State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
Environ Sci Technol. 2011 Jun 1;45(11):4951-8. doi: 10.1021/es103981w. Epub 2011 May 10.
The concentrations of Cryptosporidium in the source water of several cities of Zhejiang Province, China were determined to be in the range of 0-17 oocysts/10 L in the rainy season in 2008, with a mean value of 7 oocysts/10 L. Based on the investigation data, comprehensive risk assessment of Cryptosporidium infection was performed by considering different water intake routes as well as water consumption. Intakes of unboiled tapwater (including drinking and tooth-brushing and food and dish washing) and source water (through swimming in rivers) were estimated to be 2.59-25.9 and 0.32-0.74 L/year-person, respectively. The mortality due to Cryptosporidium infection for people in this region, excluding HIV-infected patients, was calculated as 0-0.0146 per 10(5) persons using a conditional probability formula. Disability-adjusted life years (DALYs) were used to quantify the risk of Cryptosporidium infection, for which uncertainty was analyzed. For people who consumed conventionally treated water, the DALYs due to Cryptosporidium infection were 6.51 per 10(5) (95% CI: 2.16 × 10(-5)-22.35 × 10(-5)) persons, which were higher than a risk judged acceptable by some (1.97 × 10(-5) DALYs per year), and the risk for those consuming ozone-treated water became 0.0689 × 10(-5) DALYs per year. The major risk of infection resulted from swimming in the river. This study provides a method to establish the risk of Cryptosporidium infection and optimize the scheme for reducing the risk effectively, which is useful for the modification of water quality standards based on cost utility analysis given use of DALYs.
2008 年雨季，中国浙江省几个城市的水源Cryptosporidium 浓度在 0-17 个卵囊/10 升之间，平均值为 7 个卵囊/10 升。基于调查数据，考虑到不同的饮水途径和水耗，对隐孢子虫感染进行了综合风险评估。估计未煮沸的自来水（包括饮用、刷牙、食物和餐具洗涤）和水源（通过在河流中游泳）的摄入量分别为 2.59-25.9 和 0.32-0.74 升/年/人。对于该地区的非 HIV 感染者，使用条件概率公式计算的隐孢子虫感染死亡率为 0-0.0146/10(5) 人。使用残疾调整生命年（DALYs）来量化隐孢子虫感染的风险，并对其不确定性进行了分析。对于饮用常规处理水的人，由于隐孢子虫感染而导致的 DALYs 为 6.51/10(5)（95%CI：2.16×10(-5)-22.35×10(-5))人，高于一些人认为可接受的风险（1.97×10(-5) DALYs 年），而饮用臭氧处理水的风险则降至 0.0689×10(-5) DALYs 年。感染的主要风险来自于在河中游泳。本研究提供了一种建立隐孢子虫感染风险的方法，并有效地优化了降低风险的方案，对于基于成本效用分析的水质标准修改，利用 DALYs 是有用的。
