What are some undetectable poisons

Sarin neurotoxin: odorless, difficult to detect, deadly

Anyone who accuses a party of war crimes should be able to present the murder weapon. Scientists are therefore developing new methods that prove the use of sarin in Syria.

Her name is not mentioned anywhere. The reports only mention one woman who died a dubious death on April 29, 2013. She came from the Syrian city of Sarakeb, where a helicopter dropped several containers that day. One landed right behind their house. Sarakeb is located in a rebel-controlled part of Syria and is therefore a civil war zone.

The woman and other family members were admitted to hospital with symptoms of intoxication. Her pupils were severely narrowed. Other signs indicated a so-called cholinergic crisis, a serious disorder of the nervous system. The attending doctors could not save the woman, but her relatives survived. From the beginning there was a terrible suspicion: the woman could have fallen victim to a chemical attack - carried out with the nerve agent sarin.

Several reports since 2013

The Sarakeb incident was neither the first nor the last of its kind. In the Syrian civil war, accusations about the use of chemical warfare agents such as sarin, mustard and chlorine gas are repeatedly heard. The international chemical weapons convention, which Syria has since signed, prohibits their use. Despite this, the United Nations received a total of 16 reports in 2013 alone. Poison gas attacks are also said to have occurred in several places last spring and early this year.

The opponents of the war accuse each other, and their supporters have long made the issue the subject of a global propaganda battle. Sometimes it is even said that there is no tangible evidence of the release of chemical warfare agents. This claim has now been refuted for the first time on the basis of an extensive and publicly available forensic investigation. The proof was posthumously provided by the dead woman from Sarakeb. UN officials had taken blood and tissue samples from her body. The material was then analyzed by experts from the Dutch Organization for Applied Scientific Research (TNO) and the Institute for Pharmacology and Toxicology of the German Armed Forces. The results were recently published in the journal "Journal of Forensic Toxicology".

Sarin is considered a particularly insidious poison because it is odorless and deadly even in small doses. Packed in grenades or bombs, the substance is misted when it hits. “People then breathe in this vapor,” explains TNO chemist Daan Noort. Those affected often die in agony with foam at the mouth. Sarin was originally developed in 1939 by German chemists as an organophosphorus insecticide. Unfortunately, other uses quickly became apparent. Until the 1970s, various armies had sarin-based chemical weapons at their disposal. In 1995 the Aum Shinrikyo sect used the material in an attack on the Tokyo subway. The attack claimed twelve lives and dozens of people were injured. In Syria, the number of victims is now likely to be significantly higher.

Anyone who accuses a party of war crimes should be able to present the murder weapon. But in the case of Sarin, that is an extremely difficult undertaking. “Because sarin is very difficult to track down in the environment,” emphasizes Noort. Not only can the poison be broken down by bacteria in the soil. According to the expert, it also reacts with many other substances and is particularly volatile compared to other nerve gases. So what does not go into connection with other substances, disappears in the air.

Bound to proteins

The neurotoxin binds to proteins in the human body. The resulting adducts are retained for a long time, even in survivors. The immune system apparently escapes the fact that the protein molecules are changed. That is why they are not broken down. “In principle, such adducts can still be detected weeks later,” says Noort. That makes the evidence easier. Because unlike the attack in Tokyo, where the authorities were immediately on site and were able to take samples, the situation in war zones is much more difficult.

In order to arrest the sarin in the body of the woman killed in Sarakeb, the Dutch and German researchers mainly used mass spectrometry. This method allows the exact detection of different types of molecules. Since the poison residues are mostly present in the adducts, they must first be removed from them. The actual target of sarin is the enzyme acetylcholinesterase, which controls the signal transmission at neuronal synapses. The toxin binds very specifically to the enzyme and thus blocks its function - with devastating consequences for the nervous system.

However, the process of getting hold of the killer chemical via acetylcholinesterase is hardly established, as Noort's colleague Harald John from the German Federal Armed Forces explains. The enzyme is found on the surface of red blood cells, among other things, but it is too firmly anchored there. The scientists therefore set their sights on other proteins: the butyrylcholinesterase, which floats freely in the blood plasma, for example, and the almost ubiquitous albumin. According to John, these proteins can also form adducts.

The scientists carried out a total of five different searches and actually found what they were looking for. Sarin residues detached from protein appeared not only in the blood of the dead woman, but also in the trachea, lungs, liver and kidneys. In addition, the sarin degradation product O-isopropyl-methylphosphonic acid could be detected in all sampled areas of the body - including the eyes, for example. According to John, this is caused by hydrolysis when the poison comes into contact with water or body fluids.

The now published study is the first publicly available evidence of the use of organophosphorus warfare agents in the Syrian civil war. In its investigation report of December 2013, the UN referred to several biomedical analyzes and cited their results as evidence. The details of these investigations have not yet been published, which may also have political reasons.

The Dutch and German experts are already working on refining their methods. In the future, not only the use of chemical weapons should be unequivocally proven. The scientists also want to develop rapid tests for medical purposes. This allowed the victims of poison gas attacks to be identified more quickly and treated more specifically. “That could save many lives,” says Noort.

Sarin - an extremely dangerous neurotoxin

(Spe.) According to a fact sheet from the Spiez Laboratory, sarin is one of the most dangerous chemical warfare agents manufactured for weapons purposes. The substance belonging to the group of phosphonic acid esters is liquid at room temperature, but evaporates quickly. The poison is absorbed in the liquid state through the skin and in the gaseous state through the eyes and respiratory tract. In the body, it inhibits an enzyme that plays an important role in the transmission of signals between the nerve cells of the autonomic nervous system. The result is permanent excitation of the nerves which, depending on the dose, leads to visual disturbances, eye pain, sweating, muscle cramps, shortness of breath or fatal respiratory paralysis.

Sarin is broken down relatively quickly in the environment, says Stefan Mogl, who heads the chemistry department at Spiez Laboratory. However, the degradation products can also be used to determine whether a sample contains sarin or a similar warfare agent. Examples of possible samples are parts of ammunition, soil from impact craters or items of clothing packed airtight, according to Mogl. Evidence in urine or blood samples, however, is difficult if the poisoning was several days or weeks ago.

Should Syria allow the UN to take samples in the country, it would be up to the Organization for the Prohibition of Chemical Weapons to investigate them for the UN. However, Syria is one of the few countries that has not signed the Chemical Weapons Convention. It is therefore not obliged to allow on-site inspections.

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