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Chemical weapons: what you need to know

How use of sarin, nerve agents, mustard gas in war came to be recognized as a 'moral obscenity'

Last Updated: Aug. 27, 2013

Syrian wears gas mask. (Reuters)

Syria's government has been accused of using chemical weapons in an attack that killed hundreds in August 2013. These claims are supported by online video and photos showing victims of what experts believe to be nerve gas exposure.

"Let me be clear," U.S. Secretary of State John Kerry said in response, "the indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders, by chemical weapons is a moral obscenity."

Kerry's strong language hints at the world's long and troubled relationship with these chemical agents.

After seeing chemical warfare and the horrific injuries it causes, most countries have reached a consensus: these weapons are too awful for use on other humans.

Read below to learn more about this history, and how these weapons can cause so much suffering.

Timeline: Development and use

Types of chemical weapons

Agent type Types History Symptoms


Nervous system Sarin
• VX (methylphosphonothioic acid)
• Soman
• Cyclosarin
Nerve agents were developed before and during the Second World War and are chemically related to certain pesticides. They are among the most toxic chemical weapons, attacking the functions of the central nervous system. Moderate to severe exposure: Convulsions, constricted breathing, tremors, headache, drowsiness, extreme confusion, loss of consciousness


Nervous system Phosgene
• Diphosgene
• Chlorine
• Chloropicrin
Phosgene, a colourless gas, caused 80 per cent of all chemical deaths during the First World War. These agents are designed to attack lung tissue and cause pulmonary edema, a fluid buildup that leads to respiratory failure. Difficulty breathing, coughing blood, burning eyes and throat, nausea.


Nervous system Sulfur mustard, or yperite
• Nitrogene mustard
• Lewisite
Blister agents can be deadly, but are mostly designed to burn skin, eyes and the respiratory system. Liquid and colourless in its pure state, it is often yellow-brown and smells of mustard plants when weaponized. Burns and severe skin blisters, extreme pain in throat, temporary blindness, bleeding in the respiratory tract at high doses. Vomiting and diarrhea if ingested.

Source: Federation of American Scientists
Top photo: An activist wears a gas mask in Damascus on Aug. 22. (Bassam Khabieh/Reuters)

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