Top government officials have sought to allay fears that the massive use of tear gas by police in the months-long civil unrest is posing health and environmental risks to Hongkongers.
Police have fired more than 10,000 canisters of tear gas since June in operations against anti-government protesters, raising concerns among members of the public that the crowd-control weapon could release poisonous substances, such as cyanide and dioxin, after it combusts under high temperature.
During a question-and-answer session at the Legislative Council on Wednesday, Democratic Party lawmaker Helena Wong Pik-wan asked Secretary for Food and Health Sophia Chan Siu-chee to provide details about the substances contained in tear gas.
In her reply, Chan said the Department of Health and the Hong Kong Poison Information Centre of the Hospital Authority have reviewed relevant medical literature and scientific evidence but have found no evidence on dioxin poisoning cases caused by the use of tear gas, the Hong Kong Economic Journal reported.
Given the short time of combustion of tear gas canisters, any cyanide produced would quickly disperse in the air, Chan said.
She noted that those exposed to tear gas generally experience mild respiratory and skin irritation.
“On the procurement of equipment and ammunition, the police have been sourcing globally for safe and suitable equipment and ammunition in accordance with the established procedures to meet their operational needs,” she said.
“As the procurement details of the equipment used by the police involve operational deployment, the police considered that it would be inappropriate to disclose procurement details as it would affect the police’s operational capability.”
The health chief added that the police “will continue to use tear gas in a safe manner in accordance with the guidelines issued by the manufacturer and internally”.
Asked about the release of dioxin from tear gas, Secretary for the Environment Wong Kam-sing told lawmakers that the Environmental Protection Department is collecting data on the chemical compound for November, adding that conducting tests will take time.
Wong stressed, however, that garbage burned in open air is the main source of dioxin globally.
The Democratic Party’s Helena Wong slammed the health and environment bureaus for refusing to provide more details about the use of tear gas, accusing them of having been led by the nose by the Security Bureau because they have not dared to ask further when the bureau refused to provide relevant data.
Chan Ka-hung, an epidemiologist from the University of Oxford, said police have not followed international guidelines on the use of tear gas as officers have been caught on camera multiple times firing it indoors, toward people or from high places.
He urged the government to conduct researches and release relevant data on tear gas, instead of just trying to reassure the public with words.
Chan also said it’s totally wrong for anyone to link burning garbage to the release of cyanide and dioxin in the atmosphere.
David Hui Shu-cheong, a Stanley Ho professor of respiratory medicine at the Chinese University of Hong Kong, agreed that the government should provide the public with detailed information about tear gas.
Such information includes whether tear gas has substances other than CS gas, its major component, and how high is the temperature of a tear gas canister when it is fired.
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