Limited effectiveness of home drinking water purification efforts in Karachi, Pakistan

Objective: In many developing-country urban areas, municipally supplied water is not microbiologically safe. This study evaluated drinking water quality and effect of home water purification efforts in Karachi, Pakistan. Methods: Members of 300 households, including 100 households who used the Aga Khan University Hospital Laboratory and 200 of their neighbors were interviewed. In 293 consenting households, structured observations were performed and drinking water was analyzed for the presence of coliforms, using the multiple tube fermentation technique. Results: Although 193 of the 293 households (66%) reported using some method to purify their drinking water, including 169 (58%) who boiled their water, only 48 (16%) of the drinking water samples were free of coliforms. Although a combination of boiling and filtering was the most effective method of purification, only 38% of samples that had been boiled and filtered were free of coliforms. Conclusions: Further refinements and evaluations of homebased efforts to purify and store water are needed.