4.4 Hydrogen Cyanide
A rapid-acting lethal agent, hydrogen cyanide poisons by preventing individual cells from utilizing oxygen. It was a stabilized form of hydrogen cyanide, referred to as "Zyclon B," that was used by the Nazis to kill millions of Jews in concentration camps during World War Two. Hydrogen cyanide is widely used as a pesticide, rodenticide and a fumigant. In some countries where capital punishment is still permitted, it is also used to kill. More general exposure occurs through tobacco smoke and smoke inhalation from fires.
Although hydrogen cyanide vapour will not easily cross the skin barrier, liquid hydrogen cyanide will penetrate as will an aerosol of the chemical. An exposure of up to 60 milligrams per cubic metre of air (60 mg/m3) may not cause any serious symptoms but at concentrations above 200mg/m3, death occurs in ten minutes. Above 2,500mg/m3, death is likely within one minute.
When inhaled, the gas is rapidly absorbed from the lungs and symptoms of poisoning are equally rapid. Death occurs either through heart failure or failure to breathe. No long term health implications are likely for those exposed to low concentrations. However, at concentrations which are close to lethal, the effects of hydrogen cyanide on the cell’s ability to utilise oxygen is likely to affect brain function.
