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Review

Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications

by
Joshua O. Olowoyo
1,2,*,
Olasunkanmi O. Olaiya
3,*,
Omuferen-Oke L. Oharisi
4,
Johnson A. Olusola
5,
Unathi A. Tshoni
6 and
Oluwaseun M. Oladeji
2
1
Department of Health Sciences, The Water School, Florida Gulf Coast University, Fort Myers, FL 33965, USA
2
Department of Biology and Environmental Sciences, Sefako Makgatho Health Sciences University, Pretoria 0204, South Africa
3
Institute of Ecology and Environmental Studies, Obafemi Awolowo University, Ile-Ife 220282, Nigeria
4
Faculty of Computing, Engineering and Science, University of South Wales, Treforest, Wales CF37 1DL, UK
5
Department of Environmental Science and Management, Federal University of Technology and Environmental Sciences, Iyin-Ekiti 371101, Nigeria
6
Department of Environmental Health, Faculty of Health Sciences, Doornfontein Campus, University of Johannesburg, Johannesburg 2006, South Africa
*
Authors to whom correspondence should be addressed.
Water 2026, 18(8), 886; https://doi.org/10.3390/w18080886
Submission received: 18 December 2025 / Revised: 26 February 2026 / Accepted: 27 February 2026 / Published: 8 April 2026
(This article belongs to the Special Issue New Technologies to Ensure Safe Drinking Water)
Versions Notes

Abstract

Heavy metal contamination in drinking water remains a pervasive global challenge with significant consequences for environmental quality and human health. This review synthesizes findings from recent studies examining heavy metal concentrations in different sources of drinking water, including municipal tap water, groundwater, surface water, and bottled/sachet water across various geographical regions. The study used a systematic review of studies published from 2015 to 2024. The result showed a variation in the concentrations of heavy metals from all the sources, with tap water generally exhibiting lower heavy metal levels. Pb, Fe, Mn, and other metals persist in different sources and from many regions with levels above the permissible limits recommended by the World Health Organization (WHO) in some instances, which were sometimes linked to aging distribution systems and other pollution sources. Bottled and sachet water, commonly regarded as safer alternatives, also showed some levels of heavy metals such as Pb, Cd, and Cr, reflecting inconsistent packaging or production oversight. Surface waters display variability with heavy metals pollution, driven by industrial discharge, mining activities, agricultural runoff, and urban wastewater inputs. Groundwater sources, although naturally shielded, frequently contained elevated concentrations of As, Hg, and Ni due to both geological and anthropogenic factors. Pb concentrations were below detection limit in some of the published papers; however, the values reported in this study ranged from ND to 260.0 µg/L (tap water), ND to 0.259 mg/L (surface water), ND to 0.791 mg/L (groundwater), and ND to 123.15 µg/L (bottled water). Arsenic (As) concentrations ranged from ND to 692 µg/L from different sources, with the highest concentration from groundwater. Collectively, these patterns underscore the need for strengthened monitoring frameworks, improved water treatment technologies, and integrated pollution-prevention strategies. Addressing heavy metal contamination in drinking water requires coordinated policy approach and continuous monitoring to reduce human exposure and safeguard global public health.

1. Introduction

The levels of heavy metal in drinking water sources have been a source of concern globally due to their health implications [1,2,3]. Various research activities conducted on the levels of heavy metals in drinking water have shown their presence in bottled water, groundwater, tap water and other sources [4]. Due to its presence and varying levels in drinking water, the World Health Organization has set a maximum allowable limit on heavy metals in drinking water, which is still a struggle for many developing countries to meet the standard set by the WHO [5]. Research has shown that levels of some toxic heavy metals in water, especially from most developing countries, are usually higher than the recommended limit [5].
Major heavy metal pollutants of drinking water include arsenic, cadmium, lead, mercury, and nickel and in some instances, recorded values do exceed the acceptable limits [6,7]. Prolonged exposure to these heavy metals can lead to their bioaccumulation in the human body, potentially posing serious health risks such as cardiovascular disorders, neuron damage, renal injuries, and increasing cancer and diabetes risks among others [7]. Children and developing fetuses have been reported in literature to be the most vulnerable group as regards the impact of the toxicity of these heavy metals [7]. However, the toxicity depends on their concentration, frequency of exposure and route of exposure into the body [8,9].
The presence of heavy metals may be influenced by both natural and anthropogenic sources [4]. The natural source is primarily influenced by parent material, while the anthropogenic sources may be influenced by proximity to different industrial activities, such as mining industries, vehicular emissions, agricultural sectors and leaching from pipes and fittings [10,11]. The mobility of heavy metals in soil is governed by several factors, such as the soil pH, texture, and sorption characteristics [12]. They can also be absorbed by natural mineral and organic sorbents that attract heavy metal cations through electrostatic forces [12]. In addition, from mining or polluted areas, the mobility of heavy metals is enhanced by water acidity and the presence of acid-forming sulfide minerals [13].
The main mechanism of heavy metal toxicity involves the release of reactive oxygen species (ROS), resulting in oxidative damage [7,14]. This oxidative stress can disrupt major metabolic processes and cause DNA damage [14]. While various detection methods exist, such as atomic absorption spectroscopy and inductively coupled plasma mass spectrometry, among others, many developing countries still struggle to implement advanced removal technologies due to economic constraints [6,15]. The main documented method of removing heavy metals in drinking water is the adsorption technology [16]. Other methods, such as the use of agricultural wastes such as banana peels and coconut husks, natural soils such as clay and zeolites, and modified ceramic filters, have also proved to be effective in removing heavy metals from polluted water [17]. The flotation method, ion exchange, chemical precipitation, membrane filtration, coagulation, flocculation, phytoremediation, and electrochemical methods have also been employed, though, these methods are known to be expensive and may not be affordable in some places [18]. In all, the removal efficiency is affected by the pH, metal ion concentration, and adsorbent concentration [17]. While many techniques have been reported to be adequate, there are challenges with the selective removal of diverse ions and in situations where large sludges are formed [18].
Despite the technological advancement and the reported efficiency of various methods to remove heavy metals from drinking water, several authors have reported on the different levels of heavy metals from different sources of drinking water globally. For instance, the study of Cobbina et al. [5] carried out in Ghana showed that the levels of mercury, arsenic and lead among others, in drinking water exceeded WHO limits, which may pose a significant threat to the health of people. Similarly, the study of Bortey-Sam et al., [19], showed that well water used for drinking contained Cd and Pb levels that were higher than the guideline values [20]. The objective of this review is to provide information on the concentrations and the distribution of heavy metals in different sources of drinking water including municipal tap water, groundwater, surface water and bottled water across various geographical regions. The review will provide information on the trends, the possible influence of various treatments on the levels of heavy metals and variations in trace metal levels relative to international and national drinking water quality standards. The study will also attempt to highlight health implications associated with chronic exposure to both essential and toxic heavy metals, the need for improved regulatory frameworks, and the importance of equitable access to safe drinking water. It is envisaged by the authors that such global analysis may influence the need for further research activities that may provide more effective methods and improved water treatment strategies and policies to reduce human exposure and associated health risks.

2. Methodology

The data presented in this review were obtained after carefully going through the following scientific search engines, Science Direct, Google Scholar, and PubMed. Key words used included trace metals, heavy metals, drinking water, and risk assessment, and the years 2015 to 2024. For this review, only research articles published between 2015 and 2024 that reported on the concentration of heavy metals in drinking water sources either in µg/L or mg/L were considered. Articles were selected from 2015 to 2024 to report on recent advances and current trends in the levels of heavy metals in different drinking water sources. The search uses Boolean operators such as NOT, OR and AND to search for the journals. For instance, the search included some of the following keywords: Heavy metals AND drinking water, trace metals AND drinking water, heavy metals NOT wastewater, trace metals. Articles reporting on other water sources that do not serve drinking or domestic purposes and articles reporting on the removal of heavy metals from drinking water were not considered. The initial survey using ScienceDirect with heavy metals and drinking water resulted in 4026 articles while using “heavy metals and drinking water resulted in 26,640 articles. In PubMed, “heavy metals and drinking water resulted in 696 articles while using “heavy metals and drinking water resulted in 26,640 articles. The articles were further screened to eliminate the same articles from the different websites and to remove articles that reported on water but not on heavy metals. The total number of articles that reported either heavy metals or trace metals in drinking water were 66.

3. Results and Discussion

The concentrations of all the heavy metals reported in this study are presented in Table 1, Table 2, Table 3 and Table 4. The articles reviewed reported heavy metals concentrations in either µg/L or mg/L and these units were used while discussing the findings of this study. Table 1, Table 2, Table 3 and Table 4 also indicate the analytical instrument used for the determination of heavy metal concentrations and which were mostly an atomic absorption spectrophotometer in studies mostly from the developing countries and an inductively coupled plasma mass spectrometer in studies mostly from developed countries.
Lead (Pb): The highest concentration of lead was reported in groundwater (Table 4) from a study conducted in Ghana, where levels reached 0.791 mg/L [5], followed by a study conducted in Nigeria with a value of 0.348 mg/L in bottled water [21]. In some instances, the concentrations of Pb detected in the drinking water reported were extremely low, with certain values below the detection limit [21,22,23,24] (Table 1, Table 2, Table 3 and Table 4). From Table 1, only six of the articles used in this study reported values higher than the WHO limit of 10 µg/L for lead in drinking water supplied using the tap system, while from Table 2, three of the studies reported values higher than the acceptable limit. From all the different sources of drinking water examined in this review, there were instances where highest values recorded in some studies were above the acceptable limit of 10 µg/L (0.01 mg/L) set by WHO. It should, however, be noted that Pb should not be detected in drinking water because there is no known safe exposure level. From the current review, some of the studies reported concentrations of Pb higher than the WHO limit, while there were other studies that reported values just above 10.0 µg/L which is close to the acceptable limit. The highest concentration of Pb recorded from the groundwater, as reported by [5], may be due to mining activities, runoff from domestic activities, industrial activities, and agricultural activities around the area. Lead has been identified as one of the most harmful pollutants in the environment [25] and among the ten pollutants of great concern for public health by the WHO [20]. Apart from the anthropogenic activities mentioned above, the corrosion of lead-containing pipes, fittings, and solder used in older plumbing systems may also increase the levels of lead in drinking tap water [26]. This corrosion is accelerated by highly acidic or mineral-poor water, which enables lead to seep into the water supply [27]. Lead (Pb) pollution in drinking water may arise from both natural and anthropogenic sources, with the anthropogenic source being the most implicated source of exposure, especially from the urban and industrialized environments. A study by Endale et al., [28] in Addis Ababa, Ethiopia, reported that lead concentrations may increase at taps, showing pollution within distribution systems. The primary sources of these pollutants may include the materials used for plumbing, especially when it contains lead, brass and galvanized steel pipes, and this will lead to a situation where the plumbing materials used will release more lead than plastic alternatives [28]. A study conducted in Bangladesh, however, reported that lead contamination may come mostly from anthropogenic sources, such as industrial dust, vehicle exhaust, lead pipes, faucets, and batteries [29]. It is also possible for lead to leach into groundwater from the weathering of rocks or minerals such as galena (PbS) and cerussite (PbCO3); though it has been noted that contributions from these natural sources are much more reduced when compared to anthropogenic sources. Factors such as low pH, high chloride-to-sulfate ratios, and low alkalinity have all been reported to increase the solubility and mobility of lead from pipe surfaces into the water in different water sources. Interestingly, Chowdhury et al., [30] noted that intermittent water stagnation in household plumbing may increase the exposure to lead at the tap, thereby leading to increased exposure risks for consumers, a condition that is most frequently witnessed in developing countries. Pb pollution in drinking water sources may cause significant health risk because of its ability to bioaccumulate in the human system, leading to Pb toxicity. Upon consumption, lead is absorbed into the bloodstream and become readily available in important organs of the body such as the brain, liver, kidneys, and bones, where it can remain for years [31]. Pb has no known beneficial effect or physiological function in humans, yet it can interfere with calcium-dependent cellular processes, thereby increasing its toxicity. Children are the most vulnerable group, with Pb poisoning usually leading to neurological effects [32]. Research has linked exposure to even low concentrations of Pb in drinking water to cognitive impairment, reduced intelligence quotient, behavioral disorders, and developmental disorders in children [33]. In adults, continuous Pb ingestion has been linked with hypertension, renal dysfunction, reproductive issues, and increased risks of cardiovascular disease [34].
Cadmium (Cd): A toxic heavy metal that can be present in drinking water, posing significant health risks. The World Health Organization recommends that the concentration of Cd in drinking water should not exceed 3 µg/L (0.003 mg/L) limit [35], while some studies have reported values higher than the recommended limit by WHO [36,37]. Generally, from this review, the highest cadmium concentration occurred in surface water (Table 3) from Ghana, with concentrations reaching 2.23 mg/L (2230 µg/L) [5]. Elevated cadmium levels in surface waters are often associated with industrial discharge, agricultural runoff, and mining activities. From Table 2, only one study reported value above the recommended limit [4]. Cadmium in tap water did not show any value of Cd above the recommended limit of 3 µg/L (Table 1). However, from other sources, there were values above the recommended limit (Table 2, Table 3 and Table 4). For instance, from Table 2, Olowoyo et al. [4] reported values in the range of 0.15–5.51 µg/L that were slightly above the WHO recommended limit, while from Table 3 and Table 4, where they were detected, they ranged from 0.001 µg/L to 2.23 mg/L. The highest value was recorded from the research published by [5] (Table 4), from the groundwater sources, the value ranged from 0.005 mg/L to 0.791 mg/L (Table 4). From Table 3, the highest value was obtained from report submitted by [5] in surface water from Ghana. Only seven studies in the current review reported Cd values higher than the recommended limit and it should be noted that groundwater sources accounted for three (Table 4). The principal sources of Cd in tap water comprise industrial operations, including mining activities, battery production, and metal refining. Cd may seep from galvanized pipes, antiquated plumbing systems, and phosphate fertilizers utilized in agriculture [38]. Moreover, inadequate disposal of electronic waste and industrial effluents may result in Cd contamination of groundwater and surface water, thus impacting municipal water supplies. The reportedly low levels of Cd in some water sources, such as the tap water and bottled water noted in this review, may be attributed to the efficient removal of Cd by reverse osmosis [39]. This may partly be due to its ability to reject divalent and multivalent ions based on size exclusion, charge repulsion, and diffusion mechanisms [39]. Cd exposure from drinking water presents a significant health risk due to its bioaccumulative potential. Prolonged exposure may result in renal damage, as Cd is recognized for its detrimental effects on kidney function and its capacity to reduce the body’s waste filtration efficiency [40]. It is associated with bone demineralization, resulting in osteoporosis, and has been designated as a carcinogen, heightening the risk of lung and prostate cancer. Even low levels of long-term exposure can negatively impact the liver, immune system, and reproductive health.
Arsenic (As): Studies have shown that over 150 million people around the world are exposed to high concentrations of arsenic from geological origin that exceed the WHO limit of 10 µg/L (0.01 mg/L) [41]. Arsenic in groundwater above the WHO acceptable limits have been reported from more than 70 countries around the world [42]. The concentrations of arsenic in this review from all the water sources where it was detected varied from 0.001 µg/L to 692 µg/L (Table 1, Table 2, Table 3 and Table 4). Just like the other metals above, arsenic in some reports were below the detection limit and the highest concentration was reported from a study conducted in China and this was way above the recommended limit. High arsenic concentrations in water sources are commonly linked to geogenic contamination from arsenic-rich geological formations and industrial pollution [43]. Concentrations of As reported from bottled water sources were all below or within the acceptable limit of 10.0 µg/L. Concentrations of arsenic reported in the study of Wade et al. [44] showed that some water samples tested in the study were higher than 100 µg/L but the study was not specific as to the actual source of these samples but reported that four of the samples were higher than 100 µg/L. From the study, it was estimated that 120 samples representing 50.5% of the water samples tested were above the recommended limit. The study further indicated a possible association between cardiovascular disease and arsenic at moderate exposures. This study provided a possible indication of arsenic toxicity and exposure across China’s rural communities relying on groundwater sources. Another study from China, also reported a value which was 8 times more than the acceptable limit set by WHO [45]. A similar trend was reported in the groundwater source in Bangladesh [45,46]. Over the years, it has been reported that high levels of As in groundwater are a major source of concern for global health after pathogens presence in water [47]. From the present review as shown in Table 4, higher concentrations of As were reported in groundwater sources when compared with other sources used in this review.
Chromium (Cr): None of the articles used for this review reported on the two most prominent states of Cr separately, but rather on the total Cr. Cr (III) is known to have a beneficial effect in the metabolism of glucose and lipid, while Cr (VI) is known to be highly toxic and carcinogenic [48]. The WHO set the permissible limit of Cr in water to 50 µg/L (0.05 mg/L), while the United States Food and Drug Administration (USFDA) adopted the United States Environmental Protection Agency (USEPA) drinking water standard for total chromium of 100 µg/L. The highest chromium concentration occurred in surface water (Table 4) in China, where the highest concentration was 244.4 mg/L [43]. Such high concentrations may be attributed to industrial discharges from tanneries, metal plating industries, and textile processing plants. The concentrations ranged from not detectable to 0.026 mg/L in tap water, not detectable to 190.26 µg/L in bottled water, not detectable to 126.0 µg/L in surface water and not detectable to 244.43 µg/L in groundwater (Table 1, Table 2, Table 3 and Table 4). Only four studies in this review reported values higher than 100 µg/L which is the permissible limit for human consumption using the USFDA, while with the WHO standard of 50 µg/L, six of the reported values were higher than this limit (Table 2, Table 3 and Table 4). The variations observed in the concentrations of Cr from all the reported articles indicate that the source of Cr in the environment may arise from diverse sources, indicating that it could either be from natural or anthropogenic sources. Coetzee et al. [49] reported that the source of Cr in the environment may be due to soil erosion, rock disintegration and industrial activities. Bajwa et al. [50] reported that Cr and other elements found in their study could be linked to the local natural geology, industrial activities or the use of phosphate fertilizers. Similarly, the study of Cobbina et al. [5] also suggested a natural source for the levels of Cr found in the bottled water used in their report. From the reports obtained in this study, Cr levels in most of the drinking water sources were below the acceptable limit, whether the WHO or USFDA standards are applied and where there are elevated levels of Cr in the drinking water, they are mostly associated with the natural sources and as such, using an efficient mechanism to remove it will be crucial in promoting safety.
Nickel (Ni): The WHO set a permissible limit of 70 µg/L (0.07 mg/L) for Ni, while the European Union limit is set at 20 µg/L for natural mineral water. The type of Ni formed accounts for its solubility, mobility, and bioavailability in the environment. However, from natural waters, nickel mostly occurs as Ni2+ or as complexes with hydroxide, carbonate, sulfate, and sometimes natural organic matter [51,52]. In the current review, Ni was not detected in some water samples, the highest Ni concentration obtained from published articles used in this study was from a surface water in Nigeria, with a mean value of 1.021 ± 0.1 mg/L [53] (Table 3). Elevated nickel levels are frequently associated with industrial waste disposal and corrosion of metal pipes. This value is followed by 0.953 ± 0.07 mg/L reported in groundwater water from Nigeria (Table 4). In some instances, Ni were not detected in some of the articles used in the study and where reported the highest values reported for drinking tap water, bottled water/sachet water, stream water, and groundwater were 0.951 ± 0.07 mg/L, 2.33 µg/L, 1.021 ± 0.01 mg/L and 0.953 ± 0.07 mg/L respectively (Table 1, Table 2, Table 3 and Table 4). From the report used in the study, only in the bottled water sample were all the recorded values below the recommended limit either set by the WHO or the EU. All other sources have reported values that were above the recommended limit. Sources of Ni in drinking water include the type of parent rock material (ultramafic) or ores such as pentlandite [54]. Despite the values reported in some of the studies used for this review, it should however be noted that Ni is an essential micronutrient for certain microorganisms and plants and a cofactor for enzymes such as urease and hydrogenase [55]. High concentrations of Ni in drinking water have been linked to dermal allergies, respiratory effects, nephrotoxicity, and carcinogenicity [56,57]. Over the years, Ni contamination around industrial and mining areas has been reported and usually above the permissible limit, therefore raising public health concerns [58]. In 2008, Ni was nicknamed “Allergen of the Year” due to its frequency in allergies [59]. Nickel occurs in water as the hydrated Ni2+ ion, which is a soluble form of nickel. This occurs as a natural ion leached from minerals and soils [60]. However, as reported by Haber et al. [61], Ni exposure through oral intake, particularly from drinking water, is usually lower than food sources. Sources of Ni in drinking water may be affected by factors such as materials used for the supply of the water system (water pipes) or other natural sources [60,62]. The study of Adhikari et al. [63] also reported that Ni concentrations in drinking water have been overlooked due to the limited studies on stainless steel in water distribution systems. The study ascribed the presence of Ni in drinking water from their study to the dispensers used and concluded that Ni concentrations were higher than the regulatory standard, showing that dispenser water may not always be safe. Overall, using the guidelines provided by the EU, eight of the articles used in this review showed values higher than the limit (Table 1, Table 3 and Table 4). The study of Bajwa et al. [50] also linked the presence of heavy metals in SW—Punjab region of India, including Ni, to the geological nature of the area, industrial activities and the use of phosphate fertilizers in huge quantities for agricultural purposes.
Iron (Fe): One of the most abundant elements in the Earth’s crust and frequently occurs in groundwater and surface water due to its natural geochemical behaviors [64]. While iron is essential for human health in trace amounts, excessive concentrations in drinking water pose significant aesthetic and operational challenges. High iron levels can lead to discoloration, metallic taste, staining of plumbing fixtures, bacterial growth, and clogging of distribution systems. Numerous studies from different parts of the world indicate substantial variability in the concentration of iron in water sources (Table 1, Table 2, Table 3 and Table 4). This variability results from differences in geological formations, redox conditions, climatic characteristics, land use, and the integrity of water supply infrastructure [65,66,67]. Studies from different sources of water revealed variations in iron concentrations [68,69,70,71]. From the tap water where values were above the limit of detection set in those studies, the mean value for the highest concentration was 0.139 ± 0.013 mg/L (Table 1). From Table 2, Fe was below the detectable limit in some studies, however the highest concentration was 1346.91 µg/L. Some of the reported concentrations were above the recommended limit of 0.3 mg/L, indicating widespread iron enrichment which could become apparent from the color of the water though not stated in the articles. The highest iron concentration occurred in groundwater (Table 4) in South Africa, reaching 20,843.2 µg/L [72]. Such high concentrations may be attributed to natural geological weathering of iron-bearing minerals in aquifers.
Copper (Cu): The reported concentrations as shown in Table 1, Table 2, Table 3 and Table 4, revealed that the highest copper concentration occurred in ground water with a value of 996.6 µg/L (Table 4). The authors suggested that climate and oil exploitation and effect of coal mining might have increased the levels of pollutants in the water [73]. The study further indicated that children may be at risk of the effect of arsenic and other pollutants in the area. These findings indicate widespread but uneven Cu contamination, with pronounced hotspots in developing countries. In Asia, Cu concentrations exhibited the broadest range observed in this dataset. Studies from China reported both very low values (ND to 0.040 mg/L) and exceptionally high concentrations (up to 3816.50 mg/L), indicative of the coexistence of pristine natural systems and heavily impacted industrial basins [74,75,76]. Similar extremes were documented in Pakistan, where concentrations reached 2325 mg/L [77,78], and in India, where values also ranged up to 2325 mg/L in heavily polluted locales [79,80]. These high concentrations are consistent with effluents from metal processing, mining, and industrial wastewater discharge, all of which have been identified as dominant pathways in these regions. Moderate ranges reported in Bangladesh [22,29], Nepal [24,81], and Sri Lanka [82] further demonstrate localized anthropogenic pressures superimposed on geogenic background levels.
In Africa, Cu contamination likewise varied widely. Uganda exhibited low concentrations in some samples (0.300 to 6.500 mg/L) but high values (100 to 220 mg/L and 47.00 ± 3.00 mg/L) in specific regions [53,66,77]. Algeria’s Tebessa region presented some of the highest African readings (725.1 to 1291 mg/L), consistent with mining-related impacts [73]. In Nigeria, the range (0.592 to 432 mg/L) indicated significant contamination likely linked to petroleum operations and urban effluent [53,83]. South African concentrations varied from moderate to very high (21.33 to 407.32 mg/L), reflecting contributions from mining, industrial emissions, and domestic wastewater [4,72]. These patterns collectively highlight the combined influence of industrial activity, informal waste disposal, and inadequate wastewater treatment infrastructure. Conversely, European water sources exhibited comparatively lower Cu levels. Italy and Croatia reported ranges generally below 10 mg/L [84,85,86], with occasional higher concentrations in industrial or coastal zones. These lower values align with routine monitoring, corrosion control (where copper piping is used), and stringent environmental regulation. European datasets demonstrate the benefits of mature water-management systems in preventing metal contamination. Similar reports were noted from other regions as well [2,84,87,88,89,90,91,92]. These findings mirror the global trend wherein mining districts are strongly associated with elevated Cu concentrations. Across all regions, the dominant pollution pathways consistently include mining and smelting effluents [73,90], industrial wastewater discharges [74], agricultural applications of Cu-based fungicides [50,91], and corrosion of copper plumbing [84,86]. Natural sources, including weathering of Cu-rich lithologies, contribute to elevated baseline levels in parts of Nepal, Pakistan, Bolivia, and Algeria. From a public health perspective, many of the maximum concentrations reported in the data set exceed the WHO drinking-water guideline of 2 mg/L, indicating possible risks for gastrointestinal toxicity, hepatic stress, and negative ecological impacts. Particularly concerning are extreme values above 100 mg/L—such concentrations represent severe contamination events incompatible with domestic or ecological safety without prior remediation. Overall, the results underscore that copper contamination is widespread but highly uneven, with the most pronounced exceedances occurring in regions where mining, metallurgical industries, and insufficient environmental regulation converge.
Zinc (Zn): An essential trace element, and the WHO has established a guideline value of 3000 µg/L, primarily based on aesthetic considerations (taste, turbidity, and color) rather than toxicity. However, prolonged exposure to excessively high Zn concentrations may result in gastrointestinal discomfort. Zinc was one of the most abundant heavy metals across all water sources, with concentrations spanning several orders of magnitude. From all the water sources, Zn concentration was all below the recommended limit (Table 1, Table 2, Table 3 and Table 4). From Table 1, the highest Zn concentration reported was from a study conducted in Ecuador with a value of 369.0 µg/L (Table 1). From Table 2, the highest concentration was from a study conducted in South Africa with a value of 2978.31 µg/L (Table 2). From Table 3, the value ranged from 0.001–894.75 µg/L. The highest zinc concentration occurred in groundwater (Table 4) in South Africa, reaching 19,964.5 µg/L which is above the recommended limit [72]. High zinc concentrations are commonly linked to geological mineral dissolution and industrial activities. Elevated values of Zn from tap water are commonly attributed to corrosion of galvanized pipes, brass fittings, and plumbing systems, rather than source water contamination. Although zinc is an essential micronutrient, concentrations exceeding 3000 µg/L may impart undesirable taste and indicate poor quality control during bottling, leaching from packaging materials, or inadequate treatment processes. These elevated levels are consistent with inputs from industrial effluents, urban runoff, agricultural activities, and natural weathering of Zn-rich minerals. Groundwater exhibited the widest Zn concentration range, from <1 µg/L to as high as 19,964.5 µg/L in South Africa and China [72,74]. Such extreme values far exceed aesthetic the guideline limits of the WHO: 3000 µg/L and suggest geogenic enrichment, prolonged water–rock interaction, or contamination from mining and industrial activities. These findings underscore the vulnerability of groundwater resources and the necessity for regular quality assessment before consumption.
Uranium (U): Uranium was reported in some of the articles used in this study, and in some instances, the values reported were higher than the permissible limits of 30 µg/L (0.03 mg/L) in drinking water set by WHO [93]. In the current review, uranium was reported in all the different sources of water. The highest uranium concentration was reported in ground water (Table 4) in Punjab, India, where concentrations reached 579 µg/L [50]. Elevated uranium concentrations are usually associated with natural uranium-rich geological formations. This review further showed that from the tap water sources, uranium was only reported in two of the articles used and, was not detected in some of the samples in a study of tap water samples conducted in Iran however, with a highest value of 5.59 µg/L (Table 1) [23]. From Table 2, which is either the bottled water or sachet water sample, uranium was not detected in some of the samples, and the highest value was 1.92 µg/L as reported by [37] in the study conducted in Saudi Arabia. Table 3 showed uranium to range from BDL to 41.00 µg/L in a study conducted in Nepal [81]. Uranium concentrations in Table 4 showed that the concentrations ranged from 0.001 µg/L to 579 µg/L. The highest concentration was reported by Bajwa et al. [50] from a study conducted in India. The study of Bajwa et al. [50] further reported that uranium concentrations exceeded the permissible limit in 338 out of 498 samples, representing about 68% of the water samples examined in the study. The study of Bajwa et al. [50] linked the presence of uranium in the drinking water to the possible reactions between groundwater and the soils formed from the weathering of Malani and the basement rocks (Delhi quartzite). The other possible source of uranium in the groundwater from the region was also linked to the fact that the soil of the area is rich in biocarbonates, nitrate and chloride anions [94,95]. Previous studies had suggested the presence of uranium of 2–781 μg/L with serious health conditions in humans, such as increased urinary excretion of calcium, phosphate, and glucose, suggesting nephrotoxic effects even at low exposure levels [96]. Apart from kidney contamination, high concentrations of uranium in humans can cause various cancerous diseases such as leukemia, prostate, breast, colorectal, lung, kidney, and bladder cancers among others [97,98]. Its occurrence in drinking water raises concerns because of its toxicity, with profound negative effects on the kidneys and its impact in causing cancer after prolonged exposure [98]. The study of Liesch et al., [99] noted among others that the high concentrations of elements of concern in their study may be due to local natural geology, industrial activities in the region or use of phosphate fertilizers in the region [99]. Another study in Afghanistan reported a concentration of 190 µg/L for uranium with values that were 17.2 times higher than the permissible limit [100]. The study further stated that the average uranium concentration in well drinking water from Kabul was about 9 times higher than that of 2.72 μg/L in well drinking water from Fallujah, Iraq, where depleted uranium bombs were used according to [101]. Several studies have linked exposure to uranium from drinking water to nephrotoxicity, bone and liver effects, and an increased cancer risk, especially in the case of prolonged exposure. Other studies have also reported on the associations of uranium and skeletal deformities [98,102,103]. It should, however, be noted as reported by [97], that uranium pollution is a global problem due to its presence in groundwater samples from different countries [102]. From a study conducted in Zambia near uranium mines, the report submitted by Haakonde et al., [104] showed that all the water samples, including the groundwater analyzed in the study, have concentrations of uranium higher than the permissible limit, and this was linked to the mining activities from that area thus suggesting the impact of anthropogenic sources. The study further indicated that uranium in the samples was above the safe limit for drinking water recommended by the WHO, with a mean target hazard quotient (THQ) greater than 1, indicating that consumers may be at a greater risk of potential non-carcinogenic health effects.
Manganese (Mn): An important trace element because its deficiencies can result in skeletal abnormalities, growth issues, and anemia [20]. Ingestion of excessive concentrations of Mn in drinking water, on the other hand, may have serious health consequences such as neurological impacts with impaired cognitive ability, which has been linked to Parkinson’s disease [20]. The dual role of Mn in the human body makes its presence a serious human health concern. Mn is important for normal physiological functions, including enzymatic actions, antioxidant activities, and bone development, however, the elevated concentrations of Mn in drinking water may lead to neurotoxicity [93,105]. The WHO sets a permissible limit of 400 µg/L (0.4 mg/L) for Mn in drinking water [93,106]. However, the USEPA classifies Mn as a secondary contaminant, with a health advisory value of 30 µg/L [4,13,107]. In the current review, the highest manganese concentration was reported in ground water (Table 4) in India, with concentrations that ranged from 6.35 µg/L–2339.90 µg/L [43] which exceeded the WHO acceptable limit of Mn. However, some of the studies discussed the source of Mn and linked this partly to the geological nature of the region and the presence of evaporites that are distributed unevenly in the sediments [108]. Elevated Mn levels often arise from natural mineral dissolution under reducing conditions. The concentration of Mn reported from tap water, as reported in the study of Arcentales-Ríos et al. [92], showed variations and is indicative of the inability of the traditional water purification system to remove heavy metals from water. The highest value for Mn in bottled water from Croatia, as reported by [86], showed that it was only recorded in sparkling water and reported by other authors as well [109]. A study carried out in Denmark with 643,401 enrolled participants, mainly children, found that exposure to Mn at a concentration of more than 100 μg/L during the first five years increased the risk of ADHD-Inattentive subtype, with hazard ratios of 1.51 for females and 1.20 for males [110]. Thus, supporting the need to improve monitoring methods [111]. Similarly, different epidemiological studies conducted in Canada, Bangladesh, and the U.S. showed a significant association between high levels of Mn in drinking water and reduced IQ, memory deficits, and hyperactivity in children [112,113]. In adults, according to Pajarillo et al., [114], long-term exposure to Mn is associated with neurological symptoms like those manifested in Parkinsonism, including tremors, motor dysfunction, and cognitive decline [114].
Mercury (Hg): Occurs both naturally from weathering of rocks and anthropogenically, which may be through mining activities or improper waste disposal, thereby mixing with water. It can exist in two forms in water, either as Hg0 or as Hg2+ [115]. Other scholars have suggested that Hg presence in water may take three forms, namely: elemental, inorganic, and organic mercury, with organic methylmercury having the most toxic form because of its ability to cross the blood brain barrier and its non-biodegradable nature [116], thus making mercury a toxic heavy metal of serious health concern in drinking water. Mercury exposure occurs primarily through fish consumption because of bioaccumulation over time, suggesting its presence in water and sediments and may cause toxic effects on several organs in the body, leading to neurological, cardiovascular, pulmonary, and gastrointestinal problems [117]. The WHO has set the permissible limit of Hg in drinking water to 1 µg/L, indicating a trace concentration or total absence of Hg in drinking water. From the current review, mercury was reported in all forms of drinking water and in some instances, with values above the WHO recommended limit of 1 µg/L (0.001 mg/L). From Table 1, Table 2, Table 3 and Table 4, the reported value of Hg was more noticeable from groundwater sources than from other sources. Some values of mercury reported in this study were higher than the recommended limit. The highest mercury concentration was reported in surface water with a value of 0.259 mg/L [5] in Ghana and followed by ground water 0.191 mg/L (Table 4) and however in Saudi Arabia a concentration of 78.00 µg/L in tap water was recorded (Table 1) [70]. Mercury contamination can originate from industrial emissions, mining activities, and atmospheric deposition. The study of Abanyie et al., [118] showed that 68.4% of the groundwater samples used in their study were above the permissible limit recommended by WHO. Silva et al., [119] also reported values of Hg higher than the permissible limit and linked the presence of mercury to the local regional effect of the pollutant. The study further showed that sources of Hg may include anthropogenic input because the values exceeded the natural sources. The result of the emitted Hg is primarily recalcitrant soil pools, deep ocean waters and sediments [119]. Sarkar et al., [120] also reported that the mean levels of mercury in water sources from Anambra state, Nigeria, were greater than the WHO limit, with mercury values of 0.006 mg/L. Hg presence in some of the drinking water sources may be a serious health concern due to its toxic nature. Of note is the presence of Hg from groundwater sources reported in this study. Though the studies used for this review did not indicate the Hg form, previous studies have suggested that the organic form of mercury (methylmercury) may be the most toxic because up to 90% of its form can be absorbed intestinally and can easily pass through the blood brain barrier, especially in fetuses, thereby leading to neurotoxic effects [121].
Antimony (Sb): WHO guideline value for antimony in drinking water is 20 µg/L (0.02 mg/L), based on toxicological evidence related to cardiovascular and gastrointestinal effects following prolonged exposure. The data in Table 2 and Table 3 indicate that antimony concentrations in most drinking water sources remain below the WHO guideline, although notable regional exceedances or near-threshold values were observed. The highest concentration for bottled water (Table 2) from South Africa, reached 7.23 µg/L [4]. From Table 3, the highest value was 3.082 µg/L (124). Antimony was not reported in Table 1 and Table 4 in this review. While most reported values remained below the World Health Organization (WHO) guideline value of 20 µg/L, possible contamination sources may come from industrial activities, corrosion of plumbing materials, or natural mineral dissolution [122]. These values are considerably lower than the WHO limits. In bottled and sachet water, Sb concentrations ranged from 0.410–2.145 µg/L in Poland and 0.876–3.25 µg/L in Croatia, and ND to 7.23 µg/L in South Africa [4,86,123]. These values are considerably lower than the WHO limits, indicating effective treatment processes in most commercial drinking water products. Surface water sources showed Sb concentrations between ND to 2.18 µg/L in China, and 3.082 µg/L in Turkey [76,124]. These relatively low concentrations suggest limited widespread Sb contamination in surface waters, although localized enrichment may occur in mining or industry-impacted catchments [125]. Overall, the observed Sb levels highlight the importance of continuous monitoring, particularly in urban and industrialized regions where values approach regulatory limits.
Selenium (Se): The WHO sets a health-based guideline value of 40 µg/L (0.04 mg/L) due to the risk of selenosis (hair loss, nail brittleness, neurological effects) at higher concentrations [126,127,128]. Selenium data were less frequently reported in this study. The highest selenium concentration was observed in surface water (Table 3) in Tebessa, Algeria, where concentrations ranged from 7.70–12.20 mg/L [73]. Groundwater Se concentrations ranged from 0.015 µg/L–2.64 mg/L [126,127]. These elevated concentrations are characteristic of arid and semi-arid regions where selenium-bearing minerals are mobilized under alkaline and oxidizing conditions [128,129,130]. While selenium is an essential micronutrient, excessive intake can lead to selenosis, emphasizing the importance of site-specific risk assessment [130]. Generally, selenium contamination appears to be predominantly geogenic, with groundwater showing higher susceptibility than surface water. The limited reporting of Se in tap and bottled water suggests either low concentration or insufficient monitoring, highlighting a gap in routine water quality assessment.
Across the four water sources (tap water, bottled water, surface water, and groundwater), the highest concentrations of several metals were predominantly reported in surface water and groundwater [5,43,75], likely due to direct environmental exposure, industrial effluents, and geological interactions [3]. Conversely, bottled water and tap water generally exhibited lower concentrations [4,37,52,53], reflecting treatment processes and regulatory quality control [20], although occasional elevated levels were reported [52].
Table 5 provides a summary of the highest and lowest values for all the potentially toxic elements considered in the current review. The result showed that most of the highest values recorded in this study were either from the groundwater sources or the surface water sources, while the lowest values were either from the tap water or the bottled water. The result presented thus confirmed the impact of water treatment, which was either used by different water suppliers or by the government. Contamination of surface water by heavy metals may arise from different anthropogenic activities and natural geochemical processes. The anthropogenic activities as reported in the literature may include leakages from mining operations, agricultural activities, and other industrial activities releasing significant amounts of these heavy metals into adjacent water bodies [131,132,133]. Natural weathering of metal-rich rocks and volcanic emissions can also introduce heavy metals into surface waters, although these sources are typically overshadowed by human-driven contamination in highly industrialized regions [134]. The groundwater contamination, on the other hand, may also arise from leaching and be exacerbated by both anthropogenic disturbances and natural hydrogeochemical interactions. Also, the improper disposal of industrial waste, landfill leachates, and seepage from tailing dams may also provide opportunities for heavy metals to infiltrate aquifers, especially in areas with permeable soils [135]. In many developing regions, as noted in our study, unlined waste dumps and poorly managed wastewater irrigation may also accelerate the movement of heavy metals into groundwater systems [136,137,138,139,140].
Table 1. Concentrations (µg/L * or mg/L **) of Trace and heavy metals in drinking tap water.
Table 1. Concentrations (µg/L * or mg/L **) of Trace and heavy metals in drinking tap water.
S/NMetalsConcentrationsCountry/RegionInstrument UsedRef.
1Lead1.930–9.780 *IranICP-MS[129]
0.360–146.1 *EthiopiaICP-MS[28]
2.2–5.0 *IranICP-OES[137]
0.200–14.30 *UruguayICP-MS[64]
0.04–0.16 *Costa RicaICP-MS[65]
0.10–14.22 *IranICP-MS[138]
ND–0.57 *UgandaICP-OES[66]
ND–260.0 *IranICP-MS[23]
0.04–0.14 **EthiopiaAAS[67]
0.013–53.80 *LebanonICP-MS[69]
ND–0.045 *NigeriaAAS[53]
99.00 ± 6.00 *Saudi ArabiaICP-MS[70]
2CadmiumND–0.010 *UgandaICP-OES[66]
ND–0.004 *LebanonICP-MS[69]
ND–0.10 **NigeriaAAS[53]
NDSaudi ArabiaICP-MS[70]
3Arsenic0.77 ± 0. 0 9 *Costa RicaICP-MS[65]
0–99 *IranAAS[139]
0.013–8.13 *EthiopiaICP-OES[67]
0.161 **LebanonICP-MS[69]
0.00–0.20 *UgandaICP-OES[66]
0.45–4.08 *Saudi ArabiaICP-MS[70]
4Chromium10.50 *UgandaICP-MS[27]
ND–0.58 *IranICP-MS[139]
1.190–5.970 *EthiopiaICP-MS[67]
0.013–0.026 **NigeriaAAS[53]
0.242 *LebanonICP-MS[69]
1.00–6.00 *Saudi ArabiaICP-MS[70]
5Nickel0.02–1.10 *UgandaICP-MS[66]
0.013–3.5 *EthiopiaICP-OES[67]
1.021 ± 0.1 **Nigeria AAS[53]
NDSaudi ArabiaICP-MS[70]
6Iron11.1–26.3 *UruguayICP-MS[64]
53.1–197 *Costa RicaICP MS[65]
0.900–121.0 *UgandaICP-MS[66]
ND–120.0 *IranICP-OES[139]
0.013–1073 *EthiopiaICP-OES[67]
1.130 *LebanonICP-MS[69]
139.00 ± 13.00 **NigeriaAAS[53]
1.36–19.5 *Saudi ArabiaICP-MS[70]
7Copper1.15–53.81 *IranICP-MS[139]
0.300–6.500 *UgandaICP-OES[66]
0.013–62 *EthiopiaICP-MS[67]
1.830 *LebanonICP-MS[69]
47.00 ± 3.00 **Nigeria AAS[53]
0.332–3.35 *Saudi ArabiaICP-MS[70]
8Zinc31.9–204.9 *UruguayICP-MS[64]
ND–82.80 *UgandaICP-MS[66]
ND–40.00 *IranICP-MS[139]
37.93–73.08 *EthiopiaICP-OES[67]
ND–369.0 *EcuadorICP-OES[92]
50.00 *LebanonICP-MS[69]
0.41 ± 0.025 *NigeriaAAS[53]
0.82–11.36 *Saudi ArabiaICP-MS[70]
9UraniumND–5.590 *IranICP-MS[23]
0.227 *LebanonICP-MS[69]
10Manganese0.34–86.8 *Costa RicaICP MS[65]
0.30–3.40 *UgandaICP-MS[66]
2.080–19.78 *EthiopiaICP-OES[67]
3.000–122.0 *EcuadorICP-OES[92]
0.234 *Lebanon ICP-MS[69]
NDSaudi ArabiaICP-MS[70]
11MercuryND–1.05 *IranICP-MS[138]
18.60–78.00 *Saudi ArabiaICP-MS[70]
Note: ND—Not Detected.
Table 2. Concentration (µg/L * or mg/L **) of metals in drinking bottled/sachet water.
Table 2. Concentration (µg/L * or mg/L **) of metals in drinking bottled/sachet water.
S/NMetalsConcentrationsInstrument UsedCountry/RegionRef.
1LeadND–1.24 *ICP-AESCroatia[86]
11.00–16.00 *SWASVItaly[84]
ND–0.060 **ICP-MSLebanon[69]
5.98–123.15 *ICP-MSSouth Africa[4]
<LOD–1.92 *ICP-MSSaudi Arabia[37]
0.0031–0.0032 **AASIran[36]
ND–0.35 **AASNigeria[21]
ND–0.0004 **ICP-MSSouth Africa[141]
2Cadmium0.055 *ICP-AESCroatia[86]
0.7–2.4 *SWASVItaly[84]
0.15–5.51 *ICP-MSSouth Africa[4]
<LOD–10 *ICP-MSSaudi Arabia[37]
<0.0002 **AASIran[36]
3ArsenicND–0.07 **AASNigeria[21]
0.41–1.52 *HPLC/ICP-DRC-MSPoland[123]
1.44–9.05ACP-AESCroatia[86]
ND–0.052 **ICP-MSLebanon[69]
0.65–1.96 *ICP-MSSouth Africa[4]
<LOD–3.99 *ICP_MSSaudi Arabia[37]
4ChromiumND–0.196 *HPLC/ICP-DRC-MSPoland[123]
1.40–9.94 *ICP-AESCroatia[86]
ND–0.073 **ICP-MSLebanon[69]
142.53–190.26 *ICP-MSSouth Africa[4]
0.054–0.45 *ICP-MSYemen[94]
<LOD–0.001 *ICP-MSSaudi Arabia[37]
ND **AASNigeria[21]
ND–0.021 **ICP-MSSouth Africa[141]
5Nickel0.173–0.376ICP-AESCroatia[86]
0.006–0.387 *ICP-MSYemen[94]
<LOD–2.33 *ICP-MSSaudi Arabia[37]
0.0013–0.0041 **AASIran[52]
ND–0.012 **AASNigeria[21]
ND–0.002 **ICP-MSSouth Africa[141]
6Iron2.150–6.540 *ICP-AESCroatia[86]
ND–0.270 **ICP-MSLebanon[69]
895–1346.91 *ICP-MSSouth Africa[4]
0.087–33.30 *ICP-MSYemen[94]
<LOD–2.94 *ICP-MSSaudi Arabia[37]
0.010–0.180 **AASNigeria[142]
0.045–0.050 **AASIran[36]
ND–0.06 **AASNigeria[21]
ND–0.281 **ICP-MSSouth Africa[141]
7CopperND–7.530 *ICP-AESCroatia[86]
0.083–0.37 *SWASVItaly[84]
ND–0.077 *ICP-MSLebanon[69]
21.33–407.32 *ICP-MSSouth Africa[4]
0.010–1.312 *ICP-MSYemen[94]
<LOD–1.36 *ICP-MSSaudi Arabia[37]
0.034–0.035 **AASIran[36]
ND–0.042 **ICP-MSSouth Africa[141]
8Manganese1.13–296 *ICP-AESCroatia[86]
ND–0.010 **ICP-MSLebanon[69]
16.95–268.91 *ICP-MSSouth Africa[4]
<LOD–6.79 *ICP-MSSaudi Arabia[37]
0.004–0.6 **AASNigeria[142]
ND–0.16 **ICP-MSSouth Africa[141]
ND–0.073 *ICP-MSLebanon[69]
0.002–0.096 *ICP-MSYemen[94]
<LOD–1.92 *ICP-MSSaudi Arabia[37]
9Mercury1.622–13.51 *ICP-MSYemen[94]
10UraniumND–0.073 *ICP-MSLebanon[69]
0.002–0.096 *ICP-MSYemen[94]
<LOD–1.92 *ICP-MSSaudi Arabia[37]
11Antimony0.410–2.145 *HPLC/ICP-DRC-MSPoland[123]
0.876–3.25 *ICP-AESCroatia[86]
ND–7.23 *ICP-MSSouth Africa[4]
12Zinc5.510–6.150 *ICP-AESCroatia[86]
0.345–16.1 *ICP-MSLebanon[69]
11.30–2978.31 *ICP-MSSouth Africa[4]
<LOD–14.79 *ICP-MSSaudi Arabia[37]
0.019–0.032 **AASIran[52]
ND–0.057 **ICP-MSSouth Africa[141]
Note: ND—Not Detected; LOD—Limit of Detection.
Table 3. Concentrations (µg/L * or mg/L **) of heavy metals in drinking surface water sources.
Table 3. Concentrations (µg/L * or mg/L **) of heavy metals in drinking surface water sources.
S/NMetalsConcentrationsInstrument UsedCountry/RegionRef.
1Lead0.005–0.259 **AASGhana[5]
0.05–11.98 *ICP-MSChina[43]
8.000–64.00 *ICP-MSBangladesh[29]
0.040–0.08 *ICP-MSCosta Rica[65]
7.980 *ICP-OESJoburg, South Africa[122]
0.27–0.30 **ICP-MSTebessa[73]
0.750–3.060 *ICP-MSSri Lanka[82]
0.102 **AASNigeria[53]
8.09–18.73 *ICP-MSTurkey[124]
NDAASEthiopia[71]
0.1–0.99 *GFAASTurkey[143]
2.0–18.0 *FAASPakistan[144]
2Cadmium0.01–2.23 **AASGhana[5]
0.005–0.09 *ICP-MSChina[43]
0.9–22.00 *ICP-MSBangladesh[29]
5.660 *ICP-OESJoburg, South Africa[122]
0.970–1.00 *ICP-MSTebessa[73]
0.079–1.080 *ICP-MSSri Lanka[82]
NDAASNigeria[53]
0.592 *ICP-MSTurkey[124]
0.01 **AASEthiopia[71]
0.10–0.14 *GFAASTurkey[143]
3Arsenic0.25–10 *ICP-MSChina[74]
0.001–0.115 **AASGhana[5]
0.29–33.11 *ICP-MSChina[43]
0.28–1.2 *ICP-MSCosta Rica[65]
9.32 *ICP-OESJoburg, South Africa[122]
0.35–0.40 *ICP-MSBeijing, China[145]
1.7–2.5 *ICP-MSTebessa[73]
2.40–34.30 *ICP-OESBolivia[90]
0.141–1.030 *ICP-MSSri Lanka[82]
2.9–4.60 *GFAASTurkey[143]
10–92 *ICP-MSBangladesh[29]
4Chromium0.64–22.0 *ICP-MSChina[74]
0.09–106.82 *ICP-MSChina[43]
41.00–126.0 *ICP-MSBangladesh[29]
87.40 *ICP-OESJoburg, South Africa[122]
3.10–7.10 *ICP-MSTebessa[73]
ND–2.20 *ICP-OESBolivia[90]
0.191–2.100 *ICP-MSSri Lanka[82]
0.016 **AASNigeria[53]
0.092 *ICP-MSTurkey[124]
0.01 **AASEthiopia[71]
2.30–4.30 *GFAASTurkey[143]
5Nickel0.13–10 *ICP-MSChina[74]
0.87–516.5 *ICP-MSChina[43]
0.20–0.44 *ICP-MSBeijing, China[145]
18.60–22.10 **ICP-MSTebessa[73]
0.960–11.50 *ICP-MSSri Lanka[82]
1.021 **AASNigeria[53]
0.570 *ICP-MSTurkey[124]
NDAASEthiopia[71]
13–71 *AAS (Flame)Bangladesh[29]
1.0–71 *FAAS/GFAASPakistan[144]
6Iron4.31–1548 *ICP-MSChina[43]
53.1–165 *ICP-MSCosta Rica[65]
1065–1248 **ICP-MSAlgeria[73]
1.000–305.5 *ICP-OESBolivia[90]
40.95–368.0 *ICP-MSSri Lanka[82]
0.146 **AASNigeria[53]
1.608 *ICP-MSTurkey[124]
0.01 **AASEthiopia[71]
11.00–103 *GFAASTurkey[143]
7Copper0.040–50 *ICP-MSChina[74]
0.48–52.83 *ICP-MSChina[43]
23–119 *AAS (Flame)Bangladesh[29]
0.00045–0.002 **ICP-MSTebessa[73]
0.7–14.90 *ICP-OESBolivia[90]
1.89–11.0 *ICP-MSSri Lanka[82]
0.060 **AASNigeria[53]
0.01–0.02 **AASEthiopia[71]
3.0–11.70 *GFAASTurkey[143]
8Manganese0.040–1941 *ICP-MSChina[43]
0.34–86.8 *ICP-MSCosta Rica[65]
0.24–0.46 *ICP-MSBeijing, China[145]
14.80–19.30 *ICP-MSTebessa[73]
0.040–780.5 *ICP-OESBolivia[90]
3.480–74.00 *ICP-MSSri Lanka[82]
0.06–0.07 **AASEthiopia[71]
1.80–16.10 *GFAASTurkey[143]
9Uranium14.20–18.00 *ICP-MSTebessa[73]
<LOD–41.00 *ICP-MSHungary[146]
10Mercury0.001–0.191 **AASGhana[5]
0.003–0.090 *ICP-MSSri Lanka[82]
11AntimonyND–2.18 *ICP-MSChina[76]
3.082 *ICP-MSTurkey[124]
12Zinc0.001–0.005 **AASGhana[5]
2.32–894.75 *ICP-MSChina[43]
0.150–0.65 *ICP-MSBeijing, China[145]
5.5–24.2 *ICP-MSTebessa[73]
0.80–25.40 *ICP-OESBolivia[90]
13.92–210.0 *ICP-MSSri Lanka[82]
0.111–0.41 **AASNigeria[53]
0.01–1.03 **AASEthiopia[71]
5.60–11.80 *GFAASTurkey[143]
9.0–74.0 *FAASPakistan[144]
13Selenium7.700–12.20 **ICP-MSTebessa[73]
0.283 *ICP-MSTurkey[124]
<LOD–7.00 *ICP-MSHungary[146]
Note: ND—Not Detected; LOD—Limit of Detection.
Table 4. Concentrations (µg/L * or mg/L **) of heavy metals in drinking groundwater sources.
Table 4. Concentrations (µg/L * or mg/L **) of heavy metals in drinking groundwater sources.
S/NMetalsConcentrationsInstrument UsedCountry/RegionRef.
1LeadBDL–5.737 *ICP-OESThailand[147]
ND–2.36 *ICP-OESChina[74]
0.005–0.791 **AASGhana[5]
0.050–11.98 *ICP-MSChina[43]
0.01–0.24 **AASBangladesh[22]
0.3–1.7 *ICP-MSTuscany[85]
0.04–0.15 *ICP-MSCosta Rica[65]
0.59–8.4 *ICP-MSBihar, India[126]
NDICP OESPakistan[79]
1.630 ± 0.01 *ICP-OESJoburg, South Africa[122]
0.120–12.1 *AASSri Lanka[82]
0.099–0.121 **AASNigeria[83]
BDL–46.32 *ICP-OESIndia[107]
0.04–0.387 *ICP/MSChina[148]
0–36.5 *ICP-OES/ICSouth Africa[72]
2Cadmium0–2.57 *ICP-OESChina[74]
0.01–2.227 **AASGhana[5]
0.005–0.09 *ICP-MSChina[43]
BDL–0.27 *ICP-MSTuscany, Italy[85]
0.030–0.12 *ICP-MSBihar, India[126]
0.810 ± 0.03 *ICP_OESJoburg, South Africa[122]
0.055–0.920 *AASSri Lanka[82]
ND–0.015 **AASNigeria[83]
0.00023–0.0014 **ICP-OESPakistan[79]
BDL–0.20 *ICP-OESIndia[107]
BDL–4.6ICP-OES/ICSouth Africa[72]
3ArsenicBDL–183.0 *ICP-OESThailand[147]
0.25–10 *ICP-OESChina[74]
0.0001–0.115 **AASGhana[5]
0.29–692 *ICP-MSChina[43]
0.0003–0.0215 **AASBangladesh[22]
BDL–0.69 *ICP-MSTuscany, Italy[85]
0.30–2.600 *ICP-MSCosta Rica[65]
6.250–135.0 *ICP-MSBihar, India[126]
0.030–148 *HAAS/FAASBangladesh[149]
0.67 ± 0.05 *ICP-OESJoburg, South Africa[122]
<1–179.0 *ICP-MSAlberta, Canada[150]
0.074–0.65 *AASSri Lanka[82]
6–581 *AASBangladesh[151]
0.01–0.35 **ICP-MSMexico[106]
<LOD–0.08ICP-OES/GFAASIndia[79]
BDL–130.60 *ICP-OESIndia[107]
BDL–3.6 *ICP-OESSouth Africa[72]
4Chromium0.64–22 *ICP-OESChina[74]
0.090–244.4 **ICP-MSChina[43]
0.0010–0.0020 **AASBangladesh[22]
ND–3.3 *ICP-MSTuscany, Italy[85]
0.090–1.340 *ICP-MSBihar, India[126]
0.0151–0.063 **AASCalabar, Nigeria[152]
33.70 ± 1.3 *ICP-OESJoburg, South Africa[122]
3.400–52.10 *ICP-MSTebessa, Algeria[73]
0.01–0.19 **AASIndia[153]
0.018–3.800 *AASSri Lanka[82]
0.01–0.08 **AASNigeria[83]
BDL–22.21 *ICP-OESIndia[107]
BDL–8.4 *ICP-OESSouth Africa[72]
0.015–0.0602 **ICP OESPakistan[79]
5Nickel0.13–10 *ICP-OESChina[74]
0.0022–0.0044 **ICP-OESPakistan[79]
0.870–516.5 *ICP-MSChina[43]
3.30–10.90 *ICP-MSTuscany, Italy[85]
0.500–3.530 *ICP-MSBihar, India[126]
0.829–9.060 *AASSri Lanka[82]
2.62–27.95 *ICP-OESIndia[107]
BDL–9.3 *ICP-OESSouth Africa[72]
6Iron2.7–20,843.2 *ICP-OES/ICSouth Africa[72]
4.310–1548 **ICP-MSChina[66]
0.0040–0.3200 **AASBangladesh[22]
11–1337 *ICP-MSTuscany, Italy[85]
201–1039 *ICP-MSCosta Rica[65]
0.01–22.7 **FAAS/GFAASBangladesh[149]
0.01–0.29 **721D SINGLE BEAMCalabar, Nigeria[152]
0.14–2.68 **AASLagos, Nigeria[154]
12.93–2981 *AASSri Lanka[82]
850–10860 *AASBangladesh[151]
0.0001–0.052 **ICP-MSMexico[106]
0.5–4.5 **AASNigeria[83]
0.5–4.5 **ICP-OESIndia[79]
112.61–15708.11 *ICP-OESIndia[107]
0.0003–20.843 *ICP-OESSouth Africa[72]
7Copper0.04–50 *ICP-OESChina[74]
0.510–996.6 *ICP-MSChina[43]
0.0020–0.1260 **AASBangladesh[22]
ND–6.00 *ICP-MSTuscany, Italy[85]
0.590–13.70 *ICP-MSBihar, India[126]
0.592–432 *AASSri Lanka[82]
0.05–1.8 **AASNigeria[83]
0.022–0.543 **ICP-OESPakistan[79]
BDL–13.95 *ICP-OESIndia[107]
BDL–199.6 *ICP-OES/ICSouth Africa[72]
0.02–0.12 **ICP-OESItaly[84]
BDL–279.5 *ICP-MSSouth Africa[155]
0.02–0.20AASPakistan[144]
BDL–0.003 **ICP-MSIndia[77]
8Manganese0.0004–1.968 **ICP-MSChina[43]
0.0030–0.4130 **AASBangladesh[22]
<BDL–118.0 *ICP-MSTuscany, Italy[85]
0.200–1093 *ICP-MSCosta Rica[65]
139.9–1232 *ICP_MSBihar, India[126]
0.01–0.83 **FAAS/GFAASBangladesh[149]
2.477–2241 *AASSri Lanka[82]
0.1–1.2 **AASNigeria[83]
50.0–2020 *AASBangladesh[151]
0.00001–0.07 **ICP-MSMexico[106]
6.35–2339.90 *ICP-OESIndia[107]
0.0004–1.001 *ICP-OESSouth Africa[72]
0.0030–0.4130 **AASBangladesh[22]
0.0634–0.3199 **ICP OESPakistan[79]
9Uranium0.210–0.51 *ICP-MSTuscany, Italy[85]
0.500–579.0 *Laser fluorimeterSW-Punjab, India[50]
0.001–0.049 **ICP-MSMexico[106]
10Mercury0.0001–0.191 **AASGhana[5]
0.001–0.06 *AASSri Lanka[82]
0.001–0.010 **AASIndia[79]
11Zinc1.9–19,964.5 *ICP-OESSouth Africa[72]
0.005–786.0 **AASGhana[5]
2.32–894.75 *ICP-MSChina[43]
0.0010–0.0700 **AASBangladesh[22]
BDL–120 *ICP-MSTuscany, Italy[85]
2.8–108.20 *ICP-MSBihar, India[126]
0.138–0.438 **721D Single Beam SpecCalabar, Nigeria[152]
8.107–241ICP-OESSri Lanka[82]
0.05–0.65 **AASNigeria[83]
0.05–0.65 **ICP-OESIndia[79]
BDL–363.40 *ICP-OESIndia[107]
1.9–19,964.5 *ICP-OESSouth Africa[72]
12Selenium0.210–0.900 *ICP-MSBihar, India[126]
0.015–2.64 **ICP-MSEthiopia[127]
Table 5. Concentration Ranges of Studied Heavy Metals Across Drinking Water Sources and WHO Standard Limits.
Table 5. Concentration Ranges of Studied Heavy Metals Across Drinking Water Sources and WHO Standard Limits.
S/NHeavy MetalHighest Value (µg/L or mg/L)Country/Water Source (Highest)WHO Standard Limit
1Lead0.791 mg/LGhana—Tap water10 µg/L (0.01 mg/L)
2Cadmium2.23 mg/LGhana—Surface water3 µg/L (0.003 mg/L)
3Arsenic692 µg/LChina—Groundwater10 µg/L (0.01 mg/L)
4Chromium244.4 mg/LChina—Surface water50 µg/L (0.05 mg/L)
5Nickel516.5 µg/LChina—Surface water70 µg/L (0.07 mg/L)
6Iron20,843.2 µg/LSouth Africa—GroundwaterNo health-based limit (aesthetic: 300 µg/L)
7Copper996.6 µg/LChina—Groundwater2000 µg/L (2 mg/L)
8Zinc19,964.5 µg/LSouth Africa—GroundwaterNo health-based limit (aesthetic: 3000 µg/L)
9Uranium579 µg/LIndia—Groundwater30 µg/L (0.03 mg/L)
10Manganese2339.9 µg/LIndia—Groundwater400 µg/L (0.4 mg/L)
11Mercury0.259 mg/LGhana—Surface Water6 µg/L (0.006 mg/L)
12Antimony7.23 µg/LSouth Africa—Bottled water20 µg/L (0.02 mg/L)
13Selenium12.20 mg/LAlgeria—Surface water40 µg/L (0.04 mg/L)
Note: Values compiled from studies of tap water, bottled/sachet water, surface water and groundwater. WHO limits are based on WHO Guidelines for Drinking-water Quality (4th Edition).

4. Conclusions

The compiled evidence from global studies demonstrates that trace and heavy metal contamination remains a significant concern across multiple drinking water sources, including tap, bottled/sachet, surface, and groundwater. Concentrations of several metals, particularly Pb, Cd, As, Ni, Fe, Mn, and Cr, frequently exceed internationally accepted guideline values in numerous regions, reflecting variability in water quality and highlighting persistent challenges in water treatment, distribution infrastructure, and environmental management.
Tap water generally shows lower metal concentrations than surface and groundwater; however, exceedances of Pb, Fe, and Mn in many countries underscore the influence of aging pipelines, corrosion, and inadequate monitoring. Bottled and sachet waters, often perceived as safer alternatives, also reveal occasional contamination, especially with Pb, Cd, Mn, and Cr, suggesting inconsistent regulatory enforcement and possible leaching from packaging materials.
Surface waters exhibit the highest variability and overall metal burden, reflecting both natural geochemical processes and substantial anthropogenic pressures such as mining, industrial discharge, agricultural runoff, and urban wastewater infiltration. Groundwater, though often considered more protected, also shows disturbing levels of Hg, As, and other metals in several regions, indicating geological influences as well as contamination from agrochemicals and improper waste disposal.
From the findings of this study, there is abundant evidence that the presence of these heavy metals in drinking water sources was linked to some serious health problems, therefore necessitating the importance of policy development or implementation in order to curb the problems associated with drinking contaminated water in most of the developing countries.
Largely, the findings highlight an urgent need for strengthened water safety frameworks, routine monitoring, improved treatment technologies, and more robust enforcement of regulatory limits. Reducing metal contamination requires integrated management strategies that address pollution at the source, enhance infrastructure resilience, and ensure equitable access to safe drinking water. Continued surveillance and harmonization of analytical approaches are essential to support evidence-based policy decisions and to safeguard public health globally.

Author Contributions

J.O.O.: Conceived the study, coordinated the review framework, and provided overall supervision of manuscript preparation. O.O.O.: Led the literature search and synthesis of global data on heavy metal burden, drafted the initial manuscript sections and supported manuscript editing. O.-O.L.O.: Contributed to methodological design, data collation, and critical analysis of sources; assisted in refining the discussion. J.A.O.: Managed reference organization and contributed to comparative analysis of regional case studies. U.A.T.: Provided expertise on public health implications, contributed to structuring the health risk assessment section, and reviewed the manuscript for clarity. O.M.O.: Handled data validation, prepared tables and figures, and assisted in final manuscript formatting and submission. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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MDPI and ACS Style

Olowoyo, J.O.; Olaiya, O.O.; Oharisi, O.-O.L.; Olusola, J.A.; Tshoni, U.A.; Oladeji, O.M. Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications. Water 2026, 18, 886. https://doi.org/10.3390/w18080886

AMA Style

Olowoyo JO, Olaiya OO, Oharisi O-OL, Olusola JA, Tshoni UA, Oladeji OM. Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications. Water. 2026; 18(8):886. https://doi.org/10.3390/w18080886

Chicago/Turabian Style

Olowoyo, Joshua O., Olasunkanmi O. Olaiya, Omuferen-Oke L. Oharisi, Johnson A. Olusola, Unathi A. Tshoni, and Oluwaseun M. Oladeji. 2026. "Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications" Water 18, no. 8: 886. https://doi.org/10.3390/w18080886

APA Style

Olowoyo, J. O., Olaiya, O. O., Oharisi, O.-O. L., Olusola, J. A., Tshoni, U. A., & Oladeji, O. M. (2026). Heavy Metals Burden in Drinking Water: Global Patterns, Sources, and Public Health Implications. Water, 18(8), 886. https://doi.org/10.3390/w18080886

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