This systematic review, registered on PROSPERO (ID: CRD42024545030), searched PubMed, Scopus, and Science Direct for primary studies published 2013–2023 reporting heavy metals in human breast milk and contributing maternal/environmental factors. Nine articles met inclusion criteria. The review identified Pb, Cd, Al, Cu, Cr, Hg, and As in breast milk across multiple countries, and found that food intake (seafood, fruit, canned food), water consumption, smoking, regional location, and medical conditions were associated factors. Key quantitative findings drawn from the reviewed studies include: Pb concentrations 13.22 ± 3.58 ng/mL in colostrum (Taiwan); tHg geometric mean 14 ng/mL in China; Cd 1.37 ± 0.94 ng/mL in colostrum (Taiwan); Al 56.45 ± 22.77 ng/mL in colostrum (Taiwan); As 1.50 ± 1.50 ng/mL (Taiwan).
Key numbers
From the 9 reviewed studies (geographic scope: Taiwan, Spain, Palestine, China, Sierra Leone, Poland, Mexico; dates 2013–2023):
Lead (Pb):
- Taiwan colostrum (Chao et al. 2014, n=228): 13.22 ± 3.58 ng/mL (= 13.22 µg/L); 6.49 ± 5.23 ng/mL average in another Taiwan cohort
- Palestine: elevated prevalence of Pb in urban-dwelling women (aOR 4.96; 95% CI 1.10, 22.38) vs. non-urban
Cadmium (Cd):
- Taiwan colostrum: 1.37 ± 0.94 ng/mL
- Across reviewed studies: generally <0.10 ng/mL; 14% detection rate in one Spanish study
Mercury (tHg):
- China (GM): 14 ng/mL (195/197 samples detectable); another study: 0.76 ± 0.98 ng/mL in 228 samples
Arsenic (tAs):
- Taiwan colostrum: 1.50 ± 1.50 ng/mL
- Mean across reviewed studies: ~0.6 ng/mL
Aluminum (Al):
- Taiwan colostrum: 56.45 ± 22.77 ng/mL
Chromium (Cr):
- Present in all reviewed samples in one Spanish study; did not exceed WHO limits but concentration approximately 4× higher than Hg at 2.09 mg/L in one study (range 0.95–4.18 ng/mL; note: units may be ng/mL in source)
Methods (brief)
Systematic review following PRISMA 2020. Databases: PubMed, Scopus, Science Direct. Search terms in English. Inclusion: full-text primary studies 2013–2023 reporting quantitative HM data in breast milk. Excluded: review articles, animal studies, conference abstracts. Two independent reviewers with third-reviewer arbitration. Quality appraisal using JBI tool. No meta-analysis; narrative synthesis. Nine articles included in final synthesis.
Implications
Certification: Synthesizes cross-national data on heavy metals in breast milk, confirming that Pb, Cd, tHg, tAs, Al, and Cr are consistently detected worldwide. The Taiwan colostrum Pb values (13 ng/mL) are among the highest in the recent literature and reflect urbanization and dental amalgam exposure as contributors.
Courses: Useful for teaching the contribution of diet, water, smoking, and regional environment to breast milk heavy metal concentrations. The identified associated factors (seafood for As, smoking for Pb) translate to practical dietary guidance for lactating mothers.
App: Breast milk is not in the app’s ingredient-list model but the biomonitoring data from this review supports health-effects sections.
Microbiome: Al, Pb, and Cd exposure via breast milk during infant gut colonization is directly relevant to metal-microbiome interaction; cross-link when those pages are built.