有機抗紫外線成份於加氯水中形成消毒副產物之生成潛能探討

Abstract

根據流行病學所觀察到消毒副產物與膀胱癌之關係，泳池中消毒副產物的暴露一向被視為重要的公共衛生議題；過去台灣的研究曾指出暴露於泳池中特定消毒副產物的健康風險是非常值得關注的。減少消毒副產物的前驅物濃度是一種可行的降低風險作法，而游泳者本身所帶有的汗水、尿液和一些個人護理產品等已被證明為消毒副產物的前驅物。近年來有越來越多的研究討論個人護理產品中常見物質–有機抗紫外線成份；不過，針對有機抗紫外線成份與氯系消毒劑反應之消毒副產物的相關研究並不多見。因此，本研究旨在針對氯化實驗進行討論，以增加對有機抗紫外線成份於泳池水中形成消毒副產物的了解。 本研究選擇氯仿及甲醛作為目標消毒副產物；有機抗紫外線成份部份，根據過去研究泳池中的檢出率和濃度以及個人護理產品中的檢出率，挑選包括：羥苯甲酮、奧克立林、甲氧基肉桂酸辛酯、4-甲基亞?基樟腦、水楊酸辛酯、甲基水楊醇及對二甲氨基苯甲酸異辛酯作為氯化實驗的反應物。本研究模擬實際泳池情況，針對不同的酸鹼值與游離有效氯濃度進行氯化反應實驗；每次總實驗時間為12小時且每3小時採樣一次。另外，由於紫外光也被廣泛用於消毒泳池，因此本研究也進行紫外光的介入實驗。所有實驗樣本以頂空固相微萃取搭配氣相層析質譜法分析氯仿及甲醛，並以基質匹配檢量線作為定量方法。 研究結果顯示，初始游離有效氯濃度與所形成之氯仿及甲醛呈高度正相關。此外，氯仿的生成明顯受到酸鹼值的影響，且於鹼性條件下會增加其產量。紫外光和加氯消毒同時使用時，會導致甲醛的產量大幅增加；而紫外光對於氯仿生成的影響較不明顯。 本研究發現在3 mg/L NaOCl和pH 8的條件下反應12小時後，氯仿和甲醛濃度分別為15.74 ng/mL和9.78 ng/mL。若將此濃度和過往研究泳池氯仿和甲醛的平均濃度進行比較，發現本研究氯化實驗所得到的濃度結果相當可觀。由於有機抗紫外線成份為本研究氯化實驗中唯一的碳源，因此可用以說明其對於氯仿和甲醛的生成具有重要意義。 由於游泳者不斷帶入有機紫外線成份，且氯系消毒劑被預期維持在特定濃度下，因此有機抗紫外線成份及其降解產物可能會累積在泳池的循環系統中。為了降低泳池中消毒副產物濃度，建議游泳者在下水前應先仔細沖洗身體。另外，過去曾有報導有些泳池的酸鹼值經常不符合規範，建議泳池管理者宜加強管理泳池的酸鹼值，以減少相關消毒副產物的生成。

Exposure to disinfection by-products (DBPs) in the swimming pool is a significant public health issue since its correlation with bladder cancer has been observed in epidemiologic studies. Precursor reduction was regarded as a feasible measure when the health risk of DBPs in the swimming pool was not acceptable. Bather loads, organic matter carried by the swimmers such as personal care products (PCPs), sweat, and urine, have been proved to be the organic precursors of DBPs. Even though PCPs are potential DBP precursors, most studies focused on addressing urine and sweat. Ultraviolet filters (UV filters), a typical class of ingredients in PCPs, have also been increasingly researched; however, at the moment, little is known about how they may react with chlorine-based disinfectants. Thus, this study aims to contribute to understanding the strength with which UV filters affect the concentrations of DBPs in swimming pool water. Chloroform and formaldehyde were selected as the target DBPs in this study. Based on high detection rates and concentrations in the swimming pool or PCPs, seven UV filters were chosen, including benzophenone-3, octocrylene, octyl methoxycinnamate, 4-methylbenzylidene camphor, ethylhexyl salicylate, homosalate, and 2-ethylhexyl 4-(dimethylamino)benzoate. This study simulated the actual swimming pool conditions and conducted chlorination reaction experiments for different pH values, different free available chlorine (FAC) concentrations and ultraviolet light intervention. All experimental samples were analyzed for chloroform and formaldehyde by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. A matrix-matched calibration curve was applied as the quantification method. Based on the highly positive correlation between initial FAC concentration and the formation of chloroform (R2>0.74) and formaldehyde (R2>0.91), initial FAC concentration played a vital role in the reaction. On the other hand, the changes in pH mainly influenced the formation of chloroform. Hence, more chloroform was produced in the alkaline condition. UV-C intervention with UV filters chlorination led to a dramatic increase in formaldehyde production. It becomes clear that the UV-C effect on formaldehyde production is much more significant than chloroform production. This study provides information regarding the low dose and long reaction period of mixed UV filters which might generate chloroform and formaldehyde. After 12 hours of the test for 3 mg/L NaOCl and pH of 8, the chloroform and formaldehyde concentrations were 15.74 ng/mL and 9.78 ng/mL, respectively. Compared with the average concentrations of chloroform and formaldehyde in swimming pools in previous studies, it was found that the concentration obtained by the chlorination experiment in this study was quite considerable. As the only carbon source in the chlorination experiment in this study, UV filters could be proved as a vital precursor of these two DBPs. Since swimmers are constantly bringing in organic UV filters while chlorine-based disinfectants are expected to be kept at specific concentrations, organic UV filters as well as their degradation products may accumulate in the circulation system of pool water. In order to reduce the concentration of disinfection by-products in swimming pools, swimmers are advised to wash their bodies carefully before entering the water. In addition, it has been reported in the past that the pH value of some swimming pools often does not meet the regulations. It is suggested that swimming pool managers should strengthen the management of the pH value of swimming pools to reduce the generation of related disinfection by-products.