In this study, we report the formation and cancer risk estimation of trihalomethanes (THMs) emanating from ‘ex-situ’ chlorination of shallow hand-dug well water obtained from a peri-urban area of Mufulira District, Zambia. The aim of the study was to evaluate the potential cancer risks for people in this area where chlorine water disinfection at the household level is commonly practiced. Water samples from 13 randomly selected hand-dug wells (4–8 m deep) were collected and analyzed for pH, turbidity, and dissolved organic carbon before chlorination. Then another set of water samples from the same 13 wells was chlorinated using the methods commonly practiced in this area, consistent with WHO recommended doses. The chlorination degradation products, THMs, trichloromethane, bromodichloromethane (CHCl₂Br), dibromochloromethane (CHClBr₂), and tribromomethane, were determined at three different times of 60, 180, and 300 min after chlorination, while residual chlorine was determined immediately after chlorination and at 60 and 1,440 min after chlorination. THMs were determined using gas chromatography (GC), while residual chlorine was determined colorimetrically. Then cancer risk estimation from ingestion, inhalation, and dermal routes was carried out. All water samples from the 13 wells showed elevated amounts of THMs, which also increased with increasing contact time. For instance, the concentrations of THMs at 60 min after chlorination ranged from 24.3 ± 2.0 to 61.3 ± 1.0 μg/L, while at 180 and 300 min, ranged between 85.6 ± 4.3–146.9 ± 2.5 μg/L and 188.1 ± 7.1–250.1 ± 7.1 μg/L, respectively. It was observed that tribromomethane was not detected at all in all samples, while CHCl₂Br and CHClBr₂ were only detected at 180 and 300 min post chlorination. The lifetime cancer risk estimation results showed negligible risk at 60 min post chlorination. However, at 180 and 300 min post chlorination, the results were far above negligible, but within the regulatory US EPA limits. The overall risk, however, could not be ignored, given a multiplicity of exposure to various other contaminants, raising concerns over additivity and synergistic interactive effects, particularly for non-cancer hazard indices.

在这项研究中，我们报告了从赞比亚穆富利拉区郊区获得的浅手挖井水的“异地”氯化作用产生的三卤甲烷 (THM) 的形成和癌症风险估计。该研究的目的是评估该地区人们的潜在癌症风险，该地区通常在家庭一级进行氯水消毒。收集来自 13 个随机选择的手挖井（4-8 m 深）的水样，并在氯化前分析其 pH 值、浊度和溶解的有机碳。然后使用该领域常用的方法对来自同一 13 口井的另一组水样进行氯化处理，与世卫组织推荐的剂量一致。氯化降解产物 THMs、三氯甲烷、溴二氯甲烷（CHCl ₂Br)、二溴氯甲烷 (CHClBr ₂) 和三溴甲烷，分别在氯化后 60、180 和 300 分钟三个不同时间测定，而余氯在氯化后立即测定以及在氯化后 60 和 1,440 分钟测定。THM 使用气相色谱法 (GC) 测定，而余氯则采用比色法测定。然后从摄入、吸入和皮肤途径进行癌症风险评估。来自 13 口井的所有水样均显示 THM 含量升高，并且随着接触时间的增加而增加。例如，氯化后 60 分钟的 THM 浓度范围为 24.3 ± 2.0 至 61.3 ± 1.0 μg/L，而在 180 和 300 分钟，范围为 85.6 ± 4.3–146.9 ± 2.5 μg/L 和 188.1 ± 7.1–250.1分别为 ± 7.1 μg/L。观察到在所有样品中根本没有检测到三溴甲烷，而 CHCl₂ Br 和 CHClBr ₂仅在氯化后 180 和 300 分钟时检测到。终生癌症风险估计结果显示，氯化后 60 分钟的风险可以忽略不计。然而，在氯化后 180 和 300 分钟，结果远高于可忽略不计，但在美国 EPA 监管限制范围内。然而，鉴于多种其他污染物的多重暴露，整体风险不容忽视，这引发了对可加性和协同交互作用的担忧，特别是对于非癌症危害指数。