Solar water disinfection not proving effective in field, Basel team says


Alem Kitmama, Ethiopia: safe water is a major health problem (image: WHO)

Updated 20 August  Basel, Switzerland (GenevaLunch) – Much-touted low-cost, easily applied solar treatments to disinfect water are not reducing diarrhea as expected, says a team at the Swiss Tropical Institute-University of Basel (STI). The group recommends that “Further global promotion of Sodis for general use should be undertaken with care until such evidence is available.” Daniel Maeusezahl and his team have published their findings from studies carried out in Bolivia in PLoS Medicine, a scientific journal.

Their report is a blow to hopes that developing countries can use a readily available, inexpensive solution to the often-deadly problem of diarrhea due to untreated water. Pneumonia, diarrhea and malnutrition account for most of the 10.8 million child deaths that occur annually around the world and an estimated 60 percent of these are preventable according to the STI.

The problem lies not so much in the science as in humans using the solution correctly, it appears. Ed note: a discussion comment on the study, by Zulfiqar A Bhutta, Aga Khan University in Karachi, Pakistan interprets the study somewhat differently: “The failure of some plausible interventions when implemented at scale may also reflect a failure of delivery strategies rather than an ineffective intervention.” (see Frank Stinger comment here)

The group notes that “despite an extensive Sodis promotion campaign we found only moderate compliance with the intervention and no strong evidence for a substantive reduction in diarrhoea among children. These results suggest that there is a need for better evidence of how the well-established laboratory efficacy of this home-based water treatment method translates into field effectiveness under various cultural settings and intervention intensities.”

Switzerland has been actively involved in providing and promoting safe water supplies in developing countries, working closely with a number of non-profit organizations in several countries.



  1. Frank Stinger says:

    In your article regarding the effectiveness of solar water disinfection in reducing diarrhea, you may also want to include a reference to a comment in the same publication. The author states that “The failure of some plausible interventions when implemented at scale may also reflect a failure of delivery strategies rather than an ineffective intervention” – this is probably a more balanced interpretation of the data than the one of the authors… He also concludes that “The observed direction of effect on childhood diarrhea in the Bolivia study is encouraging and supports further evaluation of low-cost and sustainable interventions to promote point-of-use water purification techniques in rural communities.”

    The comment is publicly available:

  2. Thank you for this, which provides a better balanced view. I’ll update the article I wrote. Much appreciated, Ellen

  3. hannah saltzman says:

    Regarding the treatment of water in developing countries : Do you have info on the country of Nepal and their water treatment.

  4. You might want to search the World Health Organization web site. Here is a starting point: And here is an innovative project: