Water treatment and E. coli in drinking water: Household responses to (invisible) water quality risks.

BACKGROUND: In 2024, an estimated 4 billion people lacked access to safely managed drinking water, with the greatest risks for vulnerable groups such as young children. The objective of this paper is to 1) document the share of households exposed to E. coli contamination at the water source, 2) examine whether households are more likely to treat their water when the source is E. coli contaminated, and 3) assess how household water treatment relates to E. coli levels in stored drinking water. METHODS: This paper analyzes nationally representative Multiple Indicator Cluster Surveys (MICS) data from 59,633 households in low- and middle-income countries across 25 countries in Sub-Saharan Africa, Latin America, and Asia, all of which conducted standardized water-quality tests both at the source and in stored household drinking water. The main analysis documents how household water-treatment behavior differs by the level of E. coli contamination in their water source using regression methods by controlling for the country-specific fixed effects and household characteristics. RESULTS: The study reveals that 78% of households do not treat their water, While 20% relying on sources with high E. coli contamination levels (>100 MPN/100 ml). Despite this risk, the presence of E. coli is positively associated with a higher likelihood of treating water by just 3 to 5 percentage points, depending on contamination levels, from an average baseline of 21%. The association is stronger in Latin America and weaker in Africa. Moreover, analysis of stored household drinking water reveals that a substantial share of households that report treating their water still exhibit moderate to high E. coli contamination in stored samples. CONCLUSION: Households' water-treatment behavior shows only a modest association with the invisible risk of contamination, and many households still have E. coli contaminated drinking water even after treating it. These results highlight the need for WASH strategies that go beyond promoting access to treatment-specifically, strategies that inform households about contamination risks and emphasize correct and consistent application to ensure safe drinking water.