5.3 Health Impact Assessment

8/11/2019 5.3 Health Impact Assessment

1/12

Health impact

Introduction to Household Water Treatment and Safe Storage, Mo

Dr. Sophie Boisson, London School of Hygiene & Tropical Medicine


2/12

Unsafewater

CEffectiveOption

Introduction


3/12

Transmission for fecal-

pathogens is complex

HWTS addresses only

pathway

How much diarrhoea cprevented by improving

quality alone?

Transmission of faecal-oral pathogens

Source: WEDC, Adapted from Wagner & Lanoix (1958)


4/12

Systematic reviews on health impact

0 20 40

Flocculation/disinfection

Solar disinfection

Filtration

Chlorination

Household

Source

Water supply

Water quality

% Reduction in


5/12

Intervention studies

Randomised control trials Unit of randomisation can b

household or village

Outcome can be blinded

Observational studies Before/ After

Case control studies

Ecological studies

Modelling studies

Measuring impact: evaluation designs


6/12

Function of stool con

frequency WHO definition: passase o

stools within 24-h period

Potential issues

Reporting bias Placebo effect

Hawthorne effect

Respondent fatigue

Measuring impact: outcome is diarrhoea

Boisson et al (2013)


7/12

Different magnitude of e Open trials report diarrhea re

range of 30-40%

Blinded trial report no effect

Lack of blinding of subj

outcomes risk exaggera

magnitude of impact by2008)

Adjusting for bias (Hun Went from 44% to 15% redu

adjustment

Blinded versus non-blinded trials

Clasen et al (2006)


8/12

Setting with different transmission dynamics Transmission routes

Pathogens

Treatment methods not effective against all class

of pathogens

Different levels of compliance Impact on diarrhea diminishes over time (Arnold 2006, Hunter

2009)

Efficacy versus effectiveness trials Evaluation of 3-year HWT and HWWS in GuatemalaResidual

chlorine 9% intervention vs 3% in control (Arnold 2009)

CRT of SODIS among 22 rural communities in Bolivia 32%

(Mausezhal 2009)

Potential explanation for variability


9/12

Blinded RCTs Challenges to blind effectively

Potentially unethical

Alternative health outcomes Nutritional indicators

Weight-for-age (malnutrition, diarrhoea)

Height-for-age (stunting) Environmental enteropathy

Pathogen identification

Alternatives to improve measurement?

Schmidt et al (2010)


10/12

Significant health gains

reductions in diarrhoeaan overestimation

Measuring impact on h

possible but can be co

expensive

Routine monitoring an

should focus on use be

attempting to measure

Conclusion


11/12

Systematic reviews

Arnold, B. F. & J. M. Colford, Jr. (2007) Treating water with chlorine at point-of-

use to improve water quality and reduce child diarrhea in developing countries:a systematic review and meta-analysis.Am J Trop Med Hyg,76,354-64.

Clasen, T., I. Roberts, T. Rabie, W. Schmidt & S. Cairncross (2006)

Interventions to improve water quality for preventing diarrhoea. Cochrane

Database Syst Rev,3,CD004794.

Esrey, S. A., R. G. Feachem & J. M. Hughes (1985) Interventions for the control

of diarrhoeal diseases among young children: improving water supplies and

excreta disposal facilities. Bulletin of the World Health Organization,63,757-72.

Fewtrell, L., R. B. Kaufmann, D. Kay, W. Enanoria, L. Haller & J. M. Colford, Jr.

(2005) Water, sanitation, and hygiene interventions to reduce diarrhoea in less

developed countries: a systematic review and meta-analysis. Lancet Infect Dis,

5,42-52.

Waddington, H. S., B. White, H. Fewtrell, L. 2009. Water, Sanitation and

Hygiene Interventions to Combat Childhood Diarrhoea in Developing Countries.

International Initiative for Impact Evaluation (3ie).

Further discussions abou

for health impact of HWT

Clasen T, Bartram J, Colford J, Luby S, Quick R

on Household water treatment in poor popula

evidence for scaling up now?. Environ Sci T

author reply 55455546. doi: 10.1021/es9008147

Hunter, P. R. (2009) Household Water Treatment

Comparing Different Intervention Types Using M

Sci Technol. 43(23):8991-7

Schmidt, W. P. & S. Cairncross (2009) Household

populations: is there enough evidence for scalin

Technol,43,986-92.

Additional ressources: Reviews


12/12

Arnold, B., B. Arana, D. Mausezahl, A. Hubbard & J. M. Colford, Jr. (2009) Evaluation of a pre-existing, 3-year

household water treatment and handwashing intervention in rural Guatemala. Int J Epidemiol.

Boisson S, Stevenson M, Shapiro L, Kumar V, Singh LP, et al. (2013) Effect of Household-Based Drinking Water

Chlorination on Diarrhoea among Children under Five in Orissa, India: A Double-Blind Randomised Placebo-

Controlled Trial. PLoS Med 10(8): e1001497. doi:10.1371/journal.pmed.1001497

Boisson S, Kiyombo M, Sthreshley L, Tumba S, Makambo J, et al. (2010) Field assessment of a novel

household-based water filtration device: a randomised, placebo-controlled trial in the Democratic Republic of

Congo. PLoS One 5: e12613 doi:10.1371/journal.pone.0012613

Mausezahl, D., A. Christen, G. D. Pacheco, F. A. Tellez, M. Iriarte, M. E. Zapata, M. Cevallos, J. Hattendorf, M.

D. Cattaneo, B. Arnold, T. A. Smith & J. M. Colford, Jr. (2009) Solar drinking water disinfection (SODIS) toreduce childhood diarrhoea in rural Bolivia: a cluster-randomized, controlled trial. PLoS Med,6,e1000125.

Schmidt, W. P., S. Boisson, B. Genser, M. L. Barreto, K. Baisley, S. Filteau & S. Cairncross (2010) Weight-for-

age z-score as a proxy marker for diarrhoea in epidemiological studies. J Epidemiol Community Health, 64,

1074-9.

Schmidt, W. P., B. F. Arnold, S. Boisson, B. Genser, S. P. Luby, M. L. Barreto, T. Clasen & S. Cairncross (2011)

Epidemiological methods in diarrhoea studies--an update. Int J Epidemiol,40,1678-92.

Additional ressources: studies cited

Documents

5.3 Health Impact Assessment