Academic journal article Environmental Health Perspectives

Drinking Water Salinity and Raised Blood Pressure: Evidence from a Cohort Study in Coastal Bangladesh

Academic journal article Environmental Health Perspectives

Drinking Water Salinity and Raised Blood Pressure: Evidence from a Cohort Study in Coastal Bangladesh

Article excerpt

Introduction

Low-lying deltas, such as Bangladesh, have been experiencing increasing numbers of storm surges over recent decades, inundating densely populated coastal areas (Singh et al. 2000). This trend is believed to be associated with climate change and, in combination with sea level rise, may result in contamination of unprotected drinking-water sources, such as ponds and shallow tube wells, with saline water [Hoque et al. 2016; Institute of Water Modelling (IWM) 2014]. Changes in river flow from an upstream barrage, faulty management of polders, shrimp farming, and groundwater extraction may all contribute further to salinization (Mahmuduzzaman et al. 2014). Previously, we found a mean sodium concentration in drinking water of approximately 700 mg/L (with extremes exceeding 1500 mg/L) (Khan et al. 2014) in coastal areas; this contributes substantially to the daily sodium intake of coastal populations (Scheelbeek 2015). As a consequence, the World Health Organization (WHO)-recommended daily maximum sodium intake of 2000 mg (WHO 2012b) can easily be exceeded in the area solely by drinking 2-3 L of water. Climate change predictions, including sea level rise (Hijioka et al. 2014), suggest further exacerbation of salinity problems in the future.

High dietary salt intake from food is a major risk factor for raised blood pressure (BP) worldwide (Aburto et al. 2013; Elliott et al. 1996, 2007; Elliott and Stamler 2002; Pietinen et al. 1988). However, the effects of long-term consumption of substantial amounts of sodium through drinking water on population health remain unknown.

In the present study, we explored the relationship between drinking-water salinity and BP in a coastal population in Bangladesh. We looked at the relationship between BP and drinking-water sodium concentrations in individuals whose sodium intake fluctuated during the study period. Differences in sodium concentrations occurred because users consumed drinking water from different sources [pond, tube well, managed aquifer recharge (MAR) system (Figure 1), or rainwater] or because of seasonal fluctuation of drinking-water sodium concentrations in a single source (i.e., pond). Furthermore, some participants changed their drinking-water sources during the study period. It was expected that consumers switching from ponds and tube wells to MAR sources would experience a significant decrease in their drinking-water salinity, and the study assessed whether this occurred.

Methods

For this study, ethical clearance was obtained from the National Research Ethics Committee of the Bangladesh Medical Research Council.

[FIGURE 1 OMITTED]

Three sub-districts in southwestern Bangladesh--Dacope, Batiaghata and Paikghaccha--(see Figure S1) were selected for this study because of high salinity levels in drinking water and an ongoing MAR construction project in the area [Netherlands Embassy in Dhaka 2014; Sultana et al. 2014; United Nations Children's Fund (UNICEF) 2014] (Figure 1).

Based on access and hydrological conditions, 25 villages were found suitable for MAR construction (Hasan 2012); six were prioritized based on water shortages. MAR systems in these villages were scheduled to become operational during the study period; however, some participants started drinking MAR water before the planned starting day of the scheme. All 303 families in the six MAR locations were invited to participate in the study. In addition, six other villages were randomly selected from the remaining 19 villages on the "waiting list". All households in these villages (or a randomly selected maximum of 60 households in villages with >60 households), comprising an additional 321 families, were invited to participate (see Figures S2 and S3).

Each adult within the selected households was numbered following the Kish-grid method (Kish 1949), and one adult household member was then invited for participation in the study. …

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