室內游泳池空氣中三氯胺之調查研究

Abstract

加氯是游泳池常見的消毒方式；但是游泳池含有無機或有機化合物，因此與氯反應會產生消毒副產物，而三氯胺(NCl3)即是其中之一。 三氯胺具有高揮發性，容易從游泳池水揮發至空氣中。過去文獻指出，空氣中的三氯胺是造成救生員在工作時產生呼吸道刺激、眼睛刺激等不適症狀的可能原因；儘管如此，國內尚未針對室內游泳池空氣中三氯胺濃度進行調查。 本研究首先參考過去文獻，建立三氯胺空氣採樣與分析方法：採樣器為6mL萃取管柱填充裹附磺胺酸的矽膠，經組合37mm濾紙匣後(其內裝有裹附碳酸鈉和三氧化二砷的石英濾紙)，將流量設為1L/min以進行主動式採樣。採樣結束後，石英濾紙使用10mL二次水脫附，並以離子層析儀分析。 本研究共完成10處室內游泳池共54個三氯胺空氣樣本採樣及104份工作人員問卷調查；結果顯示空氣中三氯胺的平均濃度介於0.022mg/m3~0.066mg/m3之間(平均濃度和各點的濃度均未高過WHO的建議值0.5 mg/m3)，而空氣中soluble chlorine平均濃度則介於0.018~0.14 mg/m3之間。問卷部分，104份問卷中，46%為救生員填答，49%為男性；游泳池工作產生不適症狀中，以眼睛刺激和持續咳嗽占的比例最高，分別為23.1%和22%。本研究將救生員和教練分為暴露組，其餘員工分為低暴露組進行問卷數據分析，結果發現喉嚨痛和持續有痰產生等症狀在暴露及低暴露組之間具有統計上的顯著差異，勝算比範圍分別是1.44~88.33和1.16~15.4。 本研究亦於不同高度(包括：0、0.5、1公尺)進行採樣(共24個空氣樣本)，而結果顯示空氣中三氯胺的濃度分佈與高度(0~1公尺)並無明顯相關。另一方面，本研究透過迴歸分析發現泳客人數和水中自由有效餘氯的含量會影響空氣中三氯胺的濃度(判定係數為0.81，p值為0.003)；而各國游泳池自由有效餘氯規範標準之不同，可能是本研究所觀察之三氯胺結果較文獻記載濃度為低的原因之一。 本研究調查所得之室內泳池空氣中三氯胺濃度雖然皆低於WHO規範的0.5 mg/m3，但救生員及教練等高暴露泳池員工其喉嚨痛的發生情形仍遠高於低暴露員工。因此，建議雇主仍應加強泳池通風效能；而員工若持續出現喉嚨痛等呼吸道症狀，則應釐清是否與泳池環境品質有關。 在維持游泳池水的消毒效能前提之下，水中自由餘氯對空氣中三氯胺濃度的可能貢獻似乎亦需要列入考量。另一方面，良好的通風、強化游泳池水過濾系統的效能，確保泳客具有良好的衛生習慣，同時定期更換游泳池水，則是減少空氣中三氯胺的有效方法。

Chlorination is an important treatment at swimming pools. With human-introduced compounds, various disinfection by-products (DBPs) might be formed. Among the DBPs, trichloramine appears as gaseous form in the atmosphere at indoor swimming pools. Levels of trichloramine, and its health concerns among simmers and lifeguards at indoor swimming pools have been studied in many countries previously. The purpose of this study was then to describe the scenario of trichloramine exposures at indoor swimming pools in Taiwan and to discover the factors affecting the levels of trichloramine. In this study, sampling and analysis method for airborne trichloramine was set up according to the methods published elsewhere. The trichloramine air sampler was composed with two components: the first one was 6mL cartridge tube filled with sulphamic acid coated silica gel, and the second one was 37mm sampling cassette with diarsenic trioxide and sodium carbonate coated quartz fiber filters. It was an active air sampling method, and the air flow rate was set at 1L/min. After sampling, the quartz fiber filter was desorbed by 10mL ultrapure water and further analyzed by ion chromatography. Questionnaires were administrated in this study and the information about swimming pool maintenance was also collected. Ten indoor swimming pools in Taipei were included for field sampling. Concentrations of trichloramine were found to be ranged from 0.017 to 0.15mg/m3 (total of 78 samples). For the pool workers who completed the questionnaire, 51 out of 104 were male, and 48 of them were lifeguards. Among the reported prevalence of respiratory symptoms at work, experiencing eye irritation and cough were the highest. Besides, symptom of sore throat and phlegm were more likely to happen among the high-exposed group (i.e., lifeguards and swimming instructors) than the low-exposed group (odds ratio ranged from 1.44~88.33 and 1.16~15.4 for sore throat and phlegm, respectively). On the other hand, the concentrations of free available chlorine (FAC) in pool water and the number of swimmers were significantly associated with the levels of airborne NCl3 (p-value= 0.003). It is suggested that the regulated FAC levels in different countries may cause the concentrations of trichloramine reported elsewhere to be nonidentical. To lower the level of trichloramine at indoor swimming pool, well-functioned filtration and ventilation systems as well as hygiene code for swimmers are necessary. Changing parts of pool water regularly is also an efficient way. The relatiohship between the FAC value and the airborne trichloramine level should be further concerned.