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Chemical weapons agents

Although the use of chemical weapons is banned by world treaties, their use or development can have a lasting impact on some areas.

These sites are usually found abroad where chemical warfare has been used, but the Environment Agency monitors land in the UK where the manufacture, production or disposal of chemical weapons has been carried out at any time.

Common chemical weapons agents include:


  • Description. The same chemical that kills bacteria in public water systems can be a weapon in high concentrations. Chlorine was the first chemical weapon used effectively in war -- in World War I. It is green-yellow in colour and smells like bleach.
  • Effects. It is a choking agent that irritates the eyes, nose, and respiratory tract. Symptoms of chlorine poisoning appear as runny nose, coughing, choking, and chest pain. Fluid build-up in the lungs occurs several hours after exposure. Pneumonia can follow.


  • Description. As a gas, cyanide is colourless and has a sharp, pepper-like odour. There are two kinds of cyanide, hydrogen cyanide and cyanogen chloride (cyanogen chloride turns into hydrogen cyanide inside the body).
  • Effects. They are blood agents that interfere with the use of oxygen in the body. But cyanogen chloride has strong irritating and choking effects on the eyes and respiratory tract, unlike hydrogen cyanide. Liquid forms of cyanide will burn skin and eyes. Cyanide acts quickly, but only large amounts are deadly. Cyanide poisoning can be treated with inhaled amyl nitrate, or intravenous sodium nitrite and sodium thiosulfate.


  • Description. As a weapon, liquid Lewisite smells like a geranium and is amber to dark brown in colour. The oily substance causes blisters (a blister agent) but also can be toxic to the lungs and poisonous to the whole body.
  • Effects. When inhaled in high concentrations, it can kill in as little as 10 minutes. The vapour form of Lewisite is just as dangerous, but the chemical is less effective in humid conditions. Lewisite poisoning can be treated with an antidote known as British-Anti-Lewisite, if it is administered early after inhalation.


  • Description. Mustard agents are the most widely known of the blister agents and the most common. They produce injuries that heal much more slowly and are more susceptible to infection than other chemical burns.
  • Effects. Mustard also damages eyes and airways after contact, and the gastrointestinal tract and bone marrow (where immune system cells are produced) after high doses are absorbed. Its effects are delayed, though, because it causes no pain on contact. There is no antidote to mustard poisoning. Victims' eyes should be flushed with water immediately; bleach can decontaminate skin; and oxygen should be given if mustard was inhaled.


  • Description. When it is first dispersed, phosgene looks like a fog, but it becomes colourless as it spreads, although it doesn't last long. It can smell like newly mown hay but with a poisonous, suffocating odour.
  • Effects. As a choking agent, phosgene causes fluid build-up in the lungs -- but not until as many as 48 hours after exposure. Inhalation can lead to irreversible lung damage like emphysema and fibrosis (scarring). Phosgene causes severe damage to nose and throat, and can burn skin and eyes. Victims should be given oxygen and have their eyes flushed with water or saline.

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