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Hydrogen cyanide

hydrogen cyanide

SPRI Emission Reporting Threshold
100 Kg/yr Pollutant Emissions to Air
This sheet is a generic summary, designed to give the reader a basic level of background information about the substance in question. Great care has been taken to represent as effectively and correctly as possible the broad range of (not necessarily consistent) information which is available from a variety of sources. The reader must accept therefore that this sheet has no legal status and cannot be relied upon in any legal proceedings. SEPA disclaims any responsibility or liability whatsoever for errors and omissions in this sheet.
What is it?
Hydrogen cyanide is a colourless gas or liquid with a faint almond smell. It is soluble in water to give a weakly acidic solution known as hydrocyanic or prussic acid. Hydrogen cyanide melts at 14 degrees celsius and boils at 26 degrees celsius. It is very flammable and can be explosive when exposed to air or heat or when stored for long periods of time.
What is it used for?
Hydrogen cyanide is used mainly in the manufacture of organic compounds that produce synthetic fibres and plastics. It is also used in metal processing, as an industrial cleaning agent and as an agricultural fumigant.
Where does it come from?
Most hydrogen cyanide is released into the environment from industrial activities using it. Trace amounts are found in cigarette smoke. Small amounts of hydrogen cyanide are released naturally from some plants or are formed from compounds found in the stones of some soft fruits, nuts and pulses.
How might it affect the environment?
Low levels of hydrogen cyanide (often from natural sources) are found in all parts of the environment and are not thought to cause any significant environmental damage. High concentrations following a spillage are however toxic to aquatic life and micro-organisms in soils. Hydrogen cyanide is not expected to have any significant environmental effects at a global level.
How might exposure to it affect human health?
Exposure to (naturally occurring) low concentrations of hydrogen cyanide is unlikely to damage health. High exposures following accidental releases are however very toxic. Hydrogen cyanide stops the transport of oxygen around the body and may also cause sudden loss of consciousness, weakness, headache, confusion, nausea, vomiting, irritation and eye infections. People with sensitive kidneys, respiratory tract (air passages and lungs), skin or thyroid are more prone to hydrogen cyanide poisoning. Part of the reason why hydrogen cyanide is considered potentially more dangerous is because some individuals are unable to detect it by smell.
What steps are being taken to limit the potential impacts?
In the UK (including Scotland) releases of hydrogen cyanide are controlled through the Pollution Prevention and Control (PPC) regulations; and they are classified as substances hazardous to health. European Directives controlling emissions of hydrogen cyanide include those concerned with pollution of aquatic environments (76/464/EEC); and the treatment of hazardous wastes (91/689/EEC).