Gnonsoro et al. 2021 — Heavy metals (Pb, Cd, Hg) in hydroalcoholic gels of Abidjan, Côte d’Ivoire
Gnonsoro and colleagues at LANADA (Laboratoire National d’Appui au Développement Agricole) and Université Félix Houphouët Boigny measured lead, cadmium, and total mercury in 30 hydroalcoholic gels (alcohol-based hand sanitizers) collected from supermarkets in Abidjan during the first weeks of the COVID-19 pandemic in March 2020. The paper reports per-sample bar charts and pooled mean ± SD with min/max for each metal, then calculates dermal chronic daily intake (CDI), hazard quotients (HQ), hazard index (HI), and incremental lifetime cancer risk (ILCR) using standard US-EPA dermal-exposure equations parameterised for an adult (70 kg body weight, 420 cm² hand surface area, 350 days/year for 30 years). All three metals were quantifiable in most samples but all sample concentrations fell below the Health Canada cosmetic-skin limits for Pb (10 mg/kg) and Cd (3.0 mg/kg) and below the US FDA Pb-as-impurity-in-colour-additives limit (20 mg/kg); no jurisdiction-specific limit was cited for Hg in this product class. The hazard index (∑HQ) was 7.10×10⁻⁵ — three orders of magnitude below the unit threshold — and the cumulative ILCR for Pb plus Cd was 3.07×10⁻⁸, two orders of magnitude below the 10⁻⁶ insignificance floor. Mercury contributed >99% of HI because Hg has the largest dermal permeability coefficient in the Kp set used (0.001 cm/h vs 0.0001 for Pb).
Key numbers
All concentration values are mg/kg in the as-purchased hydroalcoholic gel (density 0.79–0.99 g/mL; pH 5.37–7.14). Multiply mg/kg by 1000 to convert to ppb / µg/kg.
Heavy-metal concentrations in 30 hydroalcoholic gels (Source Table 6)
| Analyte | Mean ± SD (mg/kg) | Min (mg/kg) | Max (mg/kg) |
|---|---|---|---|
| Pb | 0.248 ± 0.110 | 0.122 | 0.715 |
| Cd | 0.006 ± 0.007 | <LOD | 0.024 |
| Hg (total) | 0.172 ± 0.134 | <LOD | 0.481 |
In ppb-equivalent units, Pb ranged 122–715 ppb (mean 248 ± 110 ppb), Cd ranged <LOD–24 ppb (mean 6 ± 7 ppb), and total Hg ranged <LOD–481 ppb (mean 172 ± 134 ppb).
Method performance (Source Table 4)
| Analyte | Recovery (%) | LOD (mg/kg) | LOQ (mg/kg) |
|---|---|---|---|
| Pb | 96.0 | 0.046 | 0.104 |
| Cd | 97.0 | 0.002 | 0.019 |
| Hg | 93.4 | 0.051 | 0.115 |
Physicochemical characteristics (Source Table 5)
| Parameter | Mean ± SD | Min | Max | WHO formulation-guide range |
|---|---|---|---|---|
| pH | 6.44 ± 0.46 | 5.37 | 7.14 | 6.0–7.0 (WHO 2010) |
| Density (g/mL) | 0.91 ± 0.05 | 0.79 | 0.99 | 0.8–1.0 (WHO 2009) |
Dermal exposure outputs (Source Table 8)
CDIdermal values were computed using the US-EPA Risk-Assessment-Guidance-for-Superfund dermal equation: CDI = (Cw·HSA·Kp·ABS·ET·EF·EP·CF)/(BW·AT). Parameter values (Source Table 2): Cw in mg/kg; HSA 420 cm² (adult hand surface area, both hands); Kp 0.0001 cm/h for Pb, 0.001 cm/h for Cd, 0.001 cm/h for Hg; ABS 0.001 for all metals; ET 0.05 hour/event; EF 350 day/year; EP 30 year; CF 0.001 L/cm³; BW 70 kg; AT 25,550 days (70-year non-cancer averaging time).
| Metric | Pb | Cd | Hg (total) | Total |
|---|---|---|---|---|
| CDIdermal mean (mg/kg/day) | 3.057×10⁻⁹ ± 1.35×10⁻⁹ | 1.38×10⁻⁹ ± 0.79×10⁻⁹ | 2.55×10⁻⁸ ± 1.48×10⁻⁸ | — |
| CDIdermal range (mg/kg/day) | 1.50×10⁻⁹ – 8.81×10⁻⁹ | 0 – 2.95×10⁻⁹ | 0 – 5.93×10⁻⁸ | — |
| HQdermal mean | 7.28×10⁻⁹ ± 3.23×10⁻⁹ | 1.56×10⁻⁷ ± 1.82×10⁻⁷ | 7.08×10⁻⁵ ± 5.52×10⁻⁵ | HI = 7.10×10⁻⁵ ± 5.52×10⁻⁵ |
| HQdermal range | 3.58×10⁻⁹ – 2.09×10⁻⁹ (sic) | 0 – 5.91×10⁻⁷ | 0 – 1.97×10⁻⁴ | 5.72×10⁻⁹ – 1.97×10⁻⁴ |
| ILCR mean | 2.59×10⁻⁸ ± 1.15×10⁻⁸ | 4.78×10⁻⁹ ± 1.56×10⁻⁹ | n/a (no CSF assigned) | ∑ILCR = 3.07×10⁻⁸ ± 1.33×10⁻⁸ |
| ILCR range | 1.27×10⁻⁸ – 4.77×10⁻⁸ | 0 – 1.80×10⁻⁸ | n/a | 1.27×10⁻⁸ – 8.24×10⁻⁸ |
Reference doses (RfDdermal) and cancer-slope factors (CSF) used in HQ/ILCR (Source Table 3): Pb RfDdermal 0.42 mg/kg/day, CSF 8.5 (kg·day/mg); Cd RfDdermal 0.005 mg/kg/day, CSF 6.1 (kg·day/mg); Hg RfDdermal 0.03 mg/kg/day, CSF not assigned (Hg “is not considered to create cancer” in the framework the authors used).
Source-page typographic note on the HQdermal Pb range: source Table 8 prints “3.58×10⁻⁹ – 2.09×10⁻⁹” with the upper bound apparently smaller than the lower bound — likely a typographical error in either the exponent or one of the mantissa values (a plausible intended upper bound is 2.09×10⁻⁸, consistent with the Pb CDI range 1.50×10⁻⁹–8.81×10⁻⁹ divided by RfDdermal 0.42; alternatively a transcription error in the lower bound). This page reproduces the published values verbatim rather than silently correcting; the typo does not affect mean HQ or HI conclusions.
Pearson correlation matrix (Source Table 7)
| pH | Density | Pb | Cd | Hg | |
|---|---|---|---|---|---|
| pH | 1.00 | — | — | — | — |
| Density | 0.10 | 1.00 | — | — | — |
| Pb | −0.13 | −0.09 | 1.00 | — | — |
| Cd | −0.42 | −0.12 | 0.10 | 1.00 | — |
| Hg | 0.19 | 0.11 | −0.14 | −0.10 | 1.00 |
No correlation reached statistical significance at p<0.05 for any pair (between heavy metals, between heavy metals and pH/density).
Regulatory benchmarks the source compares against
- Health Canada (Guidance on Heavy Metal Impurities in Cosmetics, 2016): Pb 10 mg/kg in cosmetic products applied to the skin; Cd 3.0 mg/kg as an impurity in cosmetic products.
- US FDA (21 CFR 74.1306, D&C Red No. 6 colour-additive listing): Pb 20 mg/kg as an impurity in colour additives used as ingredients in cosmetic products.
- BfR (Germany): Cd 5.0 mg/kg in cosmetics (BfR Stellungnahme 025/2006).
All measured Pb (max 0.715), Cd (max 0.024) and unstated-limit Hg (max 0.481) values were below all named cosmetic-product limits in this paper.
Methods (brief)
Thirty hydroalcoholic gels were collected from supermarkets across the district of Abidjan between 03 and 12 March 2020. The selection targeted “high-consumption brands” identified by prior interviews with cosmetics sellers (no statistical sampling frame; convenience sampling weighted toward popular Côte d’Ivoire-produced gels). Each sample (0.5 g aliquot) was digested in a Milestone Ethos microwave digester with 5 mL HNO₃ (65%, Merck) and 2 mL H₂O₂ (30%), then transferred to a 25-mL volumetric flask and brought to volume with ultrapure water before refrigerated storage.
Pb, Cd, and Hg were quantified by atomic absorption spectroscopy on a Spectra A100 Varian spectrophotometer (Australia) equipped with a GTA-110 graphite furnace, per AOAC Official Method 999.10. Instrument conditions (Source Table 1): nitrogen gas carrier at flow rate 4; Pb at 283.3 nm with atomisation temperature 2100 °C; Cd at 228.8 nm with atomisation temperature 1800 °C; Hg at 253.7 nm with “dosage temperature” 25 °C, consistent with cold-vapor sample introduction for mercury rather than thermal atomisation in the graphite furnace. Three replicate readings per sample, one per replicate. Calibration used standard solutions of lead and cadmium at 1 g/L (Normex) with five-point linear calibration. Spike recoveries were 96.0% (Pb), 97.0% (Cd), and 93.4% (Hg). Mercury speciation was not performed; the paper measures and reports total mercury.
Method validation followed ISO/TS 22176:2020 and AFNOR NF V 03-110:2010 (selective evaluation, working/linear ranges, repeatability, reproducibility). Values below LOD are reported as “not detected” (ND); values between LOD and LOQ are reported as “<LOQ”. Statistical analysis (mean, min, max, SD, Pearson correlation) used Statistica 7.1 (2006) and Microsoft Excel 2013; significance was reported at p<0.05.
Health-risk assessment used the US-EPA Risk-Assessment-Guidance-for-Superfund dermal pathway (Means 1989; Wu et al. 2009) with Côte d’Ivoire-specific exposure scenario parameters listed above. ILCR for Pb and Cd was computed against the 10⁻⁶ insignificance and 10⁻⁴ “troublesome” thresholds commonly used in EPA-derived cumulative-risk frameworks; the authors cite no Hg cancer slope factor.
Scope limitations the source itself acknowledges or that the wiki notes: The paper does not differentiate inorganic mercury from methylmercury and cannot support MeHg routing. It does not report per-sample replicate variance or any inter-laboratory comparison. The convenience-sampling design across “high-consumption brands” precludes treating the 30-sample distribution as representative of the full Abidjan market; the mean and SD describe the sampled set only. The paper does not report manufacturer or country of ingredient origin for individual samples; bulk-water trace-metal contamination in the Abidjan groundwater supply (Pb 0.02–2.80 mg/L, Ahoussi et al. 2008; Pb <0.001–0.04 mg/L and Cd <0.001–0.027 mg/L, Ahoussi et al. 2012) is named as one plausible upstream source of the Pb, Cd, and Hg traces detected. Detection-frequency per analyte is implied by the “<LOD” entries in the min column but is not stated as a fraction.
Implications
Certification: This paper contributes a 30-sample West-African hydroalcoholic-gel (alcohol-based hand-sanitizer) finished-product occurrence dataset on Pb, Cd, and total Hg in the as-sold gel basis. Hydroalcoholic gels are not currently an HMT&C product-row in the locked taxonomy; if HMT&C scope expands to hand-sanitizer / leave-on dermal-disinfection products, this source supports a Côte d’Ivoire-market 2020 occurrence anchor. All values were below Health Canada and US FDA cosmetic-skin limits but the paper provides no comparison to a hand-sanitizer-specific limit because none was named. Mercury is the dominant dermal-exposure driver in this product class because of its higher Kp; certification work in this space should require Hg speciation that this study did not perform.
Courses: A clean compact example of how dermal-pathway exposure modelling (CDI / HQ / HI / ILCR) layers on finished-product heavy-metal measurements in a personal-care matrix. Useful when teaching the difference between “concentrations in the product” and “estimated systemic dose to the consumer” for educator audiences. Also illustrates the typographical-error failure mode in published risk tables (the Pb HQ range in source Table 8 prints as a decreasing interval, which a careful reader catches but a downstream synthesis pass would silently propagate).
App: No food-occurrence data; do not route into any contamination_profile ingredient block. The product-class slug for hydroalcoholic gels / alcohol-based hand sanitizers is not yet in the wiki taxonomy; if added via a future Step 0 Lock, this source becomes the West-Africa-market anchor for that row.
Microbiome: No microbiome data in this source.
Verification notes
Provisional product-slug gap: The paper’s primary product matrix is “hydroalcoholic gels” (alcohol-based hand sanitisers, WHO type-1 biocidal product). No matching slug exists in the current taxonomy snapshot (2026-05-18). Closest extant slugs are products/hand-soap (rinse-off, different category) and products/body-hand-leave-on-skin-care (leave-on but skin-care-framed, not disinfectant-framed). Per task-scope constraints for this ingest, products: [] was left empty and a new-product-slug proposal is surfaced here for Karen’s Step 0 Lock workflow. Proposed slug: hydroalcoholic-gel-hand-sanitizer (or hand-sanitizer-alcohol-based-leave-on), HMTc category pending taxonomy review. Pre-COVID literature is thin; the 2020 Abidjan market study is one of the early systematic measurements of metals in this product class and may sit as an early occurrence anchor if/when the row is locked.
Year/citation styling: DOI 10.1007/s12011-021-02822-y was issued in 2021 (received 24 May 2021; accepted 6 July 2021; published online 7 September 2021); the print volume (Biological Trace Element Research vol. 200) carries 2022. Cite-key uses 2021 to match the DOI-issue year, the publication online date, and the Kimi-folder filename; the print-volume year is preserved in the publication frontmatter string.
Brand firewall (CLAUDE.md Part 12, locked 2026-05-17): The source repeatedly references “high-consumption brands” of hydroalcoholic gels sold in Abidjan supermarkets but does not name individual brand identities for the 30 sampled units; the bar charts (Figures 1 and 2) display sample-number 1–30 without brand attribution. No brand-stripping was needed in writing this page. Methods-section vendor names that ARE preserved per the 2026-05-17 carve-out for scientific reproducibility: Spectra A100 Varian spectrophotometer (Australia); GTA-110 graphite furnace; Milestone Ethos microwave digester; SHIMADZU UW4200H balance (Philippines); Lovibond SensoDirect 150 pH meter (Dortmund, Germany); Merck HNO₃; Normex Pb/Cd standards; Statistica 7.1 (2006). These are not Part 12 violations.
Wiki/HMTc firewall (CLAUDE.md Part 2): The source itself draws comparative conclusions against Health Canada and US FDA cosmetic limits and against other countries’ shower-gel literature (Nigeria Iwegbue et al. 2016, Korea Duck et al. 2018). Those source-internal comparisons are preserved as the paper’s own framing; this page does not synthesise across other wiki sources or propose HMTc thresholds. The Implications section names Hg-speciation as a future-certification requirement but does not quantify it.
Audit-trail note: This is a fresh ingest (NEW path) from the Kimi corruption-issue folder household_papers/01_AP_Countertop_Tile_Floor/. PDF content was first-pages-verified against the filename promise before frontmatter was committed (PDF title and authors match the Gnonsoro 2021 Côte d’Ivoire hydroalcoholic-gels paper as named; this slot does NOT have the filename/content corruption flagged in two earlier Basketter slots in the same subfolder per data/evidence/autonomy/manual-fetch-stops-2026-06-02.md).
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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.
| Commit | Date | Description |
|---|---|---|
| c1aef38 | 2026-06-02 | audit-queue: hamid2021-bacterial-plant-biostimulants-review → audited-promote |