Drinking water salinity may affect BP levels

A systematic review and meta-analysis show an association between elevated salinity in drinking water and higher systolic blood pressure (SBP) and diastolic BP (DBP) levels, particularly among individuals residing in coastal areas.

“Additionally, drinking water salinity was associated with increased risk of hypertension, irrespective of age, sex, and geographical location of the participants,” the investigators said.

Higher drinking water salinity was associated with elevated SBP (pooled mean difference [MD], 3.22 mm Hg) and DBP (pooled MD, 2.82 mm Hg). [BMJ Glob Health 2025;10:e018543]

Although modest, the MDs may have significant implications; evidence shows that every 2 mm Hg reduction in SBP is associated with a 7–10 percent reduction in cardiovascular (CV) deaths. [Lancet 2002;360:1903-1913]

“Therefore, even small increases in BP attributable to drinking water salinity could significantly raise CV risk in affected populations. Given that tens of millions of people worldwide depend on saline-intruded groundwater, the overall burden could be considerable,” the researchers said.

Compared with lower drinking water salinity, higher salinity was associated with an increased risk of hypertension (pooled odds ratio [OR], 1.26). The magnitude of the association was modestly reduced in the sensitivity analysis (pooled OR, 1.15).

Compared with the lowest quartile of salinity exposure (Q1), the adjusted ORs for CV disease-related hospital visits were 1.12, 0.13, and 1.64 for Q2, Q3, and Q4, respectively, after adjusting for annual household income and education.

Meta-regression

The association between higher drinking water salinity and increased SBP levels was also observed in studies of Asian populations and in studies conducted in 2000 and beyond (p-values for meta-regression=0.012 and 0.002, respectively).

The greater risk in Asian cohorts may be attributable to the differences in baseline salinity exposure across geographic locations. Consuming locally produced, high-sodium foods and using salty water for cooking may increase the overall risk, the researchers added.

For DBP, the association was observed in cross-sectional studies, with modest evidence from other study designs (p-value for meta-regression<0.05).

Both SBP and DBP levels were significantly higher in coastal vs non-coastal trials (p-value for meta-regression<0.05).

Underlying mechanisms

Higher sodium intake via drinking water can cause alterations in small resistance arteries, leading to increased systemic peripheral resistance and elevated BP. Other effects of higher sodium intake include reduced vascular nitric oxide, increased vascular stiffness in large arteries, and modulation of the autonomic neuronal supply and sympathetic activity, all of which can lead to elevated BP. [Eur Heart J 2018;39:3021-3104; J Vasc Res 2013;50:458-467; Eur Heart J 2020;41:3363-3373]

Higher sodium consumption also increases water retention, thereby elevating circulating blood volume, the investigators added. “This, in turn, leads to increased cardiac output and kidney perfusion pressure, triggering the pressure-natriuresis compensatory action.”

A significant global health challenge

More than 3 billion people worldwide live in coastal or near-coastal areas, and most of these areas are in low- and middle-income countries, where drinking water sources may be highly saline. [Camb Prisms Coast Futures 2023;1:e14; https://www.epa.gov/national-aquatic-resource-surveys/indicators-salinity, accessed February 16, 2026] Thus, the increased salinity – defined as the dissolved salt content of a body of water – could be a significant global health challenge, the investigators noted.

“However, the extent to which drinking water salinity, a potential environmental risk factor, is associated with elevated BP and the risk of CV outcomes (including hypertension) remains unclear,” they said.

The team identified 27 observational studies, comprising 74,063 unique participants from seven countries. Of these, 15 included coastal populations.

Policy implications

“[S]odium intake through drinking water salinity is not yet recognized as a potential risk factor for hypertension in any hypertension prevention efforts guideline,” the researchers noted. Moreover, current strategies for preventing noncommunicable diseases primarily focus on behavioural and metabolic determinants. [The Lancet 2018;392:245-252]

“Therefore, our results highlight the critical importance of recognizing environmental factors, such as increased drinking water salinity, as additional priorities in future policy development,” they said. “[O]ur findings support considering future strategies that will be mutually beneficial for environmental resilience and disease prevention.”

One proposed strategy is to conduct targeted screening for drinking water quality and hypertension risk evaluations in individuals exposed to saline water intrusion. Policymakers may also consider reducing drinking water salinity or adopting nature-based alternatives, particularly in climate-vulnerable coastal areas. [Healthcare (Basel) 2019;7:50; Environ Sci Technol 2017;51:5865-5866; https://www.who.int/publications/i/item/WHO-HSE-WSH-11.03, accessed February 16, 2026]

The researchers called for further studies to elucidate the association between drinking water salinity and clinical CV outcomes. “Additionally, as rising sea levels driven by ongoing global climate change potentially accelerate saline water intrusion, tailored adaptation strategies that provide co-benefits for maintaining optimal BP, particularly for the most vulnerable coastal populations, are necessary.”