SODIS under fire: studies pour cold water on solar disinfection

Updated - Thursday 17 September 2009

The much-lauded method of disinfecting water in plastic bottles using only sunlight might not work as well as previously thought and might even be dangerous, new research suggests. The Swiss Solar Water Disinfection (SODIS) Reference Center at SANDEC admits the technique has its weaknesses but that it is safe and should not be discouraged unless an alternate supply of safe drinking water is available.

A new study [1] on 22 rural communities in Cochabamba, Bolivia, found no significant reduction in diarrhoea among children aged five-and-under in families using SODIS. Only a third of families routinely treating their water in the recommended manner despite 80 per cent claiming to use SODIS and an intensive promotion campaign.

In a comment [2] about the study on its website, the SODIS Reference Center says that “numerous studies have reported health benefits of SODIS when it is correctly and consistently used”.

Sandec has also had to respond [3] to allegations circulating in a number of print media, especially in India, on the carcinogenic risk of (re-)using plastic PET bottles. In a study [4] that Sandec conducted with a special focus on plasticisers, it concluded that “the risk of negative health effects caused by reused PET bottles for SODIS treatment is negligible”.

[1] Mäusezahl, D. … [et al.] (2009). Solar drinking water disinfection (SODIS) to reduce childhood diarrhoea in rural Bolivia : a cluster-randomized, controlled trial. PLoS Medicine ; vol. 6, no. 8 ; e1000125. doi:10.1371/journal.pmed.1000125. See also a video about the study on SciVee below.

[2] SODIS Reference Center, 19 Aug 2009

[3] Source: Samuel Luzi, Reuse of PET Bottles for SODIS – Blessing or Curse?,Sandec News, no. 10, July 2009. See also: Scientists: avoid plastic-hardening chemical BPA, WASH News International, 16 Jun 12009

[4] Schmid, P. … [et al.] (2008). Does the reuse of PET bottles during solar water disinfection pose a health risk due to the migration of plasticisers and other chemicals into the water? Water Research ; vol. 42, no. 20 ; p. 5054-5060. doi:10.1016/j.watres.2008.09.025

Related news: Household water treatment: scaling-up is premature say researchers, Source Weekly, 13 Mar 2009

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Source: Cristina Pabón, SciDev.net, 31 Aug 2009

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