Table 2.
Information on counterfactual, outcome association and potential for bias by health outcome.
| health outcome | WASH counterfactual exposure definition | prevalence of WASH counterfactual exposure in 2016 | RR for/association between WASH counterfactual exposure and outcome# (against lowest level of exposure, e.g., unimproved WASH) | counterfactual definition used | potential for bias |
|---|---|---|---|---|---|
| diarrhoea | water: household water treatment using filtering or boiling | 33.1% (WHO and UNICEF, undated) | RR 0.52 (0.35, 0.77)* (Wolf et al., 2018a) | plausible minimum risk | predominately non-blinded intervention studies but bias-adjustment performed |
| sanitation: basic sanitation in a community >75% sanitation coverage | 45.3% (Wolf et al., 2018c) | RR 0.55 (0.34, 0.91) (Wolf et al., 2018a) | |||
| hygiene: handwashing with soap after potential faecal contact | 26.2% (Wolf et al., 2018b) | RR 0.86 (0.35, 2.07)* (Wolf et al., 2018a) | |||
| acute respiratory infections | hygiene: handwashing with soap after potential faecal contact | 26.2% (Wolf et al., 2018b) | RR 0.84 (0.79, 0.89) (Rabie and Curtis, 2006) | plausible minimum risk | predominantly non-blinded intervention studies |
| protein-energy malnutrition | same as for diarrhoea | same as for diarrhoea | combining the PAF for stunting attributable to diarrhoea (25% (8%, 38%)) (Checkley et al., 2008) with the PAF of WASH-attributable diarrhoeal disease (60% (54%, 65%)) | same as for diarrhoea | includes only WASH-attributable burden via diarrhoea, only stunting is considered as indicator for malnutrition |
| schistosomiasis | basic drinking water and basic sanitation services | basic drinking water: 87.2%; basic sanitation: 62.0% (WHO and UNICEF, undated) | basic drinking water: RR 0.53 (0.47, 0.61) (Grimes et al., 2014); basic sanitation: RR 0.65 (0.54, 0.78) (Freeman et al., 2017) | feasible minimum risk | RR estimates from observational studies only |
| malaria | safe water resource management | 0% (Keiser et al., 2005) | RR 0.21 (0.13–0.33) (Keiser et al., 2005) | theoretical minimum risk | disease burden estimates based on stronger assumptions |
| soil-transmitted helminth infections | safely managed water and safely managed sanitation services, essential hygiene conditions and essential hygiene practices | NA | RR 0 | theoretical minimum risk | disease burden estimates based on stronger assumptions |
| trachoma | safely managed water and safely managed sanitation services, essential hygiene conditions and essential hygiene practices | NA | RR 0 | theoretical minimum risk | disease burden estimates based on stronger assumptions |
RR: relative risk, NA: not applicable, # separate RR for water, sanitation and hygiene are combined using equation (2), * adjusted for potential non-blinding bias.