Mgbemena et al. 2026 — Nutrients and Heavy Metals in Baby Milk and Infant Formula, Nigeria
This 2026 study from Michael Okpara University of Agriculture (Umudike, Nigeria) analyses proximate composition, macro/micro minerals, and heavy metal concentrations in 8 baby milk (milk-based) and 12 infant formula (cereal-based) products purchased from Umuahia, Abia State. Atomic absorption spectrometry (AAS) was used for heavy metals (Pb, Ni, Cu, Cd, Cr); Target Hazard Quotient (THQ) and Hazard Index (HI) frameworks were applied. Lead concentrations in baby milk exceeded WHO limits; cadmium posed the most significant risk by HI, with an aggregate HI of 15.55 across all samples, indicating potential non-carcinogenic health concern for infants consuming these products.
Key numbers
Instrument: Perkin Elmer Analyst Model 400 AAS; aqua regia digestion (HCl:HNO3 3:1), 90 °C for 2 h. Concentrations in mg/kg (dry weight).
WHO (2023) limits cited by authors for comparison: Pb 0.03 mg/kg, Ni 0.07 mg/kg, Cu 0.7 mg/kg, Cd 0.2 mg/kg, Cr 0.3 mg/kg.
Baby Milk (n=8) heavy metal ranges (mg/kg):
- Pb: 0.07–0.14 mg/kg (70–140 µg/kg). All 8 samples exceeded the WHO limit of 0.03 mg/kg.
- Ni: 0.03–0.26 mg/kg
- Cu: 0.06–0.31 mg/kg
- Cd: 0.01–0.21 mg/kg. Samples coded A (0.01), C (0.21), D (0.08) stood out; C had the highest Cd at 0.21 mg/kg.
- Cr: 0.00–0.21 mg/kg. Samples E, F, G, H had Cr = 0.00 mg/kg; sample C and D were highest at 0.21 and 0.08 mg/kg respectively.
Infant Formula (n=12) heavy metal ranges (mg/kg):
- Pb: 0.000–0.015 mg/kg. All infant formula Pb values were below or at the WHO limit (0.03 mg/kg).
- Ni: 0.003–0.040 mg/kg
- Cu: 0.010–0.830 mg/kg (sample M was highest at 0.83 mg/kg)
- Cd: 0.006–0.043 mg/kg
- Cr: 0.000–0.006 mg/kg
Heavy metal ranking in Baby Milk: Pb > Cu > Ni > Cd > Cr. Heavy metal ranking in Infant Formula: Cu > Cd > Ni > Cr > Pb.
Risk assessment (THQ, assuming infant BW = 5 kg, daily intake = 0.1 kg/day, USEPA RfD values: Cd 0.001, Co 0.1, Cr 0.003, Pb 0.0035 mg/kg/day):
- Baby Milk: THQ for Pb ranged from 4 to 629 (i.e., massively exceeding safe threshold of 1.0), driven by the 0.07–0.14 mg/kg Pb concentrations combined with the very low RfD for Pb.
- Cadmium THQ in Baby Milk samples A, C, D exceeded 1.0 (1.6, 4.2, 2.2 respectively); sample C also had Cr THQ above 1.0.
- Infant Formula: all THQ values for all metals <1.0.
Hazard Index (HI, sum of all metal THQs across both BM and IF combined):
- Pb: HI = 4.277 (no health effect listed because individual THQ was assessed per sample, not cumulative for Pb)
- Cu: HI = 2.63
- Cd: HI = 15.55 — potential health risk flagged (HI >10 indicates possible severe chronic impact)
- Cr: HI = 3.13
Proximate composition ranges (%, dry weight): Baby Milk — moisture 3.24–6.56%, ash 2.42–3.17%, fat 11.32–28.68%, protein 11.52–16.20%, carbohydrate 50.52–72.92%. Infant Formula — moisture 7.89–9.29%, ash 1.35–2.99%, fibre 0.19–6.49%, fat 0.47–9.75%, protein 2.92–20.88%, carbohydrate 52.21–84.91%.
Macro-mineral ranges in Baby Milk (mg/kg): Ca 1391–1562, Mg 1200–1420, K 400–1340, P 890–1988, Na 250–699.
Micro-mineral ranking in both samples: Fe > Zn > Mn. Baby Milk Fe 30.00–42.01 mg/kg (none met WHO recommendation of 425.5 mg/kg); Zn 2.80–24.03 mg/kg (below WHO recommendation of 99.4 mg/kg); Mn 0.19–1.24 mg/kg.
Methods (brief)
Cross-sectional market survey in Umuahia, Abia State, Nigeria. One container per brand purchased from multiple shops over 3 months (monthly intervals). Proximate analysis by AOAC methods. Heavy metals by AAS (Perkin Elmer Analyst 400) after aqua regia digestion. No LOD/LOQ values reported. Risk assessment used THQ and HI per USEPA framework; BW assumed at 5 kg for all infants (no age stratification), daily intake 0.1 kg/day. The study does not specify arsenic, mercury, or total arsenic/inorganic arsenic measurements; these analytes were not tested. No speciation data for Cr (total only) or for any other metal. Statistical analysis by ANOVA with Duncan multiple range test (p<0.05).
Implications
Certification: Lead in Baby Milk is the standout finding — all 8 baby milk samples exceeded the WHO limit of 0.03 mg/kg (30 µg/kg), with the highest at 0.14 mg/kg (140 µg/kg). By contrast, infant formula (cereal-based) Pb was low (0–15 µg/kg). The cadmium HI of 15.55 indicates that even at concentrations that appear modest (up to 0.21 mg/kg in one baby milk sample), cumulative Cd exposure across all samples exceeds safe thresholds. This is a developing-country market context (locally produced products, Abia State Nigeria). HMT&C context: sample size is small (n=8 baby milk, n=12 infant formula), method lacks LOD reporting, and risk assessment uses a blanket 5 kg BW assumption without age stratification. Use as qualitative corroborating evidence for Pb and Cd concern in locally produced African infant formula, not as quantitative concentration data for the contamination profile.
Courses: Illustrates disparity between milk-based baby milk (higher heavy metals, particularly Pb) and cereal-based infant formula (lower heavy metals) in the Nigerian market. Demonstrates how THQ values for Pb can appear extremely high (up to 629) because the RfD for Pb (0.0035 mg/kg/day) is very low relative to typical concentrations.
App: Not suitable as primary contamination profile input due to small n, missing LOD data, no speciation, and single-city Nigerian market scope. Arsenic, mercury, Al, Sn, and U were not tested.