Paul Hynds

Review: Epidemiological evidence of groundwater contribution to global enteric disease, 1948–2015

Globally, approximately 2.2 billion people rely on groundwater for daily consumption. It is widely accepted that groundwater is more pristine than surface water but while this assumption is frequently the case, groundwater is not ubiquitously free of contaminants; accordingly, this presumption can result in an unfounded and potentially hazardous sense of security among owners, operators and users. The current paper presents a review of published literature providing epidemiological evidence of the contribution of groundwater to global human enteric infection. An emphasis is placed on enteric pathogens transmitted via the faecal-oral route, and specifically those associated with acute gastrointestinal illness (AGI). The review identified 649 published groundwater outbreaks globally between 1948 and 2013 and several epidemiological studies that show there is an increased risk of AGI associated with the consumption of untreated groundwater. The review identified that the following five pathogens were responsible for most outbreaks: norovirus, Campylobacter, Shigella, Hepatitis A and Giardia. Crudely, the authors estimate that between 35.2 and 59.4 million cases of AGI per year globally could be attributable to the consumption of groundwater. Although groundwater is frequently presumed to be a microbiologically safe source of water for consumption, this review demonstrates that consumers served by an untreated groundwater supply remain at risk to enteric disease. The authors conclude that collaboration between microbiologists, hydrogeologists and epidemiologists is needed to better understand pathogen occurrence, persistence, detection and transport in groundwater as well as build stronger epidemiological evidence documenting the true magnitude of disease associated with groundwater globally.RésuméÀ l’échelle mondiale, environ 2.2 milliards de personnes dépendent de l’eau souterraine pour leur consommation quotidienne. Il est largement admis que les eaux souterraines sont plus pures que les eaux de surface mais alors que c’est fréquemment le cas, les eaux souterraines ne sont pas complétement exemptes de contaminants ; par conséquent, cette présomption peut donner lieu à un sentiment de sécurité infondé et potentiellement dangereux parmi les propriétaires, les exploitants et les usagers. Le présent article présente une revue de la littérature publiée fournissant des preuves épidémiologiques de la contribution des eaux souterraines aux infections entériques des êtres humains au niveau mondial. L’accent est mis sur les pathogènes entériques transmis par voie féco-orale, et plus particulièrement ceux associés à une maladie gastro-intestinale aiguë (AGI). La revue a identifié 649 épidémies liées à l’eau souterraine au niveau mondial entre 1948 et 2913 et plusieurs études épidémiologiques montrant qu’il y a un risque accru d’AGI associé à la consommation d’eau souterraine non traitée. La revue a permis d’identifier que les cinq agents pathogènes suivants étaient responsables de la plupart des épidémies : norovirus, Campylobacter, Shigella, Hepatite A et Giardia. En gros, les auteurs estiment qu’entre 35.2 et 59.4 millions de cas d’AGI/an dans le monde pourraient être attribuables à la consommation d’eau souterraine. Bien que l’eau souterraine est fréquemment considérée comme étant une source d’eau microbiologiquement sûre pour la consommation, cette revue démontre que les consommateurs desservis par une alimentation en eau souterraine non traitée demeurent exposés aux maladies entériques. Les auteurs concluent que la collaboration, entre les microbiologistes, les hydrogéologues et les épidémiologistes est indispensable pour mieux comprendre la présence, la persistance, la détection et le transport des agents pathogènes dans les eaux souterraines ainsi que pour établir des preuves épidémiologiques plus solides documentant la véritable ampleur des maladies associées aux eaux souterraines au niveau mondial.ResumenA nivel mundial, aproximadamente 2.2 millones de personas dependen del agua subterránea para el consumo diario. Es ampliamente aceptado que el agua subterránea es más prístina que el agua superficial, pero si bien esta suposición es frecuente, el agua subterránea no está libre de contaminantes; Por consiguiente, esta presunción puede dar lugar a una sensación de seguridad infundada y potencialmente peligrosa entre los propietarios, los operadores y los usuarios. El presente documento presenta una revisión de la literatura publicada que proporciona evidencias epidemiológicas de la contribución del agua subterránea a la infección humana entérica global. Se hace hincapié en los patógenos entéricos transmitidos por la vía fecal oral, y específicamente los asociados con las enfermedades gastrointestinales agudas (AGI). La revisión identificó 649 brotes publicados relacionados con el agua subterránea a nivel mundial entre 1948 y 2013 y varios estudios epidemiológicos que muestran que hay un mayor riesgo de AGI asociado con el consumo de agua subterránea no tratada. La revisión identificó que los siguientes cinco patógenos fueron responsables de la mayoría de los brotes: norovirus, Campylobacter, Shigella, Hepatitis A y Giardia. Crudamente, los autores estiman que entre 35.2 y 59.4 millones de casos de AGI/año a nivel mundial podrían atribuirse al consumo de agua subterránea. Aunque se suele presumir que el agua subterránea es una fuente de agua microbiológicamente segura para el consumo, esta revisión demuestra que los consumidores que reciben servicios de suministro de agua subterránea no tratada siguen expuestos a enfermedades entéricas. Los autores concluyen que la colaboración entre microbiólogos, hidrogeólogos y epidemiólogos es necesaria para comprender mejor la presencia, la persistencia, la detección y el transporte de patógenos en el agua subterránea, así como para construir pruebas epidemiológicas más sólidas que documenten la verdadera magnitud de la enfermedad asociada al agua subterránea a nivel mundial.摘要全世界大约22亿人口依赖地下水用于日常消费。普遍认为,地下水比地表水更纯洁,在使用地下水时尽管情况如此,但地下水并不是完全没有污染物的;因此,这种假定可在拥有者、操作者和使用者中产生未发现的、潜在的安全危险感觉。本文回顾了已经发表的有关地下水对全球人类肠道感染贡献的流行病学证据的文献。重点放在了通过粪便-口途径传播的肠道病原体,特别是那些与急性胃肠疾病相关的肠道病原体。回顾确认了1948年到2013年之间已经发布的全球649次疾病爆发,几项流行病学研究显示,与使用未处理的地下水相关的急性胃肠疾病有增长的风险。回顾确认,以下五种病原体是导致大多数疾病爆发的元凶:诺瓦克病毒、弯曲杆菌、志贺氏杆菌、甲肝和鞭毛虫。作者大致估算每年全球急性胃肠疾病3520万到5940万例是由使用地下水造成的。尽管通常人们认为使用地下水从微生物学上讲很安全,但是回顾展示了使用未处理过的地下水仍然具有患肠道疾病的风险。作者最后认为,需要微生物学家、水文地质学家和流行病专家通力合作,更好地了解地下水中的病原体的发生、存留、检测和传输,以及建立全球性质的、记载着与地下水相关的、更强大的流行病证据。ResumoGlobalmente, aproximadamente 2.2 bilhões de pessoas dependem das águas subterrâneas para consumo diário. É amplamente aceito que a água subterrânea é mais pura qua a água superficial mas enquanto essa premissa é frequentemente o caso, a água subterrânea não é onipresentemente livre de contaminantes; assim essa suposiçãopode resultar em um infundado e potencialmente perigoso senso de segurança entre os proprietários, operadores e usuários. O presente artigo apresenta uma revisão da literatura publicada fornecendo evidências epidemiológicas da contribuição das águas subterrâneas para a infecção entérica humana global. É dada ênfase aos agentes patogénicos entéricos transmitidos pela via fecal-oral, e especificamente os associados à doença gastrointestinal aguda (DGA). A revisão identificou 649 surtos de água subterrânea publicados globalmente entre 1948 e 2013 e vários estudos epidemiológicos que mostram que há um risco aumentado de AGI associado com o consumo de águas subterrâneas não tratadas. A revisão identificou que os seguintes cinco patógenos foram responsáveis pela maioria dos surtos: norovirus, Campylobacter, Shigella, Hepatitis A e Giardia. Cruamente, os autores estimam que entre 35.2 e 59.4 milhões de casos de DGA/ ano globalmente poderiam ser atribuíveis ao consumo de águas subterrâneas. Embora a água subterrânea seja frequentemente considerada uma fonte de água microbiologicamente segura para o consumo, esta revisão demonstra que os consumidores atendidos por uma fonte de água subterrânea não tratada permanecem em risco de doenças entéricas. Os autores concluem que a colaboração entre microbiologistas, hidrogeólogos e epidemiologistas é necessária para compreender melhor a ocorrência, persistência, detecção e transporte de patógenos nas águas subterrâneas, bem como construir evidências epidemiológicas mais fortes que documentem a verdadeira magnitude da doença associada à água subterrânea globalmente.

A geostatistical investigation of agricultural and infrastructural risk factors associated with primary verotoxigenic E. coli (VTEC) infection in the Republic of Ireland, 2008-2013.

Ireland reports the highest incidence of verotoxigenic Escherichia coli (VTEC) infection in Europe. This study investigated potential risk factors for confirmed sporadic and outbreak primary VTEC infections during 2008-2013. Overall, 989 VTEC infections including 521 serogroup O157 and 233 serogroup O26 were geo-referenced to 931 of 18 488 census enumeration areas. The geographical distribution of human population, livestock, unregulated groundwater sources, domestic wastewater treatment systems (DWWTS) and a deprivation index were examined relative to notification of VTEC events in 524 of 6242 rural areas. Multivariate modelling identified three spatially derived variables associated with VTEC notification: private well usage [odds ratio (OR) 6·896, P < 0·001], cattle density (OR 1·002, P < 0·001) and DWWTS density (OR 0·978, P = 0·002). Private well usage (OR 18·727, P < 0·001) and cattle density (OR 1·001, P = 0·007) were both associated with VTEC O157 infection, while DWWTS density (OR 0·987, P = 0·028) was significant within the VTEC O26 model. Findings indicate that VTEC infection in the Republic of Ireland is particularly associated with rural areas, which are associated with a ubiquity of pathogen sources (cattle) and pathways (unregulated groundwater supplies).

Organic contaminant removal efficiency of sodium bentonite/clay (BC) mixtures in high permeability regions utilizing reclaimed wastewater: A meso-scale study

Wastewater reclamation now represents an effective measure for sustainable water resource management in arid regions, however wastewater components (organic micropollutants) may potentially impact local ecological and/or human health. Previous studies have shown that sodium bentonite/natural clay (BC) mixes may be used to effectively reduce riverbed infiltration in regions characterized by excessively high hydraulic conductivity. Accordingly, the current study sought to investigate the contaminant removal efficiency (Re) of several BC mass ratios in simulated dry riverbeds. Results indicate that the measured Re of NH4+-N, CODcr and BOD5 increased in concurrence with an increasing sodium bentonite ratio, up to a maximum Re of 97.4% (NH4+-N), 55.2% (CODcr), and 51.5% (BOD5). The primary contaminant removal site was shown to be the infiltration-reducing (BC) layer, accounting for approximately 40%, 60%, and 70% of NH4+-N, CODcr and BOD5 removal, respectively. Conversely, the removal efficiency of NO3-N was found to be low (<15%), while total phosphorous (TP) was found to actively leach from the infiltration-reduction layer, resulting in measured TP discharges 2.4-4.8 times those of initial infiltration values. The current study provides a technical baseline for the efficacy of sodium bentonite as an effective bi-functional material in areas utilizing reclaimed water i.e. concurrent reduction of infiltration rates (Function 1) and decontamination of reclaimed wastewater infiltration/recharge (Function 2). Findings indicate that sodium bentonite-clay mixes may represent a feasible alternative for managing recharge of non-potable aquifers with reclaimed wastewater.

Preface: Hydrogeology and human health

In the mid-1800s, Dr. John Snow (1813–1858), an obstetrician and anaesthesiologist, theorised that cholera, a highly infectious gastrointestinal infection associated with extremely high rates of mortality, was caused by faecal contamination of water supplies (Donaldson and Scally 2009). During the summer of 1854, a significant cholera outbreak occurred in the Soho district of London (UK), resulting in the deaths of 616 people. As part of this first modern epidemiological investigation, Dr. Snow noted that Bwithin 250 yards of the spot where Cambridge Street joins Broad Street there were upwards of 500 fatal attacks of cholera in 10 days (...) suspected some contamination of the water of the much-frequented street-pump (a public well) in Broad Street.^ Snow subsequently developed what is now referred to as BThe Ghost Map^, a geographical grid indicating where and when cholera cases and associated mortalities occurred in relation to the public well (Hempel 2007). Not only did the map confirm that almost all cases related to drinking water from the pump, but also that specific residential clusters were not associated with infection; for example, workers in an adjacent brewery did not contract the illness due to their daily allowance of beer. Later research discovered that the hand-dug well had been constructed just 0.9 m from a defunct septic tank/cesspit (Johnson 2006; Hempel 2007). Thus, it might be said that the science of epidemiology, considered the cornerstone of public health and defined as Bthe study and analysis of the patterns, causes, and effects of health and disease conditions within a specific population^ (Porta 2008), has its very roots in hydrogeology and the subsurface. Historically, many assumed that natural groundwaters were free of (geogenic and anthropogenic) chemical contaminants; however, this is not the case, with this presumption potentially resulting in an unfounded and potentially hazardous sense of security among owners, operators and users of water wells— for example, in an effort to reduce waterborne gastrointestinal illness in developing regions of southern Asia, the international community heavily promoted a shift from using surface water to presumably cleaner groundwater sources during the 1970s (Flanagan et al. 2012). However, at the time, high rates of naturally occurring arsenic via concurrent biogeochemical and hydrologic processes in many of these regions had not been recognised, resulting in a widespread failure to assess the chemical quality of newly developed groundwater sources (Mukherjee et al. 2006). Four decades later, the associated health crisis continues; recent figures suggest that over the coming decades, 1 in 10 adult deaths in Bangladesh may be attributable to arsenic-associated cancers, with over 700,000 people in Southeast Asia known to have been affected by arsenic-related diseases to date (Fendorf et al. 2010). High levels of geogenic arsenic have been detected in groundwater supplies from approximately 70 countries, potentially affecting up to 140 million people (Mukherjee et al. 2006). The objective and scope of this special issue, Hydrogeology and Human Health, has been borne of myriad issues and pressures pertaining to global groundwater resources, some longstanding and some more recently acknowledged. Among them, climate change, exponential population growth, increasing urbanisation, increasing food production and waste Published in the special issue BHydrogeology and Human Health^