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影音》中山大學氣膠中心:不良通風系統可能加速新冠病毒擴散

發佈日期: 2021-06-07

新冠肺炎肆虐全球,WHO已於今年4月宣布氣膠傳播(又稱氣溶膠傳播或空氣傳播)為主要傳播途徑,台灣本土亦面臨疫情爆發以來最嚴峻挑戰。國立中山大學氣膠科學中心主任王家蓁與美國奧勒岡州立大學全球衛生中心主任紀駿輝共同指出,不良通風系統可能加速疫情擴散,「加強空氣的清潔與消毒」對於阻斷病毒氣膠傳播鏈相當關鍵。改善室內通風、避免室內髒空氣的重覆循環、加裝含有可過濾氣膠微粒濾網如HEPA濾網的空氣清淨機,或於室內加裝可有效抑制病毒活性的紫外光燈(UVC)是當前可降低室內病毒氣膠傳播的有效方法。

中山大學氣膠中心主任王家蓁強調,氣膠為懸浮於空中之微小液滴或顆粒物質,人們平時講話、唱歌、咳嗽,甚至僅是呼吸時,會釋放出許多大小在5微米以下的呼氣氣膠。就物理型態而言,氣膠可以視作比一般飛沫更微細的「微飛沫」。由於顆粒大小的差異,氣膠不像飛沫液滴會受到重力主導而在數秒內快速沉降到地面,氣膠的微小粒徑使其深受空氣拖曳力影響,而在空氣中懸浮得更久,甚至在有氣流或風吹的情況下,能夠被傳播到比現行規範的社交距離更遠的距離;一旦被可能宿主吸進體內後,小顆粒的病毒氣膠可能越過鼻咽及上呼吸道直抵肺部更深處的細微支氣管甚至肺泡處而不被現行的鼻咽採樣篩檢所偵測到。因此,若僅以飛沫或接觸傳播的防疫規格進行疫情控制,是無法完全阻止氣膠傳播的,「這也說明為何許多國內外確診者,是在明明已經保持社交距離、戴上口罩的情況下依然受到感染。」

「另一個氣膠與飛沫傳播間非常重要的差異,在於氣膠會相當大程度地受到通風系統的影響,而飛沫不會。」王家蓁主任表示,保持懸浮狀態的氣膠,會隨著本身在呼吸道內產生時呼氣動作的氣流速度(如唱歌及呼吸所產生的氣膠速度即有所不同)、週邊環境氣流風向、室內通風系統,甚至建築物中央空調設計的影響,而流佈到超過現行規範之社交距離以外的地方。進一步提醒,紫外光燈(UVC)雖能有效殺死病毒,但需安裝在適當位置,例如房間上方、空氣清淨機身內或空調系統內部,以避免直射人的皮膚或眼睛造成傷害。另一方面,未來新的建築體也應強化通風系統的設計,以降低因室內環境通風不良所導致的呼吸道感染,以及傳染性疾病透過氣膠傳播的風險。

誠如《小王子》一書中著名的一句話:「真正重要的東西,用眼睛是看不見的」。此次COVID-19疫情正凸顯出社會群體中人與人間的連結之密切及深遠程度,遠超乎我們以往的認知。美國奧勒岡州立大學全球衛生中心主任紀駿輝提到,近日發表在國際權威期刊《Science》的政策論壇(Policy Forum)的專文「改變現有規範以防止室內呼吸道感染」(A paradigm shift to combat indoor respiratory infection)即明確指出,雖然全球各國的公共衛生體系過去對於食物與水源所可能導致的疾病都已建立起完善的防治規範,但對於空氣傳播所可能導致的疾病卻相對地大大忽視。經過新冠肺炎全球大流行,病原體以氣膠形式於空氣中傳播的重要性比以往更加強烈地被注意且證實,人們應改善目前防護力不足的規範及體制加以因應,以確保未來的室內空氣品質,並避免室內通風不良而導致的呼吸道感染。

【參考資料與延伸閱讀】

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