LettersHave Hong Kong protests and police tear gas taken a severe toll on the environment and wildlife?

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Hong Kong’s police, as well as its protesters, have protection from tear gas, but what about its wildlife and vegetation? Photo: AP

Published: 7:15am, 1 Dec 2019Updated: 7:15am, 1 Dec 2019

A banner is unfurled bearing the words “Warning: Tear Smoke” in both Chinese and English, quickly followed by metal canisters and trails of smoke raining down on protesters. Stinging, choking clouds of smoke have become common sights on Hong Kong streets. Equipped with gas masks, the protesters have found ways to protect themselves, but how about the local environment and wildlife?

The use of tear gas in Hong Kong has been controversial and there are worries about its health effects, and about tear gas-contaminated food (“Parents, children in march against health hazards of tear gas”, November 23). Clinical effects for humans include inflammation and irritation to the skin, eyes and airways, while people with existing respiratory ailments are at higher risk. But little is known about the effects of tear gas on animals and the environment.

Tear gas was outlawed for military use under the Geneva Protocol of 1925, yet remains a popular form of riot control worldwide. The Hong Kong Police Force use a form of tear gas known as o-chlorobenzylidene malononitrile (CS for short). The long-term effects of the irritant powder on wildlife and environment health remain unclear, while images and videos of purportedly lifeless birds after supposed exposure to tear gas have been circulating online in Hong Kong.

Given the sensitivity of birds to respiratory irritants, it comes as no surprise that such avian deaths may have occurred due to direct contact with tear gas. In fact, a 1972 study on rodents and guinea pigs found that exposure to high concentrations of CS gas can result in death due to severe lung damage.

A Hong Kong reporter was recently diagnosed with chloracne after tear gas exposure. How, then, does it affect the environment? Immediate effects can be observed, but long-term studies are limited. It will be useful to know the animal death toll in Hong Kong due to exposure to CS.