A few health impact studies are starting to emerge on the biosand filter. These look at how much impact the filters have on diarrhoea in real life situations. So far, results are encouraging and confirm the anecdotal evidence that many of us hear from sand filter users in the field.
An 8-month randomized controlled trial of the plastic biosand filter was performed in 6 rural communities in Tamale, Ghana during 2008 by Stauber et al (2012, [ref_05]). The trial was carried out in order to assess reductions in diarrheal disease and improvements in household drinking water quality. During the study, the longitudinal prevalence ratio for diarrhoea comparing households that received the filter to households that did not receive it was 0.40 (95% confidence interval: 0.05, 0.80), suggesting an overall diarrheal disease reduction of 60%.
A 6-month study carried out by Stauber et al (2009, [ref_01]) in the Dominican Republic during 2005-06 was the first health impact study to be done on the household biosand filter. The results showed that the 75 households that used the biosand filter had 0.53 times the odds of diarrhoeal disease as control households (or 47% reduced risk), indicating a significant protective effect of the BSF against waterborne diarrheal disease.
Work carried out during 6 months in 2007 in rural Kenyan households by Tiwari et al (2009, [ref_02]) found that households using biosand filters had a 54% reduction in child diarrhoea days compared to control households.
An 8-month study during 2008 in Cambodia by Stauber et al (2012, [ref_03]) looked at the impact of the plastic sand filter on diarrhoeal disease in Cambodia. The research showed that villages with plastic biosand filters had significantly lower concentrations of E. coli in drinking water and lower diarrheal disease (incidence rate ratio 0.41, 95% confidence interval: 0.24–0.69) compared to control villages - that is to say that villages using filters had 59% fewer (reported) cases of diarrhoeal disease (with a range of reduction from 31 - 76%).
An evaluation of a demand-led BSF project by Tearfund in Afghanistan revealed that users strongly believed the drinking filtered water from the BSF was resulting in a positive impact on their health. The perceived health impacts were confirmed to some extent by the self-reported rates of diarrhoea in the previous two weeks, where only 16% of those with an operating BSF reported cases of diarrhoea, while 71% of those without a BSF reported cases of diarrhoea (Burt, 2012; [ref_04]). A health impact study carried out by the Ministry of Public Health in Afghanistan found a difference in prevalence of acute diarrhoea in children under 5 years old - 71.49% of children had diarrhoea in households that did not have a filter, compared to 41.87% of children for households that did have a filter (Mashal, 2011; [ref_06]).
References: (jump back)
Ref 01: Stauber, C.E.; Ortiz, G.M.; Loomis, D.P.; Sobsey, M.D. (2009). A randomized controlled trial of the concrete biosand filter and its impact on diarrheal disease in Bonao, Dominican Republic. American Journal of Tropical Medicine and Hygiene, 2009 Feb; 80(2): 286-93. Abstract available here.
Ref 02: Tiwari, S.K.; Schmidt, W-P.; Darby, J.; Kariuki, Z. G.; Jenkins, M.W. (2009). Intermittent slow sand filtration for preventing diarrhoea among children in Kenyan households using unimproved water sources: randomized controlled trial. Tropical Medicine and International Health, Volume 14 no 11 pp 1–9 November 2009. Abstract available here.
Ref 03: Stauber, C.E.; Printy, E. R.; McCarty, F. A.; Liang, K. R; Sobsey, M. D. (2012) Cluster Randomized Controlled Trial of the Plastic BioSand Water Filter in Cambodia. Environ. Sci. Technol., 2012, 46 (2), pp 722–728. DOI: 10.1021/es203114q. Abstract available here.
Ref 04: Burt, M. (2012) Evaluation of a demand led biosand filter programme in the complex emergency context of Afghanistan. Tearfund, Teddington, UK.
Ref 05: Stauber, C.E.; Kominek, B.; Liang, K.R.; Osman, M.K.; Sobsey, M.D. (2012) Evaluation of the Impact of the Plastic BioSand Filter on Health and Drinking Water Quality in Rural Tamale, Ghana. Int. J. Environ. Res. Public Health 2012, 9, 3806-3823; doi:10.3390/ijerph9113806. Full paper available here.
Ref 06: Mashal, M.T. (2011) Socio-economic components and health impact of Bio-Sand Filter utilization for ensuring quality of drinking water in rural area of Afghanistan. Ministry of Public Health, Islamic Republic of Afghanistan.