Via electronic mail

Ms. Cheng Mei Sze, Maisie, JP
Permanent Secretary for the Environment
Environmental Protection Department
The Government of the HKSAR

November 17, 2019


Dear Ms. Cheng,

Request for immediate actions from Environmental Protection Department (EPD) to address strong public concern on toxic substance / dioxin in air

In recent weeks, there has been a widespread concern on the level of toxic substance in air and the associated short- and long-term health risk among general public especially the vulnerable groups including elders, children and chronic patients.

It was reported [1] that up to 88% of the Hong Kong population has been exposed to tear gas since June 2019. The amount of tear gas used in Hong Kong ‘is unprecedented for a tightly populated urban capital’. The gas often ‘can’t escape or has nowhere to go but up into the windows of residential tower blocks’, depending on microenvironment such as wind conditions, building density, etc.

According to literature [2], carcinogenic dioxin-like compounds are formed in chemical reactions that occur during the combustion of organic compounds in the presence of chlorinated materials. Despite the Food & Health Bureau being unable to confirm and publicize the chemical composition of the tear gas [3], the Hong Kong Police Force in a later media briefing [4] has admitted the tear gas has produced dioxin.

Therefore, it is understandable to observe a widespread concern of health risk due to tear gas or its residue at community. As an active civic organization which focuses on air pollution and public health issue, we have received lots of public enquiry in the past weeks. Specific concerns from the general public include whether it is still safe to use facilities in the community previously exposed to tear gas, and the appropriate actions to minimize health effect after exposure.

After strong public and media enquiry, the Centre for Health Protection of the Department of Health has released the Health Information on Tear Gas earlier this month [5]. It might address part of the public concern. The public fear of being exposed to toxic substance in the air, including dioxin, has escalated last week due to a suspected case [6] of reporter diagnosed with chloracne recently which has been linked directly to dioxin exposure,” according to the United States Department of Veteran Affairs [7].

According to the latest EPD reply to media enquiry [8], we understand that it might take several weeks for analysis before the level of dioxin in air to be released for October 2019. We do also note that:

  • there is only one day out of a month is selected for sampling of dioxin in each toxic air pollutant (TAP) station;
  • there are only 2 TAP stations (Central & Western and Tsuen Wan), out of the total 16 air pollution monitoring stations, which conduct regular sampling of dioxin;
  • the Central & Western station and the Tsuen Wan station are located at a height 16 meters and 17 meters above from ground respectively;
  • there is no sampling or monitoring of dioxin level in air at outdoor environment at street level, at densely populated areas in the community such as near residences, schools, parks or public transport interchanges


As a result, it is unlikely the general public is equipped with adequate information to judge whether the community is still safe for their daily living at roadside in all 18 districts in Hong Kong.


Due to strong public concern, we urge the EPD to consider the below immediate actions to address the above information gap:

i) release the data of dioxin level in October and November 2019 asap;

ii) conduct monitoring / sampling of dioxin level on every single day in both TAP stations and to release the data asap;

iii) conduct monitoring / sampling of dioxin level on every single day in all EPD’s air pollution monitoring stations and to release the data asap;

iv) immediately commence a 1-month sampling or monitoring of dioxin level at outdoor environment at all 18 districts and to release the data asap.


In order to implement (ii) – (iv), it is suggested for the Government to allocate additional resources required through emergency funding [9]. In two consecutive years (2018 and 2019), emergency funds of HK$500 million each were injected by the HKSAR Government to Hospital Authority to tackle shortage of healthcare manpower during flu peak season.

We call on the Government to acknowledge any prolong in action to fill the information gap might result in further escalating concern among the public on health and safety due to toxic substance in air and the environment.

We look forward to your reply and would be pleased to discuss these matters with appropriate officials at your convenience.



Patrick FUNG
Chief Executive Officer
Clean Air Network



[1.] Bloomberg – Millions in Hong Kong Have Been Exposed to Tear Gas Since June

Date: November 6, 2019
Date accessed: November 16, 2019


[2.] ATSDR. 1998. Toxicological Profile for Chlorinated Dibenzo-p-dioxins. Atlanta, GA: ATSDR.


[3.] Hong Kong Free Press – Hong Kong reporter diagnosed with chloracne after tear gas exposure, prompting public health concerns

Date: November 14, 2019
Date accessed: November 16, 2019


[4.] RTHK – 汪威遜承認催淚彈釋出二噁英 但指燒塑膠釋出更多

Date: November 15, 2019
Date accessed: November 16, 2019


[5.] Centre for Health Protection, Department of Health, HKSAR Government – Health Information on Tear Gas

Date: November 7, 2019
Date accessed: November 16, 2019


[6.] Hong Kong Free Press – Hong Kong reporter diagnosed with chloracne after tear gas exposure, prompting public health concerns

Date: November 14, 2019
Date accessed: November 16, 2019


[7.] US Department of Veterans Affairs – Chloracne or Acneform Disease and Agent Orange


[8.] RTHK – 環保署稱去年及今年首9月空氣中二噁英濃度沒異常

Date: November 17, 2019
Date: November 17, 2019


[9.] South China Morning Post – Emergency flu funds of HK$500 million headed to Hong Kong hospitals for second year

Date: January 29, 2019
Date of access: November 16, 2019

Story posted on
17th Nov, 2019


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