Majority of people living on earth rely on groundwater as their primary supply of water for daily needs. However, human activities continuously threaten this natural resource. In an attempt to unravel the extent of impact of human-related activities on groundwater physicochemical characteristics in Nnewi and Awka urban clusters (Nigeria), several techniques were integrated in this study. Groundwater samples were warm and acidic in nature. Concentrations of SO₄^2-, NO₃^-, PO₄^3-, Cl^-, HCO₃^-, Ca²⁺, Mg²⁺, Na⁺, and K⁺ were within set benchmarks. Water nutrient pollution index (ranging from 0.060-0.745), nitrate pollution index (varying between -0.999 and -0.790), and water pollution index (ranging from 0.057-0.630) estimated the extent of anthropogenic contamination and showed low anthropogenic impact on the groundwater physicochemical characteristics. The health risks due to the ingestion and skin absorption of the nitrate-contaminated water computed for six age groups (6-12 months, 5-10 years, 10-15 years, 15-20 years, 20-60 years, and > 60 years) showed health risk values that were < 1, implying low chronic health risks to humans. The cumulative total health hazard index ranged between 0.006 and 0.787 with a mean value of 0.167. Chemometric analyses and geochemical plots revealed the relationships between the variables and contamination sources. Chadha’s plot showed that 55% of the samples were Ca²⁺-Mg²⁺-Cl^- waters, predominating over Na⁺-Cl^- and Ca²⁺-Mg²⁺-HCO₃^- waters. Bivariate and multivariate geochemical plots also indicated low anthropogenic impact. Furthermore, principal component analysis and R-type hierarchical clustering confirmed that the groundwater chemistry and quality were mostly influenced by geogenic processes than human-related acts. Conclusively, the extent of anthropogenic influence on the groundwater physicochemical characteristics is low. These findings would be useful in future monitoring of groundwater in both urban clusters.

Contamination in coastal regions attributed to fluoride and nitrate cannot be disregarded, given the substantial environmental and public health issues they present worldwide. For effective decontamination, it is pivotal to identify regional pollution hotspots. This comprehensive study was performed to assess the spatial as well as indexical water quality, identify contamination sources, hotspots, and evaluate associated health risks pertaining to nitrate and fluoride in the Al-Hassa region, KSA. The physicochemical results revealed a pervasive pollution of the overall groundwater. The dominant water type was Na-Cl, indicating saltwater intrusion and reverse ion exchange impact. Spatiotemporal variations in physicochemical properties suggest diverse hydrochemical mechanisms, with geogenic factors primarily influencing groundwater chemistry. The groundwater pollution index varied between 0.8426 and 4.7172, classifying samples as moderately to very highly polluted. Similarly, the synthetic pollution index (in the range of 0.5021–4.0715) revealed that none of the samples had excellent water quality, with various degrees of pollution categories. Nitrate health quotient (HQ) values indicated chronic human health risks ranging from low to severe, with infants being the most vulnerable. Household use of nitrate-rich groundwater for showering and cleaning did not pose significant health risks. Fluoride HQ decreased with age, and children faced the highest risk of fluorosis. The hazard index (HI) yielded moderate- to high-risk values. Nitrate risks were 1.21 times higher than fluoride risks, as per average HI assessment. All samples fell into the vulnerable category based on the total hazard index (THI), with 88.89% classified as very high risk. This research provides valuable insights into groundwater quality, guiding water authorities, inhabitants, and researchers in identifying safe water sources, vulnerable regions, and human populations. The results highlight the need for appropriate treatment techniques and long-term coastal groundwater management plans.

In this paper, the oral and dermal health risks of potentially toxic elements in water samples collected from Ojoto area in southeast Nigeria were studied using HHRISK code and water quality index. The water samples were analysed for physicochemical parameters based on standard guidelines. Average concentration of the potentially toxic elements in the water was in the order: Pb²⁺ > Fe²⁺ > Zn²⁺ > Ni²⁺ > Cr³⁺. To assess the level of surface and groundwater pollution, water quality index was calculated. Results of the water quality index suggest that 11% of the water samples are in good condition; 25% have poor quality, 3% have very poor quality, and 53% have quality that is unfit for human consumption. The HHRISK code was used to quantify the health risks associated with the use of the water resources. Results revealed that most of the water samples expose their users to carcinogenic and non-carcinogenic health risks. Cumulative non-carcinogenic risk scores (for both children and adults) and the majority of cumulative carcinogenic risk values were found to be above regulatory limits. The adult population is exposed to lower non-carcinogenic and carcinogenic health risks, implying that children are more vulnerable. The water supplies are of substandard quality and could cause serious health issues when ingested than when used for bathing and washing purposes. Simple linear regression models showed positive agreement between the results of the WQI and HHRISK code. To safeguard the water resources, avoid additional water contamination, and reduce public health hazards associated with poor water quality, strategic mitigation strategies are recommended.