Correspondence/Rebuttal pubs.acs.org/est
Response to Comment on “A Randomized Intervention Study of Solar Disinfection of Drinking Water (SODIS) in the Prevention of Dysentery in Kenyan Children Aged under 5 Years”
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there was insufficient scientific evidence supporting its efficacy. It was to address this need to widen the evidence base, that the SODISWATER project was proposed and funded in 2005 to conduct randomized controlled field studies of the efficacy of solar disinfection of drinking water in South Africa, Kenya and Cambodia. The S African,2 Cambodian3 and Kenyan8 studies all demonstrated that when adequate levels of compliance can be achieved, SODIS was responsible for significant reductions in dysentery and nondysentery diarrhea rates compared to control populations. This work in conjunction with other studies published in the years between 2005 and today9−12 clearly demonstrates that SODIS, if it can be implemented successfully, can be an effective point-of use water treatment. In our opinion the SODIS hypothesis has been proven. For us the future challenges now lie in developing effective strategies to assist in HWTS scale-up and enhancing the microbicidal process. The comment adds that “...the recent study by du Preez and colleagues cannot be used to prove whether or not SODIS reduces diarrhoea disease”. We disagree. In their epidemiological meta-analysis assessing the evidence for bias in nonblinded controlled trails, Wood and coauthors (2008) estimated that trials with subjective outcomes exaggerated the actual effects of the outcomes by approximately 25%.13 While their study did not specifically assess point-of -use water treatment intervention, given the fact that household water treatment (HWT) may reduce diarrhea by up to 40%14 the effect of HWT adjusted by this factor of 25% still indicates a substantial protective effect. Hunter and colleagues conclude that “the real need is for studies that can give a more unequivocal indication of cause and effect or provide better quantification of effect sizes.” Clearly the ideal solution would be a randomized doubleblinded controlled trial. However, in such a study, if the caregiver is to be truly unaware of whether the water they are consuming in their household is in the intervention or control groups then a third party is required to administrate the treatment elsewhere and distribute the water to the 500−750 participating households. Since the recommendation is that SODIS water is consumed within 48 h of treatment, this distribution would have to be carried out in such a way that sufficient water was provided to each of the rural or peri-urban households every 2 days, amounting to the treatment and transport of more than 2000 L (2 metric tonnes) on each occasion. The intervention thus trialled would bear so little relationship to real-life point-of-use water treatment that the external validity of the trial would be questionable. Since the likelihood of successful project completion in the developing world is extremely sensitive to the simplicity of the trial
e thank Prof. Hunter and colleagues for their thoughtful comments. They express doubts about the reliability of self-reported data. The dysentery/diarrhea data was recorded via hard-copy “smiley-face diaries” which were filled in by the carer and simply handed over at fortnightly intervals.1,2 While it cannot fully remove the social and cultural pressures that generate courtesy-bias, this reporting methodology would be less prone to it compared to data collection through verbal interview between care-giver and data collector. Furthermore, we can point to significant improvement in the bacteriological quality of drinking water associated with SODIS treatment,2,3 which would support the hypothesis that the reduction in reported diarrhea rates was due in some part to improvement in water quality. Prof. Hunter and colleagues suggest that our measurements should be considered in light of Jamaiyah et al. (2010) who report a 1.4 cm technical error of measurement (TEM) reported for unstandardized height measurements of 130 children under age 2 years taken by public health nurses in Malaysia.4 However, the WHO Multicenter Growth Reference Study (2006) reported intra- and interexaminer TEMs of 0.23− 0.58 cm and 0.23−0.35 cm, respectively, for standardized height measurements.5 Caino et al. (2010) report a TEM for supine length = 0.15 cm (0.12−0.20 cm) for infants in the 0.32−0.84 years age range.6 As the age group increases, the TEM for height reduces as observed by Geeta et al. who reported a TEM of 0.32 cm for unstandardized height measurements taken from adults by public health nurses in Malaysia.7 We would point out that since the SODIS intervention and control groups consisted of children between the ages of 6 months to 5 years at the start of the study, only 17% (96 of 656) of our height measurements were taken from children under the age of 2 years. The statistically significant difference in the median heightfor-age of children using SODIS that we observed in the Kenya study is, indeed, small (0.8 cm 95% CI 0.7 to 1.6 cm, P = 0.031). While anthropometry was not the primary outcome measurement, it was always an important aspect of the study and considerable attention was placed on training in this area. One of the authors (M.d.P.) received training from a professional anthropometrist and it was this author who subsequently trained the Kenyan SODISWATER anthropometry team who were all medicine or (physical/social) science graduates and were well aware of the importance of accuracy and precision in anthropometric measurements. Hunter and colleagues try to group our study with “a wider trend in developing country research for persistence with studies more suitable for initial hypothesis generation”. The SODISWATER project arose in the immediate aftermath of the 2004 Indian Ocean Tsunami when SODIS researchers found many aid agencies were reluctant to consider using or promoting SODIS on the grounds that they felt, at that time, © 2012 American Chemical Society
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Environmental Science & Technology
Correspondence/Rebuttal
(9) Amin, M. T.; Han, M. Roof-harvested rainwater for potable purposes: application of solar disinfection (SODIS) and limitations. Water Sci. Technol. 2009, 60 (2), 419−431. (10) Graf, J.; Meierhofer, R.; Wegelin, M.; Mosler, H. J. Water disinfection and hygiene behaviour in an urban slum in Kenya: impact on childhood diarrhoea and influence of beliefs. Int. J. Environ. Health Res. 2008, 18 (5), 335−355. (11) Rainey, R. C.; Harding, A. K. Drinking water quality and solar disinfection: effectiveness in peri-urban households in Nepal. J. Water Health 2005, 3 (3), 239−248. (12) Rainey, R. C.; Harding, A. K. Acceptability of solar disinfection of drinking water treatment in Kathmandu Valley, Nepal. Int. J. Environ. Health Res. 2005, 15 (5), 361−372. (13) Wood, L.; Egger, M.; Gluud, L. L.; Schulz, K. F.; Jüni, P.; Altman, D. G.; Gluud, C.; Martin, R. M.; Wood, A. J.; Sterne, J. A. Empirical evidence of bias in treatment effect estimates in controlled trials with different interventions and outcomes: meta-epidemiological study. Brit. Med. J. 2008, 15 (336(7644)), 601−605. (14) Clasen, T.; Schmidt, W. P.; Rabie, T.; Roberts, I.; Cairncross, S. Interventions to improve water quality for preventing diarrhoea: systematic review and meta-analysis. BMJ [Br. Med. J.] 2007, 334 (7597), 782. (15) Clasen, T. F. Scaling up Household Water Treatment among LowIncome Populations; World Health Organization, Public Health and Environment 2009; http://whqlibdoc.who.int/hq/2009/WHO_ HSE_WSH_09.02_eng.pdf. (16) Diarrhoea: Why Children Are Still Dying and What Can Be Done; WHO/UNICEF, 2009; ISBN 978-92-806-4462-3. (17) Progress on Sanitation and Drinking-Water: 2010 Update; WHO/ UNICEF, 2010; ISBN 978-92-4-156395-6. (18) Amnesty International, . History: The Meaning of the Amnesty Candle, 1961; http://www.amnesty.ca/about/history/history_of_ amnesty_international/meaning_of_the_Amnesty_candle.php (accessed February 13, 2012).
methodology, we cannot see how a SODIS randomized doubleblinded controlled trial is logistically feasible at this time. In conclusion, most water quality intervention studies are subject to some form of bias.15 Until a methodology immune to all forms of bias can be agreed, it would be misguided to dismiss the significant reductions in disease rates resulting from these point-of-use water treatments. The estimated 1.1 billion people around the would without year-round access to safe drinking water or the economic resources to secure it16,17 would otherwise be deprived of simple low-cost HWT technologies which can make a serious impact on waterborne disease. In this regard we feel “it is better to light a candle than curse the darkness”.18
Martella du Preez† Ronan M. Conroy‡ Kevin G. McGuigan*,§
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† Natural Resources and the Environment, CSIR, PO Box 395, Pretoria, South Africa ‡ Division of Population Health Sciences, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland § Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephens Green, Dublin 2, Ireland
AUTHOR INFORMATION
Corresponding Author
*Phone: +353 1 4022207; e-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Conroy, R. M.; Elmore-Meegan, M.; Joyce, T.; McGuigan, K. G.; Barnes, J. Solar disinfection of drinking water and diarrhoea in Maasai children: a controlled field trial. The Lancet 1996, 348 (9043), 1695− 1697. (2) du Preez, M.; McGuigan, K. G.; Conroy, R. M. Solar disinfection of drinking water (SODIS) in the prevention of dysentery in South African children aged under 5 years: the role of participant motivation. Environ. Sci. Technol. 2010, 44 (22), 8744−8749. (3) McGuigan, K. G.; Samaiyar, P.; du Preez, M.; Conroy, R. M. A high compliance randomised controlled field trial of solar disinfection (SODIS) of drinking water and its impact on childhood diarrhoea in rural Cambodia. Environ. Sci. Technol. 2011, 45 (18), 7862−7867. (4) Jamaiyah, H.; Geeta, A.; Safiza, M. N.; Khor, G. L.; Wong, N. F.; Kee, C. C.; Rahmah, R.; Ahmad, A. Z.; Suzana, S.; Chen, W. S.; Rajaah, M.; Adam, M. Reliability, technical error of measurements and validity of length and weight measurements for children under two years old in Malaysia. Med. J. Malays. 2010, 65 (Suppl A), 131−137. (5) WHO, M.G.R.S.G., , Reliability of anthropometric measurements in the WHO Multicentre Growth Reference Study. Acta Paediatr. Suppl. 2006, 450, 38−46. (6) Caino, S.; Kelmansky, D.; Adamo, P.; Lejarraga, H. Short-term growth in head circumference and its relationship with supine length in healthy infants. Ann. Human Biol. 2010, 37 (1), 108−116. (7) Geeta, A.; Jamaiyah, H.; Safiza, M. N.; Khor, G. L.; Kee, C. C.; Ahmad, A. Z.; Suzana, S.; Rahmah, R.; Faudzi, A. Reliability, technical error of measurements and validity of instruments for nutritional status assessment of adults in Malaysia. Singapore Med. J. 2009, 50 (10), 1013−1017. (8) du Preez, M.; Conroy, R. M.; Ligondo, S.; Hennessy, J.; ElmoreMeegan, M.; Soita, A.; McGuigan, K. G. Solar disinfection of drinking water (SODIS) in the prevention of dysentery in Kenyan children aged under 5 years. Environ. Sci. Technol. 2011, 45 (21), 9315−9323. 3037
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