Climate change-driven water salinity linked to hypertension in coastal Bangladesh

Elevated blood pressure was found more prevalent in some Bangladeshi coastal communities and a new icddr,b study argues that higher water salinity levels, possibly triggered by climate change, may have a role in this.

Upstream water diminishes during the dry season, allowing the saline front to penetrate much deeper inland - causing salt concentration in drinking water to rise. Photo: Shumon Ahmed / icddr,b

In the study area covering 21 unions from 9 coastal districts, high blood pressure or hypertension was about 12 percent more prevalent than the national average levels. Drinking water salinity in major water sources such as groundwater was also significantly higher in these areas, notes the study supported by UK and Bangladesh collaboration under the ‘ESPA Deltas’ project.

“And there is a significant association between elevated blood pressure levels and drinking water salinity. Our evidence shows that water salinity may be responsible for the increased hypertension since higher salt intake is a prime factor for developing hypertension,” says Dr Peter Kim Streatfield, icddr,b emeritus scientist and senior author of the study published in Science of the Anthropocene.

The statistically significant association between drinking water salinity and hypertension showed seasonal variation and an increasing trend in dry season.

Explaining the link, icddr,b senior research officer and co-author of the study Mr Mahin Al Nahian informs that upstream water diminishes during the dry season, allowing the saline front to penetrate much deeper inland - causing salt concentration in drinking water to rise. “As a result, people will be consuming more salt from the same amount of water during the dry seasons and it is more likely to contribute to hypertension risks,” clarifies Mr Ali Ahmed, icddr,b research investigator and first author of the study.

More than 2000 mg of salt concentration in one litre of water significantly increases the likelihood of hypertension.

The study found higher salinity in both shallow and deep groundwater aquifers, resulting in up to 3153 mg of salt per litre for some shallow tubewells (<500 feet) and up to 6580 mg salt per litre in some deep tubewells.

Over 40 percent of people drinking water from moderate saline (2000 mg/l) sources were either hypertensive or pre-hypertensive – on the verge of developing hypertension.

Women had 31 percent higher chance of being hypertensive than men, according to the study, particularly those above the age of 35 years were more likely to grow pre-hypertension and hypertension than those below that age.


Is climate change to blame?

Climate change has arguably caused global sea levels to rise, a phenomenon that brings seawater closer to freshwater sources, contaminating freshwater and soil with higher levels of salt.

The coastal community may not be aware of the fact that they are consuming salt beyond tolerable levels. Photo: GMB Akash / icddr,b

“Increasing salinity in deep aquifers are of great concern because it develops almost permanently over a long time due to adjacent seawater levels, and is not quick to return to a normal level,” observes Dr Streatfield.

The coastal community may not be aware of the fact that they are consuming salt beyond tolerable levels, and about many associated health risks such as hypertension. Increased salinity in water may have also impacted their taste buds because many find the saline water ‘normal’ which people living outside the area find quite salty, according to the study.  

Hypertension is among the major non-communicable diseases (NCDs). Deaths and illnesses from NCDs have been rising steadily across the world, particularly in lower and middle-income countries, according to World Health Organization (WHO). NCDs are estimated to a cause of 67 percent of all deaths in Bangladesh, notesWHO. Data from icddr,b’s Matlab Health and Demographic Surveillance System (HDSS) has also shown similar findings.

Dr Quamrun Nahar, head of the Initiative for Climate Change and Health at icddr,b, stresses the need to carry out research in relation to climate change and health. “The coastal people of Bangladesh are at the forefront of climate change, and such health consequences of climate change may worsen in future scenarios,” she cautions.

Dr Nahar refers to another icddr,b study conducted in Chakaria, a rural Southeastern coastal area in Bangladesh, which found a significantly higher chance of high salt intake among housewives and those living in the coastal area compared with people who were engaged in labour-intensive occupations and who lived in hilly areas. She emphasised developing strategies to combat the effects of high level drinking water salinity on human health.

Dr Streatfield also urges water resources management and public health specialists to consider implementing mitigation projects to manage water ecosystems threated by climate change-induced effects.

Muhammad Nabil