Department of Public Health, Maragheh University of Medical Sciences, Maragheh, Iran; Student Research Committee, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
Environmental Health Engineering Research Center, Kerman University of Medical Sciences, Kerman, Iran; Department of Environmental Health, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran.
Ecotoxicol Environ Saf. 2020 Apr 1;192:110286. doi: 10.1016/j.ecoenv.2020.110286. Epub 2020 Feb 6.
Trihalomethanes (THMs) in drinking water are associated with many chemical parameters in water. However, the available evidence on the relationship between physical parameters of the water distribution system (WDS) and THMs is still scarce; therefore, this study aimed to compare the THMs concentration in the old and new WDS in Yazd, Iran. Moreover, we investigated the seasonal trend and health risk assessment of exposure to THMs through ingestion, dermal, and inhalation pathways. Mann-Whitney test was applied to compare THMs between old and new WDS as well as fall season and winter season. The order of THM concentrations was: chloroform > BDCM > DBCM > bromoform. The maximum levels of THMs in the fall and winter were 31 and 39 ppb, respectively, which were less than the WHO recommended limits for drinking water, i.e., <200 ppb. There was a significant difference between the concentration of BDCM in autumn and winter (P-value = 0.01). There was a marginally significant difference between THM concentration in the autumn and winter (P-value 0.09). The total concentration of THMs and chloroform in the old WDS were significantly higher than the new WDS. The mean values of lifetime cancer risks (LTCR) for oral, dermal, and inhalation exposure pathways to THMs were in the acceptable and low-risk levels. The inhalation exposure pathway had the highest LTCR from among the three mentioned exposure pathways. The hazard index was found to be < 1 through oral and dermal pathways. Moreover, the sensitivity analysis revealed that the ingestion rate for oral exposure, the exposure time for dermal and exposure duration for the inhalation exposure pathway had the highest impact on chronic daily intake (CDI). Our finding confirmed that THM concentration in tap water was associated with the lifespan of WDS and this finding could be useful for urban planners and decision-makers.
饮用水中的三卤甲烷（THMs）与水中的许多化学参数有关。然而，关于供水管网系统（WDS）物理参数与 THMs 之间关系的现有证据仍然很少；因此，本研究旨在比较伊朗亚兹德新旧 WDS 中的 THMs 浓度。此外，我们通过摄入、皮肤和吸入途径调查了暴露于 THMs 的季节性趋势和健康风险评估。Mann-Whitney 检验用于比较新旧 WDS 以及秋季和冬季的 THMs 浓度。THM 浓度的顺序为：三氯甲烷>溴二氯甲烷>二溴一氯甲烷>溴仿。秋季和冬季 THMs 的最高水平分别为 31 和 39 ppb，均低于世界卫生组织（WHO）推荐的饮用水限值，即<200 ppb。秋季和冬季 BDCM 浓度之间存在显著差异（P 值=0.01）。秋季和冬季 THM 浓度之间存在边际显著差异（P 值=0.09）。旧 WDS 中总 THMs 和三氯甲烷的浓度明显高于新 WDS。口服、皮肤和吸入暴露途径的终生癌症风险（LTCR）的平均值处于可接受和低风险水平。在上述三种暴露途径中，吸入暴露途径的 LTCR 最高。通过口服和皮肤途径，危害指数<1。此外，敏感性分析表明，口服暴露的摄入率、皮肤暴露的暴露时间和吸入暴露途径的暴露时间对慢性日摄入量（CDI）的影响最大。我们的发现证实了自来水中 THM 浓度与 WDS 的寿命有关，这一发现对城市规划者和决策者可能有用。
