Environmental Engineering Reference
In-Depth Information
In our study the lack of blinding may have reduced motivation in the control com-
munities. However, the number of households lost during follow-up and the number
of days under observation were almost identical in both arms. Additionally, the control
communities knew that they would receive the intervention after study end. Finally,
a reduction of diarrhea frequency of 20% might be insuffi cient to be well perceived,
that is, have a noticeable impact in a population with a high burden of child diarrhea
and will, thus, not result in a sustainable behavioral change. Faecal contamination in
about 60% of the yards indicates a highly contaminated environment with presumably
a large potential for transmission pathways other than consuming contaminated water.
This simultaneous exposure to a multiplicity of transmission pathways may explain
why we found no signifi cant diarrhea reduction due to SODIS.
On the other hand, our result of a 19% reduction in diarrheal episodes appears to
be roughly consistent with results of the two other SODIS trials both from Maasai cul-
tural settings conducted by Conroy and colleagues among children <6 year and 5-16
year of age. They report a 16% reduction (in <6 year olds, 2-week prevalence of 48.8%
in intervention, and 58.1% in control group) [8] and a 10.3% reduction in the 2-week
diarrhea prevalence (in 5-16 year olds) [7]. However, these randomized controlled tri-
als were undertaken in a socio-cultural setting assuring a 100% compliance (as stated
by the authors) in water treatment behavior through social control by Maasai elders
who promoted the method [7, 8]. In the results presented in these studies adjusted
models with post hoc selected covariates were presented (i.e., no unadjusted models
were provided). These trials were carried out in conditions of heavily contaminated
drinking water and very high diarrhea rates—important considerations when attempt-
ing to generalize these results. The only other—quasi-randomized—trial to estimate
the effect of solar water disinfection was carried out in the urban slum in Vellore and
resulted in a remarkable reduction of diarrhea among children <5 year (IR ratio, 0.64;
95% CI 0.48-0.86) despite 86% of SODIS users also drinking untreated water [9].
To our knowledge this is the fi rst community-randomized trial and the largest
study so far to assess the effectiveness of the SODIS method under typical social and
environmental conditions in a general rural population setting where children drink
untreated water.
Our study was suffi ciently powered to detect a 33% reduction in the effectiveness
of the SODIS intervention, and we accounted for clustered design in our analysis. On
the basis of a post hoc sample size calculations using the model-based estimate for the
between-cluster variability (k = 0.27), we would have needed a study 2.5 times larger
for a 20% difference to be signifi cant.
The implementing NGO, which had global experience in disseminating SODIS,
adapted a campaign to the local and cultural needs and also involved the public health
and educational system in the roll-out. This comprehensive SODIS campaign resulted
in a mean SODIS usage of 32% on any given study day. In using the SODIS-use indi-
cator on the basis of the personal judgment of community-based staff, we intended to
measure actual use in combining objective, visible signs of use (e.g., bottles exposed
to sunlight) with proxies more responsive to actual treatment behavior (e.g., SODIS
water can be offered to drink upon request). We consider this a restrictive, more
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