Oduro et al. 2023 - Heavy metals in cereal-based breakfast meals, Kumasi, Ghana

Oduro et al. measured total As, Cd, Cr, Mn, Ni, and Pb in 54 locally produced cereal-based breakfast meals purchased from markets in the Kumasi Metropolis, Ghana. The sample set included breakfast cereals, biscuits, and bread types, grouped for reporting by cereal base: wheat, rice, maize, oats, and millet/sorghum. The paper also estimated dietary intake, hazard quotients, and cancer risk across infants, toddlers, children, adolescents, adults, and older adults, and attempted an in-vitro bioaccessibility screen.

Key numbers

Total concentrations in Table 1 are mg/kg in powdered cereal-based food.

Source comparator values shown in Table 1: As 0.2 mg/kg, Cd 0.1 mg/kg, Cr 1 mg/kg, and Pb 0.2 mg/kg. The table shows no maximum-limit comparator for Mn or Ni. As, Cd, Cr, and Pb were above their shown comparators in every cereal class.

Bioaccessibility screen: most in-vitro extracts were below detection limits, so bioaccessibility was not calculated and relative bioavailability was assumed to be 1 in risk calculations. The source lists extract detection limits of As <1.7 ug/L, Cd <2.2 ug/L, Cu <1.0 ug/L, Ni <2 ug/L, and Pb <1.4 ug/L. The Cu line is retained here as a source-side note even though Cu was not one of the Table 1 analytes.

Selected estimated dietary intake (EDI) findings from Table 2, expressed as EDI x 10^-3 mg/kg bw/day:

Hazard quotient findings from Table 3:

• Cd HQ was above 1 in every age group and cereal class. Table 3 ranges: infants 11.35 to 12.55; toddlers 12.14 to 13.43; children 4.10 to 4.54; adolescents 5.05 to 5.70; adults 4.67 to 4.98; elderly 4.56 to 5.05.
• Ni HQ was above 1 in every age group and cereal class. Table 3 ranges: infants 22.35 to 25.88; toddlers 23.92 to 27.70; children 8.08 to 9.36; adolescents 10.86 to 12.58; adults 9.50 to 11.00; elderly 8.98 to 10.41.
• Cr, Mn, and Pb HQ values were below 1 in all Table 3 rows.
• As HQ was above 1 for infants and toddlers in all cereal classes, but below 1 for the older age groups in Table 3.

Cancer-risk findings from Table 4:

• Pb CR is reported as x 10^-5 and ranges from 2.28 to 7.46 across age groups and cereal classes. The Results text describes Pb cancer risk as below the USEPA threshold, while also later stating that As, Cd, and Pb are above the de minimis 10^-6 level.
• As CR is reported as x 10^-3 and ranges from 3.0 to 9.82 across age groups and cereal classes.
• Cd CR is reported as x 10^-3 and ranges from 61.53 to 188.25 across age groups and cereal classes.

Methods

The study purchased 54 locally produced cereal-based breakfast meals from markets in the Kumasi Metropolis in December 2021: 31 breakfast cereals, 20 biscuits, and 3 bread types. Samples were grouped by the main cereal class: wheat, rice, maize, sorghum/millet, and oats. Samples were milled with a stainless-steel laboratory blender for about 20 minutes and sieved through a <250 micron mesh.

Total-metal screening used a Niton XL3t GOLDD+ XRF spectrometer calibrated with NIST 2711. Quantification used ICP-MS after microwave acid digestion: approximately 0.5 g sample, 9 mL concentrated nitric acid, 3 mL hydrochloric acid, 15 minutes in an Anton Paar Multiwave GO Plus microwave system, dilution to 40 mL, and USEPA Method 200.8 analysis.

In-vitro bioaccessibility used a USEPA glycine extraction protocol: 1.00 +/- 0.05 g sample in 100 +/- 0.5 mL glycine extraction fluid at pH 1.5, end-over-end rotation in a 37 +/- 2 deg C water bath for 1 hour, filtration through a 0.45 um cellulose acetate filter, and ICP-MS analysis. The source text prints “USEPA Method 2008.8” in this subsection; the preceding ICP-MS method section and reference list identify USEPA Method 200.8.

Quality control included procedure blanks, reagent blanks, NIST 1575a control samples, duplicates, and standard-reference-material recoveries. Reported recoveries were As 92 +/- 11%, Cd 85 +/- 5%, Cr 91 +/- 16%, Mn 90 +/- 9%, Ni 98 +/- 6%, and Pb 99 +/- 6%. Method detection limits ranged from 0.5 mg/kg for As to 3.4 mg/kg for Mn, and duplicate relative percent differences ranged from 9% to 14%.

Health-risk calculations used estimated dietary intake, hazard quotient, and cancer-risk equations. EDI was calculated in Palisade @Risk software using cereal-meal intake values of 265 g/day for adolescents, adults, and older adults, and 106.9 g/day for infants, toddlers, and children. The study used body weights of 62 kg for adolescents, 74 kg for older adults, 70 kg for adults, 23 kg for children, and 12 kg for infants/toddlers. The RfDs listed by the source were Cr 1.500, Cd 0.001, Pb 0.00357, Ni 0.02, Mn 0.140, and As 0.0003 mg/kg bw/day. Potency factors for cancer risk were As 1.5, Cd 15, and Pb 8.5 x 10^-3.

Speciation and methods caveats

• Arsenic is total arsenic. The paper does not perform inorganic-arsenic speciation.
• Chromium is total Cr. The paper does not perform Cr-VI speciation.
• The study reports total concentrations in powdered finished foods, not raw grain.
• Bioaccessibility values were not calculated because the in-vitro extract concentrations were below detection limits.
• Table 2 and the narrative text conflict for at least one Cd EDI value: the text says wheat Cd EDI reaches 13.59 x 10^-3 mg/kg bw/day in toddlers, while Table 2 lists wheat at 12.36 and millet/sorghum at 13.43. This page follows Table 2.
• The paper’s cancer-risk narrative treats Pb inconsistently: it states that Pb cancer risk is below the USEPA threshold, but also states that mean cancer-risk values for As, Cd, and Pb are above the de minimis 10^-6 level.

Implications

Standards work: This source contributes Ghana-market finished-food evidence for total As, Cd, Cr, Mn, Ni, and Pb in cereal-based breakfast foods. It is relevant to breakfast cereals, grain-based biscuits/snacks, bread-and-baked goods, and the wheat/rice/maize/oat/non-rice-grain ingredient routes. The strongest source-specific signals are the high Cd and Ni hazard quotients and the clear need to preserve total-As rather than iAs interpretation.

Courses: The paper is useful for teaching the difference between total concentration, in-vitro bioaccessibility, EDI, HQ, and cancer-risk outputs. The source’s below-LOD bioaccessibility extracts sit in tension with the conservative assumption of relative bioavailability equal to 1 for risk calculations.

App: The sample set can support Ghana/Kumasi jurisdiction-labeled occurrence context for cereal-based breakfast foods, provided displays preserve the finished-food basis, total-As speciation caveat, and the broad cereal-class grouping rather than treating the data as raw-grain measurements.

Wiki pages this source may touch

• arsenic-total
• cadmium
• chromium
• manganese
• nickel
• lead
• wheat
• rice
• maize
• oat
• cereals
• non-rice-grains
• breakfast-cereals
• snacks-crackers-biscuits
• bread-and-baked-goods

Verification notes

• Merge-enhanced 2026-05-18 from the full manual-fetch PDF path and SHA-256 recorded in frontmatter.
• Replaced older HMTc-threshold and cross-corpus comparison language with source-only implications.
• Corrected older HQ ranges for Cd and Ni; Table 3 reports Cd and Ni HQ values above 1 in all age groups and cereal classes, not below 1.
• Corrected the comparator framing: Table 1 shows comparator values for As, Cd, Cr, and Pb, but no maximum-limit comparator for Mn or Ni.
• Strict brand-firewall check: no consumer brands are named; instrument, reference-material, and software vendor names are retained only as Methods details under the Part 12 scientific-method exception.

Page history

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