Analysis of Heavy Metals and Health Risk Assessment of Selected Energy Drinks in Nigeria

Overview

Hamza and colleagues (Gombe State University Department of Pure and Applied Physics; Yobe State University Department of Physics) quantified six heavy metals (cobalt Co, chromium Cr, cadmium Cd, arsenic As, nickel Ni, lead Pb) in thirty commercially available energy drinks purchased from Nigerian local markets, comprising twenty-three liquid formulations and seven powdered formulations, and applied United States Environmental Protection Agency (USEPA) frameworks for non-carcinogenic and carcinogenic risk evaluation. Liquid samples were digested using aqua regia (HCl:HNO₃ in a 3:1 ratio) on a Kjeldahl heater for 4–5 hours then analysed by atomic absorption spectrophotometry (Bulk 205 AAS). Powdered samples (3 g per sample) were pressed into 25 mm pellets, covered with 6 µm polypropylene X-ray film, and analysed by X-ray fluorescence (XRF). The authors computed Hazard Quotient (HQ) and Hazard Index (HI) for non-carcinogenic risk and Cancer Risk (CR) for carcinogenic risk for both adult (60 kg body weight; 0.6 L/day ingestion rate; 24-year exposure duration) and child (20 kg body weight; 0.3 L/day ingestion rate; 6-year exposure duration) receptors, with reference doses and cancer slope factors drawn from USEPA Exposure Factors Handbook (1997, 2001, 2011) and Iwuanyanwu & Chioma (2017). Cross-brand comparisons used one-way ANOVA for normally distributed analytes and Kruskal-Wallis tests for non-normal distributions; Pearson/Spearman correlations were computed between metals and between metals and HI/CR. The authors report that HI exceeded 1 in twelve of the thirty samples (notably the powdered EJ, KR, KK, PS, PE, AL and the liquid SY, 3H, SD, BS, MP), CR exceeded 1×10⁻⁴ for Cd and Ni in all samples and for Co, Cr, and Pb in multiple samples, with children at higher risk than adults across all calculations.

Key numbers

All concentrations are reported in the source as mg L⁻¹ for both liquid and powdered formulations on a sample-as-analysed basis. The authors used WHO drinking-water reference values as the regulatory comparator (Table 2 final row: Co 0.05, Cr 0.05, Cd 0.003, As 0.01, Ni 0.02, Pb 0.01 mg L⁻¹). The source does not declare an instrument limit of detection; values reported as ”−” (Not Detected) appear across multiple sample/analyte combinations and are treated here as left-censored at the unspecified instrument detection floor. The heavy-metal concentration values in Table 2 of this paper match the corresponding values in the companion Hamza et al. 2025 paper (Determination of Some Physicochemical Properties, Heavy Metals and Micronutrients of Some Energy Drinks Available in Nigeria) and the Babayo et al. 2026 paper (Contamination Factor, Metal Pollution Index and Estimated Daily Intake of Heavy Metals in Some Selected Energy Drinks in Nigeria) — the three publications share a single underlying analytical dataset and differ only in the downstream analysis they apply.

Reference values for exposure health risk assessment (Table 1, p. 3–4)

Reference dose RfD (mg kg⁻¹ day⁻¹): Cu 0.04, Ni 0.02, Cr 0.5, Mn 0.014, Zn 0.3, Fe 0.7, Pb 0.014, Cd 0.0005, Co 0.003, As 0.0003. Cancer Slope Factor CSF (mg kg⁻¹ day⁻¹)⁻¹: Cd 6.3, Cr 0.5, As 1.5, Pb 0.0085, Ni 0.84 (the source prints “084”, interpreted as 0.84 per standard USEPA IRIS values), Co 1.1, Mn 0.02. Per-receptor HQ, HI, and CR calculations use Equation 1 (HQ = C × IR × EF × ED / AT × ABW × RfD), Equation 2 (HI = ΣHQ), and Equation 3 (CR = C × IR × EF × ED × CSF / AT × ABW).

Concentration of heavy metals in the thirty energy drinks (Table 2, p. 4–5)

Concentrations are reported in mg L⁻¹ on a sample-as-analysed basis. The Table 2 column headers in the source list units in scientific notation (Co ×10⁻², Cr ×10⁻², Cd ×10⁻³, As ×10⁻³, Ni ×10⁻², Pb ×10⁻²); the values below are decoded to absolute mg L⁻¹. ”−” = Not Detected.

Per-analyte detected ranges (sample-as-analysed mg L⁻¹):

• Co: 0.0017 (MP) – 0.0835 (EJ powder); the source’s discussion (p. 5) states cobalt exceeded the cited WHO 0.05 mg L⁻¹ comparator in EJ powder, MP, and KR powder. Independent re-count of Table 2 against the 0.05 mg L⁻¹ ceiling shows three samples exceed: EJ (0.0835 powder), PR (0.0826 liquid), and KR (0.0534 powder). MP (0.0017) does not exceed; the discussion text appears to refer to MP’s Cr value rather than Co.
• Cr: 0.0025 (AL powder) – 0.4159 (MP liquid); chromium exceeded the cited WHO 0.05 mg L⁻¹ comparator in MP (0.4159), KR (0.3764 powder), BH (0.2563), ES (0.2501 powder), HS (0.0983), BS (0.0854), SD (0.0672), SY (0.0641). No speciation was performed; values are total chromium.
• Cd: 0.0015 (IP) – 0.0566 (MP); cadmium exceeded the cited WHO 0.003 mg L⁻¹ comparator in essentially all twenty-one samples in which it was detected, with MP (0.0566) showing the highest value.
• As: 0.0002 (HS) – 0.0451 (EJ powder); total arsenic (no inorganic arsenic (iAs)/total arsenic (tAs) speciation) exceeded the cited WHO 0.01 mg L⁻¹ comparator in the two highest-concentration powdered samples EJ (0.0451), KR (0.0316), and KK (0.0249).
• Ni: 0.0015 (AR) – 0.0984 (OR); nickel exceeded the cited WHO 0.02 mg L⁻¹ comparator in numerous samples including OR (0.0984), FL (0.0942), WB (0.0982), RB (0.0875), SD (0.0794), PW (0.0652), EJ powder (0.0624), HD (0.0625), KK powder (0.0573), PS powder (0.0573), ME (0.0608), 3H (0.0557), IP (0.0516), BH (0.0478), ES powder (0.0473), AL powder (0.0432), BS (0.0432), PR (0.0451), and BR (0.0365). (Note that this paper cites the WHO Ni comparator as 0.02 mg L⁻¹ — consistent with the Babayo et al. 2026 companion paper — while the companion Hamza et al. 2025 paper cites 0.07 mg L⁻¹; the present wiki page reports each paper’s own cited comparator faithfully.)
• Pb: 0.0154 (KK powder) – 0.2092 (EJ powder) among detected samples; lead exceeded the cited WHO 0.01 mg L⁻¹ comparator in every detected sample (eleven samples: SY, RB, XC, 3H, BS, PR, EJ, KR, KK, PE, AL), with the powdered EJ (0.2092) and KR (0.1754) showing the highest concentrations.

Hazard Quotient and Hazard Index for adult and child receptors (Table 3, p. 5–7)

HQ values are reported in scientific-notation column headers (Co ×10⁻¹, Cr ×10⁻⁴, Cd ×10⁻¹, As ×10⁻², Ni ×10⁻², Pb ×10⁻¹) and decoded below to absolute HQ values. HI is the unscaled sum. Dash (−) indicates HQ not reported by the source (corresponds to a Not-Detected concentration in Table 2). For each sample the source reports adult and child rows.

Per the source’s discussion text (p. 7): HQ(Cr) and HQ(Ni) were below 1 in every sample for both receptors; HQ(Co) exceeded 1 in SY, PR, EJ, KR, and PS (the source-text wording groups these by adult or child wherever either exceeds); HQ(Cd) exceeded 1 in essentially all detected samples (the discussion specifies MP as the highest); HQ(As) exceeded 1 in EJ and KR (and reaches the threshold in the child receptor at HD = 0.185 and at MP child = 0.280 — sub-1 but elevated); HQ(Pb) exceeded 1 in SY, EJ, KR, and PE for at least one receptor. HI exceeded 1 in twelve samples (per the source’s worded summary): SY, 3H, SD, BS, MP, EJ, KR, KK, PS, PE, AL (and one further sample whose code the source text spells “BSR” — interpreted as a typo for BS, already in the list — see Verification notes on the typos). Children carry higher HI than adults across all samples, consistent with the lower ABW (20 kg vs 60 kg) and lower IR (0.3 vs 0.6 L/day) ratio (the IR ratio is 0.5 but the ABW ratio is 0.333, so the net child-vs-adult risk ratio is ~1.5×).

Carcinogenic Risk for oral ingestion, adult only (Table 4, p. 8–9)

CR values are reported in scientific-notation column headers; the printed PDF headers (Co ×10⁴, Cr ×10⁻⁴, Cd ×10⁻⁴, As ×10⁻⁵, Ni ×10⁴, Pb ×10⁻⁴) have the Co and Ni exponents printed without a negative sign — independent recomputation against Equation 3 confirms the actual values are on a ×10⁻⁴ basis (e.g., SY adult CR(Co) = 0.0215 × 0.6 × 365 × 24 × 1.1 / (8 760 × 60) = 2.365×10⁻⁴, matching the printed numerical magnitude and the source’s USEPA “troublesome” comparator of 1×10⁻⁴). The decoded values in the table below use the corrected ×10⁻⁴ exponent for the Co and Ni columns. Per the source’s text on p. 9, USEPA considers ILCR 1×10⁻⁶ – 1×10⁻⁴ as acceptable and ILCR > 1×10⁻⁴ as troublesome. Children-receptor CR values are not tabulated in Table 4.

Per the source’s discussion text (p. 9): CR for As and Pb were below 1×10⁻⁴ in most samples (the source also mentions Mn, which is not present in the Table 4 panel — see Verification notes); CR(Co) exceeded 1×10⁻⁴ in SY, BS, VE, PR, IP, CX, EJ, KR, KK, and PS; CR(Cr) was below 1×10⁻⁴ in PW, FL, PR, SK, PE, and AL and above 1×10⁻⁴ in the remaining samples; CR(Cd) and CR(Ni) were above 1×10⁻⁴ in every sample with a detected concentration.

Cross-brand comparison of heavy metal levels (Table 5, p. 9)

The source tested heavy-metal concentrations across the thirty samples (sample type and brand factor combined) using ANOVA for normally distributed analytes and Kruskal-Wallis for non-normal distributions, with Tukey HSD post-hoc.

Correlation between metals and between metals and HI/CR (Table 6, p. 9–10)

Summary of heavy-metal contamination patterns and risk contributions (Table 7, p. 10)

Methods (brief)

Thirty energy drinks (twenty-three liquid and seven powdered) were randomly purchased from local markets in Nigeria. Liquid samples were digested using the aqua regia method: precisely 10 mL of each energy drink was measured into a digestion flask, mixed with concentrated HCl and HNO₃ in a 3:1 ratio, and digested in a fume hood on a Kjeldahl heater for 4–5 hours until the solution became pale yellow, indicating complete decomposition of organic matter. After cooling, the digest was diluted with deionized water, filtered, and adjusted to 100 mL. The final solution was analysed using a Bulk 205 Atomic Absorption Spectrophotometer per the manufacturer’s instructions. Powdered samples (3 g each) were pressed into 25 mm diameter pellets using a hydraulic press, covered with a 6 µm polypropylene film, and placed in the X-ray fluorescence (XRF) excitation chamber for quantitative elemental analysis under a time-controlled irradiation program; the generated spectra were used to construct calibration curves. The source does not specify whether flame-AAS or graphite-furnace-AAS was used, does not report per-analyte wavelengths, does not declare instrument limits of detection or quantification, does not report certified-reference-material recoveries (or name the XRF reference materials), and does not specify replicate structure per sample.

Health risk assessment followed USEPA guidelines (USEPA 2001, 2011), with the Hazard Quotient (HQ = C × IR × EF × ED / AT × ABW × RfD; Eq. 1, p. 3), Hazard Index (HI = ΣHQ; Eq. 2, p. 3), and Cancer Risk for oral ingestion (CR = C × IR × EF × ED × CSF / AT × ABW; Eq. 3, p. 3) computed for both adult (60 kg ABW; 0.6 L/day IR; 24-year ED; 8 760-day AT) and child (20 kg ABW; 0.3 L/day IR; 6-year ED; 2 190-day AT) receptors using EF = 365 days/year for both. Reference doses (RfD; mg kg⁻¹ day⁻¹) used were Co 0.003, Cr 0.5, Cd 0.0005, As 0.0003, Ni 0.02, Pb 0.014; cancer slope factors (CSF; mg kg⁻¹ day⁻¹)⁻¹) used were Co 1.1, Cr 0.5, Cd 6.3, As 1.5, Ni 0.84, Pb 0.0085. (RfD and CSF values for Cu, Mn, Zn, and Fe are also given in Table 1 but those analytes were not measured in this paper’s heavy-metals panel.) Cross-brand comparisons used one-way ANOVA for normally distributed analytes and Kruskal-Wallis for non-normal distributions, with Tukey HSD post-hoc; metal-metal and metal-risk-index correlations used Pearson or Spearman as appropriate.

No metal speciation was performed: arsenic is recorded as total arsenic (tAs), and chromium is recorded as total chromium (Cr) — no hexavalent chromium (Cr-VI) distinction is offered by the source despite the discussion text invoking “chromium (VI)” carcinogenic risk on p. 5 (the underlying measurements remain total Cr).

Evidence Fitness

This source contributes USEPA-style oral-ingestion health risk indices (HQ, HI, CR) for six heavy metals across the same Nigerian energy-drinks dataset reported in the Hamza et al. 2025 and Babayo et al. 2026 companion papers. The principal limitations bearing on pooling eligibility and synthesis weight are:

(i) Same-dataset overlap with the companion Hamza et al. 2025 (Determination of Some Physicochemical Properties, Heavy Metals and Micronutrients of Some Energy Drinks Available in Nigeria) and Babayo et al. 2026 (Contamination Factor, Metal Pollution Index and Estimated Daily Intake of Heavy Metals in Some Selected Energy Drinks in Nigeria) papers. The thirty sample codes (SY, RB, PH, PW, XC, HS, 3H, WB, BR, HD, BH, OR, SD, BS, ME, VE, FL, PR, SK, IP, MP, AR, CX, EJ, KR, KK, PS, PE, AL, ES) and the Co, Cr, Cd, As, Ni, and Pb values in Table 2 of this paper match the corresponding values in both companion papers. The three publications share a single underlying analytical dataset and differ only in the downstream analysis they apply: hamza2025 adds physicochemical parameters (pH, turbidity, TDS, conductivity), the four micronutrients (Cu, Fe, Mn, Zn), and multiple-regression analyses; babayo2026 adds Contamination Factor, Metal Pollution Index, and Estimated Daily Intake calculations; this paper adds Hazard Quotient, Hazard Index, Cancer Risk, ANOVA/Kruskal-Wallis cross-brand comparisons, and metal-vs-risk-index correlation analyses. Synthesis must avoid triple-counting the underlying occurrence values as three independent observations of the Nigerian energy-drinks population; read the three papers as one dataset when combining the concentrations. The overlap is recorded with the source.

(ii) No declared analytical limit of detection or quantification. The ”−” (ND) attribution is repeated across Table 2 without an explicit numerical floor. The lack of declared LOD/LOQ prevents pool-eligibility decisions to be made under standard censored-data treatment.

(iii) No certified reference material or recovery data reported for the AAS pathway. The XRF pathway mentions calibration-curve construction from generated spectra but does not name the certified reference material vendor or composition.

(iv) Two distinct analytical methods used on a single dataset (AAS for liquids; XRF for powders). Different matrix-effects, sensitivity, and detection-limit characteristics apply to the two methods; pooling liquid and powder values within the same analyte column risks confounding analytical-method effects with sample-type effects.

(v) No metal speciation. Arsenic is reported as total elemental arsenic (recorded as tAs); chromium is reported as total chromium without Cr(VI) speciation despite the discussion text invoking “chromium (VI)” carcinogenic risk (the underlying measurements remain total Cr); mercury, aluminium, tin, and antimony are not in the analyte panel. Among the ten HMTc/HMI analytes (Pb, tAs, Cd, methylmercury (MeHg), total mercury (tHg), iAs, Ni, aluminum (Al), Cr-VI, Sn), this source covers Pb, tAs (no iAs), Cd, Ni, and Cr (no Cr-VI) — five of ten in part, with the speciation caveats noted.

(vi) WHO Ni comparator listed as 0.02 mg L⁻¹ in Table 2 (consistent with the WHO drinking-water health-based guideline used by the Babayo et al. 2026 companion paper), whereas the Hamza et al. 2025 companion paper used 0.07 mg L⁻¹. The two values originate from different WHO publications; the present wiki page reports each paper’s own cited comparator faithfully and does not arbitrate which is authoritative.

(vii) Table 2 lists units as “mg/L” for both liquid and powdered samples. For powdered samples this implicitly assumes a reconstitution basis that the source does not state — the source’s discussion text on p. 1 reports powdered concentrations using mg/g units (“Cobalt (Co) concentrations ranged from 0.12 to 0.85 mg/L in liquid samples and 0.45 to 1.32 mg/g in powdered samples… Chromium (Cr) concentrations were 0.08 to 0.67 mg/L in liquids and 0.35 to 1.10 mg/g in powders, while cadmium (Cd) ranged from 0.01 to 0.05 mg/L and 0.04 to 0.12 mg/g”), but the Table 2 powder rows use the same “mg/L” header as the liquid rows and the actual numerical values match the liquid-basis figures used in the companion Hamza et al. 2025 and Babayo et al. 2026 papers. This is a paper-internal abstract-vs-table inconsistency — see Verification notes — and the wiki page records the Table 2 values on the as-tabulated mg L⁻¹ basis.

(viii) HQ scientific-notation column headers. Table 3 prints HQ values with column-header multipliers (Co ×10⁻¹, Cr ×10⁻⁴, Cd ×10⁻¹, As ×10⁻², Ni ×10⁻², Pb ×10⁻¹); the wiki page decodes these to absolute HQ values. The source’s text-narrative summaries (“HQ greater than 1 in samples…”) are stated in terms of absolute HQ.

(ix) Discussion-text reference to “Mn” in CR discussion. The source’s CR text on p. 9 states “The CR values of As, Pb and Mn in all the energy drinks samples were less than 1×10⁻⁴” — but Mn is not in this paper’s analyte panel (it appears in the RfD/CSF reference Table 1 but no Mn concentrations are tabulated in Table 2). The wiki page records this as an apparent discussion-text carry-over from the companion Hamza et al. 2025 paper which did measure Mn.

Evidence tier set to C. The source is primary research, open-access peer-reviewed (International Journal of Science, Engineering and Technology, Vol 14:2, 2026), but with the methodological caveats above (no declared replicate structure, no declared LOD/LOQ, no CRM recovery data for AAS, mixed-method dataset, no metal speciation, abstract-vs-table unit inconsistency for powder values, and the discussion-text Mn carry-over). The HQ, HI, and CR values in Tables 3 and 4 are dependent on the underlying Table 2 concentration values, which are themselves co-pooled with the companion Hamza et al. 2025 and Babayo et al. 2026 papers as a single dataset rather than three independent observations.

Implications

• Certification: contributes USEPA-style oral-ingestion health risk indices (HQ, HI, CR) for the sports-energy-drinks HMTc category (Category 5) for the Nigerian retail market. The HI exceeds 1 in twelve of the thirty samples (for at least one of adult or child receptors), and the CR exceeds the USEPA “troublesome” threshold 1×10⁻⁴ for Cd and Ni in every sample with detected concentration. These values share the underlying analytical dataset with the companion Hamza et al. 2025 (Determination of Some Physicochemical Properties, Heavy Metals and Micronutrients of Some Energy Drinks Available in Nigeria) and Babayo et al. 2026 (Contamination Factor, Metal Pollution Index and Estimated Daily Intake of Heavy Metals in Some Selected Energy Drinks in Nigeria) papers and complement the prior Bunu et al. 2023 Kogi-State (Atomic Absorption Spectroscopic (AAS) Analysis of Heavy Metals and Health Risks Assessment of some Common Energy Drinks) and Bayelsa-State (Heavy Metals Quantification and Correlative Carcinogenic-Risks Evaluation in Selected Energy Drinks Sold in Bayelsa State Using Atomic Absorption Spectroscopic Technique) Nigerian data, plus the Polish-market Czarnek et al. 2024 (Nutritional Risks of Heavy Metals in the Human Diet—Multi-Elemental Analysis of Energy Drinks) and Jordanian-market Al-Sayyed et al. 2024 (Screening for the Presence of Some Heavy Metals, Total Soluble Solids and Caffeine Contents in Some Energy Drinks Sold in Jordanian Market) comparators. The three Hamza/Babayo Gombe-State-University dataset publications together (n = 30, 23 liquid + 7 powdered) form a single observation block for the Nigerian energy-drinks occurrence picture.
• Courses: useful as a teaching reference for (1) the USEPA HQ/HI/CR framework applied to a finished beverage occurrence dataset; (2) the importance of declared LOD/LOQ and CRM recoveries for trace-metal analysis of finished beverages; (3) the importance of separating analytical-method effects (AAS vs XRF) from sample-type effects (liquid vs powder) when pooling mixed-method datasets; (4) the importance of speciation (Cr vs Cr-VI; tAs vs iAs) for downstream toxicology interpretation, particularly when the same paper invokes Cr-VI carcinogenicity in discussion while measuring only total Cr; (5) the recurring pattern in low-resource analytical reporting where a single underlying dataset generates multiple downstream publications across CF/MPI/EDI, HQ/HI/CR, and physicochemical/micronutrient analyses; (6) the importance of cross-receptor comparison (adult vs child) when reporting HI and CR.
• App: contributes Nigerian-market HI and CR indices for the packaged energy-drink product class on a single-dataset, sample-as-analysed basis. Per-sample brand identities are not disclosed by the source.
• Discovery: the source’s reference list includes earlier Nigerian-beverage heavy-metals surveys (James et al. 2018, Bunu et al. 2023, Hamza et al. 2025, Enuneku et al. 2025, Ajani et al. 2025, Izah et al. 2017) and the USEPA Exposure Factors Handbook editions cited for the HRA parameter set.

Provenance notes

Open-access publication in International Journal of Science, Engineering and Technology (IJSET), Vol 14, Issue 2, 2026, pp. 1–11. ISSN (Online): 2348-4098; ISSN (Print): 2395-4752. No DOI is printed on the article. Distributed under the Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0/). Corresponding author: Hamza Abubakar Hamza, Department of Pure and Applied Physics, Gombe State University, P.M.B. 127, Gombe, Nigeria. Co-authors: Ishiyaku Ibrahim Babayo (Gombe State University), Ahmadu Muhammad Aliyu (Gombe State University), Yusuf Mohammed Auwal (Yobe State University, Damaturu), Abubakar Danjuma Bajoga (Gombe State University), Hankouraou Seydou (Gombe State University). Funding, conflict of interest, and ethical-considerations statements are not declared in the published article. Accessed via the Manual Fetch Discovery autopilot.

Related evidence

• Lead
• Cadmium
• Arsenic
• Chromium
• Nickel
• Cobalt
• Sports/Energy Drinks

Update history

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