and plants and produced by certain bacteria, fungi, and algae. It is present in a number of compounds such as hydrogen cyanide, sodium cyanide, and potassium cyanide.
In Zimbabwe, sodium cyanide is commonly used by artisanal/small scale miners in gold processing.
Main sources of cyanide contamination. Cyanide is used in a number of industries and is found at low levels in air from car exhausts.
The major uses of cyanide are as an intermediate in the production of a number of chemicals and as an insecticide for fumigating enclosed spaces.
Hydrogen cyanide has been used in gas chamber executions. Two most important uses of other cyanide compounds are in electroplating and metal treatment, including gold processing.
Effects of cyanide on the Environment
Cyanide and other dangerous chemicals, such as mercury, are commonly used in artisanal gold mining.
Since gold mines are almost always set up near rivers, often excess chemicals are distributed directly into waterways, thus polluting water sources.
Once it becomes imbedded in soil or water, cyanide is extremely toxic to humans. Artisanal gold mining also presents several environmental challenges due to the inherent digging of soil and rinsing involved in artisanal mining.
Siltation, erosion, and soil degradation can be issues in rivers used for mining. Rivers are also commonly diverted as a way to access mineral rich riverbeds.
The digging of mines can also spread harmful materials, such as lead, that are located within the soil.
The conservation of forests is also a great concern as many artisanal mining operations take place in and around forests that are home to vast amounts of biodiversity, artisanal mining operations often cut down trees to clear space for their camps.
On human beings
Cyanide is extremely toxic to humans; long-term inhalation of cyanide affects the central nervous system.
Short-term inhalation exposure to 100 milligrams per cubic meter (mg/m3) or more of hydrogen cyanide causes death in humans.
Severe exposure to lower concentrations (6 to 49mg/m3) of hydrogen cyanide causes a variety of effects in humans, such as weakness, headache, nausea, increased rate of respiration, and eye and skin irritation.
Continuous exposure to cyanide in humans via inhalation results in effects such as headaches, dizziness, numbness, tremor, and loss of visual sharpness.
Other effects include cardiovascular and respiratory effects, an enlarged thyroid gland, and irritation to the eyes and skin.
On animals
Animal studies have reported effects on the nervous, cardiovascular, and respiratory systems.
In high concentrations, cyanide is toxic to aquatic life, especially fish which are one thousand times more sensitive to cyanide than humans.
Zimbabwe recorded the worst ecological disaster last year which resulted in the death of over 100 elephants at Hwange National Park due to cyanide poisoning. Animal studies have suggested that oral exposure to cassava (a cyanide-containing vegetable) may be associated with malformations in the fetus and low fetal body weights.
Legal framework for the use of cyanide
Many countries, including Zimbabwe recommend that mines that use cyanide do so in a manner consistent with the International Cyanide Management Code, which involves minimising the amount of cyanide used; designing measures to protect surface and groundwater; designing and operating systems that reduce cyanide levels in effluent; and preventing spills.
The Environmental Management Act Cap (20:27) as read with Statutory Instrument 12 of 2007, Hazardous Substances, Pesticides and Toxic Substances Regulations state that, any person who imports, transports, stores or sells any hazardous substance must have a license for each purpose.
Cyanide is a hazardous substance, and legislation requires it to be transported, handled, and disposed of by fully trained personnel in certified storage containers. Its disposal and discharge into the environment at mine sites is regulated through the use of permits and licences.
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