When Climate Change Drives Saline Drinking Water: Public Health Implications

In recent years, climate change has been profoundly altering sources of domestic water supply across many parts of the world. Rising sea levels, stronger storms, prolonged droughts, and changing rainfall patterns have led to saltwater intrusion into freshwater sources, particularly in coastal areas. As a result, many communities are increasingly compelled to rely on saline drinking water, characterized by elevated sodium concentrations beyond typical levels.

This situation raises a critical question: Does long-term consumption of saline drinking water pose risks to human health? A large-scale systematic review, published in the European Journal of Epidemiology in 2025, provides concerning evidence addressing this issue.

What Did the Study Examine?

This study is a systematic review, meaning that the researchers did not conduct new experiments but instead synthesized and critically evaluated existing scientific evidence on the same topic. The review included a total of 22 studies, encompassing data from more than 860,000 individuals. These studies were conducted across multiple countries, primarily in regions heavily affected by saltwater intrusion.

The analysis focused on drinking water with sodium concentrations exceeding 200 mgNa/L—a level that the World Health Organization (WHO) currently considers mainly from the perspective of taste acceptability, rather than as a health-based threshold. The review examined three main categories of health outcomes: cardiovascular health and blood pressure, kidney function, and pregnancy and neonatal outcomes.

1. Effects on Cardiovascular Health and Blood Pressure

Most of the reviewed studies reported a clear association between saline drinking water and elevated blood pressure, as well as an increased risk of cardiovascular disease. Several studies identified a dose–response relationship, indicating that higher sodium concentrations in drinking water were associated with higher blood pressure levels and a greater prevalence of hypertension.

However, not all studies yielded consistent findings. A small number reported inconclusive or even slightly protective effects. The authors suggest that this variability may be partly explained by the mineral composition of saline water, which often contains higher levels of calcium, magnesium, and potassium—minerals considered beneficial for cardiovascular health and potentially capable of attenuating the adverse effects of sodium.

Nevertheless, when the totality of evidence is considered, the overall pattern indicates predominantly adverse cardiovascular effects associated with high sodium concentrations in drinking water.

2. Effects on Kidney Function

Although fewer studies examined kidney-related outcomes, the findings in this area were relatively consistent. The evidence suggests that consumption of water with high sodium content is associated with reduced kidney function and indicators of renal stress or damage, such as hyperdilute urine and increased protein excretion. These effects are of particular concern in populations that rely on saline drinking water over extended periods due to the lack of alternative water sources.

3. Impacts on Pregnancy and Neonatal Health

Pregnant women are identified as one of the most vulnerable populations to saline drinking water exposure. The reviewed studies indicate that women who consume water with elevated sodium levels face a higher risk of gestational hypertension and preeclampsia. Some studies also reported associations between saline drinking water and increased neonatal and infant mortality, highlighting potential intergenerational health consequences.

Why Is This Issue Becoming More Serious?

Overall, the review presents a clearer picture: saline drinking water is not merely an environmental or infrastructure issue, but a genuine public health concern. According to the review, climate change is expected to further exacerbate saltwater intrusion into freshwater systems in the future, even if global mitigation efforts succeed. Consequently, an increasing number of people may experience chronic exposure to saline drinking water, leading to a growing burden of cardiovascular, renal, and pregnancy-related health outcomes—particularly in socioeconomically vulnerable communities.

A key point emphasized by the authors is that the World Health Organization currently does not provide a health-based guideline value for sodium in drinking water. The commonly cited threshold of 200 mgNa/L is based largely on palatability, rather than on evidence of long-term health risks. This lack of a health-based standard poses challenges for policymakers, especially in regions where controlling drinking water salinity is difficult, and where populations face sustained exposure.

Source: Springer Nature