Home-based drinking water purification through sunlight : from promotion the health effectiveness

Diarrhoeal diseases constitute a significant illness burden for children living in lowincome countries. Children under the age of five years suffer about four billion diarrhoea episodes per year, 90% of which occur in developing countries. Diarrhoeal illness accounts for more than four percent of the “disability adjusted life years" lost to the worldwide illness burden. ‘Unsafe water, sanitation and hygiene’ are the main global risk factors for diarrhoeal diseases. Current strategies for providing safe water to more than one billion people are being reshaped. Since the formulation of the seventh Millennium Development Goal (MDG), the focus is on large-scale and sustainable approaches. Target 10 of the MDGs includes halving the number of people without access to safe water and sanitation facilities by 2015. Solar water disinfection (SODIS) is a home-based – or ‘point-of-use’ – water purification and safe storage method that could support the achievement of this goal, by providing safe drinking water to populations in need. The method consists of exposing water-filled, transparent PET bottles to full sunlight for about one day. Our main objective of this project was to measure the effectiveness of solar water disinfection on the health of children under the age of five years. Based on a Latin American dissemination programme and further pilot studies in Bolivia (2001) and Bangladesh (1999/2000) on need assessment approaches in the domain of household water management, we decided to carry out the research in 10 rural Bolivian communities situated in the district of Mizque (Department of Cochabamba) from 2001 until 2003. A case-control study was embedded in a morbidity surveillance scheme and complemented with cross-sectional surveys, in order to comprehensively describe the outcome: the impact of the SODIS method on the frequency of childhood diarrhoea. We developed three SODIS promotion strategies that used various communication channels to reach the target population: i) monthly community-based workshops; ii) monthly household visits; and iii) a school campaign in 11 school centres of the district. During four months of weekly diarrhoea monitoring we interviewed 100 cases, as well as 171 controls; the latter were randomly selected from the entire population. One-hour semistructured interviews with mothers of selected study children were carried out to assess relevant risk factors for child diarrhoea. We then compared the diarrhoea incidence rates in study children between families who applied the SODIS method with different intensities, and adjusted the results for major known confounding factors (e.g. age, sex, hand washing). In addition, the quality of household drinking water was analysed repeatedly, which enabled us to calculate the efficacy of the SODIS method under natural conditions representing daily Bolivian life in rural areas. We also repeatedly examined stool samples from community children for the presence of protozoa and helminths, to identify the main transmission pathways of these potentially diarrhoea-causing parasites. The implementation of the SODIS method was challenging, as the target population did not immediately recognise benefits of using the new method. About 20% drank SODIS purified water on more than five days per week, and about 40% consumed the SODIS water less frequently. The individual promotion strategies affected the population in different ways: e.g. household visits increased adoption of the SODIS method and the school campaign enhanced awareness about germs and diseases. Such extensive promotion strategies may not be suitable for large-scale promotion of the SODIS method. The assessment of motivational messages directed towards tangible benefits for the population may prove essential to increase compliance. Once the population was introduced to the SODIS method, we assessed its effect on the study childrens’ health. The use of the SODIS method averted up to 75% of the diarrhoea episodes in a rural Bolivian child under five years of age. The impact was less, when families used the method less frequently (60%), indicating a dose-response relationship between the intensity of use (or compliance to the SODIS method) and reduction in diarrhoeal illness. In order to translate individual risk reductions to an impact measure at population level, we employed population-attributable fraction estimates using an uptake rate of the SODIS method of 20% in the community. Those calculations indicated that 15% of all child diarrhoeal illnesses in the population could be averted if the SODIS method would be consistently used. The high diarrhoea incidences in children under the age of five (about 6 episodes per year) were not reflected in the infection data. It may therefore be assumed that bacteria and viruses (which we did not investigate in this study) caused most diarrhoea episodes in this setting. We found that children would be re-infected rapidly after treatment for protozoa or helminth infection – 50% of the children were re-infected in the elapse of two month, mainly through Giardia lamblia and Entamoeba hist/disp. The age of the child, socioeconomic status and hygiene indicators in the household were main risk factors for reinfection. Water-borne transmission of these protozoa was not dominant in this setting. The high efficacy of the SODIS method in producing pathogen-free drinking water in the field is the foundation for a high effectiveness on people’s health. SODIS-purified drinking water contained 90% less faecal coliform contamination than untreated drinking water. Families that left their water exposed for at least two days, achieved a significantly better purification effect, almost reaching the WHO recommendations of zero-tolerance of indicator bacteria in drinking water. These results support our findings of a high effectiveness of the SODIS method on child health due to the purification of their drinking water. Increased purification efficacy of SODIS due to prolonged exposure time further indicates that SODIS user instructions could be further revised to guarantee best efficacy under field conditions. In rural Bangladesh, people were forced to switch from arsenic- to microbiologically contaminated drinking water sources. Diarrhoea rates were similar between intervention families that switched water sources, with people drinking groundwater, indicating that the SODIS method was efficacious enough to maintain water quality. We also learnt important aspects on the use (e.g. bottle scarcity in rural areas) and determinants for uptake and possible sustainable use of the method (e.g. acceptable alternative water source). Specific community selection criteria, including normative and perceived needs, were formulated for a subsequent need assessment in the Bolivian setting. Since the start of our activities, we were challenged with developing and validating indicators to classify families according to their use of the SODIS method, as no standards existed. In Bolivia, the combination of three indicators for the uptake of SODIS may best estimate the use of the method in families during a one-time evaluation visit: reported use (sensitivity: 73%), observed use (specificity: 82%) and frequency of drinking SODIS water in the last week (positive predictive value: 85%). The indicators can be measured rapidly and easily through especially appointed staff during programme evaluation. The most precise indicator is the repeated observation of SODIS purified water at the home during unannounced visits. The finding of a significant impact of the SODIS method on child health is consistent with our other findings of a dose-response relationship, high efficacy under field conditions and the efficacious protection from diarrhoeal diseases in Bangladesh. Future research should confirm these findings under a multitude of environmental, geographical and cultural settings and study designs, to produce reliable evidence of the methods’ effectiveness in improving the health of populations. The current research raised issues regarding the implementation of and compliance of the population to the SODIS method in combination with the possibility to guarantee its water-purification ability. This also raised questions on the costs in relation to the benefits of the SODIS method from the individual to the programme – and planners’ level; and the likelihood that the planner may no longer perceive the method as an intermediate but rather as a permanent solution to provide safe drinking water. In the future, investigations should: (i) define tangible benefits for target populations, that can later also be applied in social marketing strategies for the broader promotion and higher acceptance of the method in the population. In this context, user instructions should be adapted to guarantee water quality during large-scale promotion activities, (ii) assess the costs of the SODIS method at individual-, programme- and planners’ level. This will allow decision making at regional level, and comparison with other point-of-use methods at policy level, (iii) consider in the planning process with the local people that the SODIS method should not replace future permanent and durable solutions for drinking water (“SODIS is only a valuable means to the end”). This is the first research that evaluated various levels of the solar disinfection method (efficacy, promotion, compliance, use, health effect) in different settings. Also, this study estimated the effectiveness of the method on the health of young children at population level applying an innovative population-based approach. It demonstrated with confidence that the method is efficacious in reducing the diarrhoea burden in a child population. Due to its simplicity and almost ubiquitous applicability, solar disinfection is applicable in various settings, but the long-term use of the method also depends on the political will and the availability of subsidies (e.g. for motivational campaigns, or bottle provision). This project, with its multiplicity of findings served to inform and support a randomised control trial on the effectiveness of solar water disinfection in a rural area of Bolivia, and current endeavours in the national SODIS dissemination programme. At regional level, we mostly increased awareness about the application of the SODIS method that we hope will stimulate regional development. The ultimate decision-maker will always be the consumer and potential beneficiary.