Bunu et al. 2023 — Heavy metal occurrence and carcinogenic-risk evaluation of energy drinks sold in Bayelsa State, Nigeria

Bunu and colleagues (Niger Delta University, Wilberforce Island; Bayelsa Medical University, Yenagoa) quantified lead, cadmium, iron, and zinc in eleven energy-drink brands purchased from general markets in Amassoma and Yenagoa, Bayelsa State, Nigeria, using atomic absorption spectrophotometry after concentrated-nitric/perchloric-acid wet digestion. The authors computed Estimated Daily Intake (EDI), Chronic Daily Intake (CDI), and Target Hazard Quotient (THQ) per sample against WHO permissible-limit and EPA Reference-Oral-Dose comparators, framing the study as a carcinogenic-risk evaluation. The principal finding is that every one of the eleven samples exceeded the WHO 0.01 mg L⁻¹ permissible limit for lead (Table 1 range 0.018–0.332 mg L⁻¹), while cadmium was below the detection floor (<0.002 mg L⁻¹) across all samples, iron sat below the WHO 1.0–3.0 mg L⁻¹ band (0.026–1.85 mg L⁻¹), and zinc sat below the WHO 5.00 mg L⁻¹ ceiling (<0.002–0.493 mg L⁻¹). Despite the uniform lead exceedance against the WHO drinking-water-equivalent ceiling, the authors compute Pb THQ values of 0.029–0.286 (all <1) and conclude that no carcinogenic health risk is associated with consumption.

Key numbers

All concentrations are reported in the source as mg L⁻¹ on an as-sold beverage basis. The source does not report a replicate structure (n per sample), an instrument limit of detection, certified-reference-material recovery, or analytical blank-correction details. The instrument is identified only as “Atomic Absorption Spectrometer, Model D1971/4691” (Materials and Methods, p. 1). The Cadmium column for every sample is reported as “<0.002 mg L⁻¹”, which is treated as the de facto Cd detection floor for this study; Zn values reported as “<0.002 mg L⁻¹” are similarly treated as below-detection.

Element-symbol convention used by the source. The source uses the symbol “Pd” throughout (in all four tables, the abstract, the discussion, and the conclusion) to denote the element measured as lead. The paper’s introduction explicitly identifies the metal as lead (“lead, cadmium, iron, and zinc”), and the cited WHO 0.01 mg L⁻¹ permissible limit and 3.5 × 10⁻³ EPA reference oral dose correspond to lead, not to palladium. “Pd” in the source’s tables is therefore a clear typographical error for “Pb”. This wiki page records the values as lead (Pb) throughout and uses the abbreviation Pb in the metals frontmatter per CLAUDE.md Part 14.

Heavy metal concentrations in eleven energy-drink samples (Table 1, p. 2, mg L⁻¹)

*Reported as “Pd” in the source; recorded here as Pb (see element-symbol convention note above).

Per-analyte detected ranges across the panel of eleven samples:

• Pb: 0.018–0.332 mg L⁻¹ (all eleven samples above the WHO 0.01 mg L⁻¹ permissible limit; eleven of eleven exceedances).
• Cd: all eleven samples <0.002 mg L⁻¹ (below the de facto detection floor; the source does not declare an instrument LOD, so 0.002 mg L⁻¹ is the assumed analyte-specific reporting floor).
• Fe: 0.026–1.85 mg L⁻¹ (eleven of eleven below the WHO 3.0 mg L⁻¹ upper bound; one sample, D11 at 1.85 mg L⁻¹, sits above the 1.0 mg L⁻¹ lower bound of the WHO 1.0–3.0 mg L⁻¹ band; D7 at 1.65 mg L⁻¹ and D10 at 1.27 mg L⁻¹ likewise sit above the 1.0 mg L⁻¹ lower bound).
• Zn: detected in five of eleven samples at 0.047–0.493 mg L⁻¹; six samples <0.002 mg L⁻¹; all reported values well below the WHO 5.00 mg L⁻¹ ceiling.

Estimated Daily Intake (Table 2, p. 2, mg L⁻¹ as reported by source)

EDI formula reported by the source: EDI = Cm × Cf × Df / Bw, where Cm = metal concentration, Cf = conversion factor (0.085), Df = daily intake of drinks (30 cL), Bw = average body weight (65 kg).

Chronic Daily Intake (Table 3, p. 3, mg L⁻¹ as reported by source)

CDI formula reported by the source: CDI = Cm × EDI × EFi × IR / Bw × AT, where ED = exposure duration (24 y), EFi = exposure frequency (365 d/y), IR = intake rate (0.03 kg/person/day), AT = average time (365 d × 24 y = 8,760).

Target Hazard Quotient (Table 4, p. 3)

THQ formula reported by the source: THQ = CDI / RfD; CDI = Chronic Daily Intake, RfD = Reference Oral Dose.

Per-analyte THQ ranges: Pb 0.029–0.286 (eleven of eleven THQ <1); Cd uniformly 0.11 (1.1 × 10⁻¹) across all samples (computed from the censored Cd <0.002 mg L⁻¹ measurement); Fe 0.143–8.000 (eight of eleven samples Fe THQ ≥1, namely D1, D2, D4, D6, D7, D9, D10, and D11); Zn 0–0.0167.

Regulatory and comparator anchors cited by the authors

• WHO permissible limits (Table 1, p. 2): Pb 0.01 mg L⁻¹, Cd 0.003 mg L⁻¹, Fe 1.0–3.0 mg L⁻¹, Zn 5.00 mg L⁻¹.
• EPA Reference Oral Doses (Table 1, p. 2): Pb 3.5 × 10⁻³, Cd 5 × 10⁻⁴, Fe 7 × 10⁻³, Zn 3 × 10⁻¹ mg/kg/day.
• WHO daily-intake standards (Table 2, p. 2): Pb 3.6 µg/day/kg, Cd 1 µg/day/kg, Fe 20.5 mg/day, Zn 11 mg/day.
• The source cross-references a prior Southwest-Nigeria energy-drinks study (Bunu et al. 2023, Pharmacology and Toxicology of Natural Medicines, the source’s [24]) which the present authors report found Mg, Zn, Pb, As, and Al above recommended concentrations in some samples.

Methods (brief)

Eleven energy-drink samples (labelled D1–D11) were purchased in no particular order from supermarkets in Amassoma and Yenagoa, Bayelsa State, Nigeria. The source names eleven commercial brands in the methods inventory; this wiki page does not reproduce those brand identifiers because the source does not attach specific brand identities to the D1–D11 sample labels (see Brand firewall note in Verification notes). Glassware was decontaminated by 24-hour soak in 10% v/v nitric acid solution followed by purified-water rinse, dust-free air-drying, and storage.

Sample digestion followed the 2002 American standard test method described by Bray et al. 2004 (the source’s reference [17]). About 20 mL of sample plus 10 mL of nitric acid were transferred into a beaker and heated at 120–150 °C on a heating mantle in a fume cupboard, with periodic HNO₃ addition to prevent dryness. After approximately 40 minutes, 2 mL of perchloric acid (HClO₄) was added and digestion continued until a clear solution was obtained. After cooling, the digestate was transferred to a 25 mL volumetric flask and made up to volume with distilled water. A parallel procedure (per the source’s text, p. 1–2) used 50 mL of well-mixed sample with 4 mL concentrated HNO₃ and 2 mL HClO₄, evaporated near dryness, refluxed on a hot plate until a light clear residue was obtained, treated with an additional 2 mL HNO₃, filtered to remove insoluble materials, brought to 25 mL with distilled water, and stored in a 125 mL polypropylene bottle prior to AAS aspiration. The wiki page records both digestion descriptions as the source presents them; the source does not explain why two parallel digestion procedures are described or which one produced the values reported in Table 1.

Metal concentrations were quantified using an Atomic Absorption Spectrometer, Model D1971/4691. The instrument was described as a “solar thermo elemental atomic absorption spectrometer” in the Table 1 header. The source does not specify whether flame or graphite-furnace AAS was used, does not specify wavelengths for each analyte, does not report instrument limits of detection or limits of quantification, does not report certified-reference-material recoveries or analytical blank-correction details, and does not specify whether each sample was run as a single measurement or in replicate. Data analysis used “an Excel spreadsheet, 2016”.

The Cadmium column reports every sample as “<0.002 mg L⁻¹”; the Zinc column reports six samples (D2, D3, D4, D5, D7, D8) at the same “<0.002 mg L⁻¹”; and the control (deionized water) sample reports “<0.009 mg L⁻¹” for lead. These values are treated as analyte-specific reporting floors for the present study.

EDI was computed per sample as Cm × 0.085 × 0.30 / 65, with Cm in mg L⁻¹, the conversion factor 0.085 unitless, daily-drink-intake volume 30 cL (0.30 L), and body weight 65 kg (Table 2 footnote, p. 2). CDI was computed per sample as Cm × EDI × EFi × IR / (Bw × AT), with ED = 24 y, EFi = 365 d/y, IR = 0.03 kg/person/day, and AT = 8,760 d (Table 3 footnote, p. 3). THQ was computed per sample as CDI/RfD using the EPA Reference Oral Doses reported in Table 1 (Table 4 footnote, p. 3).

No metal speciation was performed: lead (recorded as “Pd” in the source), cadmium, iron, and zinc are reported as total elemental concentrations.

Evidence Fitness

This source contributes direct primary occurrence values for finished energy drinks sold in two Bayelsa State, Nigeria markets. The principal limitations bearing on pooling eligibility and synthesis weight are:

(i) Small sample size and no declared replicate structure. Eleven samples are reported, but the source does not state whether each tabulated value is a single measurement, a duplicate mean, or a triplicate mean. This is adequate for an exploratory market-screening report but limits inference to the broader Nigerian energy-drinks population.

(ii) No declared analytical limit of detection or quantification. The instrument-LOD floor is inferred from the <0.002 mg L⁻¹ entries in the Cd column and from the <0.009 mg L⁻¹ entry in the deionized-water control for Pb, neither of which the source explicitly identifies as the LOD. The lack of declared LOD/LOQ and the lack of certified-reference-material recovery data prevent independent verification of analytical quality control.

(iii) No certified reference material or recovery data reported. The Bray et al. 2004 digestion is referenced but no spike-recovery, CRM (e.g., NRCC, NIST), or method-blank data are presented.

(iv) No metal speciation. Inorganic vs total Cr, MeHg vs total Hg, iAs vs tAs distinctions are not applicable to the present analyte panel (Pb, Cd, Fe, Zn are routinely reported as total elemental). The chromium, mercury, arsenic, aluminum, tin, nickel, antimony, and uranium panels were not measured.

(v) EDI/CDI/THQ computations report values not arithmetically reproducible from the stated formulas. Applying the EDI formula in the Table 2 footnote (EDI = Cm × Cf × Df / Bw with Cf=0.085, Df=0.30, Bw=65) to D1’s Pb concentration of 0.276 mg L⁻¹ yields 1.08 × 10⁻⁴, not the 0.108 reported in Table 2 for D1. The reported value is approximately 1,000× the formula’s output; a unit-basis or scaling factor not stated in the source’s footnote appears to have been applied. The Cd EDI column reports a uniform 0.001 mg L⁻¹ for all eleven samples despite all eleven Cd concentrations being censored at <0.002 mg L⁻¹ — i.e., the source has propagated a single below-detection value through the EDI computation without flagging the censoring. The CDI and THQ tables share the same internal-arithmetic anomaly. These downstream-computation tables should not be relied upon for pool-eligible exposure or risk inputs without re-derivation from the Table 1 concentrations using a stated, internally consistent formula. The Table 1 raw concentration values are recorded here as the authoritative dataset.

(vi) Paper-internal numerical inconsistency between the abstract/discussion and Table 1 for Pb. The Discussion (p. 3) states “The concentration of Lead for all the samples of energy drinks was between 0.018 and 0.276 mg L⁻¹” but Table 1 reports D11 at 0.332 mg L⁻¹, above 0.276. The Table 1 figures are recorded as the authoritative dataset on the present page.

(vii) Paper-internal numerical inconsistency between the abstract/discussion and Table 3 for Fe CDI. The Discussion (p. 3) and abstract both state Fe CDI ranges 0.001 to 0.050, but Table 3 reports D11 Fe CDI at 0.056. The Table 3 figures are recorded as the authoritative dataset.

(viii) Paper-internal element-symbol typographical error. The source uses “Pd” (the symbol for palladium) throughout to denote lead. The associated WHO 0.01 mg L⁻¹ permissible limit and 3.5 × 10⁻³ EPA RfD are the lead values; palladium is not a routine AAS analyte at the cited concentrations in beverages. The present wiki page records the analyte as lead (Pb).

(ix) Conclusion characterizes the THQ result as “no carcinogenic health potential risks” despite every sample exceeding the WHO Pb permissible limit. The source’s conclusion is a non-carcinogenic risk statement only — THQ measures non-carcinogenic hazard, not carcinogenic risk — and does not address that every sample exceeds the cited WHO 0.01 mg L⁻¹ Pb compliance ceiling by a factor of 1.8 to 33. The wiki records the THQ values as reported and the WHO-exceedance pattern as reported, without reproducing the conclusion’s framing.

Evidence tier set to C. The source is primary research, peer-reviewed (International Journal of Chemistry Research, Innovare Academic Sciences, Vol 7, Issue 4, 2023), but with the methodological caveats above (no declared replicate structure, no declared LOD/LOQ, no CRM recovery data, internal-arithmetic anomalies, internal-numerics inconsistencies between body text and tables, and a paper-wide element-symbol typographical error). Tier-B would require declared replicate structure, declared LOD/LOQ, ICP-MS or graphite-furnace AAS for trace analytes, CRM-anchored QC, and reconciled internal numerics. The Table 1 raw concentrations are pool-considerable for Pb, Fe, and Zn at C-tier weight with explicit notation of the (i)–(ix) caveats; the downstream EDI/CDI/THQ tables are not pool-eligible as computed.

Implications

• Certification: contributes direct primary occurrence values for the sports-energy-drinks HMTc category (Category 5 row 9), specifically for the Nigerian retail market. The Pb column reports universal exceedance against the WHO 0.01 mg L⁻¹ compliance ceiling (eleven of eleven samples), with a maximum of 0.332 mg L⁻¹ at D11. The Cd column is uniformly below the 0.002 mg L⁻¹ reporting floor and contributes left-censored data only. The Fe and Zn columns sit below their WHO ceilings across the panel. These values complement the Polish-market ICP-MS data (Czarnek et al. 2024, this wiki), the Jordanian-market flame-AAS data (Al-Sayyed et al. 2024, this wiki), and the Nigerian-market data (Babayo et al. 2026, this wiki, Bauchi State). The Bunu Pb range 0.018–0.332 mg L⁻¹ for Bayelsa State, when juxtaposed against the Babayo Bauchi-State distribution, will be considered by the synthesis pass for the Nigerian-energy-drinks occurrence picture as a whole.
• Courses: useful as a teaching reference for (1) the limitations of single-laboratory AAS screening without declared LOD/LOQ or CRM recovery for trace metals in beverages; (2) the importance of internal-consistency cross-checks between abstract, discussion, and tabulated values during peer review; (3) the distinction between non-carcinogenic hazard (THQ) and regulatory-compliance ceiling (WHO permissible limit) — a uniform THQ <1 does not negate a uniform WHO-ceiling exceedance for a regulated heavy metal; (4) the propagation of below-detection censored values through downstream exposure and risk computations without flagging the censoring.
• App: contributes Nigerian-market occurrence values for the sports/energy-drinks product class. Per-brand identities are not disclosed by the source (samples are labelled D1–D11 with brand identities listed only as a collective inventory in the methods); no brand-firewall handling per CLAUDE.md Part 12 was required on the values side.
• Discovery: the source’s reference list includes a preceding Bunu-led Southwest-Nigeria energy-drinks study (Pharmacology and Toxicology of Natural Medicines, 2023, the source’s [24]) reported to find Mg, Zn, Pb, As, and Al above recommended concentrations in some samples — a candidate companion source for the Nigerian-energy-drinks occurrence picture, and an additional Aendo et al. 2019 (Thailand, the source’s [23]) carcinogenic and non-carcinogenic risk assessment of heavy metals in duck eggs and meat for cross-product comparison.

Provenance notes

Open-access article distributed under CC BY 4.0 (license declaration on p. 1 of the PDF: ”© 2023 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)”). Received 18 August 2023; revised and accepted 22 September 2023; published in International Journal of Chemistry Research, Volume 7, Issue 4, 2023, pp. 1–4. DOI: 10.22159/ijcr.2023v7i4.224. Online ISSN: 0976-5689. Journal homepage: https://ijcr.info/index.php/journal. Corresponding author: Samuel J. Bunu (pharmsamuelbunu@gmail.com). Affiliations: Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmacy, Niger Delta University, Wilberforce Island, Bayelsa, Nigeria (Bunu, George, Ebeshi); Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Bayelsa Medical University P.M.B. 178 Imgbi Road, Yenagoa, Bayelsa, Nigeria (Alfred-Ugbenbo). Acknowledgement: the Head and staff of the Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmacy, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria. Conflict of interest: none declared. Accessed via the Manual Fetch Discovery autopilot.

Wiki pages this source may touch

• lead
• cadmium
• iron
• zinc
• sports-energy-drinks

Verification notes

Element-symbol convention. The source uses “Pd” (the chemical symbol for palladium) throughout the abstract, the discussion, the conclusion, and all four tables to denote the analyte the source’s introductory text identifies as “lead” and against which the source’s tables compare to the WHO 0.01 mg L⁻¹ permissible limit and 3.5 × 10⁻³ EPA Reference Oral Dose — both of which are lead-specific values. This is a typographical error in the source; palladium is not a routine AAS-via-Bray-2004 analyte at the cited concentrations in beverages, and the introductory text explicitly identifies the four analytes as lead, cadmium, iron, and zinc. This wiki page records the analyte as lead (Pb) throughout and uses Pb in the frontmatter metals: field per CLAUDE.md Part 14. The source’s “Pd” usage is preserved in direct quotes where applicable and noted explicitly in the Key numbers section.

Speciation handling per CLAUDE.md Part 14. This source measures total elemental Pb, Cd, Fe, and Zn by AAS without speciation. Pb, Cd, Fe, Zn are recorded as such in the metals: frontmatter field (no iAs/tAs, MeHg/tHg, or Cr-VI/Cr distinctions applicable to this panel). Mercury, arsenic, chromium, aluminum, tin, antimony, nickel, and uranium were not in the source’s analyte panel and are not recorded. Among the ten HMTc/HMI analytes, this source covers Pb and Cd only (two of ten).

Products frontmatter. The products: frontmatter lists sports-energy-drinks only. The source’s matrix is energy drinks, which the wiki taxonomy locates as HMTc Category 5 row 9 (“Sports/energy drinks”) per wiki/products/sports-energy-drinks.md. The eleven samples are commercially marketed energy drinks (specifically named brands in the methods inventory consistent with the energy-drinks product class); routing to soft-drinks-carbonated-beverages as a second product would over-route on a category basis. The conservative routing is to sports-energy-drinks only.

Ingredients frontmatter. The ingredients: field is empty. The energy drinks measured are finished beverages, not single-ingredient measurements. The source does not measure heavy-metal content at the ingredient level.

Matrices frontmatter. The matrices: field uses energy-drinks (established vocabulary, used in czarnek2024-heavy-metals-energy-drinks, alsayyed2024-heavy-metals-energy-drinks-jordan, babayo2026-heavy-metals-energy-drinks-nigeria).

Jurisdictions frontmatter. NG (Nigeria). The sample population is restricted to general-market supermarkets in Amassoma and Yenagoa, Bayelsa State, Nigeria.

Brand firewall per CLAUDE.md Part 12 (strict reading, locked 2026-05-17). The source names eleven commercially marketed energy-drink brands in its Materials and Methods section as a collective inventory of the brands sampled (the eleven samples are labelled D1–D11 in all tables). The source does not attach specific brand identities to the D1–D11 sample labels, so no per-brand contamination value can be reported and no brand-by-brand ranking is implicit in the data. Nonetheless, the strict Part 12 reading prohibits reproducing the inventory list of brands in wiki page content, since doing so converts source-disclosed brand identities into a wiki-side disclosure that the named brands were sampled and quantified for heavy-metal content. The wiki page therefore describes the sample population as “eleven commercially marketed energy-drink brands purchased in no particular order from general-market supermarkets in Amassoma and Yenagoa, Bayelsa State, Nigeria” without naming the eleven brands. The methods section’s scientific-method vendor identities (Atomic Absorption Spectrometer Model D1971/4691) are retained under the Part 12 scientific-method-vendor exception locked 2026-05-17. Brand-by-brand handling, where it would be desired by the wiki/HMTc certification process, belongs in the private brand-intelligence build described in CLAUDE.md Part 26.

Wiki/HMTc firewall per CLAUDE.md Part 2. No HMTc threshold proposals, no consumer-audience risk advisories, and no synthesis claims of the form “this confirms the literature consensus that…” appear in this wiki page body. The observation that every one of the eleven samples exceeds the WHO 0.01 mg L⁻¹ Pb permissible limit is reported as the source itself reports it — as a comparison against the regulatory comparator value the source itself cited — and is not framed as an HMTc threshold recommendation or as a consumer-safety claim. The Evidence Fitness section’s flagging of the source’s own conclusion language (“no carcinogenic health potential risks”) is a methodological observation about the source’s internal logic, not a wiki-side risk advisory.

Paper-internal inconsistencies recorded faithfully and flagged.

1. The element symbol “Pd” is used throughout the source for the analyte identified as lead in the introduction. Recorded as Pb in this wiki page; the source’s “Pd” usage is preserved in direct mention.
2. The Discussion reports Pb concentration range “0.018 to 0.276 mg L⁻¹” but Table 1 D11 reports 0.332 mg L⁻¹; Table 1 is recorded as the authoritative dataset.
3. The Discussion reports Fe CDI range “0.001 to 0.050” but Table 3 D11 reports 0.056; Table 3 is recorded as the authoritative dataset.
4. The EDI values in Table 2 are approximately 1,000× the value the Table 2 footnote’s formula would yield; a unit-basis or scaling factor not stated in the footnote appears to have been applied. The Table 1 raw concentrations are the authoritative dataset; the Table 2/3/4 downstream computations are recorded as the source presents them but are flagged as not arithmetically reproducible from the stated formulas and not pool-eligible.
5. The Cd EDI column reports a uniform 0.001 mg L⁻¹ for all eleven samples despite all Cd concentrations being censored at <0.002 mg L⁻¹; the source has propagated a single below-detection value through the EDI computation without flagging the censoring.
6. The Conclusion characterizes the result as “no carcinogenic health potential risks” despite (a) every sample exceeding the WHO 0.01 mg L⁻¹ Pb permissible limit and (b) the THQ being a non-carcinogenic-hazard quotient, not a carcinogenic-risk metric. Recorded faithfully; not framed as a wiki-side risk advisory.

Audit application (2026-06-06). Fresh-context Agent subagent audit (verdict PROMOTE; all five checks ✅ clean with one ⚠️ minor on Check 1 Fe-THQ enumeration wording). Independent re-verification of the Fe THQ column against Table 4 confirmed eight of eleven samples (D1, D2, D4, D6, D7, D9, D10, D11) at Fe THQ ≥1; the original page text said “six of eleven” with a parenthetic self-correction to seven, and the audit subagent independently arrived at seven. Both pre-correction wordings under-counted because D9 (Fe THQ = 1.143) was missed. Corrected to “eight of eleven” with the full enumeration. No other audit findings warranted page changes.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.