Georgia's authorities used a World War One-era chemical weapon to quell anti-government protesters last year, evidence gathered by the BBC suggests.
You could feel [the water] burning, one of the protesters said of water cannon turned on him and others on the streets of the capital Tbilisi. A sensation, he said, which could not immediately be washed off.
Demonstrators against the Georgian government's suspension of its European Union accession bid have complained of other symptoms too - shortness of breath, coughing, and vomiting that lasted for weeks.
The BBC World Service has spoken to chemical weapons experts, whistleblowers from Georgia's riot police, and doctors, and found the evidence points to the use of an agent that the French military named camite.
The Georgian authorities said our investigation findings were absurd and the police had acted legally in response to the illegal actions of brutal criminals.
Camite was deployed by France against Germany during World War One. There is little documentation of its subsequent use, but it is believed to have been taken out of circulation at some point in the 1930s, because of concerns about its long-lasting effects. CS gas - often referred to as tear gas - was used as a replacement.
Konstantine Chakhunashvili was one of those who gathered outside Georgia's parliament in Tbilisi during the first week of protests - which began on 28 November 2024. Demonstrators were incensed by the ruling party's announcement that it was pausing EU accession talks. The goal of EU membership is enshrined in Georgia's constitution.
Georgia's police responded with a variety of riot-control measures including the use of water cannon, pepper spray and CS gas.
Dr Chakhunashvili, a paediatrician who was among those sprayed by the cannons, and who has taken part in many of the demonstrations, said his skin felt like it was burning for days, and the sensation couldn't be washed away. In fact, he said, it was worse when trying to wash it off.
Dr Chakhunashvili wanted to find out if others had suffered similar effects. So he appealed, via social media, for those also targeted by crowd control measures during the first week of the demonstrations to fill out a survey. Nearly 350 people got in touch, and almost half said they had suffered one or more side-effects for more than 30 days.
These long-term symptoms ranged from headaches, to fatigue, coughs, shortness of breath and vomiting.
His study has since been peer reviewed and has been accepted for publication by Toxicology Reports, an international journal. Sixty-nine of those surveyed by Dr Chakhunashvili were also examined by him and found to have significantly higher prevalence of abnormalities in the electrical signals in the heart.
Dr Chakhunashvili's report echoed the conclusion that local journalists, doctors, and civil rights organisations had come to - that the water cannon must have been laced with a chemical. They had called on the government to identify what had been used, but the Ministry of Internal Affairs - responsible for the police - refused.
Several high-level whistleblowers connected to the Special Tasks Department - the official name of Georgia's riot police - helped the BBC determine this chemical's likely identity. A former head of weaponry at the department, Lasha Shergelashvili, believes it is the same compound he was asked to test for use in water cannon in 2009.
When watching footage of the protests last year, he immediately suspected that demonstrators were being subjected to the same chemical. Mr Shergelashvili found it difficult to breathe after standing close to where it had been sprayed, and he and his colleagues could not easily wash it off.
Mr Shergelashvili said that as a result of his tests, he recommended against the chemical's use. But he says the water cannon vehicles were nevertheless loaded with it - and that this remained the case at least up until 2022, when he quit his job and left the country.
The BBC obtained a copy of the inventory of the Special Tasks Department, dated December 2019, which contained two unnamed chemicals. One was identified as trichloroethylene (TCE), and the second was suspected to be bromobenzyl cyanide, also known as camite.
Prof Christopher Holstege, a toxicology expert, confirmed that symptoms reported by exposed individuals aligned with camite's effects. He cautioned that the use of such an outdated and dangerous chemical could violate international law.
The Georgia government has maintained that their actions were legal and necessary in response to protests they deemed criminal. Despite declining demonstrations, protests continue in Georgia against what is viewed as a move towards authoritarianism and alignment with Russian interests.
