Health Stream Literature Summary - Issue 58 - June 2010

Quality of drinking-water at source and point-of-consumption--drinking cup as a high potential recontamination risk: a field study in Bolivia
Rufener, S., Mausezahl, D., Mosler, H.J. and Weingartner, R. (2010) Journal of Health, Population, and Nutrition, 28(1); 34-41.

In developing countries, the majority of households do not have piped water supplies and have to collect and transport drinking water from an external source, often hundreds of metres away from home. The microbiological quality of water in transportation vessels and storage vessels in the home is often lower than at the source, suggesting that contamination may occur during the process from collection of water to consumption. Faecal contamination may occur when drinking water is stored in the open inside the household. The main cause of deteriorating water quality is due to contamination by hands or domestic animals. The detrimental effects of in-house contamination are known, however the exact point of contamination is still unclear. This study aimed to locate intrinsic and specific points where faecal contamination may occur in the process from the point-of-collection to the point-of-use. The quality of the water was measured at all stages along the potential contamination pathway from the water source to the drinking cups used in the household. This study focused on water collected from reservoirs, dugwells or bowser trucks.

The study was conducted in Boliva and participating households were situated in three different geographical regions, i.e. in the highlands, the valley and the lowlands. There were 27 rural households in the highlands sampled, 25 rural households in the lowland, and 29 semi-urban households in the valley. Two of the 83 households approached refused to participate. For each of the 81 participating households, water samples were collected from their drinking water sources, transport vessels, treated water and a drinking cup during unannounced visits. The transport vessel in most of the households (89%) also served as the storage vessel. There were 347 microbiological analyses conducted immediately on-site using a membrane-filtration method. The quality of the water was quantitatively assessed through the enumeration of colony-forming units (CFUs) of Escherichia coli, which was used as an indicator of faecal contamination. Information on water, sanitation practices and demographic data were collected through a structured questionnaire administered to the person responsible for the management of drinking water in the household. Questions were related to water-extraction patterns, type of water transport, water treatment methods and cleaning habits, type and material of water-related issues and sanitation facilities.

Overall, community-based pipe-tap systems were most frequently used (58%). Bowser trucks as a water source served 36% of the households studied. Sanitary inspections indicated that all the sources monitored were classified as being at 'intermediate' to 'very high' levels of risk for contamination. Of the households visited, 44% used plastic-cups for drinking, 24% used cups made of tin or other metals and glasses or glass-cups were used in 11% of homes. Buckets, barrels and canisters were the main transport vessels. Only 14 of the 78 observed transport vessels were covered with a lid. There were 42% of the households that cleaned their transport vessel with detergent and only 31% of those that used a detergent daily. Drinking cups were washed in 96% of the households with only 48% cleaning these at least once a day. About 70% of families reported treating water by boiling or SODIS (solar disinfection) before consumption, but not all were able to show evidence of treated water at the time of the visit. The quality of drinking water was found to deteriorate steadily along the pathway from the supply source to the drinking cup. The median concentration of E. coli increased significantly from 0 CFU/100 mL (interquartile range (IQR): 0-13) at the source to 8 CFU/100 mL (IQR: 0-550) at the point-of-consumption in the home. After transportation of water, home-based water treatments reduced the median concentration to 0 CFU/100 mL (IQR: 0-1), however, recontamination at the point-of-consumption significantly reduced the quality of water in the cups (median=8). There were only 36% of the treated water samples that were free from E. coli.

Boiling or SODIS were used in 56% of households and none reported using chlorination. In one of the 15 households that boiled their water, water samples from the cooking pot still contained E. coli. In 10 of the 30 households that practised SODIS, water samples from the treatment devices still contained E. coli. The failure observed in the SODIS procedure was considered due to insufficient exposure of bottles to sunlight. Of the 34 clean treatment samples, 65% remained clean, however, recontamination occurred at the point-of-consumption in the remaining 35%. The median contamination of water from drinking cups at the households not treating drinking water was more than four times higher (median=34 CFU/100 mL; IQR:4-2,400) than that of the households treating their drinking water (median=0 CFU/100 mL; IQR:0-34). There was no significant relationship between the quality of drinking water at the source and the quality of water in drinking cups within the households (n=79, partial Spearman rank correlation coefficient = -0.01, p=0.95, adjusted for water-treatment behaviour). Therefore pathogen-free water at the source does not guarantee safe and pathogen-free drinking water at the point-of-consumption.

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