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Acute tear gas health hazards pointed by a French health report

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The French society of toxicology just published a report about “tear gas usage and its short and long term toxic effects”. L’Obs exclusively released this document.

By Emmanuelle Anizon

Published June 27th 2020 at 9 a.m., update 9:45 a.m.

A man throws a tear gas grenade back, in Bordeaux, December 5 2019. (NICOLAS TUCAT / AFP)

French society of toxicology-chemistry, Paris, published a report about “tear gas usage and its short and long term toxic effects”. 126 pages, over a year of hard work by Alexander Samuel. L’Obs was already the first magazine to publish a portrait of this maths high school teacher, PhD in molecular biology, and disheveled haired itching powder who accidentally leaded a healthcare team in doing blood and urine analysis on Yellow Vests Movement protestors in France, to detect presence of Cyanide in tear gas, and its consequence on public health.

“Tear gas harmfulness has already been largely questioned worldwide, but such a review had never been written, says André Picot, head of the Society Of Toxicology-Chemistry. Most of the studies are not publicly available because they are limited to the military domain. This work is of public interest”. Burning hot news, while protesters are drowning in tear gas clouds every day around the world.

What does this review say? Outside of technical biological analysis, which we will not comment out of complexity, this review describes tear gas effects and highlights the importance of cyanide in producing those effects. Each CS tear gas molecule that is absorbed will release two cyanide molecules. Absorption is not only respiratory, but can also be cutaneous.

This review describes the mechanism of cyanide poisoning (blocking the respiratory chain and causing an oxidative stress), and details what happens to the human body even at low dose intoxication. This molecule mainly affects brains, livers and kidneys. Eyes would also be affected (cataract…). It has an effect on central nervous system (headache, anwiety, dizziness, confusion, loss of consciousness, paralysis and even coma), on the respiratory tract (hyperventilation, tachypnea, dyspnea or apnea in extreme cases), on the cardiovascular system (hypotension, palpitations, arrythmia, tachycardia…), and even causing damage to thyroid, gastro-intestinal system (nausea, vomiting, diarrhea), musculo-skeletal system (muscular rigidity), liver… In New Jersey, the Department of Health calls protesters who are exposed to check up their livers and kidneys. “Why is nothing done in France? Asks Alexander Samuel. For political reasons, the scientific aspect is not explored.”

Deaths ?

In his review, Alexander Samuel reminds events in which CS could have caused death, directly or indirectly. “A link is often established by families and friends between tear gas exposure and death, but there are often discussions and there is rarely clear evidence. Recently in the United States, a young woman died from a pulmonary issue just after a demonstration with strong tear gas exposure. It was first said it might be due to tear gas, then discussed… We will probably never know. In France, Steve Maïa Caniço, a young man from Nantes drowned in June 2019 after falling in the Loire river during the music fest in June 2019. This happened just after a police charge with at least 33 tear gas grenades in les than half an hour. Enough to disorient someone… And yet, I regret no forensic analysis

Alexander Samuel hopes his work will trigger more awareness.

“What I have written interrogates. I would like other people to start working on answering those questions I raise.”

He still goes on interacting with scientists, sociologists, and Non-Governmental Organizations (like Amnesty International, who just launched a website dedicated to tear gas). He already teaches dangers of using tear gas through web conferences to police officers… from Chile.

Emmanuelle Anizon

Protection against tear gas


Tear gas is actually not a gas, but consists of solid particles in suspension. The average diameter is 8 microns, larger than the 3 microns of most filters block, so an A-P3 filter is enough to protect your airways.

To check if the mask is properly adjusted, block the air inlet where the filter is located with your hand and check if you can breathe: if it is the case, air passes through the sides and the mask is not adjusted tightly enough.

Résultat de recherche d'images pour "lunettes chantier étanches""

Protective goggles must be waterproof, to avoid the penetration of solid particles. However, it is better to take impact resistant glasses (risk of shots from rubber bullets), swimming pool glasses can cause damage by breaking.

film étirable manuel cast 15 microns 300 m x 450 mm

To protect themselves from skin penetration, some use plastic film, or put on gloves and waterproof clothing…

Extinguish pellets

Traffic cone
Pellet Trap
Campden tablets could be added to water for better efficiency

Post Exposure

After exposure, it is important to take a COLD shower to avoid opening of skin pores and letting the molecules in.
Clothing should be removed as soon as possible and then insulated or washed. In case of young children exposure, it may be useful to remove the clothes immediately and put on a survival blanket. Exposure should be minimized by removing contaminated clothing which may come into contact with the child, including that of adults nearby.

Post exposure products

We do not recommend the use of any of these products, we only list the products already used, recommended by some or existing.

CS is more irritating at high temperatures, and can only irritate in the presence of water (humidity, sweat, etc.). US soldiers use a decontamination technique which consists of drying the exposed area off, then applying decontaminant and washing it off.

In the field, many techniques have been developed, here are their advantages and disadvantages. We do not recommend the use of any of these products, and all drugs or medical devices should only be taken in the presence of a doctor.

Following exposure to tear gas, washing / rinsing using a Gaviscon® or Maalox® mixture with water in the presence of a doctor will reduce the burning sensation of the skin and mouth and prevent product penetration. An alcohol-free cleansing wipe can be used to remove as much product as possible from the skin. However, in case of excessive application, these products are irritants.
The use of Dacryoserum® in the presence of a doctor will only serve to dissolve the product in the eyeball, but in no case will prevent its penetration.
If rinsed with water, it must be cold in order to avoid an opening of the pores which would favor penetration of the product. The skin should be rubbed without irritating it. This action is to be carried out at the end of the day. Do not use soap at first. Take the opportunity to rinse your mouth and throat (by gargles) and eyes. Also rinse hair thoroughly before using a mild shampoo.
Eye and skin washed with Diphoterine® in the presence of a doctor, an aqueous solution containing amphoteric salts are recommended by some and rejected by others. Two views clash because, according to certain industrial hygiene specialists and certain chemists, this neutral pH product does not contain any particular or special products which can prove its usefulness.

Post-Cyanide exposure

To prevent risks due to exposure to cyanide by CS gas metabolism, André Picot, a famous french chemist, gave us dietary advice

The elements below are used in large quantities by the body to get rid of cyanide produced by the metabolism of CS gas, which ultimately leads to deficiencies and fatigue. We have completed the initial list of recommended foods. You can recover these elements by a simple and natural means: alimentation:

SULFUR: parsley, radishes, leeks, beans, lentils all foods containing natural sulfur garlic, onion, shallots, chives, cabbage, turnips, tap water, mineral water (especially those containing sulfates), wines (sulfites)…

B12: good quality calf’s liver (without hormones) meat, milk, kidneys, brewer’s yeast, edible seaweed, cod liver oil (in order of importance in intake: liver, caviar, mackerel, oysters, herring, beef , trout, tuna, sea bass, emmental, camembert, egg, plaice, fresh cottage cheese).

COBALT: cobalt food supplement in organic stores

In addition, when after manifestation you present extreme fatigue for several days, it may be useful to follow these dietary recommendations:

ZINC AND SELENIUM (anti-fatigue): broccoli, hazelnuts, nuts, almonds, chocolate, oysters, grilled wheat germ, veal liver, braised beef, dried shiitakes (mushrooms), grilled or oven-roasted squash seeds, crab, lentils, tartar or raw ground beef


Tuesday, November 5th, 2019

Emilien Urbach

Whistleblower. The young biologist from Nice highlights large doses of cyanide in the blood of demonstrators exposed to this chemical weapon.

“Cyanide in the tear gas used for law enforcement? Would the government poison the population? Unthinkable! It was the first reaction of Alexander Samuel, a math teacher and doctor of biology, when the yellow vest Julien Chaize, in April 2019, asked him to study this hypothesis. Six months later, the young scientist from Nice is convinced, significant doses of poison circulate in the blood of gassed demonstrators.

This conviction disturbs. On Saturday November 2, Alexander was taken into police custody on the grounds that he was implicated in a symbolic, bio-painted attack on a bank. He denies it but remains locked up for forty-eight hours. His home is searched. Its computer equipment and many documents are thoroughly inspected. A military manual from 1957, “on protection against combat gases”, is seized and destroyed.

Away, he observes the violence

This episode is apparently unrelated to his research on tear gas. In any case, the biologist has already compiled his work in a report. It will be published in the coming days by the Toxicology Chemistry Association, founded by André Picot, honorary director of the chemical risk prevention unit at the CNRS. The latter will co-sign the Alexander publication alongside other researchers and doctors.

There was nothing to suggest such a result when, at the beginning of spring, Alexander went for the first time to a demonstration of yellow vests. “I was suspicious,” he admits. In the Alpes-Maritimes, the far right was very present at the start of the movement and my environmental convictions were at odds with the demands linked to fuel taxes. Curious, however, he went to the rally organized on March 23 in Nice.

At a distance, he observes the violent police charges during which the head of Attac, Geneviève Legay, is seriously injured. Alexander does not attend the scene directly but he sees the street medics, these militant rescuers who intervene during the demonstrations, prevented from intervening and being arrested. Alexander films. He was immediately placed in police custody. It’s his first time.

“I was shocked,” says the scientist. The conditions of my detention, the lies of Emmanuel Macron and the prosecutor concerning Geneviève Legay made me stand in solidarity with the movement. He decides to gather everything that could make it possible to establish the truth and to pass it on to yellow vests who intend to seize the United Nations. Among them, Julien Chaize wants to convince him to look into the case of a demonstrator who, following an exposure to tear gas, displayed an abnormally high level in the blood of thiocyanate, molecule formed after the assimilation of cyanide by the liver.

This is an isolated case. Impossible for Alexander to see in it evidence of massive poisoning of the population. Incredulous, he participated in other demonstrations and observed the reactions of people exposed to the gases. Vomiting, irritations, disorientation, loss of consciousness … these fumes don’t just make you cry.

Alexander consults the scientific literature. The tear gas component used in France is 2-Chlorobenzylidene malonitrile. As it is considered a chemical weapon, its use is prohibited in the context of armed conflicts. Not for policing. For the biologist, the verdict is clear, this molecule, once present in the blood, releases cyanide. Several studies since 1950 confirm this. None said otherwise. But this poison is also present in cigarettes and a multitude of foods. Its dangerousness is therefore a question of dosage. How to measure it?

Alexander and three doctors in yellow vests then proposed to the demonstrators to have their blood analyzed to determine a level of thiocyanate. But this marker is not reliable enough. Cyanide must be quantified. However, the poison is only detectable in the blood for a few tens of minutes. Armed with a kit of tests, prescriptions and forms to be signed by the candidates for an exam, they decided to take blood and urine samples directly during the demonstrations of April 20 and May 1.

The results are edifying

The results of the first samples confirm the significant presence of cyanide, but do not give the precise dosage. On June 8, in Montpellier, the team perfected their protocol. Alexander, the three doctors and a few accomplices make themselves guinea pigs from their experience. They test their blood before the demonstration and afterwards. The results are edifying. Scientific community considers cyanide poisoning

Émilien Urbach

Alexander Samuel, the man who investigates tear gas used against “yellow vests”

Alexander, at a national yellow vest protest in Montpellier. (©Xavier Malafosse/Sipa Press / Xavier Malafosse)

PhD in biology, Alexander Samuel investigates dangers of tear gas, used massively in France against “yellow vests”. His method : entering in the tear gas cloud and analyzing blood and urine.

By Emmanuelle Anizon

Published on July 24th 2019 at 2.00 p.m.

We already saw him, multiple times, going into the white cloud and coming out minutes later, his long redhead mane in a hot mess, scarlet eyes and face, crying, coughing, tottering and almost fainting. Alexander Samuel, 34 years old, PhD in molecular biology, maths teacher in a public professional high school in Grasse, France, and philosophy dabster, would never have imagined breathing voluntarily tear gas in the middle of demonstrations. Neither crossing France with tubes of blood and urine in his car trunk, like a drug dealer, looking for a lab which could accept his cargo. Even less being convened by French justice for “endangering people’s live”. Him, whose only assumed violence consists of yelling regularly into a microphone, surrounded by his metal bandmates.

Alexander engaged by accident, on March 23rd 2019. On that day, the “politically very left wing tending” teacher comes as an “observer” to a “yellow vest” protest in Nice. He gets in touch with SOS UN, who are inventorying police brutality. “When I told them I was PhD in biology, they asked me if I could help them analyze the tear gas effects. They described me numerous symptoms : stomach ache, nausea, vomiting, muscle aches, severe migraines, but also loss of consciousness, pulmonary problems, heart problems, liver problems … “Yellow vests” had been hospitalized. They evoked potential cyanide poisonings. Cyanide ! I thought they were nuts ! But since there were many testimonies, I decided to dig it…”

Alexander Samuel, PhD in biology, experimenting during a « yellow vest » protest in Paris. (Bruno Coutier pour « l’Obs »)

Alex loves to dig. Already at the University of Nice, the brilliant PhD student half French half German had stood out for his propension to put his obstinate nose into affairs – misappropriation of subsidy, syndicate corruption, and other favoritism. “Alex is a researcher who finds, testifies Guillaume, a former comrade back in time. He accumulated evidences, gathered documents, recorded conversations. He combined methods of an investigator and a scientist”.

The teacher immersed himself into “literature”, as scientists say, reading everything that got published on the subject in scientific papers. And he methodically reports on his website. He discovers that “CS” gas used by police officers does not directly contain cyanide, but that one of its components, malonitrile, is metabolized into cyanide in the human body.

A public health issue

One can endure cyanide at low levels : smokers, people who eat cabbage, almonds or cassava. At higher doses, cyanide can cause hypoxia, lack of oxygen. It can kill in some cases, even if it did not happen yet in France. Alex explains :

“The person who got gassed endures some kind of strangulation. What is the health consequence of being strangled once a week ? We are told that tear gas are not dangerous, but we don’t know the long term health effects.”

The researcher spends days and nights on what he considers as “a public health issue : tear gas used nowadays massively by police forces, and not only on “yellow vests” : the “pont de Sully” ecologists, the young people at the music fest party in Nantes and people or businesses close to the demonstrations, all were exposed to tear gas. And even policemen, who are the first exposed !

Most of the time, they wear gas masks protecting them, but on June 28th, on the Sully bridge, a commander lost consciousness because of tear gas.

Read also : « Où est Steve ? », voilà LA question

Cyanide disappears in less than thirty minutes after tear gas exposure. But it leaves a marker in the body, thiocyanate, which can be detected during a few weeks after exposure. “I saw some “yellow vest” analysis results twice or even three times higher than normal values !” says Alex, who then contacts many toxicologists, doctors, scientists in France and abroad. Reactions are contrasted, some tell him he is totally wrong, like Jean-Marc Sapori, from the antipoison center in Lyon, and some encourage him to go on his “remarkable” work like André Picot, president of the Toxicology – Chemistry association, others even tell him

“Be careful, you are addressing a too dangerous subject”.

He calls a lot, and he gets called ore and more. A secret agent wants to give him confidential documents about tear gas victims during the Algerian war. Dozens of “yellow vests” want to testify, and send him their results.

“We are compiling their symptoms in a table, and we notice some new weird symptoms. For instance, many women, even menopaused, are having heavy menstrual bleeding”.

A doctor from the University Medical Center of Lyon writes him about a patient, gased multiple times, having a heavy liver disease from unknown cause : “I wonder if that could explain his pathology” she says.

How to prove the link between pathology and tear gas ?

What should we answer ? How could we prove irrefutably that link ? Since health authorities don’t address the issue and the interior ministry repeats “Move along, nothing to see”, Alex, three doctors – Renaud, anesthesiologist resuscitator, Josyane, generalist and Christiane, ophthalmologist -, nurses and some “yellow vests” decided to do blood uptake directly on demonstration site.

Christiane, ophtalmologist, member of Alex’s team.(©Xavier Malafosse/Sipa Press)

During his research, Alex found a Swiss company, Cyanoguard, selling kits to detect instant cyanide levels in blood : “It works like a breathalyzer. If the color turns purple, there is a dangerous level of cyanide. They are very serious, they published in the excellent journal of the Royal Society of Chemistry and FBI uses their tools!”. Alex and the doctors buy ten kits, 15€ each, and plan to send some other blood samples to a laboratory to make the classical thiocyanate analysis : “Combining both results, the reliability of our results will be reinforced”. And that’s how, on Saturday April 20th in Paris, “yellow vests” could see, in the middle of the smokes, spitting,  flashball shots and crowd movement, a little group equipped with helmets, glasses, syringes and tubes to do blood uptake on the pavement.

Results were deceiving : color change with cyanokit was difficult to interpret. “Cyanoguard told us “it’s positive” but I wasn’t sure”. Other surprise : the thiocyanate results, analyzed by the only French lab performing them in Lyon came back negative. “Even for smokers, which is impossible ! » says Alex sniggering. He often sniggers, giggling and narrowing his nose, like kids do. The teacher does not want to believe that those results are being faked voluntarily, but he thinks it would be appropriate to perform new analysis abroad in foreign “independent” labs.

Doctors are presented like murderers

On May 1st, during a very agitated demonstration in Paris, the little group backslides, this time in a building lobby, behind closed doors. “Yellow vests were waiting outside to duff us up”. The group was worried. In a background interior war inside SOS UN, Alex and the doctors left, a controversy started. Videos from blood uptakes were circulating on social networks where doctors were presented as murderers.

Read also : On a suivi des « gilets jaunes » devenus black blocs

Medias relay words from a “yellow vest” whose blood got collected, accusing the team for having abused of her weakness; the council of the Order of Doctors, asked about it, explains that it is not forbidden to do a blood uptake in the street, but it has to follow certain conditions. “Our blood uptakes were done respecting all security conditions, and everyone who gave his blood signed an informed consent” assure the three doctors from the team. A preliminary investigation is opened. At Alex’s high school, the director received messages calling him “illuminated”.

The team is doing blood analysis at the first floor of a Montpellier fastfood turned into a clandestine field hospital. (©Xavier Malafosse/Sipa Press / Xavier Malafosse

With this tempest, some in the groupe got scared and gave up. Not Alex, who decided to start from scratch with a reckless kernel of his team. They are reproached taking blood from others ? They will take their own blood. Not in the streets, but in the first floor of a fast-food in Montpellier, transformed into a clandestine field hospital (with the complicity and help of the manager, a “yellow vest” supporter”). That day, “l’Obs” was present, and the maker of the cyanokits too, he came in person to supervise the operation. This time, the cyanide level is quantified. Alex analyses :

“We are passing from a 0 or 0,1 mg/l value before tear gas exposure to 0,7 mg/l, the dangerousness threshold being at 0,5mg/l. It’s the sign that cyanide and tear gas are linked !”

But for toxicologists, the numbers from that non homologated kit will not be an official evidence. Alex went in person to a prestigious Belgian university to analyse the thiocyanate levels of the blood samples. 24 hours driving. The professors, very interested, received him for a long time but their laboratory declared itself incompetent. “They do not want to get involved, they know the French state will be confronting them” interprets Alex. Fear or not, he had to look somewhere else. Germans hesitated, sent him to a British lab which accepted. But when the tubes arrives, it was too late : “Pff… they are hemolyzed”, sighs Alex. Translate it : dated.

They risk correctional court

The series continued, but we will pass the episodes. We will just note a mass spectrometry analysis with distribution of urine collection pots to “yellow vests”. “They are very mistrustful. We collected only two samples, mine included” confesses Alex. Two, it’s very few. But, for 50€ each analysis, he couldn’t have paid much of them anyways. Including cyanokits, sending costs, analysis costs, lawyers, car transport, the teacher says he paid about 5000€, a big part of what he spared for his installation work in his new apartment.

He tells it with his unchangeable smile, nose and eyes narrowed. He says he doesn’t care. What he cares more about, is this preliminary investigation opened for “endangering people’s lives” and “prohibited interventional research”. Beginning of July, himself and three doctors got convoked by justice and thoroughly interrogated. They risk correctional court. They should quit ? Why go on in such a mess of hassles ? “We will not drop it until a serious epidemiologic study starts”. With the three doctors, Alex will call the High Authority of Health. Until then, he goes on digging.

About tear gas

Tear gas is a chemical compound causing eye and respiratory irritations. Like every chemical weapon, its usage is forbidden in the context of armed conflict by the international convention of Geneve (1993). Paradoxically it does not apply public order maintenance.

There are different kinds of gases. In France, police uses CS (chlorobenzylidene malononitrile) more and more massively, like the demonstrations showed it during the past years. The dangerousness of those gases is proportional to their concentration and depends on the conditions of their usage. Officially it is not lethal, but deaths have been reported by its usage in closed rooms, like during the Waco siege 1993 in the United States, or in Egypt and in Bahrein during population uprising.

In France, « CS concentration in grenades is 10%” tells us the general direction of the police, precising “It has been over 20 years that we are using this gas, if it was dangerous, we would have been the first victims, and police syndicates would have denounced it”.

Emmanuelle Anizon