By Tamara Mathias and Ruhi Soni

(Reuters) – The use of tear gas to control crowds of protesters in the Chinese-ruled city of Hong Kong could have dangerous effects on health and the environment, a group of academics warns.

In an article last month in The Lancet, researchers from the Chinese University of Hong Kong (CUHK) called for government-led decontamination efforts in areas where tear gas has been dispersed, including residential neighborhoods and commercial shopping centers. They also commented on the lack of official guidelines on how to protect against side effects.

Since the article was published, Hong Kong’s Food and Health Bureau has acknowledged risks of tear gas exposure and advised citizens to wear masks, rubber gloves and aprons when removing residual material. ( The government’s Centre for Food Safety provided advice on how to protect food from being contaminated. (

Dr. Kevin Hung, an assistant professor of emergency medicine at CUHK and coauthor of the Lancet article, called the government guidelines “good and transparent,” especially since they acknowledge the lack of data on long-term health risks.

“To some people, tear gas sounds very benign – like ‘okay, you have some tears, it’s like cutting an onion!'” he said.

“But actually it’s much more than that… I think our primary goal as academics was to raise awareness.”

In a phone interview with Reuters Health, one protester who has been exposed to teargas described the experience as akin to “having your face shoved into mushed up jalapeños”

In its official notice, the government said exposure could cause a “stinging and burning sensation to eyes and other mucous membranes, tearing, salivation, runny nose, tight chest, headache, nausea, burning sensation of skin, and erythema of skin.”

“These symptoms will usually disappear within a short time after exposure to tear gas,” the government said.

However, The Lancet article cites a 2017 review of previous studies that altogether followed thousands exposed to chemical irritants. That review found two deaths and permanent disabilities, such as blindness, in 58 people. (

Hong Kong, an important trade center for China, has been rocked by anti-government protests since June.

Demonstrators are angry at what they see as Chinese meddling in freedoms promised to the former British colony in 1997. China denies interfering and says it is committed to the “one country, two systems” formula put in place at the time.

Authorities have repeatedly used tear gas containing the chemical irritant o-chlorobenzylidene malononitrile.

Dr. David Hui, a respiratory physician at CUHK who was not involved in the article, told Reuters Health he has treated about twenty reporters and photographers and a small number of protesters.

Unlike protesters, who disperse when police launch teargas cannisters, journalists tend to rush forward to capture the event and as a result are among the most vulnerable, he said.

Freelance reporter Teele Rebane, who has covered the protests, can confirm.

“By now, I just recognize the sound of the tear gas gun go off,” she said in a phone interview.

“And I know that in a second, there’s going to be teargas everywhere so I better mask up.”

Hui has prescribed antihistamines for shortness of breath, nasal steroids to decrease inflammation, topical steroids for rash and blisters and asthma medication to those with lung disorders, who are at an increased risk.

“Protesters actually try not to turn up at the public hospital for fear of their information being leaked to the police,” he said.

Hung confirms this, adding that incidents of tear gas-related health issues have likely been underreported.

“People are increasingly worried that there are other harmful chemicals that are generated after tear gas has been deployed,” he said.

“The government has not properly responded to our call for environmental monitoring and health authorities are yet to publish formal numbers on how many people have been affected.”

In an email, a spokesperson from the Government of the Hong Kong Special Administrative Region said tear gas is among “non-lethal operational options” used by police to disperse crowds when necessary.

“The Police understands the community’s concerns about the use of tear gas near residential buildings, and will take into account the safety and interests of the affected people as far as possible when using tear gas,” the spokesperson said.

SOURCE: The Lancet, online October 14, 2019.