Environmental NGO Greenpeace has claimed that the blue liquid fired from water cannons could contain toxic substances despite assurances from Hong Kong police that the liquid is “harmless.”

Law enforcement started using trucks armed with water cannons in late August, targeting protesters who threw hard objects or Molotov cocktails at riot police. Besides water, the water cannon can also fire a blue liquid which causes severe skin irritation.

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A water cannon truck in Causeway Bay. File photo: May James/HKFP.

On Thursday, Greenpeace said that it had obtained a sample of the liquid, and preliminary lab tests showed that it contains dye and adhesive. The test results have not yet shown any toxic substances, but the group said that the liquid’s composition was “not just dye.”

“We deduce that the ‘coloured liquid’ may contain harmful tear spray solution (including Pelargonic Acid Vanillylamide Solution), or Chloroacetophenone or 2-Chlorobenzylidene malononitrile, two kinds of toxic tear-inducing chemicals,” the group said.

The group said it cited from a Legislative Council document, expert opinions, the Handbook of Toxicology of Chemical Warfare Agents, and reactions from members of the public who were exposed to the liquid.

“Even though the chemicals in the ‘coloured liquid’ have a low level of lethality, it may cause severe and immediate discomfort to the human body,” Greenpeace added.

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Photo: Studio Incendo.

Citing medical literature, the group said that the chemicals present in pepper spray and tear spray may damage eyesight, cause skin irritation and inflame the respiratory system.

Greenpeace questioned why the police had not disclosed the chemical composition of the blue liquid, saying that many people – including street cleaners, reporters, restaurant owners and customers – have been affected.

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In response, the Hong Kong police said on Friday that the blue liquid was a “non-toxic coloured substance” and was “harmless to the human body.” The aim of the liquid was to help police identify whether protesters had been present at a particular place, it added.

Police said that the effect of tear spray – the Pelargonic Acid Vanillylamide Solution – was similar to that of pepper spray, and will only cause temporary discomfort. The effects will cease in 10 to 15 minutes after the affected body parts were washed with water and exposed to fresh moving air.

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Photo: Studio Incendo.

The blue liquid and the tear spray are deployed via water cannon depending on the situation, a spokesperson added.

In 2018, the Hong Kong government announced that it would purchase three water cannon trucks worth HK$27 million. Despite pressure from pro-democracy lawmakers, the usage guidelines for the trucks have never been publicly revealed.

Water cannons were deployed against pro-democracy protesters around three months after the start of large-scale street clashes, sparked by a now-withdrawn anti-extradition bill that would have allowed fugitive transfers to mainland China.

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Holmes Chan is a reporter at Hong Kong Free Press. He covers local news with a focus on law, politics, and social movements. He studied law and literature at the University of Hong Kong.