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一群關心雀鳥安危的香港觀鳥會職員的公開信

2019/11/19 — 15:15

過去一個多月香港觀鳥會收到不少有關催淚氣體對雀鳥影響的查詢,職員們已查閱不少科學文獻並草擬相關回應,但因為內部決策層意見不一,遲遲未能作出適切的回應。我們一群香港觀鳥會辦事處職員就此表示遺憾,並決定以個人身份表達我們的意見。我們認為就一些客觀的事實,市民大眾應有知情權。

反送中條例引發的社會運動持續近半年,我們一直十分關注事件,亦對近月多宗雀鳥疑受催淚氣體影響而死傷的事件感到憂慮。作為一群關心雀鳥的自然保育工作者,我們有責任為雀鳥及大自然發聲。儘管我們並非毒理學、生理學或藥理學的專家,我們仍想分享一下翻閱科學文獻後的初步發現。

胡椒噴霧及催淚氣體是常用於人群控制的刺激物。雖然兩種鎮暴劑在人體引起的刺激徵狀有些相似,包括眼鼻灼熱、咳嗽及喉嚨不適,但實際上它們是兩種不同的物質。辣椒素是胡椒噴霧的有效成分,源於辣椒屬植物的果實如辣椒。而催淚氣體的有效成分為 o-Chlorobenzylidenemalononitrile (CS) 。它是一種粉末狀的合成化學物,通常透過罐內燃燒製造出來的氣體或煙霧散播在空氣中。它在環境中殘留的時間不定,取決於其化學形態和水解速率等因素,有研究指出其在雪中可存留長達 30 天 [1]

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除了化學物的濃度及接觸時間的長短會影響其刺激程度,人和動物細胞中離子通道的化學敏感度亦會有所影響。辣椒素對人類及哺乳類動物是極度刺激的,因其啟動了體內細胞的 TRPV1 離子通道,但鳥類對此物質卻不敏感 [2] 。外國很多研究已經指出 CS ,即使在低濃度的情況下,都對人類和哺乳動物有刺激性 [3] 。這是因啟動 TRPA1 離子通道而引起 [4] ,而該離子通道在家禽(即鳥類)的化學敏感度與其他脊椎動物包括人類亦相似 [5] 。所以我們有理由推斷催淚氣體會刺激甚至危害鳥類,尤其是不能走避飛走的雛鳥。

我們和市民大眾一樣,都關注催淚氣體對野生鳥類的潛在影響。然而,我們沒有相關專業知識去判斷催淚氣體對野生鳥類的實際影響,並調查最近的鳥類傷亡事件。此外,因為學術界均缺乏這方面的研究,我們亦很難估計使用這些鎮暴劑對生態系統的潛在影響。因此,我們促請政府公佈各鎮暴劑(包括催淚彈、胡椒噴霧、藍色水劑等等)的成分及其化學品安全技術說明書、監察及公開鎮暴劑在環境及動物屍體內殘留化學物的水平,並委派受專業訓練及備有合適保護裝備的團隊清潔受影響地方,以確保市民、環境及動物的健康及安全。

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此外,有不少市民在不同地區都發現雀鳥屍體,並擔心雀鳥受催淚氣體傷害而死亡。由於我們沒有毒理學及化驗方面的專業知識、技術及設備,而且現行法例規定只有政府有關部門及認可持牌人士才可以處理雀鳥屍體及化驗,我們無法得知雀鳥死亡的確實原因,或有沒有受其他因素(如催淚氣體)的影響。但根據我們過往的觀察及經驗,並留意案發的周邊環境,我們推測不少雀鳥很有可能是因撞擊玻璃而死。其實不少留鳥及過境遷徙雀鳥都因為撞擊都市大廈的玻璃幕牆而集體死亡,現時正值遷徙季節鳥撞情況更加明顯,可是事件一直都未能引起市民大眾及樓宇管理者充分關注。玻璃或一些透明/反光物料是有機會對雀鳥構成威脅,因為物料反射了附近植被/樹木/天空的影像,或者雀鳥能看到透明物料另一面的植物/樹木,以為能飛過去而導致撞擊受傷或死亡。我們希望各方能採取一些緩解措施(如加添防鳥撞貼紙、使用不透明物料、不清洗使物料表面不反光等等),以減低雀鳥因撞擊而受傷或死亡的機會。

最後,香港不只是一個高樓林立、人山人海的地方,還有不少野生動物適應了城市的環境,成為我們的好鄰居。在這艱難的時候,我們懇請政府及各界別人士能盡忠職守及保持克制,以減低衝突事件的傷害,並保障市民、動物及生態環境的健康,讓城市中的人和野生動物都得以安居。

一群關心雀鳥安危的香港觀鳥會職員

2019 年 11 月 19 日

*以上內容並不代表香港觀鳥會立場

註:

  1. Army, Marine Corps, Navy, Air Force. (2005). FM 3-11.9 Potential Military Chemical/Biological Agents and Compounds. US Army Chemical School, Ft. Leonard Wood, MO. Available from: https://fas.org/irp/doddir/army/fm3-11-9.pdf
  2. Jordt, S.E. and Julius, D. (2002). Molecular Basis for Species-Specific Sensitivity to “Hot” Chili Peppers. Cell, Volume 108, Issue 3, p421-430. DOI: https://doi.org/10.1016/S0092-8674(02)00637-2
  3. Committee on Acute Exposure Guideline Levels; Committee on Toxicology; Board on Environmental Studies and Toxicology; Division on Earth and Life Studies; National Research Council. (2014). Tear Gas (CS) In Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 16. Washington DC: National Academies Press. Available from: https://www.ncbi.nlm.nih.gov/books/NBK224932/
  4. Lindsay, C.D., Green, C., Bird, M., Jones, J.T.A., Riches, J.R., McKee, K.K., Sandford, M.S., Wakefield, D.A. and Timperley, C.M. (2015). Potency of irritation by benzylidenemalononitriles in humans correlates with TRPA1 ion channel activation. Royal Society Open Science. 2: 140160. DOI: http://dx.doi.org/10.1098/rsos.140160
  5. Saito, S., Banzawa, N., Fukuta, N., Saito, C.T., Takahashi, K., Imagawa, T., Ohta, T. and Tominaga, M. (2014). Heat and Noxious Chemical Sensor, Chicken TRPA1, as a Target of Bird Repellents and Identification of Its Structural Determinants by Multispecies Functional Comparison. Molecular Biology and Evolution. 31(3):708–722. DOI:10.1093/molbev/msu001

*  *  *

For the past month or so, the Hong Kong Bird Watching Society (HKBWS) received a number of enquiries expressing concerns on the potential impacts of tear gas on wild birds. Office staff studied various scientific publications and drafted a corresponding reply. But there is a divergence of views between decision makers within HKBWS, thus failing to make an appropriate and timely response to the issue. We, as staff of HKBWS, express our regrets on this and decided to express our views in our own capacity. We consider that there are facts which are objective in nature and the general public deserves to know.

The social movement triggered by the extradition bill has been going on for almost half a year. We have been paying close attention to the incident and are also worried about the casualties of birds which are suspected to be affected by tear gas. As a group of bird caring nature conservationists, we do have the duty to voice out for the birds and the natural environment. Despite the fact that we are not specialized in toxicology, physiology or pharmacology, we would still like to share the preliminary findings of our literature review in response to the above concerns.

Pepper spray and tear gas are commonly used irritants in crowd control. Although the irritating symptoms of these two riot control agents caused in humans maybe similar, with symptoms including burning sensation in eyes and nose, coughing and throat irritation, they are in fact two different substance. Capsaicin is the active ingredient in pepper sprays and is derived from the fruit of plants in the Capsicum genus, such as chili peppers. The active ingredient in tear gas is o-Chlorobenzylidenemalononitrile (CS). It is a powder-like synthetic chemical compound that is often delivered via the gas/fume of burning canisters into the air. Its persistence in the environment varies and can be as long as 30 days in snow, depending on factors including its chemical forms and the rate of hydrolysis [1].

The degree of irritation is related to not only the exposed concentration and duration, but also the chemical sensitivity of the ion channel in human and animal cells. Capsaicin is noxious to mammals like humans due to the activation of the TRPV1 ion channel, but that in birds were found to be insensitive to the compound [2]. Many overseas studies showed that CS is an irritating agent to both humans and mammals even at low concentrations [3]. The irritation caused is related to the TRPA1 ion channel activation [4], which its chemical sensitivity in chicken (i.e. avifauna) is similar to that in other vertebrates including human [5]. As such, it is not unreasonable to expect that exposure to tear gas and its residues would to be irritating or even harmful to birds, particularly nestlings which are not able to avoid tear gas by moving away.

We share the same concerns of the general public on the potential impacts of tear gas on wild birds. Yet it is hard for us to determine the actual harm in birds from the use of tear gas and investigate the recent bird casualty cases as we do not possess relevant expertise. It is also difficult to estimate the potential impacts of these riot control agents on the ecosystem as there is a lack of research and studies on such topic. Therefore, in order to safeguard the health of the general public, the environment and animals, we urge the Government to disclose the composition and their material safety data sheet for all the riot control agents (including tear gas, pepper spray, blue-coloured water, etc.), monitor and make public the level of residue chemicals from the riot control agents in the environment and in animal carcases, and designate special teams with professional training and adequate protective gears to clean up the affected area.

In addition, many members of the public found dead birds in various locations in the city and worried they were killed by tear gas. However, as we do not possess the expertise, skills and resources on toxicology and laboratory testing, as well as handling of bird carcases and necropsy are only limited to relevant Government departments and authorised licensees under the existing legislation, we cannot know the exact cause of death for these birds, or if there are any other factors affecting their death (e.g. tear gas). From our past observations and experience and according to the surrounding environment where the bird carcases were discovered, we consider that many birds died very likely due to collision on glass. In fact, many residents and migrants were found dead collectively as they hit on glass façades of buildings, and such problem of bird strike is particularly obvious now during the migratory season, yet their deaths did not raise adequate attention from the public or the management team of the buildings in the past. Glass or transparent/reflective materials are threatening to birds, as they either reflect images of nearby vegetation/trees/sky or are transparent so the vegetation/trees on the other side can be seen, giving a false impression to the birds that they can pass through and thus leading to casualties by direct collision. We hope all parties and sectors can implement mitigation measures to reduce the chance of birds being injured or killed by collision (such as adding window markers to prevent bird strike, use of opaque materials, not cleaning the material to remain its non-reflectiveness, etc.).   

Hong Kong is not just a place filled with skyscrapers and people, various wildlife has also adapted to this urban environment. We urge the Government and all sectors to remain conscientious, dutiful and calm in each of our roles during this hard time, so as to minimize the damages and injuries in clashes and to safeguard the health of Hong Kong citizens, animals and our environment, such that harmony can be restored in the city.

From a group of HKBWS staff caring for birds

19 November 2019

*The above does not represent the views of HKBWS

Footnotes:

  1. Army, Marine Corps, Navy, Air Force. (2005). FM 3-11.9 Potential Military Chemical/Biological Agents and Compounds. US Army Chemical School, Ft. Leonard Wood, MO. Available from: https://fas.org/irp/doddir/army/fm3-11-9.pdf
  2. Jordt, S.E. and Julius, D. (2002). Molecular Basis for Species-Specific Sensitivity to “Hot” Chili Peppers. Cell, Volume 108, Issue 3, p421-430. DOI: https://doi.org/10.1016/S0092-8674(02)00637-2
  3. Committee on Acute Exposure Guideline Levels; Committee on Toxicology; Board on Environmental Studies and Toxicology; Division on Earth and Life Studies; National Research Council. (2014). Tear Gas (CS) In Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 16. Washington DC: National Academies Press. Available from: https://www.ncbi.nlm.nih.gov/books/NBK224932/
  4. Lindsay, C.D., Green, C., Bird, M., Jones, J.T.A., Riches, J.R., McKee, K.K., Sandford, M.S., Wakefield, D.A. and Timperley, C.M. (2015). Potency of irritation by benzylidenemalononitriles in humans correlates with TRPA1 ion channel activation. Royal Society Open Science. 2: 140160. DOI: http://dx.doi.org/10.1098/rsos.140160
  5. Saito, S., Banzawa, N., Fukuta, N., Saito, C.T., Takahashi, K., Imagawa, T., Ohta, T. and Tominaga, M. (2014). Heat and Noxious Chemical Sensor, Chicken TRPA1, as a Target of Bird Repellents and Identification of Its Structural Determinants by Multispecies Functional Comparison. Molecular Biology and Evolution. 31(3):708–722. DOI:10.1093/molbev/msu001

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