Drinking Water Salinity and Maternal Health in Coastal Bangladesh: Implications of Climate Change.

Background: Drinking water from natural sources in coastal Bangladesh has become contaminated by varying degrees of salinity due to saltwater intrusion from rising sea levels, cyclone and storm surges and upstream withdrawal of freshwater. Objective: Our objective was to estimate salt intake from drinking water sources and examine environmental factors that may explain a seasonal excess of hypertension in pregnancy. Methods: Water salinity data (1998-2000) for Dacope, in rural coastal Bangladesh, were obtained from the Centre for Environment and Geographic Information System. Information on drinking water sources, 24-hour urine samples and blood pressure were obtained from 343 pregnant Dacope women during the dry season (October 2009 - March 2010). The hospital-based prevalence of hypertension in pregnancy was determined for 969 pregnant women (July 2008 - March 2010). Results: Average estimated sodium intakes from drinking water ranged from 5 to 16 g/day in the dry season, compared to 0.6 - 1.2 g/day in the rainy season. Average daily sodium excretion in urine was 3.4 g/day (range 0.4 - 7.7 g/d). Women who drank shallow tubewell water were more likely to have urine sodium > 100 mmol/d than women who drank rainwater (OR=2.05, 95% CI: 1.11 - 3.80). The annual hospital prevalence of hypertension in pregnancy was higher in the dry season (12.2%, 95% CI: 9.5 - 14.8) than the rainy season (5.1%, 95% CI: 2.91 - 7.26). Conclusions: The estimated salt intake from drinking water in this population exceeded recommended limits. The problem of saline intrusion into drinking water has multiple causes and is likely to be exacerbated by climate change induced sea-level rise.