Adverse health outcomes associated with drinking highly saline water: a systematic review

In climate change-affected coastal areas, sea level rise, storm surges, droughts and altered rainfalls are significantly increasing salinity levels in drinking water sources. This is a major public health problem that affects many millions of people. We systematically reviewed and assessed the strength and quality of the evidence on the relationship between drinking water with high sodium levels (> 200 mgNa/l) and adverse cardiovascular, renal, and pregnancy-related health outcomes, following the PRISMA guidelines, the ROBINS-E Cochrane tool and the Navigation Guide. From five bibliographic databases, we identified 22 relevant studies, some of which assessed more than one health domain. The evidence was of moderate quality and strength. 14 analyses from eight studies at low risk of bias and four studies at moderate risk of bias, linked drinking high-salinity water to adverse health outcomes including hypertension and cardiovascular disease, impaired renal function, gestational hypertension and preeclampsia, and higher infant mortality. Eight studies were inconclusive. Three analyses, of which two at low risk of bias, associated drinking high-salinity water to improved health outcomes. Overall, our findings suggest that salinisation of drinking water sources is likely to increase adverse cardiovascular, renal, and pregnancy-related health outcomes. This conclusion highlights the importance of effective and timely adaptation at scale, and calls for a revision of the WHO guidelines for the intake of salt from water. The latest WHO guidelines (2022) do not set any health-based standard for sodium levels in drinking water, a problem that affects millions of people and will worsen with climate change.