Introduction

Weapons of mass destruction usually refer to a nuclear, radiological, biological, or chemical weapon that is capable of causing widespread death and demoliton.

The use of chemical weapons is considered illegal and unethical. Generally, this is because they cause unnecessary suffering, sometimes on innocent civilians, and have indiscriminate effects. Also, some agents of these weapons have delayed reactions and inflict harm on a large amount of people unintentionally, when their original aim was to fire at their opponent's army only.

Some of the chemicals/compounds found in such chemical weapons include:

CW Agent Group	Persistency	Rate of Action
Choking Agents
Chlorine (Cl)	Low	Variable
Phosgene	High	Variable
Blister Agents
Nitrogen mustard (HN)	High	Delayed
Blood Agents
White phosphorus	High	Variable
Sarin (GB)	Low	Very rapid

Nitrogen Mustard

Nitrogen mustard is a chemical compound, with chemical formula C₆H₁₃Cl₂N

It is composed of Carbon (C) , Hydrogen (H), Chlorine (Cl), and Nitrogen (N).
Nitrogen mustards can be clear, pale amber, or yellow-colored when in liquid or solid form.
The nitrogen mustards are also known by their military designations of HN-1, which was originally designed to remove warts but was later identified as a potential chemical warfare agent, HN-2, which was designed as a military agent but was later used in cancer treatment, and HN-3, which was designed solely as a military agent. Nitrogen mustards are not found naturally in the environment.

Nitrogen mustard is a blister agent, and exposure to it in liquid form is more likely to produce second- and third- degree burns and later scarring than is exposure to nitrogen mustard vapor.
Extensive breathing in of the vapors can cause chronic respiratory disease and long-lasting eye problems. Nitrogen mustards may cause bone marrow suppression beginning as early as 3 to 5 days after exposure. Bone marrow suppression can cause anemia, bleeding, and increased risk for infection. If severe, these effects could lead to death. During the 1930's, several reports were published on the synthesis of nitrogen mustard agent and its remarkable blistering effect. The mechanism of action and symptoms largely agree with those described for mustard agent. Germans and Americans started the military production of nitrogen mustard agent in 1941 and 1943, respectively, whereas the development in England was abandoned following an explosion. There is no verified use of nitrogen mustard agents as chemical weapons and their usefulness is restricted by these types of agents being unsuitable for storage.

This chemical also affects  the environment, in which HN-2 decomposes before its boiling point is reached or condenses under all conditions; the reactions involved could generate enough heat to cause an explosion. Prolonged or repeated exposures to nitrogen mustards have caused cancer in animals. Some evidence exists that prolonged or repeated exposures to nitrogen mustards cause leukemia in humans. Contact with metals may evolve flammable hydrogen gas. Polymerization of HN-2 results in components that present an explosion hazard in open air. When heated, vapors may form explosive mixtures with air, presenting an explosion hazard indoors, outdoors, and in sewers. However, some studies show that because mustard changes to other chemicals in the environment, as it is highly reactive and decomposes in nature, it will not concentrate in plants or animals.
No specific antidote exists for nitrogen mustard exposure. Treatment consists of removing the nitrogen mustard from the body as soon as possible and providing supportive medical care in a hospital setting.

Chlorine

Chlorine is a chemical element, with chemical symbol Cl.

Chlorine is very harmful to the human body, however, its effects depend on the amount of chlorine a person is exposed to, how the person was exposed, the length of time of the exposure, and initially on the health of the person or condition of the environment when exposure occurs. 
When chlorine gas comes into contact with moist tissues such as the eyes, throat, and lungs, an acid is produced that can damage these tissues.
It is a choking (pulmonary) agent. Breathing small amounts of chlorine for short periods of time affects the human respiratory system. Effects differ from coughing and chest pain, to water retention in the lungs (pulmonary edema).
These effects are not likely to occur at levels of chlorine that are normally found in the environment. Human health effects associated with breathing or otherwise consuming small amounts of chlorine over long periods of time are not known. 
Since chlorine is used in cleaning agents, such as bleach, some studies show that workers in such industrial fields develop adverse effects from repeat inhalation exposure to chlorine, but others will not. 
During World War I, chlorine gas was used as a chemical weapon, released in massive clouds by the German army to cause lung damage and terror downwind of its release.












Chlorine is also harmful to the environment, as it reacts with water to produce acids, that are corrosive and damage cells in the body on contact. 
Chlorine dissolves when mixed with water. It can also escape from water and enter air under certain conditions. 
Once in air or in water, chlorine reacts with other chemicals, organic or inorganic, to form chlorinated chemicals or salts.
Because of its reactivity chlorine is not likely to move through the ground and enter groundwater.
Plants and animals are not likely to store chlorine. However, laboratory studies show that repeat exposure to chlorine in air can affect the immune system, the blood, the heart, and the respiratory system of animals.
Chlorine causes environmental harm at low levels. Chlorine is especially harmful to organisms living in water and in soil.
No antidote exists for chlorine exposure. Treatment consists of removing the chlorine from the body as soon as possible and providing supportive medical care such as inhaled breathing treatments for wheezing in a hospital setting.

White Phosphorus

White phosphorus is a material made from a common allotrope of the chemical element phosphorus, with chemical symbol P_4. 

It is a toxic, yellowish, waxy solid that ignites spontaneously in air and glows in the dark. It is used by the military in various types of ammunition because it spontaneously catches fire in air.

Breathing white phosphorus for short periods may cause coughing and irritation of the throat and lungs. Breathing white phosphorus for long periods may cause a condition known as "phossy jaw" which involves poor wound healing of the mouth and breakdown of the jaw bone.

Eating or drinking small amounts of white phosphorus may cause liver, heart, or kidney damage, vomiting, stomach cramps, drowsiness, or death. We do not know what the effects are from eating or drinking very small amounts of white phosphorus-containing substances over long periods of time. Skin contact with burning white phosphorus may burn skin or cause liver, heart, and kidney damage.

It is a systemic (blood) agent. Its initial explosion can produce extensive, deep second and third degree burns that carry a great risk of death due to the absorption of phosphorus into the body through the burned area, resulting in liver, heart and kidney damage, and in some severe cases multiple organ failure. White phosphorus continues to burn unless deprived of oxygen or until it is completely consumed. Smoke inhalation can cause illnesses or death. White phosphorus smoke irritates the eyes, mucous membranes of the nose, and respiratory tract in moderate concentrations, while higher concentrations can produce severe burns.

This chemical was used in the Gaza War (2008-2009) where phosphorus shells exploded over populated civilian areas, including a crowded Palestinian refugee camp and a United Nations school where civilians were seeking refuge. Also, the injuries were suspected in the cases of ten burn victims. 


When white phosphorus enters the environment through the discharge of wastewater, it ends up in surface waters near the factories that use it. It is not likely to spread, because it reacts with oxygen fairly quickly. When phosphorus ends up in air through exhausts it will usually react with oxygen right away to be converted into less harmful particles. However, when phosphorus particles are in air they may have a protective coating that prevents chemical reactions. In soil phosphorus will remain for several days before it is converted into less harmful substances. But in deep soils and the bottom of rivers and lakes phosphorus may remain for a thousand years or so.

There is no antidote for white phosphorus toxicity. 

Phosgene

Phosgene is a chemical compound, with chemical formula COCl_{2.
It is composed of the elements Carbon (C), Oxygen (O), and Chlorine (Cl).}
Poisoning caused by phosgene depends on the amount of phosgene to which a person is exposed, the route of exposure, and the length of time that a person is exposed. Phosgene gas and liquid are irritants that can damage the skin, eyes, nose, throat, and lungs. Most people who recover after an exposure to phosgene make a complete recovery. However, chronic bronchitis and emphysema have been reported as a result of phosgene exposure. This colorless gas is a choking agent and has gained infamy for its use as a chemical weapon in WW1. 

Exposure to high levels of Phosgene may seriously harm and even kill wildlife. However, these effects are only likely when large amounts of Phosgene are released - for example, as a result of an accidental spill. Typical environmental levels are not sufficiently high to cause significant effects. It is not              considered likely that Phosgene pollution has any effects on the global environment. Human phosgene toxicity cases occur in too sporadic and sudden a fashion to allow randomized clinical trials. And so clearly, intentional exposure of human subjects to phosgene would be considered unethical.

Treatment for phosgene exposure consists of removing phosgene from the body as soon as possible and providing supportive medical care in a hospital setting. No antidote exists for phosgene. Exposed people should be observed for up to 48 hours, because it may take that long for symptoms to develop or reoccur.

Sarin

Sarin is a chemical compound, with chemical formula C₄H₁₀FO₂P.
It is composed of Carbon (C), Hydrogen (H), Fluorine (F), Oxygen (O), and Phosphorus (P).
Sarin is a human-made chemical warfare agent classified as a nerve agent. Nerve agents are the most toxic and rapidly acting of the known chemical warfare agents. The extent of poisoning caused by sarin depends on the amount of sarin to which a person was exposed, how the person was exposed, and the length of time of the exposure. Symptoms likely will appear very soon after exposure. 




This chemical has severe biological effects, along with others, that will prevent the proper operation of an enzyme that acts as the body’s “off switch” for glands and muscles, that will therefore be constantly stimulated. It will attack the nervous system and prevent nerve endings in muscles from switching off. Death will usually occur as a result of asphyxia due to the inability to control the muscles involved in breathing function.




Exposed people may become tired and no longer be able to keep breathing. Sarin is the most volatile (easily and quickly evaporate from a liquid into a vapor and spread into the environment) of the nerve agents. Because it evaporates so quickly, sarin presents an immediate but short-lived threat. People severely exposed to sarin are less likely to survive.

An example of when sarin was used is in 2004 when Iraqi insurgents detonated a 155 mm shell containing binary precursors for sarin near a U.S. convoy in Iraq. The shell was designed to mix the chemicals as it spins during flight, but released only a small amount of sarin gas, either because the explosion failed to mix the binary agents properly or because the chemicals inside the shell had degraded with age. Two United States soldiers were treated after displaying the early symptoms of exposure to sarin.

Sarin is a vapor, and therefore is heavier than air. It remains very low to the ground, and can affect animals and plants quite quickly and easily. Sarin degrades very quickly in the environment. However, as the temperature increases, Sarin's lethal duration increases. Treatment consists of removing sarin from the body as soon as possible and providing supportive medical care in a hospital setting. Antidotes are available for sarin. They are most useful if given as soon as possible after exposure.

References: 

-Centers for Disease Control and Prevention

-Medscape