Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Road, Taipei 106, Taiwan.
Environ Sci Technol. 2013 May 7;47(9):4104-12. doi: 10.1021/es304976q. Epub 2013 Apr 19.
The use of cytotoxic substances, such as 5-fluorouracil and cyclophosphamide, is carefully controlled; however, these medications may still enter bodies of water through wastewater discharge. These substances may pose risks to stream and river life, as well as to humans via drinking water. In this study, the photochemical fate of 5-fluorouracil and cyclophosphamide was investigated in synthetic waters and four river waters and was found to be the most important attenuation process for each entity in natural surface waters. Bicarbonate alone was found to react with the excited states of 5-fluorouracil, thus enhancing direct photolysis rates. In the presence of nitrate and significant amounts of bicarbonate (close to 2 mM), 5-fluorouracil was rapidly removed (within 1 day) through indirect photolysis. In contrast, natural attenuation was of low importance for cyclophosphamide in most surface waters studied. A long, shallow river or lake with a long residence time (>7 days), very low alkalinity, and significant nitrate levels (>5 mg-N L(-1)) may be an exception. The phototransformation product of 5-fluorouracil was also identified. However, the total organic carbon experiments yielded important results: photolysis resulted in quick transformation of 5-fluorouracil but minimal mineralization. Additional studies of the toxicity of photobyproducts of 5-fluorouracil are needed to determine the true risk to human health of 5-fluorouracil contamination of surface water, given its near-total photodegradation and resultant, deceptively low detection rate in surface waters.
细胞毒性物质（如氟尿嘧啶和环磷酰胺）的使用受到严格控制；然而，这些药物仍可能通过废水排放进入水体。这些物质可能对溪流和河流中的生命以及通过饮用水对人类构成风险。在这项研究中，研究了氟尿嘧啶和环磷酰胺在合成水和四条河水中的光化学命运，并发现它们是天然地表水中每种物质最重要的衰减过程。仅碳酸氢盐就被发现与氟尿嘧啶的激发态反应，从而提高了直接光解速率。在硝酸盐和大量碳酸氢盐（接近 2 mM）存在的情况下，氟尿嘧啶通过间接光解迅速去除（在 1 天内）。相比之下，在大多数研究的地表水，自然衰减对环磷酰胺的重要性较低。长而浅的河流或湖泊，停留时间长（>7 天），碱度低，硝酸盐水平高（>5 mg-N L(-1)）可能是一个例外。还确定了氟尿嘧啶的光转化产物。然而，总有机碳实验产生了重要的结果：光解导致氟尿嘧啶快速转化，但矿化程度很低。需要进一步研究氟尿嘧啶光产物的毒性，以确定氟尿嘧啶对地表水的污染对人类健康的真正风险，因为它几乎完全光降解，导致在地表水检测率低得令人上当。
