Work

Source-water salinity measured by electrical conductivity in Bangladesh, 2025: a nationally representative cross-sectional survey

Year: 2026

Type: preprint

Abstract: Background In coastal Bangladesh, salty drinking water has been linked to higher blood pressure. The 2025 Multiple Indicator Cluster Survey measured electrical conductivity, a marker of salinity, in household water sources. Its report did not estimate how many people were affected or where they lived. Objectives We estimated how many people live in households whose tested water source has high salinity and where they live. We also examined differences by household characteristics and source type, and overlap with arsenic. Methods Electrical conductivity was measured in the water source of 6,040 households in all 64 districts, February to June 2025. The main outcomes were conductivity above 1,500 and above 3,000 µS/cm, the survey’s risk classes, not health-based standards. Estimates used the survey weights and design. Results The tested source exceeded 1,500 µS/cm in 5.3% of households (95% confidence interval 4.7 to 5.9). Meter calibration was not documented, and most scenarios gave 4.5% to 6.2%. About 9.0 million people (7.9 to 10.1) lived in these households, including 1.8 million above 3,000 µS/cm. The 19 coastal districts held 26% of households but 70% of those above 1,500 µS/cm. Prevalence was similar across wealth groups and in households with a pregnant woman. Within the coastal zone, deep and shallow tube wells had high conductivity in similar shares (16.1% against 17.9%). After adjustment for district, deep wells had about 18% lower conductivity, but this difference was smaller and uncertain within subdistricts and differed by region. Conclusions Millions of people live in households whose water source is highly saline, mostly in the coastal zone. Deep wells were not reliably less saline than shallow wells, and a source that is safe for arsenic may still be salty. National water surveys should measure salinity alongside arsenic and test water in more than one season.

Source: medRxiv

DOI: 10.64898/2026.10.10.26364870