BACKGROUND:
One of the most important and challenging environmental health tasks worldwide is the provision of sufficient amount and adequate quality of drinking water for the public, especially in arid regions. Water shortage is a critical issue in most parts of the Middle East, even for wealthy countries. The United Arab Emirates (UAE) is not an exception, where bottled water is favored to tap water, which poses sustainability issues in the fight against climate change and microplastics pollution. This systematic review aims to synthesize evidence on the quality of bottled water in comparison to tap water in the UAE.

METHODS:
The systematic review followed the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) 2020 guidelines. A structured search of peer-reviewed publications was performed in five scientific databases. Screening, data extraction and risk of bias assessment were carried out by two reviewers independently. Data were synthesized in summary tables.

RESULTS:
14 papers were finally included in this systematic review. All were cross-sectional studies from four of the seven Emirates of the UAE. Seven studies investigated components in bottled water, six in tap water and one in both, comparing their results to various national and international standards. The studies detected several parameters out of the normal range, especially in tap water, where physical parameters, such as turbidity and electrical conductivity, chemical parameters, such as chlorine and several metals, including carcinogens, and biological parameters, such as various bacteria and fungi, were found at unhealthy levels. In contrast, problems with bottled water were mainly limited to a few chemicals, such as fluoride, nitrite and bicarbonate.

CONCLUSIONS:
The findings revealed quality issues with tap water in the UAE. To assure an environmentally and economically sustainable provision of healthy drinking water to the population, evidence-based actions need to be taken.