Besides, interventions cannot be seen as independent events, as potential disbenefits may emerge from investing in one area without commensurate investment in the other. For example, inadequate water quality at the point of consumption may undermine the benefits from water supply improvement (Fewtrell, 2005), and sanitation facilities without hygiene promotion may end up not being used (Tremolet et al., However, a few studies show that multiple interventions do not necessarily bolster the impact on health.