Background Sodium (Na + ) in saline water may increase blood pressure ( BP ), but potassium (K + ), calcium (Ca 2+ ), and magnesium (Mg 2+ ) may lower BP . We assessed the association between drinking water salinity and population BP . Methods and Results We pooled 6487 BP measurements from 2 cohorts in coastal Bangladesh. We used multilevel linear models to estimate BP differences across water salinity categories: fresh water (electrical conductivity, <0.7 mS/cm), mild salinity (electrical conductivity ≥0.7 and <2 mS/cm), and moderate salinity (electrical conductivity ≥2 and <10 mS/cm). We assessed whether salinity categories were associated with hypertension using multilevel multinomial logistic models. Models included participant‐, household‐, and community‐level random intercepts. Models were adjusted for age, sex, body mass index ( BMI ), physical activity, smoking, household wealth, alcohol consumption, sleep hours, religion, and salt consumption. We evaluated the 24‐hour urinary minerals across salinity categories, and the associations between urinary minerals and BP using multilevel linear models. Compared with fresh water drinkers, mild‐salinity water drinkers had lower mean systolic BP (−1.55 [95% CI : −3.22–0.12] mm Hg) and lower mean diastolic BP (−1.26 [95% CI : −2.21–−0.32] mm Hg) adjusted models. The adjusted odds ratio among mild‐salinity water drinkers for stage 1 hypertension was 0.60 (95% CI : 0.43–0.84) and for stage 2 hypertension was 0.56 (95% CI : 0.46–0.89). Mild‐salinity water drinkers had high urinary Ca 2+ , and Mg 2+ , and both urinary Ca 2+ and Mg 2+ were associated with lower BP. Conclusions Drinking mild‐salinity water was associated with lower BP , which can be explained by higher intake of Ca 2+ and Mg 2+ through saline water.

We evaluated the effectiveness of a sand barrier around latrine pits in reducing fecal indicator bacteria (FIB) leaching into shallow groundwater. We constructed 68 new offset single pit pour flush latrines in the Galachipa subdistrict of coastal Bangladesh. We randomly assigned 34 latrines to include a 50 cm thick sand barrier under and around the pit and 34 received no sand barrier. Four monitoring wells were constructed around each pit to collect water samples at baseline and subsequent nine follow-up visits over 24 months. Samples were tested using the IDEXX Colilert method to enumerate E. coli and thermotolerant coliforms most probable number (MPN). We determined the difference in mean log 10 MPN FIB counts/100 mL in monitoring well samples between latrines with and without a sand barrier using multilevel linear models and reported cluster robust standard error. The sand barrier latrine monitoring well samples had 0.38 mean log 10 MPN fewer E. coli (95% CI: 0.16, 0.59; p = 0.001) and 0.38 mean log 10 MPN fewer thermotolerant coliforms (95% CI: 0.14, 0.62; p = 0.002), compared to latrines without sand barriers, a reduction of 27% E. coli and 24% thermotolerant coliforms mean counts. A sand barrier can modestly reduce the risk presented by pit leaching.

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Table SI1: FT-IR vibrational frequencies for main functional groups and 1 H NMR chemical shifts of different type of protons present in compounds C1-C6 Wavenumber (cm -1 ) Functional groups (CH, aliphatic) (C=O in ester) (C=C, vinyl) (C=C, aromatic) (N=N)

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Managed aquifer recharge (MAR), a hydro-geological intervention designed to dilute groundwater salinity, pumps pond water treated through a slow sand filter into the underground aquifers. We evaluated the microbiological safety of the resulting MAR water at sites from three districts in southwest coastal Bangladesh. We collected monthly paired pond-MAR water samples from July 2016-June 2017 and enumerated fecal coliforms and E. coli using the IDEXX quanti-tray technique, by the most probable number (MPN) method. We used WHO risk categories for microbiological quality; no risk (<1 MPN), low risk (1-10 MPN) and moderate to high risk (>10 MPN per 100 mL water). We estimated the difference in mean log10 MPN in pond and MAR water using linear mixed effect models with random intercepts and cluster adjusted robust standard error. Almost all pond water samples (292/299, 98%) had moderate-to high-risk level (>10 MPN) fecal coliforms and E. coli (283/299, 95%). In contrast, 81% (242/300) of MAR water samples had no or low risk level fecal coliforms (0-10 MPN), of which 60% (179/300) had no fecal coliforms. We detected no or low risk level E. coli in 94% (283/300) of MAR water samples of these 80% (240/300) had no E. coli. MAR samples had lower mean log10 MPN fecal coliforms (-2.37; 95% CI: -2.56, -2.19) and E. coli (-2.26; 95% CI: -2.43, -2.09) than pond water; microbial reductions remained consistent during the wet (May-October) and dry seasons. MAR-systems provided water with reduced fecal indicator bacteria compared to infiltered pond water.

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