Amplification of DNA from soil is often inhibited by co-purified contaminants. A rapid, inexpensive, large-scale DNA extraction method involving minimal purification has been developed that is applicable to various soil types (1). DNA is also suitable for PCR amplification using various DNA targets. DNA was extracted from 100g of soil using direct lysis with glass beads and SDS followed by potassium acetate precipitation, polyethylene glycol precipitation, phenol extraction and isopropanol precipitation. This method was compared to other DNA extraction methods with regard to DNA purity and size.

Water safety plans (WSPs) are promoted by the WHO as the most effective means of securing drinking water safety. To date most experience with WSPs has been within utility supplies, primarily in developed countries. There has been little documented experience of applying WSPs to small community-managed systems, particularly in developing countries. This paper presents a case study from Bangladesh describing how WSPs can be developed and implemented for small systems. Model WSPs were developed through consultation with key water sector practitioners in the country. Simplified tools were developed to translate the formal WSPs into a format that was meaningful and accessible for communities to use. A series of pilot projects were implemented by Non-Governmental Organisations (NGOs) across the country covering all major water supplies.The results show that WSPs can be developed and implemented for small community managed water supplies and improve the sanitary condition and water quality of water sources. Hygiene behaviour improved and household water quality showed a significant reduction in contamination. Chlorination was found to be important for some technologies, thus increasing the costs of water supply and raising important problems with respect to transfer to the communities. Simple tools for community monitoring were found to be effective in supporting better water safety management.

A rapid, inexpensive, large‐scale DNA extraction method involving minimal purification hasbeen developed that is applicable to various soil types. DNA was extracted from 100 g of soilusing direct lysis with glass beads and sodium dodecyl sulphate (SDS) followed by polyethyleneglycol precipitation, potassium acetate precipitation, phenol extraction and isopropanolprecipitation. The crude extract could be used in PCR directed at high‐copy number (bacterialsmall subunit rRNA) and single‐copy (fungal β‐tubulin) genes.

A wide range of microbial and chemical characteristics in drinking water have the potential to affect human health. However, it is not possible or practical to test drinking water for all potentially harmful characteristics. If drinking water is contaminated, people may already be exposed by the time test results are available. The 'boil water alert' issued in Sydney, Australia in 1998 following the detection of Cryptosporidium and Giardia in the finished water supply, highlighted the uncertainties associated with the public health response to test results.The Sydney experience supports the international consensus that a preventive risk-management approach to the supply of drinking water (manifesting as water safety plans (WSPs)) is the most reliable way to protect public health. A key component of a comprehensive WSP is that water suppliers and health authorities must have plans to respond in the case of water contamination and/or outbreaks. These plans must include clear guidance on when to issue warnings to consumers, and how these warnings are to be communicated. The pressure on health authorities to develop clear and systematic boil-water guidance will increase as utilities all over the world develop their WSPs.

The main response to arsenic contamination of shallow tubewells in Bangladesh is the provision of alternative water supplies. To support decision-making in relation to alternative water supply selection, the Arsenic Policy Support Unit commissioned the development of a tool for estimating disease burdens for specific options using disability-adjusted life years as the metric. This paper describes the assumptions in dose-responses, relationships between microbial indicators and pathogens, water consumed and population characteristics used, and presents a case study of how the tool was applied. Water quality data and dose-response models were used to predict disease burdens due to microbial pathogens and arsenic. Disease burden estimates predicted by the tool were based on evidence in the published literature. There were uncertainties in key assumptions of water consumed and the ratio of microbial indicators and pathogens, which led to broad confidence intervals and the need to consider the results in a wider context and further research needs. Deep tubewells and rainwater harvesting had the lowest disease burden estimates, while pond sand filters and dug wells had much higher predicted disease burden due to frequent microbial contamination. The need for rigorous water supply protection through water safety plans was highlighted. At present, the risk assessment is useful for informing judgement by experienced water and health professionals and identifying key research questions. Improved arsenic dose-response models and a better understanding of the relationship between microbial indicators and pathogens in tropical settings are required.