The Trench


Chloropicrin and its alleged use in the Ukrainian war (part 2)

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The first of three parts in this blog series reviewed the allegations of Russian chemical weapon (CW) use in the Ukrainian war from its start in 2014 until today. The Ukrainian delegate reported 1,060 incidents since the Russian invasion in February 2022 at the meeting of the Executive Council of the Organisation for the Prohibition of Chemical Weapons (OPCW) in March 2024. On 23 May, the Wall Street Journal quoted Ukrainian sources that the number of CW incidents was quickly approaching the 2,000 mark:

As of May 3, the Support Forces have confirmed 1,891 such attacks since they began tracking data, 444 of them in April, an increase of 71 confirmed incidents from the month prior. These numbers are an incomplete picture, as it often isn’t possible to get to the location where a gas was used to collect a sample or interview soldiers because of the intensity of the fighting.

Virtually all allegations involve riot control agents (RCAs) – CS and CN – delivered mainly by hand grenades dropped from unmanned aerial vehicles (UAV) into trenches and hideouts. However, as noted in the previous part, the US asserted on 1 May that Russia was also using a different agent, chloropicrin.

This second instalment looks into the specific allegation of chloropicrin use. Despite the US assertion, only three such claims from Ukrainian sources are public, but concrete evidence of when, where and how the chloropicrin was used is lacking. Notwithstanding, the allegation cannot be entirely dismissed. In April 1989, Soviet troops violently broke up demonstrations in the Georgian capital Tbilisi. The three RCAs they used? CS, CN and chloropicrin.

Chloropicrin and its military and civilian uses

The Scottish chemist John Stenhouse first prepared chloropicrin (CCl3NO2) from sodium hypochlorite and picric acid in 1848. Even though the latter only contributed the NO2 group to the new compound, the ‘picrin’ part – derived from the Ancient Greek root pikr (bitter) – stayed.

The rise of a military combat agent

Chloropicrin made its debut as a warfare agent in the First World War. Imperial Russia introduced it to the battlefields in August 1916. Other belligerents soon followed. The Germans first used it on the Italian front during the spring of 1917. To the British, it became known by its code PS. The French called it Aquinite, and the Germans Klop. (SIPRI, The Rise of CB Weapons, 1971, 43-45)

US World War 2 poster (Smells like flypaper? Then it is CNS rather than PS)

The agent was a powerful lachrymator, a colourless (yellow-greenish with impurities), oily liquid with a pungent smell. However, in higher concentrations, it causes lung irritation, nausea, and vomiting. It could saturate contemporary charcoal filters and thus penetrate gas masks, causing soldiers to take them off and expose themselves to other toxic agents. For this purpose, the belligerents mixed chloropicrin with lethal agents such as phosgene or diphosgene. Among other formulations was the German and Allied mixture of 80% chloropicrin and 20% stannic chloride, coded by the US as NC. (Fries and West, Chemical Warfare, 1921, 58, and Roark, A Bibliography of Chloropicrin, 1848-1932, 1934, 1-2)

Although its utility as a combat agent had diminished by the end of the First World War, some military forces retained chloropicrin in their arsenals. The US Chemical Warfare Service kept CNS, a liquid mixture of 23% CN (the lachrymatory agent), 38.4% chloropicrin and 38.4% chloroform, until after the Second World War. It was a semi-persistent harassing agent that did not hydrolyse easily. It could linger about one hour in the open and two hours in the woods during summer. It persisted for six hours in the open and about a week in the woods in winter. With such time frames, enemy soldiers could conceivably have been expected to relax their gas mask discipline, only to be gradually exposed to the lurking CNS and suffer profuse lachrymation and respiratory irritation, followed by nausea and vomiting. Exposed soldiers might also have experienced choking sensations, and while gasping for air, they would have inhaled more of the toxicant. Its prolonged effects make it unsuitable for training or riot control. (Jacobs, War Gases, 1942, 24, Department of the Army, Potential Military Chemical/Biological Agents and Compounds, December 1990, 57, and Hoenig, Compendium of Chemical Warfare Agents, 2007, 147-149)

During the Cold War, the Soviet Union and other Warsaw Pact countries seem to have reserved chloropicrin for training purposes and riot control. For example, the East German military chemist Siegfried Franke warned in his textbook not to use chloropicrin as a training agent near fires because of its thermal instability. (Franke, Lehrbuch der Militärchemie, Band 1, 1977, 167) Indeed, at high temperatures, chloropicrin decomposes to phosgene, nitrogen dioxide, and other irritants. (Gupta, ed., Handbook of Toxicology of Chemical Warfare Agents, 2015, 509) During the mass demonstrations in Tbilisi in April 1989, chloropicrin was reported to be one of the chemical substances used by intervening Soviet troops, which contributed to the large number of casualties among the protestors (see below).

The emergence of chloropicrin as a dual-use chemical

Whereas chloropicrin had few, if any, commercial uses before the First World War, it found widespread utility as a fumigant after the Armistice. In 1907, the Austrian Chemische Fabrikwerke G.m.b.H. proposed chloropicrin emulsified in water with soap as an insecticide. The first experiments with the chemical as a fumigant were undertaken in the US and Italy in 1917 and France in 1918. (Roark, A Bibliography of Chloropicrin, 1848-1932, 1934, 1-2)

In Great Britain, chloropicrin. among other chemicals, was tested for control of fungi, nematodes and wireworms and its beneficial effect on soil bacteria between 1918 and 1920. During the 1920s and 1930s, scientists conducted further research into chloropicrin as a nematicide to kill soil-borne roundworms living off crops, resulting in considerably higher crop yields. The Soviet Union, too, was interested in chloropicrin not just for warfighting but also for pest control and prescribed its use to kill gophers. (Hart, The Analysis of Competing Hypotheses in the Assessment of Chemical Warfare Activities, 2014, 116, fn 561) However, the Commissariat of Chemical Industry ceased chloropicrin production during the Second World War. Consequently, the USSR lost tens of thousands of tonnes of stored grain due to massive weevil infestations during the famine of 1946-1947. (Ganson, The Soviet Famine of 1946–47 in Global and Historical Perspective, 2009, 16)

An OPCW report from 2022 on the most traded scheduled chemicals lists chloropicrin’s common commercial uses as a soil disinfectant for controlling nematodes, soil insects, soil fungi and weed seeds; for fumigation of stored grain to control insects and rodents; and for glass houses and mushroom house fumigation. It is also a raw material in organic synthesis, e.g. in the production of dyes. Estimates put the market value of chloropicrin at USD 414.16 million in 2023.

Chloropicrin and the Chemical Weapons Convention

Chloropicrin thus became a dual-use commodity. The Chemical Weapons Convention (CWC) lists it as a toxic chemical in Schedule 3 in the Annex on Chemicals. It means it was produced, stockpiled or used as a CW but may be manufactured or traded in large commercial quantities for purposes not prohibited under the convention. State parties must annually report aggregate national data for the previous year on the amounts of each Schedule 3 chemical produced, imported and exported.

Another consequence of chloropicrin’s listing in one of the schedules is that no state party can retain the agent for riot control purposes. Under CWC Article III, 1(e), state parties must declare any RCAs in their possession. The obligation applies also if the chemical is part of a mixture with other RCAs. Ahead of the First CWC Review Conference (28 April – 9 May 2003), the OPCW Technical Secretariat produced a Consolidated Unclassified Verification Implementation Report covering the period since entry into force of the CWC on 29 April 1997. It noted (para. 4.1):

The ongoing clarification procedures between States Parties and the Secretariat have ensured that three States Parties that have declared chloropicrin (or its mixtures) as RCAs have either amended their initial declarations, or informed the Secretariat that they intend to delete these chemicals from their list of RCAs.

No future report on verification or the status of CWC implementation for a Conference of the State Parties or a Review Conference has returned to chloropicrin as an RCA.

How concrete is the evidence of CW use in Ukraine?

Despite the sharp increase in CW allegations since December of last year (summarised in the first instalment of this blog series), one aspect is missing. That is concrete proof: publicly available evidence in the form of technical reports, witness statements, images of persons exposed to the agents, hospital scenes, or the site of impact with conspicuous features to enable determination of its precise location. Does this mean the allegations are exaggerated or part of a media manipulation or disinformation campaign? Not necessarily, but the absence of different strands of evidence complicates independent assessment of the CW claims and the framing of a clear violation of the CWC or the laws of armed conflict.

There may be good reasons for the lack of evidentiary materials.

First, the effects of exposure to RCAs disappear quite fast once a victim moves away from an affected area. Rare would be the situations that require extensive medical attention or evacuation of military personnel to dressing stations or hospitals. It is worth pointing out that in the summer of 1982, Iran was already alleging Iraqi tear gas use in the 1980-1988 Gulf War. No pictures or other evidence to support these early claims emerged. Things changed in the final months of 1983 when Iraq introduced mustard agent and the neurotoxicant Tabun to the battlefields. Evidence of Iranian CW victims was aplenty.

Second, the Ukrainian reports come from the trenches and active battle zones. This situation contrasts starkly with, for instance, the Syrian civil war and its lack of clear frontlines. The Syrian government often targeted rural settlements and towns in the hands of regime opponents or terrorist entities such as the Islamic State in Iraq and the Levant (ISIL) or other militant Islamic combatants. Reporters, humanitarian organisations and locals in those areas documented the chemical attacks as soon as they took place. The agents used by government forces were mostly lethal in the form of the nerve agent sarin or chlorine. The UN Secretary-General deployed an investigative team (with experts seconded from the OPCW) in 2013, and the OPCW set up its own Fact-Finding Mission to look into allegations of CW use after Syria had become a party to the CWC. The respective investigation reports confirmed multiple chemical warfare incidents.

Third, Ukraine maintains a strict information management policy, especially concerning its casualty figures. Humanitarian organisations do not seem to be active near the frontlines. Occasionally, an international journalist appears embedded with a Ukrainian frontline unit, and then only for a short time. Many CW reports reach the broader public via military bloggers using communication channels such as Facebook, Telegram, Twitter, and WhatsApp, as well as through organisations like Bellingcat or the Institute for the Study of War, which monitor communications and analyse battlefield developments. Such information often comes in snippets, easily repeated but not consistently fact-checked (if at all possible).

Fourth, until now, the Ukrainian government does not appear to have discerned any significant advantage in broadly publicising CW incidents and has not yet requested the OPCW to initiate an investigation into alleged CW use. (Preparations now seem underway for the first technical assistance visit, which may validate Ukraine’s initial investigative results.)

Reports on chloropicrin use

On 7 August 2023, the Strategic Communications Department, General Staff of the Armed Forces of Ukraine (UAF StratCom) alleged that Russia had launched two chemical attacks in the area of Novodanilivka on the previous day. The message on Telegram, citing Brigadier General Oleksandr Tarnavskyi, then commander of the Tavria operational-strategic group, reported two strikes from Multiple Launch Rocket Systems (MLRS) with ‘ammunition containing a chemical substance (probably chloropicrin)’. It added that there were no fatalities or other casualties.

Six months later, General Tarnavskyi alleged – this time via his personal Telegram channel – that on 8 February, ‘the Russians [had] dropped 6 munitions containing the tear-reducing and suffocating chemical substance chloropicrin (probably K-51 grenades) from UAVs’. His message came about a week after Newsweek cited Colonel Oleksandr Shtupun, spokesperson for the Tavria Ukrainian military group (commanded by General Tarnavskyi) on the southeastern front line, that Russian forces had been using ‘K-51 grenades with chloropicrin’.

Besides these three allegations of Russian chloropicrin use, an earlier press item dated 24 September 2022 mentioned a drone dropping containers, presumably K-51 grenades, filled with ‘chlorine’ the day before. Several reports have associated a chlorine smell with chloropicrin use.

Assessing the chloropicrin allegations

As observed in the previous section about reports on RCA use, the chloropicrin allegations lack context and precision, too.

The three statements identifying chloropicrin all originated from the Tavria operational-strategic group. (‘Tavria’ refers to an area between the Dnieper and Molochna rivers in southeast Ukraine.) Only the August 2023 statement cites a location, namely the ‘area of Novodanilivka’, presumably the village about 70 kilometres southeast of Zaporizhzhia. (As a Ukrainian journalist noted at the time, there are several places with that name in Ukraine.)

No report describes any consequences of exposure. According to the Telegram message, the attack near Novodanilivka produced no casualties despite the rocket barrages. Some international news outlets with journalists in Ukraine, such as Le Monde (France), The Telegraph (UK) and the Wall Street Journal (USA), quoted local officials or medical staff on CW casualties and cited claims about several toxic agents, including hydrogen cyanide, chlorine and chloropicrin. Interviewed in Kyiv by Le Monde in January 2024, the head of investigations for Ukraine’s prosecutor general, Yuriy Belousov, confirmed scores of chemical incidents, most of which involved CS from K-51 grenades. He also referred to a fatality caused by an ‘unknown gas’. However, again, concrete evidentiary elements supporting the allegations were missing. Nor did the articles link the casualties with specific incidents. The Wall Street Journal quoted Captain Dmytro Serhiyenko, assistant to the commander of the Analytical Centre of the Ukrainian Army’s Support Forces, that his team had found two grenades containing chloropicrin at abandoned Russian positions. He gave no precise locations and did not show the journalist any tangible proof.

The referenced delivery systems are problematic, too. The MLRS-launched rockets with chloropicrin would imply a significant escalation relative to CS or CN hand grenades. They presuppose a payload with a substantial volume of liquid in each rocket and a mechanism to disperse the droplets over a target area. In other words, a munition designed specifically for CW delivery in contravention of the CWC.

The two other cases and the one presuming a chlorine filling mention K-51 grenades with different degrees of certainty. However, the K-51 hand grenades are unsuited for a liquid agent. They are fitted with an ignition mechanism to aerosolise CS or CN solid particles via combustion.

Ukrainian communications on chloropicrin to the OPCW

Since the Russian invasion in February 2022, Ukraine made several interventions at CWC Conferences of the States Parties and Executive Council meetings. It referred only once to chloropicrin, namely in a document attached to a statement to the 105th session of the Executive Council (5-8 March 2024). The legend to two pictures said: ‘Improvised explosive devices equipped with ammonia, chloropicrin and other irritant agents’.

How might Russia deploy chloropicrin?

Identifying one or more types of munition for agent delivery poses the biggest challenge to a plausible explanation for Russia’s alleged chloropicrin use.

The three chloropicrin allegations suggest K-51 hand grenades and rockets fired from an MLRS. The K-51 grenades generate a particle aerosol of a solid lachrymatory agent such as CS through combustion. As noted earlier, chloropicrin is an oily liquid, and the ignition’s heat might decompose rather than disperse it.

Artillery rockets would hold a much larger volume of the agent. They would release it in droplets at a certain height above the target, affecting a sizeable area. The communication in August 2023 explicitly stating that there were no victims is, therefore, remarkable, even more so when considering the reported casualties from RCS as a consequence of lack of training and adequate protective equipment.

Therefore, The Russian forces must have used a different type of munition to hold and disperse a liquid agent through a small explosive device to break the shell and produce tiny droplets or a spraying mechanism. Possibly, these might be older munitions dating back to the Soviet era or modified or improvised dispersal devices (as suggested in the Ukranian document to the OPCW Executive Council). In addition, chloropicrin might be an ingredient in a liquid solution with an RCA, such as the CNS agent.

Protests in Tbilisi, 1989

History offers a hint of what to look for. On 9 April 1989, Soviet troops of the Ministry of the Interior and the Red Army violently ended demonstrations in the Georgian capital Tbilisi. More than twenty people died, and there were hundreds of other casualties. In the ensuing days, many demonstrators sought hospital treatment for symptoms suggestive of toxic exposure. Physicians for Human Rights (PHR) sent a medical mission to Tbilisi. It concluded that the Soviet troops likely used chloropicrin along with CN and CS (Leaning, Barron and Rumack, Bloody Sunday: Trauma in Tbilisi, February 1990).

At the time, Soviet authorities eventually conceded having used CN and did not deny CS (p. 27). However, many victims displayed skin and mucosal blisters, bronchoconstriction, and pulmonary oedema. Forty per cent of the patients questioned also reported vomiting (pp. xii and 26). These clinical signs and symptoms led PHR to suspect chloropicrin. It eventually identified the toxic agent through mass spectroscopy in a canister retrieved from the protest scene. As the report noted, ‘The contents of the spray canister were shown to yield a pattern of mass peaks unique for chloropicrin and distinct from CN’ (p. 32).

Several video recordings of the incidents in Tbilisi were available. One recording, according to the PHR report, ‘showed four separate arcs of smoke shot across the crowd, compatible with grenade-launched canisters of gas.’ Eyewitnesses also described

the soldiers as carrying hand-held canisters with white shafts and red nozzles which they sprayed directly into the faces of demonstrators. Those who had been sprayed described the sensation as one of cold liquid, which then burned, and smelled of rotten fruit. One man (a neurosurgeon on volunteer duty at the demonstration) said the spray in his face had an oily consistency that lingered on his moustache (pp. 29-30)

In other words, the mass spectroscopy result and the testimonial point to chloropicrin being part of a liquid mixture with the lachrymator CN. After a detailed review with medical team members from Médecins sans frontières (MSF), PHR and MSF assessed that ‘chloropicrin was the most probable additional toxic agent’ (p. 33). At the end of the mission, the PHR and MSF teams met with the Georgian Minister of Health, Dr Iraki Menagarishvilli, who agreed with the findings and had them announced on Georgian Television (pp. 43-44).

Two years later, in March 1991, the Georgian Commission on 9 April Events responded to the report by the Soviet procurator N. S. Tribun, ‘Concerning the Results of the Investigation of the Criminal Case Concerning Officials and Military Personnel of the USSR MVD Internal Forces and the Soviet Army, Who Took Part in the Stopping of an Unauthorised Mass Meeting in the City of Tbilisi on 9 April 1989’. The response noted that the troops of the Ministry of the Interior did not have the legal authority to deploy agents such as CN, CS and chloropicrin according to an ukase issued by the USSR Supreme Soviet Praesidium on 28 July 1988. It identified Major General I. Yefimov and his superior, Colonel General Igor Rodionov, Commander of the Transcaucasia Military District, as criminally responsible for the events. The report also associated the lachrymator CS with K-51 grenades (pp. 43-44).

Possible delivery systems used in Ukraine

Interestingly, the analysis of events in Tbilisi brings up the three agents Russia is allegedly using in Ukraine today. It reveals the use of a mixture of CN and chloropicrin. Also, it identifies three types of weapons for delivering chemical substances, namely the K-51 grenade, a grenade launcher and a hand-held sprayer.

Still, the document attached to the Ukrainian statement at the March OPCW Executive Council meeting may be a good starting point to sketch a picture of possible weapons involved:

According to the conclusion of the Chief of the Chemical and Biological Defence Troops of the Support Forces Command of the Armed Forces of Ukraine, the means of delivery of munitions equipped with hazardous chemical agents are UAVs (74%), artillery (13%), grenade launchers (1%) and other (12%). The types of ammunition that are armed with hazardous substances are K-51 (71%), gas (17%), VOG (11%) and liquid (1%). Most of the munitions were used during the daytime (93%), and at night (7%).

On the one hand, the paragraph lists weapons that are separable from the chemical payload (and are therefore not a chemical weapon as defined in the CWC). On the other hand, it identifies munitions that deliver the toxic agent onto the target. The meaning of references to ‘gas’ and ‘liquid’ together with two grenade types is unclear. If the K-51 and VOG contain solids (which is the case), then the 1% liquid agent might point to chloropicrin, which, intriguingly, might be associated with grenade launchers (also 1%). The 17% gas is more difficult to assess, but it might refer to (toxic?) smoke for which similar munitions might have been used. I am not a munitions expert, but the supposition offers a basis for hypothesising.

Ukrainian documents and press reports refer to additional types of munitions: DROFA-PM, K-51, RG-Vo (RH-Vo), RGR, Teren-6, VGM 93.200, Vprysk-P, and VOG (VOH). The Wall Street Journal article of 23 May cites the recovery of ‘two grenades containing chloropicrin at abandoned Russian positions’ but does not describe them or identify their type. The statement to the OPCW Executive Council presents detailed information on the K-51, RG-Vo and RGR grenades. However, many links to web pages cited in the document are no longer available, and some also seem to have been removed from the Wayback Machine.

The table below summarises the types of Russian weapons Ukraine links with a toxic chemical. None are explicitly associated with chloropicrin. The two items marked in blue identify potential candidates. They are fired with grenade launchers and, provided they are modified, the grenades could hold a liquid and spray it over the target from a certain height. The chloropicrin may be mixed with CN or CS. It should be noted that there is a Russian patent for a solvent for CN, CS and other solid lachrymatory agents, which the inventors submitted in 2008 and was published in 2010. It mentions the potential application in small types of munitions used in smooth-barrelled shooting devices. [Note: The following pictures show variants of the grenades under consideration, not necessarily the chemical model.]

Associated agent

DROFA-PM grenade
CS Hand grenade (Source)

K-51 grenade
CS Plastic casing (Source)

RG-Vo grenade
CN, CS Metal casing (Source)

RGR grenade
CS Designed for use by special forces (Source)

CS UKR hand grenade. Exported. The basis for Russian counter-claims of CW use. (Source)

VGM93.200 grenade and GM-94 grenade launcher
CS (PS?)

(Variants are high-explosive, rubber, smoke, and thermobaric)

Fired from hand-held pump-action grenade launcher GM-94 (Source)

Vprysk-P grenade
CN Russian grenade. Exported. No current claim of use in UKR. (Source)

VOG grenade and image of air-bust potential

Variants are high-explosive and smoke; also, improvised and adapted versions

244 incidents were claimed in February 2024. Fired from a belted automatic grenade launcher; a steel cartridge with an internal explosive charge. May discharge payload from a certain height. (Source)

Some final thoughts

Concerns are rising about the fast-growing number of reported incidents involving the use of RCAs as a method of warfare since December 2023. Among them are a few – so far, three explicit ones – with chloropicrin as an agent. The US considered them sufficiently alarming to determine that Russia is breaching the CWC, despite Moscow’s claims that it eliminated all its CW in 2017.

For independent observers, the CW allegations are plausible. Still, they lack the necessary lines of evidence seen abundantly during the Iran-Iraq War, the Iraqi campaigns against its Kurdish population and the still ongoing Syrian civil war that would give the confidence to complain that Russia is violating the CWC.

The first instalment of this blog, posted two weeks ago, summarised the allegations involving RCAs. This second part focusses specifically on chloropicrin. Publicly available information is sparse, and the statements associating the agent with K-51 grenades are simply implausible (unless modified, but no indication suggests this might be the case). Yet, they cannot be dismissed out of hand given the experiences in Tbilisi, Georgia, in April 1989. That is, before the breakup of the Soviet Union. Troops from the Ministry of the Interior and Red Army units violently broke up demonstrations, and, according to official Georgian reports, they acted in contravention of Soviet law. Detailed reports by foreign humanitarian organisations described their extensive use and the medical impact of RCAs, including chloropicrin.

The present analysis has then tried to imagine how Russia might use chloropicrin, even though Ukrainian sources have claimed only three specific incidents but provided no details. The purpose is, therefore, not to interpret the few factual elements to support a particular scenario. Instead, this examination attempts to identify possible markers for assessing future allegations when using publicly available resources.

So far, no party to the convention has requested an investigation by the OPCW Technical Secretariat. At the time of writing, it appears that Ukraine and the OPCW have concluded an agreement on immunities and security arrangements, and a technical assistance visit may take place in the next month or two.

The third and final instalment will look into how the international community can act to have the allegations confirmed or denied. Leaving them unaddressed will undermine the overarching norm against CW and the CWC’s legal authority. Given that chloropicrin is a Schedule 3 chemical, any use in combat implies the presence of an active CW armament programme. Even with Moscow’s interpretation that the CWC prohibition applies only to scheduled chemicals and agents that were ‘produced’, Russia would have to admit that it violates international disarmament law by its standards.


Part 1: Chemical warfare allegations in the Ukrainian war

Part 3: International responses to alleged CW use in Ukraine

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