Application of Helminth ova infection dose curve to estimate the risks associated with biosolid application on soil

Helminth ova (HO) are the main biological concern when reusing sludge for agricultural production. Worldwide sludge regulations consider a permissible range of 0.25-1 HO/gTS. Such limits are unaffordable to most developing countries, due to high helminth ova content in sludge, and the lack of viable technology to inactivate them as needed. The quantitative microbial risk assessment (QMRA) is a useful tool to estimate the risk of treated sludge, considering feasible and viable limits. QMRA, however, has not been applied before for HO because no dose-infection curve was available. Therefore, the objectives of this paper are: to build up a risk-based model designed for untreated wastewater exposure (i.e., land irrigation) using Ascaris lumbricoides eggs as indicators for HO, and apply the results to assess health risk (i.e., Ascaris lumbricoides infection) associated with consumption of crops grown on biosolid-enriched soil. Data showed that it may be feasible to update HO threshold in biosolids from developing countries without significantly increasing risks. To reduce health risk from HO, it may be wiser to achieve feasible and evidence-based standards, than to set unaffordable limits in these countries. QMRA data suggested additional protection measures, such as biosolid application rates, crop restriction, and produce better washing practices.     

Estimation of norovirus infection risks to consumers of wastewater-irrigated food crops eaten raw

A quantitative microbial risk analysis—Monte Carlo method was used to estimate norovirus infection risks to consumers of wastewater-irrigated lettuce. Using the same assumptions as used in the 2006 WHO guidelines for the safe use of wastewater in agriculture, a norovirus reduction of 6 log units was required to achieve a norovirus infection risk of ~10^-3 per person per year (pppy), but for a lower consumption of lettuce (40–48 g per week vs. 350 g per week) the required reduction was 5 log units. If the tolerable additional disease burden is increased from a DALY (disability-adjusted life year) loss of 10^-6 pppy (the value used in the WHO guidelines) to 10^-5 pppy, the required pathogen reduction is one order of magnitude lower. Reductions of 4–6 log units can be achieved by very simple partial treatment (principally settling to achieve a 1-log unit reduction) supplemented by very reliable post-treatment health-protection control measures such as pathogen die-off (1-2 log units), produce washing in cold water (1 log unit) and produce disinfection (3 log units).     

Estimation of norovirus and Ascaris infection risks to urban farmers in developing countries using wastewater for crop irrigation

A quantitative microbial risk analysis—Monte Carlo method was used to estimate norovirus and Ascaris infection risks to urban farmers in developing countries watering their crops with wastewater. For a tolerable additional disease burden of10^-4 DALY loss per person per year (pppy), equivalent to 1 percent of the diarrhoeal disease burden in developing countries, a norovirus reduction of 1–2 log units and an Ascaris egg reduction to 10–100 eggs per litre are required. These are easily achieved by minimal wastewater treatment—for example, a sequential batch-fed three tank/pond system. Hygiene improvement through education and regular deworming are essential complementary inputs to protect the health of urban farmers.     

Assessment of E. coli and Salmonella spp. infection risks associated with different fecal sludge disposal practices in Thailand

The proper management of fecal sludge (FS), to block the transmission pathways of pathogens, is rarely enforced in many parts of the world. Health risks associated with different disposal practices of FS in peri-urban settings of a large metropolis in Thailand were assessed; Tha Klong sub-district with indiscriminate FS dumping, and Klong Luang sub-district which has an FS treatment system. The study showed that indiscriminate FS dumping from along the canal banks and discharge of market waste were likely the major sources of E. coli and Salmonella spp. in contamination of the canal water. The increased microbial pathogen concentrations near the FS treatment facility also indicated contamination risks from poorly designed treatment facilities. Quantitative microbial risk assessment (QMRA) indicated very high water-related infection risk levels compared to the actual locally recorded disease occurrences. These results indicated that the QMRA model needs to be modified to take account of immunological differences between populations in developed countries, where the model was developed, and developing countries. In addition, further sensitivity factors are needed to reflect different societal behavior patterns, and therefore contact with potentially contaminated water, in different sub-populations of many less developed communities.     

婴幼儿放射防护装置与多种方法配合使用减少辐射剂量的应用研究

目的：探讨婴幼儿放射防护装置与多种方法配合使用以减少辐射剂量的临床应用价值。方法：在婴幼儿放射防护装置检查床上,使用3块倒U形有机铅玻璃罩和垂直铅挡板组成相对独立的空间,通过调节有机铅玻璃罩和垂直铅挡板不同位置以达到辐射防护的目的,并与婴幼儿体位固定支具,采用监控摄像头、调节照射野、靶一片距及室内温度等方法采取低剂量方法,最大限度降低患儿辐射剂量。结果：通过婴幼儿放射防护装置与辅助设备的使用,有效提高了在CT扫描、DR摄影等各种患儿检查时的成功率,确保影像质量,避免重复检查,减少了患儿辐射剂量。结论：有效减少患儿辐射剂量和其他人群的照射,遵循X射线检查的正规化和辐射防护最优化原则,在获得必要诊断信息的同时使受检儿童受照剂量保持在合理的最低水平。