SODIS under fire: study pours cold water on solar disinfection

“Doubt has been cast on a much-lauded method of disinfecting water using only sunlight, after a study found that it doesn’t reduce diarrhoea among children in families using the technique” SciDev.net reports.

“Solar Water Disinfection (SODIS), a low-cost water purification method that uses only sunlight to disinfect water, is currently used by about three million people in 30 countries, according to the SODIS Reference Centre [at SANDEC] in Switzerland”.

“Laboratory and community studies have shown that the method is effective. But a PLoS Medicine study published [on 18 August 2009] on 22 rural communities in Cochabamba, Bolivia, found no significant reduction in diarrhoea among children aged five and under in families using SODIS”.

“The authors suggest that more research is needed into how the laboratory results can be replicated on the ground and until this is done they say that campaigners should be careful about advocating SODIS”.

“Mercedes Iriarte, co-author of the study and a researcher at the Water and Environmental Sanitation Centre of San Simón University, in Bolivia, told SciDev.Net that in the laboratory there is better control of all factors”.

“Iriarte says that in the laboratory, clean, clear, pH-neutral water is contaminated with known microorganisms to evaluate the method but that in the field researchers should consider other factors such as cloudiness of the water”.

“Margot Franken, a researcher with the environmental quality unit at San Andrés University in Bolivia, told SciDev.Net that low efficacy of the method could also result from inadequate exposure to sunlight”.

Compliance was also low, with only a third of families routinely treating their water in the recommended manner despite 80 per cent claiming to use SODIS at the beginning and end of the study and an intensive promotion campaign.

Link to full article in PLoS Medicine.

See a video about the study on SciVee.

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

Earlier in 2009 Wolf-Peter Schmidt and Sandy Cairncross concluded that the widespread promotion of household water treatment (HWT) is premature given the available evidence. This is echoed by the latest review of impact evaluations examining effectiveness of water, sanitation and hygiene (WSH) interventions by the International Initiative for Impact Evaluation (3ie).

In a comment about the study on its website, the SODIS Reference Centre says that “numerous studies have reported health benefits of SODIS when it is correctly and consistently used”. They cite the example of a study where “the incidence of cholera during an epidemic in Kenya was 88% lower among SODIS than non-users”.

“A well-known weakness of the SODIS process is that it is often not used consistently or is used to treat only a fraction of the drinking water consumed”, the statement continues. “Beneficial health impacts associated with the use of SODIS may also be compromised by poor sanitation and hygiene. Nonetheless, we feel that people should not be discouraged from continuing to use SODIS or from adopting it unless an alternate supply of safe drinking water is available”.

The SODIS Reference Centre/Sandec has also had to respond to “allegations circulating in a number of print media in developing countries on the carcinogenic risk of (re-)using PET bottles”. These “unfounded media reports” are drawn from research that show that antimony and phthalic acid and phthalate esters can leach from PET bottles. Sandec conducts its own study, together with Empa (Swiss Federal Laboratories for Materials Testing and Research) on “the migration of organic compounds – with special focus on plasticisers – into the water contained in PET bottles bottles under typical SODIS conditions”. “According to the results of this study, the risk of negative health effects caused by reused PET bottles for SODIS treatment is negligible”. SANDEC plans to repeat the study in India “to confirm the harmless nature of the technology in a country where media reports on the dangers of PET bottles are particularly widespread”.

Source: Samuel Luzi, Reuse of PET Bottles for SODIS – Blessing or Curse?, Sandec News, no. 10, July 2009

But SODIS is not off the hook yet, as a new danger is looming. In April 2009, scientists at Goethe University found that PET plastics may contain hormone-disrupting chemicals that leach into the water, Discovery News reported. According to researchers, it now appears that some as-yet-unidentified chemicals in PET plastics have the potential to interfere with estrogen and other reproductive hormones in the same manner that bisphenol A (BPA) and phthalates are suspected of doing.

Scientists: avoid plastic-hardening chemical BPA

The Endocrine Society, a professional organization of scientists who do hormone research, on June 10, 2009, issued a statement calling for better scientific studies into health effects of the plastic-hardening compound bisphenol A (BPA) and other substances suspected of disrupting the body’s endocrine functions (EDCs).

BPA, a synthetic estrogen, is used in the manufacture of polycarbonate water bottles and other food packaging; baby bottles; the epoxy resin lining of cans; and PVC water pipes. The National Institutes of Health has found that it can leach into food and beverages; a May [2009] report from researchers from the Harvard School of Public Health showed that hard-plastic drinking bottles containing BPA leach “notable amounts of the controversial chemical into people’s bodies,” The Boston Globe reported May 22, 2009.

Studies, including those presented at The Endocrine Society’s annual meeting June 10-13 in Washington, have reported that exposure to BPA and other EDCs affect male and female development, prostate cancer, thyroid disease and cardiovascular disease.

[...] The Endocrine Society said, “Results from animal models, human clinical observations and epidemiological studies converge to implicate EDCs as a significant concern to public health.”

During the society’s 91^st Annual Meeting, several studies were presented that show BPA can affect the hearts of women and can permanently damage the DNA of mice, UPIand ScienceDaily recently reported. Scientists also reported during the meeting that human exposure to BPA may be much higher than the recommended safe daily dose, entering the human body from a variety of sources, UPI reported June 11, 2009.

The Endocrine Society is urging humans to avoid using products that are known to contain BPA and other EDCs, according to its statement. It also stated the Society’s intent to actively engage “in lobbying for regulation seeking to decrease human exposure to the many endocrine-disrupting agents.”

New US Food and Drug Administration (FDA) Commissioner Dr. Margaret Hamburg said this month that the agency is reexamining its position about the safety of BPA in food containers. [In] December [2008], the FDA agreed to continue to its review of BPA in food contact applications, while maintaining the position that the chemical is safe. That decision followed a finding in October [2008] by a panel of FDA scientific advisors that FDA’s draft safety assessment of the chemical in food contact applications was inadequate. In August 2008, the FDA said that the public was not at risk from BPA, as WaterTech Online® reported.

The American Chemical Council (ACC) June 10 released a statement in response to the recent Endocrine Society research. In its statement, the ACC said: “These brief presentations on unpublished research are difficult to assess for significance to human health, since they have not been peer-reviewed or published in scientific literature and few details are available in conference abstracts. Bypassing the scientific process in favor of sensational press releases is a scare tactic that will not promote public health.”

Health Canada, the Canadian national health agency, said it has no safety concerns about the presence of the plastic-hardening chemical bisphenol A (BPA) in 18.5-liter (5-gallon) polycarbonate drinking water bottles, according to a recent report on the Health Canada Web site.

“The levels of BPA in these containers were very low and pose no safety concerns,” Health Canada reported, citing findings of a study by its Bureau of Chemical Safety entitled “Survey of Bisphenol A in Bottled Water Products.”

In April 2009, scientists at Goethe University found that polyethylene terephthalate, or PET, plastics, of which individual bottled water containers commonly are made, may contain hormone-disrupting chemicals that leach into the water, Discovery News reported. According to researchers, it now appears that some as-yet-unidentified chemicals in PET plastics have the potential to interfere with estrogen and other reproductive hormones in the same manner that BPA and phthalates are suspected of doing.

Source: WaterTech Online, 12 Jun 2009 ; WaterTechn Online, 16 Jul 2009 ; WaterTech Online, 28 Apr 2009