Three decades of Nigerian bottled water quality research: a systematic review of contaminants and research gaps for environmental toxicology.

Bottled water consumption is widespread in Nigeria, yet the contaminant profile of these products and the implications for human exposure remain incompletely characterized. This systematic review synthesizes Nigerian bottled water quality research published between 1992 and 2025, drawing on 58 studies from major scientific databases. Analyses include temporal trends in research activity, types of contaminants investigated, and collaboration patterns among researchers. Results show marked geographical imbalance. About 79.5% of all research output focuses on southern Nigeria, while 14 states have no published data on bottled water quality. Studies of traditional contaminants, including heavy metals and microbial indicators, dominate the literature. Investigation of Contaminants of Emerging Concern, such as pharmaceuticals, personal care products, and microplastics, began only in 2020 despite more than two decades of global research on these substances. International collaborations (22.4% of studies) enabled advanced analytical methods but also revealed limited independent capacity for comprehensive contaminant detection. Without systematic data on bottled water contaminants across all regions, population exposure assessments remain incomplete. The delayed attention to emerging contaminants limits understanding of chronic exposure to chemical mixtures. This review supports prioritizing future toxicological research and strengthening environmental health monitoring in Nigeria and similar developing regions.