Health authorities are particularly concerned about water security in Enugu, southeast Nigeria and heavy metal (HM) pollution. The HM profiles of 51 samples collected from 17 different commercial bottled water brands in Enugu were examined using an flame atomic absorption spectroscopy. Cd, Cr, Cu, Pb, Ni, and Zn had mean values of 0.15 ± 0.03, 0.03 ± 0.02, 0.16 ± 0.03, 0.13 ± 0.02, and 0.02 ± 0.01 mg/L, respectively. The highest levels of Pb2+ were 0.27 mg/L in Exalté, Ni2+ 0.26 mg/L in Jasmine, Cd2+ 0.36 mg/L in Ezbon, Cr3+ 0.07 mg/L in Trinity, Cu2+ 0.04 mg/L in Bigi, and Zn2+ 0.02 mg/L in Aquarapha. The amounts of Cr, Cu, and Zn were below the allowable limits; nevertheless, the Pb content in eight bottled water samples exceeded both the Nigerian and World Health Organization (WHO)/U.S. Environmental Protection Agency (USEPA) permissible limits. The Cd2+ and Ni2+ levels in the 11th and 4th bottled water samples were above the WHO/USEPA-approved limits. Statistical evaluation revealed significant differences in the amounts of HM ions in the samples (p < 0.05). The findings indicated that concentration levels of Cd2+ Ni2+, and Pb2+ pose a public health concern that needs to be addressed due to potential risk to consumer health.

  • Pb detected in the remaining nine samples and exceeded the allowable limits set by the World Health Organization (WHO) and U.S. Environmental Protection Agency (USEPA).

  • Cd2+ was found in 11 bottled water samples, all of which were above the WHO and USEPA acceptable limits.

  • The result (dendrogram) showed five clusters, with Cu being more related to Zn than to Pd, Ni, Cd, and Cr.

  • The use of nanofiltration and microfiltration is known to remove hexavalent chromium (Cr(VI)).

The survival of all life forms depends on water and water absorption is an important means of nutritional nourishment for the human body (Peletz et al. 2018). The main objective of the campaign by the concerned health organizations is the use of safe and uncontaminated drinking water, which is considered a health priority (Cronk et al. 2015). Because the majority of illnesses in undeveloped countries are linked to the consumption of contaminated and dirty water (Peletz et al. 2018). As a consequence, water poisoning ultimately accounts for nearly a third of deaths in most poor countries (Dijkstra & de Roda Husman 2014; Kant & Graubard 2017). However, the contamination of drinking water sources by heavy metals (HMs) in the Enugu metropolis and the associated health risks (Nduka et al. 2023) are studied by the scarcity of data. Therefore, bottled water is a reasonable alternative when the quality of the drinking water or the water treatment is questionable (Cohen et al. 2022).

HMs become dangerous when their levels exceed the recommended safe limits (Agwu et al. 2023). Humans can be exposed to HM ions from both direct and indirect sources, including food, drinking water, exposure to industrial activities, and exhaust fumes (Pujari & Kapoor 2021). Several mineral elements, particularly metal ions, play a dual role in the functioning of the human body; although some are harmful in large doses, others are important in trace amounts (Ogamba et al. 2021). The entry and accumulation of HMs in the internal organs are the cause of numerous chronic diseases (Kapoor & Singh 2021). If the packing material leaks, the bottled water could potentially be contaminated. Previous studies have shown that toxic metals can get into plastic water bottles from polyethylene terephthalate (PET) (Ahimbisibwe et al. 2022). Also, the risk of water contamination from metals penetrating the bottle wall can increase due to prolonged storage of these bottled water at ambient temperature. This constraint applies to all the samples discussed in this study area (Molaee Aghaee et al. 2014). As a result, it is essential to continuously evaluate the quality of bottled water to preserve public health (Amarachi et al. 2023).

HM poisoning due to bottled drinking water contamination is a serious global problem. According to Ayodhya (2023), the most commonly analysed HM ions are zinc (Zn), copper (Cu), lead (Pb), tin (Sn), cadmium (Cd), chromium (Cr), iron (Fe), and mercury (Hg). Their toxicity comes from the bond formation of metals with the thiol group of proteins which alters the biochemical life cycle when they get into the cell. The current method of detecting HM ions by bottled water industries relies on shipping samples to a licensed laboratory for analysis. The method has complicated processing, expensive instruments, and time-consuming operations; but simple and cheap methods for identifying metal ions are highly desirable for detecting metal ions in bottled drinking water for consumers (Ayodhya 2022).

Additionally, studies on packaged water quality in Enugu, Nigeria, have not utilized the techniques applied in the current investigation to evaluate water quality and identify potential health risks associated with consumption. Moreover, despite these water firms' continual expansion, there has never been a comprehensive evaluation of the quality of the bottled water samples in the region. The Enugu region of Nigeria's coal mining industry has large amounts of mine tailings generated, which are dumped on the ground and in landfills, where it eventually enter surface runoff and groundwater (Obiadi et al. 2016). Another important factor is that, despite the findings of previous work (Osinowo 2016; Umoafia et al. 2023), water quality is still a concern within the community and the works suffered from the conventional approach, hence we propose to handle this difficulty through another approach. Therefore, this study aims to use flame atomic absorption spectrometry to measure the levels of toxic HM ions such as cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) in commercial bottled water brands sold in the Enugu market and to compare the results with Nigerian and global drinking water standards.

Description of the study area

The study was conducted in Enugu Metropolitan City, the provincial capital of southern Enugu State in Nigeria, as shown in Figure 1. The local governments of Enugu East, North, and South are part of the Enugu metropolis. The population of the city has expanded from 3,170 in 1921 as a coal mining hamlet to 722,664 in 2006 as an administrative and commercial nerve centre (Eze 2021). It is estimated that more than 1 million people live there today. The research area is situated in southeast Nigeria's humid tropical rainforest zone and is bounded by longitudes 7.27°E to 7.32°E and latitudes 6.24°N to 6.30°N. There are two main seasons in the area: the rainy (wet) and the Harmattan (dry) seasons (Osinowo 2016).
Figure 1

Google study map. (a) Map of Nigeria. (b) Map of Enugu State Nigeria. (c) Map of Enugu metropolitan area.

Figure 1

Google study map. (a) Map of Nigeria. (b) Map of Enugu State Nigeria. (c) Map of Enugu metropolitan area.

Close modal

Chemicals and reagents

The matrix used for the method blank was Li2CO3 (99%, Kiran Lighi, Laboratories, India). Standard stock solutions (1,000 ppm) of the HMs, Cd, Cr, Cu, Pb, Ni, and Zn, were adopted to generate calibration standards and spiking standards. Deionized water was used for the study's operation. Glass and plastic wares used in the analysis were washed with distilled water and then immersed overnight in a 10% (v/v) HNO3 solution before being repeatedly rinsed with deionized water.

Sample collection

Fifty-one samples of 0.75 L bottled water from 17 different commercial domestic bottled water brands were randomly collected from shops and supermarkets in the Enugu metropolis, Nigeria in the first quarter of 2018. Three samples with different production dates for each brand were collected. The bottles were transferred to the Chemical Analysis Laboratory of the Projects Development Institute (PRODA), Enugu, where they were stored at 4°C until analysis (performed within a week). Among the popular brands of bottled water are Swan, Bigi, Ragolis, Lucozade Hydropure, Eva, Aquafina, Nestle, La Sien, Event, Cascade, Aquarapha, Ivy, Rovia, Trinity, Exalté, Ezbon, and Jasmine.

Sample digestion for the analysis of HMs

Five millilitre of concentrated nitric acid (HNO3) and 5 mL of concentrated sulphuric acid (H2SO4) were added to each bottled water sample in the laboratory (Lu et al. 2022). The solution was then boiled until the volume was reduced to 15–20 mL, whereupon a clear solution resulted (Huang et al. 2020). After digestion, this sample was allowed to cool down to room temperature. Then, it was filtered with Whatman's 0.45 μm filter paper. The final volume was diluted to 100 mL with deionized water and then stored for analysis.

Equipment

For the measurement of HMs (Cd, Cr, Cu, Pb, Ni, and Zn) a flame atomic absorption spectrophotometer Buck Scientific Model 210/211 VGP (East Newark, USA) with deuterium lamp background correction and hollow cathode lamps was used. A pH meter (Mettler Toledo Seven Compact pH/Ion metre and an In-lab Expert Pro-ISM pH electrode) was used to measure the pH of each sample of bottled water. The instrumental parameters were adjusted according to the manufacturer's recommendations. A calibration curve was constructed by plotting the analytical signal versus the HM concentration in a series of working standard solutions (Tibebe et al. 2022).

Quality assurance and analysis

With strict adherence to protocols, quality assurance and quality control approaches were utilized to ensure the reliability of the results. The analytical grade reagents and high-purity chemicals were all used. Glassware used for laboratory analysis was carefully cleaned with detergent and frequently immersed in deionized water. For the dilutions, deionized water was employed. A blank solution was scanned 25 times to determine the limits of quantification and detection of atomic absorption spectrophotometers (AAS). Then, the standard deviations for the noise levels generated by each of the problematic elements were calculated. It is noted that the instrumental detection limit (IDL) is the concentration equal to three times the standard deviation of the blank signal (IDL) (Ewuzie et al. 2021). The IDL was estimated in this study and is displayed:
formula
(1)
where Sbl represents the calibration blank's standard deviation.
Each element's limit of detection (LOD) was determined by
formula
(2)
where Sbl is the method blank's standard deviation.
The limit of quantitation (LOQ) was calculated by
formula
(3)
where Sbl is the blank method standard deviation. The precision and repeatability of the analytical technique were evaluated by spiking and homogenizing three replicates of each of the three randomly selected samples. Each sample received three additions of the element of interest at the following concentrations: Cd (0.5, 2.0, and 3.0 mg/L), Cr (0.25, 0.5, and 1.0 mg/L), Cu (0.5, 2.0, and 3.5 mg/L), Pb (2.0, 5.0, and 10.0 mg/L), Ni (2.0, 4.0, and 8.0 mg/L), and Zn (0.25, 0.5, and 1.0 mg/L). Using common calibration curves, the absorbance data from the AAS were interpreted into concentrations. The essential elements were purchased as 1,000 mg/L single element standards from Fluka AG Chemische Fabrik 9,470 Buchs, Switzerland, then diluted with 10% HNO3 to generate the calibration curves for AAS analysis. The Buck Scientific Model 210/211 VGP was used for the HM analysis (Cd, Cr, Cu, Pb, Ni, and Zn), according to standard methods for the examination of water described by Tibebe et al. (2022). Using certified standard reference solutions for Cd, Cr, Cu, Pb, Ni, and Zn manufactured by BDH Chemicals, UK, the sensitivity and effectiveness of the methods used in the chemical analysis were evaluated in terms of recovery and repeatability. The results of the recovery evaluations show that 94, 100, 92, 98, 93, and 95% of Cd, Cr, Cu, Pb, Ni, and Zn were recovered, respectively. These results were in the range of 80–120% acceptable for metal analysis (Ewuzie et al. 2021). The precision of the assay was expressed as the relative standard deviation (RSD) of duplicate measurements. The RSD values for the matrix spike samples are 5.23, 2.85, 3.45, 2.88, 0.19, and 4.21%, respectively, which are below the required 15% control limits. They showed that the process had good accuracy and precision (Ewuzie et al. 2021).

Determination of HMs

Using the method described in previous work by Umoafia et al. (2023), a flame atomic absorption spectrophotometer (Buck Scientific, Model: 210/11 VGP, Newark, NJ, USA) was used to measure the concentrations of HMs (Cd, Cr, Cu, Pb, Ni, and Zn) in the pretreatment samples. The final metal concentrations in the bottled water samples were calculated using the formula below:
formula
(4)
where M is the concentration of the metal in the original sample (mg/L), C is the concentration of metal in the analytical sample determined from the standard curve (mg/L), V is the volume of the analytical sample (mL), and SV is the volume of the sample used for concentration (mL) (in this case 100 mL).

Working conditions for instruments

The operating conditions for a flame atomic absorption spectrophotometer are shown in Table 1.

Table 1

Instrument operating conditions and detection limits for the determination of metals

ElementPbNiCdCrCuZn
Lamp current (mA) 
Slit width (nm) 0.7 0.2 0.7 0.7 0.7 0.7 
Wavelength (nm) 283.3 232.0 228.8 357.9 324.7 213.9 
Flame gas A-Ac A-Ac A-Ac A-Ac A-Ac A-Ac 
Instrument detection limit (mg/L) 0.010 0.002 0.003 0.006 0.015 0.005 
The method detection limit (mg/L) 0.011 0.023 0.012 0.016 0.018 0.017 
Limit of quantification (mg/L) 0.057 0.087 0.065 0.078 0.093 0.084 
ElementPbNiCdCrCuZn
Lamp current (mA) 
Slit width (nm) 0.7 0.2 0.7 0.7 0.7 0.7 
Wavelength (nm) 283.3 232.0 228.8 357.9 324.7 213.9 
Flame gas A-Ac A-Ac A-Ac A-Ac A-Ac A-Ac 
Instrument detection limit (mg/L) 0.010 0.002 0.003 0.006 0.015 0.005 
The method detection limit (mg/L) 0.011 0.023 0.012 0.016 0.018 0.017 
Limit of quantification (mg/L) 0.057 0.087 0.065 0.078 0.093 0.084 

Note: A-Ac = Air-Acetylene.

Lead

Nine bottled water samples, including Swan, Bigi, Eva, Nestle, Event, Cascade, Aquarapha, Ivy, and Ezbon, showed that lead levels were below the detection threshold limit (Figure 2 and Table 2). The range of metals detected in the remaining nine samples exceeded the allowable limit set by the WHO (World Health Organization), USEPA (U.S. Environmental Protection Agency), and Nigerian Standards for Drinking Water Quality (NSDWQ) (0.01, 0.015, and 0.01 mg/L), respectively. La Sien (0.03 mg/L), Lucozade Hydropure (0.09 mg/L), Aquafina (0.26 mg/L), Exalté (0.27 mg/L), Rovia (0.14 mg/L), Trinity (0.18 mg/L), Ragolis (0.07 mg/L), and Jasmine (0.02 mg/L) were the products with the highest concentrations of lead. These samples contain statistically significant amounts of lead (p < 0.05). It is important to remember that lead consumption in humans causes serious health problems that damage the central nervous system of developing fetuses, as newborns are more susceptible to Pb concentrations than adults (Reuben et al. 2017). In addition, lead poisoning damages the haemoglobin synthesis, the kidneys and reproductive systems, and the gastrointestinal tract (Rehman et al. 2018). Additionally, continued exposure leads to hypertension, permanent brain damage, and encephalopathic symptoms. Due to Pb toxicity, a recent article (Chowdhury et al. 2022) recommends using agricultural waste, forest waste, and biotechnology adsorbents to remove lead from water due to their long contact times and high adsorption capacities.
Table 2

Mean concentrations of metals (mean ± SEM, n = 3) in bottled water samples

Water samplesPb (mg/L)Ni (mg/L)Cd (mg/L)Cr (mg/L)Cu (mg/L)Zn (mg/L)
Swan BDL BDL BDL BDL BDL BDL 
Bigi BDL BDL BDL 0.02 ± 0.001 0.41 ± 0.001 BDL 
Ragolis 0.07 ± 0.001 BDL 0.02 ± 0.001 0.01 ± 0.001 BDL BDL 
Lucozade Hydropure 0.09 ± 0.001 BDL BDL 0.01 ± 0.002 0.08 ± 0.001 BDL 
Eva BDL BDL BDL 0.01 ± 0.001 BDL BDL 
Aquafina 0.26 ± 0.002 0.41 ± 0.006 0.22 ± 0.003 BDL BDL 0.02 ± 0.001 
Nestle BDL BDL 0.02 ± 0.001 0.01 ± 0.001 BDL BDL 
La Sien 0.03 ± 0.001 BDL 0.13 ± 0.001 0.01 ± 0.001 0.05 ± 0.001 BDL 
Event BDL 0.05 ± 0.001 0.22 ± 0.004 0.04 ± 0.006 BDL BDL 
Cascade BDL 0.41 ± 0.009 0.15 ± 0.001 0.04 ± 0.005 0.06 ± 0.001 BDL 
Aquarapha BDL BDL BDL 0.06 ± 0.001 BDL BDL 
Ivy BDL BDL BDL 0.02 ± 0.001 BDL BDL 
Rovia 0.14 ± 0.001 0.13 ± 0.001 0.09 ± 0.001 0.03 ± 0.001 0.11 ± 0.001 BDL 
Trinity 0.18 ± 0.033 BDL 0.12 ± 0.001 0.07 ± 0.001 0.23 ± 0.001 0.01 ± 0.001 
Exalté 0.27 ± 0.001 BDL 0.16 ± 0.001 BDL BDL BDL 
Ezbon BDL BDL 0.36 ± 0.001 0.04 ± 0.001 0.15 ± 0.001 BDL 
Jasmine 0.02 ± 0.001 0.21 ± 0.001 0.14 ± 0.001 0.04 ± 0.001 BDL BDL 
Mean concentration 0.13 ± 0.02 0.24 ± 0.01 0.15 ± 0.03 0.03 ± 0.02 0.16 ± 0.03 0.02 ± 0.01 
Guideline values for drinking water WHO 0.01 0.07 0.003 0.05 2 5 
USEPA 0.015 - 0.005 0.1 1.3 100 μg/L 
NSDWQ 0.01 0.02 0.003 0.05 1 3 
Water samplesPb (mg/L)Ni (mg/L)Cd (mg/L)Cr (mg/L)Cu (mg/L)Zn (mg/L)
Swan BDL BDL BDL BDL BDL BDL 
Bigi BDL BDL BDL 0.02 ± 0.001 0.41 ± 0.001 BDL 
Ragolis 0.07 ± 0.001 BDL 0.02 ± 0.001 0.01 ± 0.001 BDL BDL 
Lucozade Hydropure 0.09 ± 0.001 BDL BDL 0.01 ± 0.002 0.08 ± 0.001 BDL 
Eva BDL BDL BDL 0.01 ± 0.001 BDL BDL 
Aquafina 0.26 ± 0.002 0.41 ± 0.006 0.22 ± 0.003 BDL BDL 0.02 ± 0.001 
Nestle BDL BDL 0.02 ± 0.001 0.01 ± 0.001 BDL BDL 
La Sien 0.03 ± 0.001 BDL 0.13 ± 0.001 0.01 ± 0.001 0.05 ± 0.001 BDL 
Event BDL 0.05 ± 0.001 0.22 ± 0.004 0.04 ± 0.006 BDL BDL 
Cascade BDL 0.41 ± 0.009 0.15 ± 0.001 0.04 ± 0.005 0.06 ± 0.001 BDL 
Aquarapha BDL BDL BDL 0.06 ± 0.001 BDL BDL 
Ivy BDL BDL BDL 0.02 ± 0.001 BDL BDL 
Rovia 0.14 ± 0.001 0.13 ± 0.001 0.09 ± 0.001 0.03 ± 0.001 0.11 ± 0.001 BDL 
Trinity 0.18 ± 0.033 BDL 0.12 ± 0.001 0.07 ± 0.001 0.23 ± 0.001 0.01 ± 0.001 
Exalté 0.27 ± 0.001 BDL 0.16 ± 0.001 BDL BDL BDL 
Ezbon BDL BDL 0.36 ± 0.001 0.04 ± 0.001 0.15 ± 0.001 BDL 
Jasmine 0.02 ± 0.001 0.21 ± 0.001 0.14 ± 0.001 0.04 ± 0.001 BDL BDL 
Mean concentration 0.13 ± 0.02 0.24 ± 0.01 0.15 ± 0.03 0.03 ± 0.02 0.16 ± 0.03 0.02 ± 0.01 
Guideline values for drinking water WHO 0.01 0.07 0.003 0.05 2 5 
USEPA 0.015 - 0.005 0.1 1.3 100 μg/L 
NSDWQ 0.01 0.02 0.003 0.05 1 3 

BDL, below detection limit.

Figure 2

Concentration of lead (Pb) in different brands of bottled water.

Figure 2

Concentration of lead (Pb) in different brands of bottled water.

Close modal

Nickel

Twelve table water samples were tested and the Ni2+ concentration was below the detection threshold: Swan, Bigi, Ragolis, Lucozade Hydropure, Eva, Nestle, and La Sien. The other table water samples were Exalté, Ezbon, Aquarapha, Ivy, and Trinity. The LOD technique for nickel was below the WHO and NSDWQ allowable limits of 0.07 and 0.02 mg/L, respectively. Figure 3 revealed the ‘Event’ bottled water contained 0.05 mg/L of nickel, which was less than the WHO level but more than the Nigerian limit shown in Table 2. Ni2+ concentrations in Aquafina (0.41 mg/L), Cascade (0.41 mg/L), Rovia (0.13 mg/L), and Jasmine (0.26 mg/L) were all above WHO and NSDWQ-approved limits. The Ni2+ concentration in these samples was also statistically significant (p < 0.05). Importantly, nickel plays a crucial role in the formation of red blood cells, but is toxic at high doses. Negligible levels of Ni2+ do not damage biological cells, but exposure to high levels over a long period as observed in some bottled water samples can damage cells, decrease body weight, and cause liver and heart damage (Soroush et al. 2016). The Ni2+ content in bottled water is expected to increase over time due to the increasing use of certain materials and consumers exposed to long-term accumulation. Therefore, Ni2+ removal can be achieved by employing ion exchange bed treatment which offers a high adsorption efficiency of 152.846 mg/g (Al-Abbad & Al Dwairi 2021).
Figure 3

Concentration of nickel (Ni) in different brands of bottled water.

Figure 3

Concentration of nickel (Ni) in different brands of bottled water.

Close modal

Cadmium

Six bottled water samples that showed Cd2+ concentrations below the detection limit are Lucozade Hydropure, Swan, Bigi, Ivy, Aquarapha, and Eva are among the specimens as shown in Figure 4. However, Cd2+ was found in 11 bottled water samples, all of which were above the WHO, USEPA, and NDWQS acceptable limits (0.003, 0.005, and 0.003 mg/L) for the presence of Cd2+. Ragolis (0.02 mg/L), Nestle (0.02 mg/L), Aquafina (0.22 mg/L), La Sien (0.13 mg/L), Cascade (0.15 mg/L), Rovia (0.09 mg/L), Event (0.22 mg/L), Trinity (0.12 mg/L), Exalté (0.16 mg/L), Ezbon (0.36 mg/L), and Jasmine (0.14 mg/L) are among them. The concentration of Cd2+ in these samples was statistically significant (p < 0.05). Even in low concentrations, cadmium is the deadliest element in the food chain, but unlike other HMs, Cd2+ is not essential to living organisms. In addition to increasing blood pressure, Cd2+ toxicity leads to kidney failure and lung cancer in humans, as well as thinning of the bone structure. It causes bronchitis, emphysema, and anaemia in adults and has immediate effects in children as well (Balali-Mood et al. 2021). Due to the widespread contamination and its toxicity, there is a lot of interest in getting rid of Cd2+ at all costs. Therefore, due to their exceptional adsorption tendencies towards HM ions or ion exchange resins, scientists have investigated the use of inexpensive materials such as industrial and agricultural waste instead of expensive commercial activated carbon (Pyrzynska 2019).
Figure 4

Concentration of cadmium (Cd2+) in different brands of bottled water.

Figure 4

Concentration of cadmium (Cd2+) in different brands of bottled water.

Close modal

Chromium

Three bottled water samples having chromium concentrations below the detection limit are shown in Figure 5. These were Swan, Aquafina, and Exalté. Chromium average level in Aquarapha (0.06 mg/L) and Trinity (0.07 mg/L exceeded the WHO. and NSDWQ specified permissible limit but lower than the USEPA recent updated limit of 100 μg/L (Monga et al. 2022). It has been suggested that the observed similar variation in their means (p > 0.05) was caused by the fact that they were made in Enugu. The chromium levels in the remaining bottled water were below acceptable standards from the WHO, USEPA, and NSDWQ. The two most common oxidation states of chromium are trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)). However, the hexavalent state is more dangerous. Excessive exposure to this metal can damage the liver and kidneys, cause skin ulcers, and have negative effects on the central nervous system (Georgaki & Charalambous 2022). In addition, it irritates the gastrointestinal mucosa to irritate and eventually leads to the death of humans (10 mg/kg body weight as hexavalent chromium) (Monga et al. 2022). Therefore, the use of nanofiltration and microfiltration in the water treatment process is known to remove hexavalent chromium (Cr(VI)) (Zolfaghari & Kargar 2019) while the chemical coagulation and electrocoagulation processes can efficiently remove trivalent chromium (Cr(III)) (Martín-Domínguez et al. 2018).
Figure 5

Concentration of chromium (Cr) in different brands of bottled water.

Figure 5

Concentration of chromium (Cr) in different brands of bottled water.

Close modal

Copper

Nine bottled water samples that had copper concentrations below the detection threshold of 0.018 mg/L are Jasmine, Event, Ivy, Ragolis, Eve, Aquafina, Nestle, Event, and Ragolis (Figure 6). The other samples had metal concentrations of 0.41 mg/L for Bigi, 0.08 mg/L for Lucozade Hydropure, 0.06 mg/L for Cascade, 0.11 mg/L for Rovia, 0.23 mg/L for Trinity, and 0.15 mg/L for Ezbon, respectively. The lowest concentration was found in La Sien with 0.05 mg/L. The observed concentration in each sample is below the WHO, USEPA, and NSDWQ-approved limits of 2, 1.3, and 1 mg/L, respectively. This indicated that none of the bottled water samples examined posed a risk to human health due to copper toxicity and the low levels should be adhered to by all water bottling companies, particularly avoiding the bottling of turbid or cloudy water (Cao et al. 2023).
Figure 6

Concentration of copper (Cu) in different brands of bottled water.

Figure 6

Concentration of copper (Cu) in different brands of bottled water.

Close modal

Zinc

Zn is a metal that enters the environment through a variety of routes, primarily through the erosion of soil particles containing Zn, both in surface and groundwater. (Noulas et al. 2018). Except for the Trinity (0.01 mg/L) and Aquafina (0.02 mg/L) bottled water samples, all 15 water samples had zinc concentrations below the detection threshold are shown in Figure 7. The concentration ranges acceptable by WHO and NSDWQ are 5 and 3 mg/L, respectively. Zinc toxicity is not an issue in any of the bottled water samples. Zinc is an essential trace mineral involved in the physiological and metabolic processes of many living things, including humans. On the other hand, too high a zinc content can be harmful to living beings and impart an undesirable astringent taste to the water.
Figure 7

Concentration of zinc (Zn) in different brands of bottled water.

Figure 7

Concentration of zinc (Zn) in different brands of bottled water.

Close modal

pH of bottled water samples

The determination of pH of the samples of bottled water is presented in Table 3. pH does not directly harm human health unless mixed with other chemicals and when at high acidity or alkalinity levels. Consequently, the WHO guidelines stated that the recommended pH limit is 6.5–8.5 and same as NSDWQ but USEPA set pH limits of 6.5–9.0 (Hansen et al. 2018). Bottled water samples with pH levels below 4 taste sour and are acidic, and water samples above 8.5 have an unsightly alkaline taste. Dangerous trihalomethanes are formed at lower pH levels (Kumari & Gupta 2023). When the pH falls below 6.5, rust begins to form in pipes releasing toxic metals such as Cu, Pb, Cd, and Zn. The pH values of eight bottles of water, including those from Bigi (6.15), Aquafina (6.13), Nestle (6.43), Event (4.91), Cascade (6.45), Trinity (5.93), Exalté (5.90), and Ezbon (5.62), were outside the WHO recommended range of 6.5–8.5.

Table 3

pH of the bottled water samples

LabellingBottled water brandspHLabellingBottled water brandspH
Swan 7.37 10 Cascade 6.45 
Bigi 6.15 11 Aquarapha 6.64 
Ragolis 6.92 12 Ivy 6.87 
Lucozade Hydropure 7.99 13 Rovia 7.29 
Eva 7.09 14 Trinity 5.93 
Aquafina 6.13 15 Exalté 5.90 
Nestle 6.43 16 Ezbon 5.62 
La Sien 7.89 17 Jasmine 6.86 
Event 4.91    
LabellingBottled water brandspHLabellingBottled water brandspH
Swan 7.37 10 Cascade 6.45 
Bigi 6.15 11 Aquarapha 6.64 
Ragolis 6.92 12 Ivy 6.87 
Lucozade Hydropure 7.99 13 Rovia 7.29 
Eva 7.09 14 Trinity 5.93 
Aquafina 6.13 15 Exalté 5.90 
Nestle 6.43 16 Ezbon 5.62 
La Sien 7.89 17 Jasmine 6.86 
Event 4.91    

Note: Standard pH: 6.5–8.5.

Contrarily, samples from Bigi, Aquafina, Nestle, Event, Cascade, Trinity, Exalté, and Ezbon table water samples were less alkaline than 6.5, with ‘Event’ samples' pH of 4.91 causing the most concern. According to a study by Wright (2015), using acidic water to cleanse and treat skin and hair can be beneficial as it has antibacterial properties. However, acidic water exposes the user to HMs and damages dental and bone health. Low pH levels may be due to chlorination and requires additional purification such as reverse osmosis and carbon distillation in the bottled water treatment.

Statistical analysis

Using Windows-based SPSS version 25.0 (IBM Corp., USA) software, descriptive statistics were used to analyse the data. To check if there were any apparent changes in the mean amounts of HMs in samples of bottled water, an analysis of variance (ANOVA), factor analysis, etc. were also carried out. In addition, post hoc tests were performed to determine where the differences within groups occurred once a statistically significant ANOVA result was obtained and a P-value ≤ 0.05 was considered significant according to the definition of statistical significance.

Factor analysis

Principal component (PC) scree plot

Screen plotting in SPSS at an eigenvalue of ≥1 was used to identify the number of PCs accounting for the selected HM concentrations in different water samples. The scree plot result is shown in Figure S1. Depicts the strong statistical significance of five PCs extracted at eigenvalue ≥1 which are used for the principal component analysis (PCA) of this study. The identified PCA commonalities represent the percentage of variances of the HMs extracted to account for the five PCAs adopted. The result from Table S1 showed 100% of variances of the HMs extracted to account for the 16 varying water sample companies. The total variance shown in Table S2 represents the extracted five major component factor solutions. The eigenvalue for the first PCA is 5.500 representing about 34.373% of the total variance while the second PCA has an eigenvalue of 4.075 making up for 25.471% of the total variance with a cumulative of 59.844%. Thus, this process continued till the fifth PCA with an eigenvalue of 1.011 representing 6.318% of total variance on a total cumulative variance of 100%.

Principal component matrix

The component matrix arising from the second PC (Table S3) showed that in the first PC, eight water sample companies (Swan, Eva, Aquafina, Lasien, Aquarafa, Ivy, Rovia, and Exalté) loaded strongly with a high correlation coefficient of 86.9. 88.2, 65.1, 50.4, 88.2, 88.2, 74.7, and 58.6%, respectively. While Swan, Eva, Aquarafa, and Ivy showed a strong negative correlation, Aquafina, Lasien, Rovia, and Exalté maintained a strong positive correlation. However, on the second PC, Nestle, Event, Cascade, Exbon, and Jasmine showed a strong positive correlation at 79.5, 87, 55.7, 60.2, and 74.8%, respectively, Locazade hydropure maintained a strong negative correlation at 79%. This relationship established above continued until the fifth PC.

Hierarchical component analysis

Tables S4 and S5 show that the hierarchical cluster analysis was performed to observe how the sampled six HMs (Pd, Ni, Zn, etc.) correlated with the various water samples (Swam, Ivy, Eva, etc.). The result (dendrogram) showed five clusters, with Cu being more related to Zn than Pd, Ni, Cd, and Cr. Similarly, Pd is related to Zn and Ni more than it relates to Cu, Cd, and Cr as shown in Tables S4, S5, and Figure S2.

Pearson and pattern correlation analysis

Pearson correlation matrix (Table S6) showed a strong positive correlation between Swam and Eva, Ragolis and Locozade, Cascade and Aquarafa, Lasien and Nestle, Event and Nestle, Lasien and Event, Swan and Aquarafa, Swan and Ivy, Locade and Rovia, Aquafina and Roviaragolis and Exalté, Nestle and Exbonevent and Exbon, Jasmire and Aquafina, Jasmire and Event, and Jasmire and Cascade at 99.9, 58.1, 99.9, 75.2, 77.1, 83.2, 75.2, 99.9, 55.4, 69.7, 93.9, 80.8, 96.8, 85.4, 58.5, 80.6, and 93.4%, respectively. However, a strong negative correlation was only encountered between Jasmire and Locade at 55.4%. Similarly, the pattern matrix which represents the loadings of variables in an oblique rotation was used. Each row of the pattern matrix is essentially a regression equation where the standardized observed variable is expressed as a regression coefficient. Thus, from the first PC (Table S7) Swan, Eva, Ivy, and Aquafina loaded negatively strongly with a regression coefficient of −100% each. In the second PC, Exbon, Lasien, Nestle, and Event bottled water samples showed strong positive regression coefficients at 98.8, 94.5, 91.3, and 90.4%, respectively. Considering the third PC, Trinity, Locade, and Rovia loaded strongly with a positive regression coefficient of 91.8, 82.9, and 66.7%, respectively, while Ragolis and Exalté loaded strongly positively at 97.2 and 92.3%, respectively, at the fourth PC. The fifth PC had the remaining bottled water variables loaded strongly with a positive correlation coefficient.

The contamination of bottled water samples by HMs in the Enugu metropolis and the associated health risks are serious health issue due to leakage, exposure, absorption, consumption, and lack of data. Using FAAS to analyse the samples of each of the three replicates by spiking and homogenizing selected samples, LOD, LOQ, IDL, and standard deviation were taken into account. From the results, it can be concluded that trace metals of concern occur in bottled water sold in the Enugu metropolis. Out of the 17 analysed samples, Cd ions were detected in 11 samples, Pb ions in 8 samples, Cu ions in 7 samples, and Ni ions in 6 samples. Cr was detected in all the samples except Aquafina and Exalté, while Zn was only detected in Aquafina and Trinity. All HM ions were detected in Aquafina except Cr and Cu ions; La Sien except Ni and Zn ions; Jasmine except Cu and Zn ions; and Cascade except Pb and Zn ions. In contrast, Rovia and Trinity showed a higher additional presence of metals because of only Zn and Ni, respectively. Hence, from the present findings, the least contaminated bottled water samples were Eva > Aquaphor ≤ Ivy ≤ Nestle, while Cd and Cr were the most frequently occurring HM ions and Zn was the least. Therefore, the study confirmed the presence of HM components in commercial bottled water samples, which can interact in more complicated ways at higher or lower pH values. The PCA showed strong statistical significance, while the hierarchical component analysis showed a strong correlation with the various samples. Hence, the use of activated carbon, ion exchangers, and nanofiltration is recommended to reduce all HM ions to the barest minimum. It is expected that these measures when implemented will help to protect the health of the population and significantly improve the quality of bottled water in Enugu. Further work can be carried out according to these recommendations.

Future research recommendations

The study, therefore, highly recommends the following for the effective removal of these toxic metals:

  • The producer can apply selective separation of species at controlled pH levels to improve water quality.

  • The human health effects of co-exposure to metals and other HMs (such as Pb and Cd) need to be better understood. Regulatory authorities may relate co-exposure situations and other aspects to the maximum metal levels in drinking water (e.g. treatability and toxicological implications).

  • Significant amounts of HMs can escape from tanks and piping systems, resulting in significant leaks significantly. There is a good chance that several factors, including water pH, dwell time, temperature, pipe material, sanitizer type and dosage, and the age of the tanks and pipes, will affect the release of metals. The results of their interactions as well as the effects of these substances on HM leaching could be clarified by additional research.

  • Technologies based on adsorption, coagulation, precipitation, and filtration are expected to generate significant amounts of HM-contaminated waste when applied in combination with one another. Saturated media and liquid wastes with HM contents should be disposed of properly. Several strategies could be employed to solve this issue. One such technique is to combine HM-contaminated materials with solid waste or engineered components, such as glass, brick, concrete, or cement blocks, and then carefully dispose of the resulting mixture.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

Agwu
E. J.
,
Odanwu
S. E.
,
Ezewudo
B. I.
,
Odo
G. E.
,
Nzei
J. I.
,
Iheanacho
S. C.
&
Islam
M. S.
2023
Assessment of water quality status using heavy metal pollution indices: A case from Eha-Amufu catchment area of Ebonyi River, Nigeria
.
Acta Ecol. Sin.
doi:10.1016/j.chnaes.2023.02.003
.
Ahimbisibwe
O.
,
Byamugisha
D.
,
Mukasa
P.
,
Omara
T.
&
Ntambi
E.
2022
Leaching of lead, chromium and copper into drinks placed in plastic cups at different conditions
.
Am. J. Anal. Chem.
13
,
9
19
.
doi:10.4236/ajac.2022.132002
.
Al-Abbad
E. A.
&
Al Dwairi
R. A.
2021
Removal of nickel (II) ions from water by Jordan natural zeolite as sorbent material
.
J. Saudi Chem. Soc.
25
,
101233
.
doi:10.1016/j.jscs.2021.101233
.
Amarachi
N.
,
Austin
T.
,
Michael
O.
,
Bilar
A.
&
Christopher
A.
2023
Quality assessment and health impact of bottled water in Uratta, Imo state: A retrospective study
.
Sustain. Water Resour. Manag.
10
,
3
.
doi:10.1007/s40899-023-00982-4
.
Balali-Mood
M.
,
Naseri
K.
,
Tahergorabi
Z.
,
Khazdair
M. R.
&
Sadeghi
M.
2021
Toxic mechanisms of five heavy metals: Mercury, lead, chromium, cadmium, and arsenic
.
Front. Pharmacol
12, 643972.
Chowdhury
I. R.
,
Chowdhury
S.
,
Mazumder
M. A. J.
&
Al-Ahmed
A.
2022
Removal of lead ions (Pb2+) from water and wastewater: A review on the low-cost adsorbents
.
Appl. Water Sci.
12
,
185
.
doi:10.1007/s13201-022-01703-6
.
Cohen
A.
,
Cui
J.
,
Song
Q.
,
Xia
Q.
,
Huang
J.
,
Yan
X.
,
Guo
Y.
,
Sun
Y.
,
Colford
J. M.
&
Ray
I.
2022
Bottled water quality and associated health outcomes: A systematic review and meta-analysis of 20 years of published data from China
.
Environ. Res. Lett.
17
,
13003
.
doi:10.1088/1748-9326/ac2f65
.
Cronk
R.
,
Slaymaker
T.
&
Bartram
J.
2015
Monitoring drinking water, sanitation, and hygiene in non-household settings: Priorities for policy and practice
.
Int. J. Hyg. Environ. Health
218
,
694
703
.
doi:10.1016/j.ijheh.2015.03.003
.
Dijkstra
A. F.
,
de Roda Husman
A. M.
,
2014
Chapter 14 – Bottled and drinking water
. In:
Food Safety Management
(
Motarjemi
Y.
&
Lelieveld
H.
eds.).
Academic Press
,
San Diego
, pp.
347
377
.
doi:10.1016/B978-0-12-381504-0.00014-7
.
Georgaki
M.-N.
&
Charalambous
M.
2022
Toxic chromium in water and the effects on the human body: A systematic review
.
J. Water Health
21
,
205
223
.
doi:10.2166/wh.2022.214
.
Hansen
T. H.
,
Thomassen
M. T.
,
Madsen
M. L.
,
Kern
T.
,
Bak
E. G.
,
Kashani
A.
,
Allin
K. H.
,
Hansen
T.
&
Pedersen
O.
2018
The effect of drinking water pH on the human gut microbiota and glucose regulation: Results of a randomized controlled cross-over intervention
.
Sci. Rep.
8
,
16626
.
doi:10.1038/s41598-018-34761-5
.
Huang
Z.
,
Liu
C.
,
Zhao
X.
,
Dong
J.
&
Zheng
B.
2020
Risk assessment of heavy metals in the surface sediment at the drinking water source of the Xiangjiang River in South China
.
Environ. Sci. Eur.
32
,
23
.
doi:10.1186/s12302-020-00305-w
.
Kant
A. K.
&
Graubard
B. I.
2017
A prospective study of water intake and subsequent risk of all-cause mortality in a national cohort
.
Am. J. Clin. Nutr.
105
,
212
220
.
doi:10.3945/ajcn.116.143826
.
Kapoor
D.
,
Singh
M. P.
,
2021
10 - Heavy metal contamination in water and its possible sources
. In:
Heavy Metals in the Environment: Impact, Assessment, and Remediation
(
Kumar
V.
,
Sharma
A.
&
Cerdà
A.
eds.).
Elsevier
, pp.
179
189
.
doi:10.1016/B978-0-12-821656-9.00010-9
.
Kumari
M.
,
Gupta
S. K.
,
2023
Trihalomethanes (THMs) in wastewater: Causes and concerns BT
. In:
Cost-efficient Wastewater Treatment Technologies: Engineered Systems
(
Nasr
M.
&
Negm
A. M.
eds.).
Springer International Publishing
,
Cham
, pp.
421
439
.
doi:10.1007/698_2022_872
.
Lu
T.
,
Peng
H.
,
Yao
F.
,
Nadine Ferrer
A. S.
,
Xiong
S.
,
Niu
G.
&
Wu
Z.
2022
Trace elements in public drinking water in Chinese cities: Insights from their health risks and mineral nutrition assessments
.
J. Environ. Manage.
318
,
115540
.
doi:10.1016/j.jenvman.2022.115540
.
Martín-Domínguez
A.
,
Rivera-Huerta
M. L.
,
Pérez-Castrejón
S.
,
Garrido-Hoyos
S. E.
,
Villegas-Mendoza
I. E.
,
Gelover-Santiago
S. L.
,
Drogui
P.
&
Buelna
G.
2018
Chromium removal from drinking water by redox-assisted coagulation: Chemical versus electrocoagulation
.
Sep. Purif. Technol.
200
,
266
272
.
doi:10.1016/j.seppur.2018.02.014
.
Molaee Aghaee
E.
,
Alimohammadi
M.
,
Nabizadeh
R.
,
Jahed Khaniki
G.
,
Naseri
S.
,
Mahvi
A. H.
,
Yaghmaeian
K.
,
Aslani
H.
,
Nazmara
S.
,
Mahmoudi
B.
&
Ghani
M.
2014
Effects of storage time and temperature on the antimony and some trace element release from polyethylene terephthalate (PET) into the bottled drinking water
.
J. Environ. Heal. Sci. Eng.
12
,
133
.
doi:10.1186/s40201-014-0133-3
.
Nduka
J. K.
,
Umeh
T. C.
,
Kelle
H. I.
,
Mgbemena
M. N.
,
Nnamani
R. A.
&
Okafor
P. C.
2023
Ecological and health risk assessment of heavy metals in roadside soil, dust and water of three economic zone in Enugu, Nigeria
.
Urban Clim.
51
,
101627
.
doi:10.1016/j.uclim.2023.101627
.
Noulas
C.
,
Tziouvalekas
M.
&
Karyotis
T.
2018
Zinc in soils, water and food crops
.
J. Trace Elem. Med. Biol.
49
,
252
260
.
doi:10.1016/j.jtemb.2018.02.009
.
Obiadi
I. I.
,
Obiadi
C. M.
,
Akudinobi
B. E. B.
,
Maduewesi
U. V.
&
Ezim
E. O.
2016
Effects of coal mining on the water resources in the communities hosting the Iva Valley and Okpara Coal Mines in Enugu State, Southeast Nigeria
.
Sustain. Water Resour. Manag.
2
,
207
216
.
doi:10.1007/s40899-016-0061-8
.
Ogamba
E. N.
,
Charles
E. E.
&
Izah
S. C.
2021
Distributions, pollution evaluation and health risk of selected heavy metal in surface water of Taylor Creek, Bayelsa State, Nigeria
.
Toxicol. Environ. Health Sci.
13
,
109
121
.
doi:10.1007/s13530-020-00076-0
.
Osinowo
O. O.
2016
Water quality assessment of the Asata River catchment area in Enugu Metropolis, Southeast Nigeria
.
J. African Earth Sci.
121
,
247
254
.
doi:10.1016/j.jafrearsci.2016.06.009
.
Peletz
R.
,
Kisiangani
J.
,
Bonham
M.
,
Ronoh
P.
,
Delaire
C.
,
Kumpel
E.
,
Marks
S.
&
Khush
R.
2018
Why do water quality monitoring programs succeed or fail? A qualitative comparative analysis of regulated testing systems in sub-Saharan Africa
.
Int. J. Hyg. Environ. Health
221
,
907
920
.
doi:10.1016/j.ijheh.2018.05.010
.
Pujari
M.
,
Kapoor
D.
,
2021
1 - Heavy metals in the ecosystem: Sources and their effects
. In:
Heavy Metals in the Environment: Impact, Assessment, and Remediation
(
Kumar
V.
,
Sharma
A.
&
Cerdà
A.
eds.).
Elsevier
, pp.
1
7
.
doi:10.1016/B978-0-12-821656-9.00001-8
.
Pyrzynska
K.
2019
Removal of cadmium from wastewaters with low-cost adsorbents
.
J. Environ. Chem. Eng.
7
,
102795
.
doi:10.1016/j.jece.2018.11.040
.
Rehman
K.
,
Fatima
F.
,
Waheed
I.
&
Akash
M. S. H.
2018
Prevalence of exposure of heavy metals and their impact on health consequences
.
J. Cell. Biochem.
119
,
157
184
.
doi:10.1002/jcb.26234
.
Reuben
A.
,
Caspi
A.
,
Belsky
D. W.
,
Broadbent
J.
,
Harrington
H.
,
Sugden
K.
,
Houts
R. M.
,
Ramrakha
S.
,
Poulton
R.
&
Moffitt
T. E.
2017
Association of childhood blood lead levels with cognitive function and socioeconomic status at age 38 years and with IQ change and socioeconomic mobility between childhood and adulthood
.
JAMA
317
,
1244
1251
.
doi:10.1001/jama.2017.1712
.
Tibebe
D.
,
Hussen
M.
,
Mulugeta
M.
,
Yenealem
D.
,
Moges
Z.
,
Gedefaw
M.
&
Kassa
Y.
2022
Assessment of selected heavy metals in honey samples using flame atomic absorption spectroscopy (FAAS), Ethiopia
.
BMC Chem.
16
,
87
.
doi:10.1186/s13065-022-00878-y
.
Umoafia
N.
,
Joseph
A.
,
Edet
U.
,
Nwaokorie
F.
,
Henshaw
O.
,
Edet
B.
,
Asanga
E.
,
Mbim
E.
,
Chikwado
C.
&
Obeten
H.
2023
Deterioration of the quality of packaged potable water (bottled water) exposed to sunlight for a prolonged period: An implication for public health
.
Food Chem. Toxicol.
175
,
113728
.
doi:10.1016/j.fct.2023.113728
.
Wright
K. F.
2015
Is your drinking water acidic? A comparison of the varied pH of popular bottled waters
.
J. Dent. Hyg. JDH
89
(
Suppl 2
),
6
12
.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).

Supplementary data