Philip-Slaboh et al. 2023 — Heavy metals in diabetic and non-diabetic postpartum breast milk
This cross-sectional study compared concentrations of toxic heavy metals in breast milk from 144 postpartum mothers (72 diabetic, 72 non-diabetic) in Yenagoa, Nigeria, collected 5–6 weeks after delivery. All four metals measured (arsenic, lead, mercury, cadmium) were detected at concentrations exceeding WHO permissible limits in the majority of participants from both groups. No significant difference in metal concentrations was found between diabetic and non-diabetic mothers.
Key numbers
| Metal | Group | Mean (SD) ng/mL | Min ng/mL | Max ng/mL | WHO limit ng/mL | % above WHO limit |
|---|---|---|---|---|---|---|
| Arsenic | Diabetic | 0.63 (0.36) | 0.0 | 1.2 | 0.0 | 63.9 |
| Arsenic | Non-diabetic | 0.65 (0.36) | 0.0 | 1.2 | 0.0 | 62.5 |
| Lead | Diabetic | 13.20 (5.13) | 4.3 | 22.4 | 5.0 | 95.8 |
| Lead | Non-diabetic | 12.24 (5.13) | 3.8 | 22.3 | 5.0 | 95.8 |
| Mercury | Diabetic | 2.98 (1.91) | 0.0 | 6.3 | 1.7 | 68.1 |
| Mercury | Non-diabetic | 3.08 (1.74) | 0.0 | 6.3 | 1.7 | 72.2 |
| Cadmium | Diabetic | 3.32 (1.86) | 0.0 | 6.3 | 1.0 | 84.7 |
| Cadmium | Non-diabetic | 3.24 (1.87) | 0.0 | 6.3 | 1.0 | 86.1 |
Methods
Breast milk samples (10 mL per participant) were analyzed using Atomic Absorption Spectrophotometry with graphite furnace (GFAAS; PinAAcle 900AA) for lead, cadmium, and arsenic, and Direct Mercury Analyzer (DMAS 80A) for mercury. Samples were digested with 65% nitric acid in a microwave digestion system at 90°C for 60 minutes. Detection limit: 1 ng/mL for GFAAS; 0.005 ng/mL for DMAS. Each sample was analyzed twice and results averaged.
Implications
This study establishes that breast milk contamination with all four primary heavy metals of concern to infant health is endemic in Yenagoa’s environment, independent of maternal diabetes status. The high prevalence of concentrations exceeding WHO limits (>62% for arsenic and mercury, >84% for cadmium, >95% for lead) reflects environmental contamination from crude oil extraction, illegal refining, and agricultural activities in the Niger Delta region. Breast milk appears to be a bioaccumulation medium for environmental exposure; the postpartum period does not selectively mobilize metals from maternal bone or tissue stores relative to non-pregnant lactation. Findings underscore the need for ingredient-specific contamination baselines in Nigerian-produced infant formulas and dietary supplements as alternatives to breast milk when maternal environmental exposure is documented.
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