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

Aneire Ehmar Khan
Medical Research Council/Health Protection Agency Centre for Environment and Health and Department of Epidemiology and Biostatistics, School of Public Health, and Grantham Institute for Climate Change, London, United Kingdom

Andrew Ireson
Department of Civil and Environmental Engineering, Imperial College London, London, United Kingdom

Sari Kovats
Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom

Sontosh Kumar Mojumder
Upazilla Health Complex, Dacope, Khulna, Bangladesh

Amirul Khusru
Department of Cardiology, Shaheed Sheikh Abu Naser, Specialised Hospital Khulna, Khulna, Bangladesh

Atiq Rahman
Bangladesh Center for Advanced Studies, Dhaka, Bangladesh

Paolo Vineis
Medical Research Council/Health Protection Agency Centre for Environment and Health and Department of Epidemiology and Biostatistics, School of Public Health, and Grantham Institute for Climate Change, London, United Kingdom

Abstract/ Executive Summary:

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. Water salinity data (1998–2000) for Dacope, in rural coastal Bangladesh, were obtained from the Centre for Environment and Geographic Information System in Bangladesh. Information on drinking water sources, 24-hr urine samples, and blood pressure was obtained from 343 pregnant Dacope women during the dry season (October 2009 through March 2010). The hospital-based prevalence of hypertension in pregnancy was determined for 969 pregnant women (July 2008 through March 2010). Average estimated sodium intakes from drinking water ranged from 5 to 16 g/day in the dry season, compared with 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/day). Women who drank shallow tube-well water were more likely to have urine sodium > 100 mmol/day than women who drank rainwater [odds ratio (OR) = 2.05; 95% confidence interval (CI), 1.11–3.80]. The annual hospital prevalence of hypertension in pregnancy was higher in the dry season (OR = 12.2%; 95% CI, 9.5–14.8) than in the rainy season (OR = 5.1%; 95% CI, 2.91–7.26). 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.

Keywords: Climate change, Hypertension, Maternal health, Pregnancy, Salinity intrusion

Location: Dacope Upazilla, situated under the Khulna district in Bangladesh

Start Date:

End Date:

Program Area: Risk Management in Agriculture

Commodity: Water salinity

Objectives:

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.

Methodology:

Study area and populations: The area included in our study is Dacope Upazilla (subdistrict), situated under the Khulna district in Bangladesh’s southwest coastal region. Dacope is divided into nine administrative unions that comprise 107 villages, with a total population of 157,500 people. It is intersected by a river network, the Passur River being the largest. This region’s rivers are tidal (ranging between 2 and 4.5 m), with semidiurnal, fortnightly, and seasonal variation in water levels. Salinity in drinking water: indirect estimates. The main sources of drinking water in the area include shallow and deep tube wells, ponds, rivers, and rainwater. Water may or may not be filtered before drinking. Rainwater, collected from roofs and stored in large numbers of relatively small containers, is assumed to have negligible levels of salinity. Indirect estimates of individual salinity intake from groundwater and river water were determined based on salinity data for 1998– 2000 from the Centre for Environment and Geographic Information System (CEGIS) in Bangladesh. These data included monthly measurements of salinity in shallow and deep groundwater tube wells at various sites in the Khulna region and in the Passur River. All measurements were converted from decisiemens per meter, a measure of electrical conductivity, into an equivalent concentration of parts per thousand (ppt), assuming that 1 ppt is approximately equivalent to 0.64 dS/m (Ayers and Westcot 1985). We used spatially and temporally (monthly) averaged river and shallow tube-well salinities to estimate average levels of salt consumption from river water and shallow groundwater, respectively. For our estimates, we assumed a conservative water intake of 2 L/day per person. Sample of pregnant women and measurement of urinary sodium. A network of health assistants, under the supervision of the Upazilla Health Complex (UHC) in Dacope, regularly identify and monitor all pregnant women between the ages of 13 and 45 years, in every village of the subdistrict, with a measurement of blood pressure at gestational week 20. Three hundred forty-three pregnant women, a random sample from the monitored women, were enrolled in the study between October 2009 and March 2010 (dry season). Women referred for hypertension in pregnancy. We also analyzed data from the UHC, the only hospital in the subdistrict. Pregnant women are tested for proteinuria (a symptom of preeclampsia) by health workers during routine pregnancy monitoring at week 20 and if they have high blood pressure or edema. Women diagnosed with mild hypertension with or without preeclampsia are treated at home but are referred to the hospital for more severe or refractory conditions. We determined the prevalence of hypertension in pregnancy among 969 pregnant women (13–45 years of age) who visited the UHC for antenatal care or pregnancy-related complications or were referred to the UHC for severe hypertension between July 2008 and March 2010. Data were collected from medical records on patient diagnosis, age, residence (village), and distance from the UHC. Cutoff point for urinary sodium and blood pressure. A cutoff point of 100 mmol/day was chosen to classify high salt excretion as an outcome. This threshold was selected based on its association with increased systolic and diastolic blood pressure in the Intersalt study (Elliott et al. 1996; Intersalt Cooperative Research Group 1988). We chose cutoff values for diastolic and systolic blood pressure levels of > 85 mmHg and > 130 mmHg, respectively, because levels higher than those are considered “hypertensive.” Statistical analysis. Using logistic regression, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) for urinary salt excretion > 100 mmol/day according to water source, and for diastolic blood pressure > 85 mmHg and systolic blood pressure > 130 mmHg according to quartiles of urinary sodium concentration. p-Values for trend were also estimated by logistic regression.

Source of Information: Environmental Health Perspectives • volume 119 | number 9 | September 2011

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Discovery of the presence of high levels of salt in drinking water sources in rural coastal Bangladesh is a cause of public health concern and a challenge for the government of Bangladesh, donor communities, and nongovernmental organizations. Our findings suggest that the mean sodium intake in pregnant women is well above WHO/FAO– recommended levels and above those of many other countries. We hypothesize that increasing salt intake during the dry season might contribute to the seasonal pattern of hypertension in pregnancy in coastal Bangladesh, and the problem may be exacerbated by future sea-level rise and environmental change. Hypertension in pregnancy is associated with increased rates of adverse maternal and fetal outcomes, both acute and long term, including impaired liver function, low platelet count, intrauterine growth retardation, preterm birth, and maternal and perinatal deaths (Sibai 2002). The adverse outcomes are substantially increased in women who develop superimposed (pre)eclampsia. With a growing concern for rising salinity, awareness and interest in climate change impacts on water sources are also increasing. Adaptation practices to improve coping mechanisms and reduce vulnerabilities of communities are being advocated, including measures to increase storage capacity of rainwater and apply desalination processes. More research is required to improve the management of fresh surface water and groundwater resources in these areas and to explore rainwater harvesting as a sustainable solution. Bangladesh stands at the forefront of saltwater contamination. However, the same trend potentially affects all 11 Asian large river deltas, and other major deltas, notably the Nile and the Mississippi (Parry et al. 2007).

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