UCD School of Agriculture, Food Science and Veterinary Medicine, College of Life Sciences, Agriculture and Food Science Centre, Belfield, Dublin 4, Ireland.
Sci Total Environ. 2010 Jan 15;408(4):740-53. doi: 10.1016/j.scitotenv.2009.11.008. Epub 2009 Nov 27.
Cryptosporidium species are protozoan parasites associated with gastro-intestinal illness. Following a number of high profile outbreaks worldwide, it has emerged as a parasite of major public health concern. A quantitative Monte Carlo simulation model was developed to evaluate the annual risk of infection from Cryptosporidium in tap water in Ireland. The assessment considers the potential initial contamination levels in raw water, oocyst removal and decontamination events following various process stages, including coagulation/flocculation, sedimentation, filtration and disinfection. A number of scenarios were analysed to represent potential risks from public water supplies, group water schemes and private wells. Where surface water is used additional physical and chemical water treatment is important in terms of reducing the risk to consumers. The simulated annual risk of illness for immunocompetent individuals was below 1 x 10(-4) per year (as set by the US EPA) except under extreme contamination events. The risk for immunocompromised individuals was 2-3 orders of magnitude greater for the scenarios analysed. The model indicates a reduced risk of infection from tap water that has undergone microfiltration, as this treatment is more robust in the event of high contamination loads. The sensitivity analysis highlighted the importance of watershed protection and the importance of adequate coagulation/flocculation in conventional treatment. The frequency of failure of the treatment process is the most important parameter influencing human risk in conventional treatment. The model developed in this study may be useful for local authorities, government agencies and other stakeholders to evaluate the likely risk of infection given some basic input data on source water and treatment processes used.
隐孢子虫是一种与胃肠道疾病有关的原生动物寄生虫。在世界范围内发生了几起引人注目的暴发疫情后，它已成为主要公共卫生关注的寄生虫。开发了一种定量蒙特卡罗模拟模型，以评估爱尔兰自来水中隐孢子虫的年感染风险。该评估考虑了原水中的潜在初始污染水平、各种处理阶段（包括混凝/絮凝、沉淀、过滤和消毒）后的卵囊去除和消毒事件。分析了一些方案来代表公共供水、团体供水计划和私人井的潜在风险。在使用地表水的情况下，为了降低消费者的风险，额外的物理和化学水处理是很重要的。除了在极端污染事件下，免疫功能正常的个体每年因感染疾病的模拟风险低于 1 x 10(-4)（美国环保局设定）。对于分析的情况，免疫功能低下的个体的风险要高 2-3 个数量级。该模型表明，经过微滤的自来水感染风险降低，因为这种处理在高污染负荷的情况下更稳健。敏感性分析强调了流域保护的重要性和常规处理中充分混凝/絮凝的重要性。处理过程失效的频率是影响常规处理中人类风险的最重要参数。本研究中开发的模型可以为地方当局、政府机构和其他利益相关者提供有用的信息，以便在给定水源和处理过程的基本输入数据的情况下，评估感染的可能风险。
