源分离尿液收集、利用的病原性健康风险计算评估

Microbial health hazard assessment associated with the utilization of source-separated human urine

为了明确源分离生态卫生系统收集、利用尿液过程中所导致的人体健康风险,对尿液中病原体的含量进行了调查分析,采用蒙特卡洛方法对尿液收集、利用环节所导致的健康风险进行了模拟计算。结果表明,尿液中的病原体主要来自粪便的交叉污染,细菌和隐孢子虫等不会造成大的风险,风险主要来源于病毒,即使摄入剂量很低（1mL）的、没处理过的尿液,其中的病毒也会对人体健康产生很高的风险（0.02-0.87 a^-1,均值为0.08 a^-1）。尿液浇灌施肥时造成的感染风险和尿液的储存时间有关,经过30 d的储存后,细菌和原生动物的尿液对人体的感染风险都很低,然而对于在5℃下储存6个月的尿液或20℃下储存1个月的尿液,轮状病毒的感染风险概率为10-1a^-1的数量级。如果尿液喷洒前在20℃下储存6个月,平均风险会降低到10-5a^-1数量级。对食用尿液浇灌的农产品进行的风险计算表明,浇灌两周后采摘食用蔬菜造成的健康风险为10-9a^-1数量级,可以忽略不计。

The paper is to introduce a microbial health hazard assessment associated with the utilization of source-separated human urine.The reason why we would like to pick up the research topic is to make benefits of the urine utilization as a natural fertilizer in agriculture in favor of reducing the nitrogen and phosphorus load in the domestic sewage and transmitting human excreta with less fresh water in comparison with the conventional gravitational flow drainage system.However,it is necessary to identify the infectious hazards of disease when handling and using the urine so as to protect people＇s health and promote the development of ecological sanitation environment.In this study,we have collected data of human faecal sterols in the urine and worked out the faeces content in it based on the average sterol level in them.Then we have done the evaluation of the amount of pathogen in the isolated urine by utilizing the epidemiological data on the pathogens in human faeces,with the level and probability distribution of the pathogen in the urine.And,then,assessment has been done as to the pathway,the dosage,and the frequency of human exposure to the urine when handling the unstored urine,inhaling aerosols created in handling the urine to be used,and next consuming the grain products fertilized with the urine.Furthermore,we have accounted the pathogenic health risk associated with different urine exposure cases with the Monte-Carlo method and a Crystal Ball 7.0 software.Statistically speaking,it would be unacceptable that the accidental ingestion of 1 mL of unstored fresh urine is likely to bring about health hazard originated from the viruses equal to 0.02-0.87 a^-1 at an average of 0.08 a^-1.The hazard caused by inhaling urine aerosols depends on urine storage time.Though the hazard that may be caused by the bacteria and protozoa is very low with the storage time of 30d,the infection hazard of rotavirus turned out to be at the level of 10-1 a^-1 for the urine after being kept for 6 months at 5 ℃ or 1 month at 20 ℃.However,if it is stored for 6 months at 20 ℃ before being used,the average hazard could be reduced to the level of 10^-5 a^-1.Thus,it can be seen that the hazard that may result from the consumption of vegetables fertilized with urine such as lettuce and cucumber after two weeks is found at the level of 10^-9 a^-1,which can actually be negligible.