Overview
This systematic review and meta-analysis pooled data on metal(loid) concentrations from 42 studies across Sub-Saharan Africa and Mediterranean Europe to quantify regional differences in lactational infant exposure. Weighted mean concentrations revealed substantial disparities: Sub-Saharan Africa showed significantly higher cadmium, lead, and mercury in breast milk, while Mediterranean Europe had elevated selenium and iron. Key determinants included maternal smoking, dietary patterns, occupational exposure, and water source.
Key numbers
Weighted mean concentrations by region (µg/L):
| Metal | Sub-Saharan Africa (n samples) | Mediterranean Europe (n samples) | p-value |
|---|---|---|---|
| Aluminum | 12.65 ± 4.27 (44) | 35.99 ± 101.43 (92) | 0.13 |
| Arsenic | 0.72 ± 0.82 (160) | 1.07 ± 1.41 (410) | 0.003 |
| Cadmium | 12.38 ± 1.21 (569) | 0.22 ± 0.51 (1089) | <0.0001 |
| Mercury (total) | 2.01 ± 1.37 (120) | 0.95 ± 4.32 (410) | 0.008 |
| Lead | 14.96 ± 8.10 (980) | 1.16 ± 4.00 (1074) | <0.0001 |
| Nickel | — | 5.27 ± 12.63 (360) | — |
| Chromium | — | 5.23 ± 23.64 (360) | — |
Sub-Saharan Africa study population: Cd range 0.01–29 µg/L; Pb range 2.15–38 µg/L. One Ghana study (Asamoah-Antwi et al., 2020) measured both total Hg (0.40 ± 0.35 µg/L) and methylmercury (0.18 ± 0.15 µg/L) in mature milk from 48 mothers.
Methods
Systematic review adhering to PRISMA 2020 guidelines with database searches (PubMed, Scopus, Google Scholar through December 2023) for studies reporting metal(loid) concentrations in human breast milk of healthy women from Sub-Saharan Africa or Mediterranean Europe. Quality assessed using 7-point scale (6-7 high, 4-5 moderate, ≤3 low). Weighted mean and pooled standard deviation calculated by region and analyte; regional differences tested via independent sample t-test.
Implications
Elevated cadmium and lead in Sub-Saharan African breast milk represent direct infant toxicological concern requiring urgent public health response. The systematic quantification of regional disparities supports certification and regulatory thresholds tuned to local exposure contexts. Identified determinants (smoking, diet, occupational exposure, water quality) are actionable targets for courses and brand education.
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