GOING UNDERGROUND: HUMAN PATHOGENS IN THE SOIL-WATER ENVIRONMENT

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Outbreaks of human pathogens such as Escherichia coli O157 (E. coli) attract media attention due to the potentially severe threat to health and life. Contaminated food is not the only source of infection. Microbial pathogens are widespread in both rural and urban environments and the soils and water resources around us may act as stores or pathways for movement of these organisms. At present, the problem is best understood in a rural context where farm animals provide a source of pathogens to the environment via their wastes. Previous work shows how pathogens survive and move through soils and provides information on their abundance at source and in vulnerable 'receptors' such as rivers, reservoirs and shallow wells. More recent 'catchment scale' models are able to relate variations in agricultural land use (which affects pathogen input, survival and movement) to pathogen levels in areas downstream, such as coastal bathing waters and shellfish beds. Trends in climate, urban development, water resource policy and human attitudes towards health and environmental hazards may increase the potential risk from human pathogens in soil and water resources. An increase in flooding, abstraction of groundwater, use of the canal and river network to distribute water around the country, and reuse of lightly treated 'grey' water may affect the pathogen load of the water and soils we use in towns and cities as well as rural areas. Other potential sources are leaking sewers, fly-tipping and even accidental or deliberate release of pathogens from industry or 'bio-terrorism'. In order to assess and manage this general environmental risk we need to identify and address many scientific, epidemiological and policy questions which are currently unanswered. These include: What soil microenvironments might prolong pathogen survival? How does changing soil water content affect pathogen movement and storage in soils? Will soils store and transport hazardous microbes after air or surface contamination has dispersed? Can we measure the current health effects of environmental pathogen contamination in the general population? Is the hazard acute (due to single events) or chronic (due to background contamination)? How will climate change, shifts in land use and extreme events affect the spatial distribution of pathogen sources and receptors? Are urban populations more vulnerable to pathogens than rural populations through lack of exposure? What activities or social factors might increase a person's level of vulnerability? How should planning and health protection measures be constructed to pre-empt future health risks from pathogens in the soil-water environment? To respond to these challenges we require a broad skills base covering microbiology and the physical processes of pathogen interactions with soil and water; catchment risk assessment; water resource management; human health and epidemiology; and environmental / public health policy. This proposal will convene 5 themed meetings over a 15 month period involving a core interdisciplinary Working Group and additional invited expertise. The outcomes will be: a comprehensive critical review of the current state of the science, risks and policy in the UK, published in a high quality peer-reviewed journal; a detailed set of recommendations for research priorities and policy directions; and at least one proposal for a larger-scale interdisciplinary research consortium based on the outcomes of the review.