Keywords
chemical contamination, arsenic
fluorides
nitrates
health risk assessment
meta-analysis
How to Cite
Abstract
Introduction
Groundwater is a vital source of drinking water globally, particularly in rural areas and places with infrastructure constraints. However, chemical contaminants from both natural (geogenic) and anthropogenic sources—including arsenic, fluoride, and nitrates—pose severe long-term threats to human health.
Purpose
This study aimed to quantitatively synthesize chemical contamination levels in drinking water from wells, boreholes, and distribution networks, identify main contamination drivers, and evaluate non-carcinogenic and carcinogenic health risks worldwide.
Methods
A systematic search across PubMed, Scopus, Web of Science, Cochrane Library, ScienceDirect, Google Scholar, and HAL identified quantitative studies evaluating chemical contaminants in drinking water published between 2014 and 2024. Exceedance rates of World Health Organization (WHO) guidelines were combined using a random-effects meta-analysis model. Subgroup analyses examined geographic regions, hydraulic structure types, and methodological quality evaluated via the Newcastle-Ottawa Scale (NOS). Health risks were assessed using the Hazard Index (HI) and lifetime Cancer Risk (CR).
Results
Across 62 included studies (N=62), the combined global rate of exceeding drinking water health standards was 30.8%. Nitrates exhibited the highest exceedance rate (41.5%), followed by fluorides (38.2%) and arsenic (32.7%). The overall combined HI was 1.84 (95% CI [1.41, 2.39]), and the lifetime carcinogenic risk reached 4.72×10−5. Africa demonstrated the highest contamination exceedance (57.3%), significantly surpassing Europe (13.5%; p<.001). Traditional unprotected wells were the most vulnerable water source (45.8% exceedance). Methodological quality significantly modulated estimates (p<.001), with lower-quality studies overestimating contamination rates.
Conclusion
Chemical groundwater contamination represents a major global health risk. Strengthening routine water quality monitoring, adopting contaminant-specific treatment technologies, and prioritizing water safety within public health governance—particularly in mining and rural regions—are critical to mitigating chronic toxic exposure. Protocol registration: PROSPERO (CRD420261398101).
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