Since the anti-extradition bill movement erupted more than two months ago, the Hong Kong police have fired more than 1,800 rounds of tear gas at protesters.
On Aug. 5 alone, the law enforcement personnel fired more than 800 tear gas rounds.
In many cases, the police were using tear gas in residential neighborhoods, and also in districts where there are a number of care and attention homes for the elderly as well as primary and secondary schools.
As the officers continue to fire tear gas into densely populated urban areas and even, on several occasions, inside MTR stations, it raises concerns about the impact of their actions on public health.
Based on some of the metallic cases recovered at protest scenes, we can tell that one of the models of the tear gas canister used by the police is the US-made MP-6M5-CS, which is a cluster projectile that can release up to five separate submunitions filled with gas agents, allowing the tear gas to be spread over a large area.
If we refer to the user guide provided by the manufacturer of the MP-6M5-CS rounds, we will find that this model of tear gas canister can only be used outdoors.
Mainly composed of a chemical compound known as the “CS”, which presents itself in the form of solid powder under normal temperature, the MP-6M5-CS quickly turns into an aerosol as a result of heat, after being fired from a riot control launcher, and then releases the compound aerially.
Once coming into contact with the mucous membranes and skin tissues of the human body, the CS spray can immediately cause severe allergic reactions such as an acute burning sensation.
For the elderly, children and people with respiratory problems, the CS spray can prove particularly harmful, since it can often result in symptoms including breathing difficulties, asthma attacks, or sometimes even death.
Although in the past, there were studies suggesting that brief exposure to tear gas in low concentrations wouldn’t constitute long-term health issues, recent data indicates that exposure to tear gas at an average concentration of 0.75 mg per cubic meter for an hour could lead to serious physical distress.
Some overseas medical experiments have also suggested that people who have been exposed to tear gas in the past may suffer a higher risk of developing chronic bronchus and respiratory tract disorders such as chest pain, lung injury and breathing problems in the future.
As the riot police have been frequently using tear gas to repel protesters in narrow streets and alleys as well as in densely populated neighborhoods in recent weeks, many citizens may have been exposed to such gas agent beyond safe levels.
Unfortunately, what I have found disappointing is that so far the government has not yet put the existing guidelines on using tear gas to any rigorous review.
Worse still, the administration is continuing to look the other way, or even seems to courage, as frontline police officers keep on using tear gas against protesters recklessly, and on several occasions, even in indoor areas.
Since tear gas is a kind of aerosol that contains countless crystalline particles and is a lot denser than air, it is difficult to evaporate.
What is more, tear gas remnants can stay in the atmosphere for a long time, and can easily adhere to textile fibers and get into the ventilation or air-conditioning systems of buildings, thereby posing athreat to citizens’ health.
Given the air pollution and health risks caused by tear gas, I believe the police must exercise restraint when carrying out their duty, as well as review and strictly follow the guidelines on using it.
Meanwhile, the government should conduct studies on the concentration of tear gas remnants in the community, and bear the responsibility of controlling and cleaning up this harmful substance so as to protect public health.
This article appeared in the Hong Kong Economic Journal on Aug 16
Translation by Alan Lee
[Chinese version 中文版]
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