Monitoring drinking water quality in nationally representative household surveys: cross-sectional analysis of 20 Multiple Indicator Cluster Surveys 2014-2019

Background The Sustainable Development Goals set an ambitious new benchmark for safely managed drinking water services (SMDW), but many countries lack data on the availability and quality of drinking water. Objectives To quantify the availability and microbiological quality of drinking water, monitor SMDW and examine risk factors for E. coli contamination in 20 low-and middle-income countries. Methods A new water quality module for household surveys was implemented in Multiple Indicator Cluster Surveys. Teams used portable equipment to measure E. coli at the point of collection (PoC, n=48,323) and at the point of use (PoU, n=51,345) and asked respondents about the availability and location of drinking water services. E. coli levels were classified into risk categories and SMDW was calculated at the household- and domain-levels. Modified Poisson regression was used to explore risk factors for contamination. Results E. coli was commonly detected at PoC (range 16-90%) and was more likely at PoU (range 20-97%). Coverage of SMDW was 56% points lower than improved drinking water with water quality the limiting factor for SMDW in 14 countries. Detection of E. coli at PoC was associated with use of improved water sources (RR=0.64 [0.52-0.78]) located on premises (RR=0.78 [0.67-0.91]) but not with availability (RR=0.94 [0.82-1.06]). Households in the richest quintile (RR=0.67 [0.50-0.90]) and in communities with high (>75%) improved sanitation coverage (RR=0.95 [0.91-0.98]) were less likely to use contaminated water at PoU whereas animal ownership (RR=1.08 [1.03-1.14]) and rural residence (RR=1.11 [1.03-1.19]) increased risk of contamination. Discussion Water quality data can be reliably collected in household surveys and can be used to assess inequalities in service levels, to track the SDG indicator of SMDW, and to examine risk factors for contamination. There is an urgent need to implement scalable and sustainable interventions to reduce exposure to faecal contamination through drinking water.