Heavy Metal Content in Breast Milk and Contributing Environmental and Maternal Factors: A Systematic Review

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. Of 355 records screened, 22 articles were assessed full-text and 9 met inclusion criteria. The review identified Pb, Cd, Al, Cu, Cr, Hg, and As (with Ni and Zn in some studies) in breast milk across studies from Taiwan, Spain, China, Palestine, Nigeria, Egypt, and Slovenia, 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 (Chao, Taiwan, n=34); Pb 6.49 ± 5.23 ng/mL in mature milk (Lin, Taiwan, n=228); tHg geometric mean 14 ng/mL in 195/197 samples (Li, China); Cd 1.37 ± 0.94 ng/mL in colostrum (Chao, Taiwan); Al 56.45 ± 22.77 ng/mL in colostrum (Chao, Taiwan); As 1.50 ± 1.50 ng/mL in colostrum (Chao, Taiwan).

Key numbers

From the 9 reviewed studies (geographic scope: Taiwan, Spain, China, Palestine, Nigeria, Egypt, Slovenia; publication window 2013–2023):

Lead (Pb):

• Chao 2014 (Taiwan, n=34): 13.22 ± 3.58 ng/mL in colostrum; range 0.45–22.36 ng/mL across colostrum/transitional/mature milk; colostrum significantly higher than mature/transitional (p < 0.01).
• Lin 2023 (Taiwan, n=228): 6.49 ± 5.23 ng/mL in mature breast milk.
• Shawahna 2021 (Palestine, n=80): 11/80 (13.8%) samples exceeded the WHO recommended lead level; adjusted odds ratio of breast-milk Pb ≥ 5 ng/mL was 4.96 (95% CI 1.10–22.38) for women in the major (urban) region versus rural locations.
• Philip-Slaboh 2023 (Nigeria): Pb detected in 95.8% of diabetic and 95.8% of non-diabetic mothers’ milk (mirrored prevalence as reported).
• Tratnik 2019 (Slovenia): mean Pb 0.23 ng/mL (units as reported by the review).

Cadmium (Cd):

• Chao 2014 (Taiwan, n=34): 1.37 ± 0.94 ng/mL in colostrum (highest among lactation stages).
• Castro 2021 (Spain): Cd detected in 14% of samples; below 0.10 mg/L in those samples.
• Philip-Slaboh 2023 (Nigeria): Cd detected in 84.7% of diabetic versus 86.1% of non-diabetic mothers’ milk.
• Mansour 2015 (Egypt): mean Cd 0.025 ± 0.024 ng/mL (Zagazig); 0.348 ± 0.154 ng/mL (Belbees); 0.012 ± 0.122 ng/mL (Abokabeer).

Mercury (tHg):

• Li 2014 (China): geometric mean 14 ng/mL; detectable in 195/197 samples.
• Lin 2023 (Taiwan, n=228): mean 0.76 ± 0.98 ng/mL in mature milk.
• Philip-Slaboh 2023 (Nigeria): Hg detected in 68.1% of diabetic versus 72.2% of non-diabetic mothers’ milk.
• Tratnik 2019 (Slovenia): mean Hg 0.14 (units as reported by the review).

Arsenic (tAs):

• Chao 2014 (Taiwan, n=34): 1.50 ± 1.50 ng/mL in colostrum.
• The review reports mean arsenic concentrations around 0.6 ng/mL for both diabetic and non-diabetic women in another included study.
• Philip-Slaboh 2023 (Nigeria): As detected in 63.9% of diabetic versus 62.5% of non-diabetic mothers’ milk.
• Tratnik 2019 (Slovenia): mean As 0.18 (units as reported by the review).

Aluminum (Al):

• Chao 2014 (Taiwan, n=34): 56.45 ± 22.77 ng/mL in colostrum.
• Motas 2021 (Spain): Al among elements highest in industrial-zone mothers (versus agricultural zone).

Chromium (Cr) and copper (Cu):

• Castro 2021 (Spain): both Cu and Cr present in all samples but did not exceed 0.5 ng/mL; Cr also among elements highest in the agricultural-zone subset reported by Motas 2021 alongside Mg and Fe.

Other elements reported by the review:

• Castro 2021 (Spain): Mg detected in 75% of samples, median 33.35 mg/L (IQR 31.23–37.88 ng/mL — units as reported, with apparent unit inconsistency between mg/L and ng/mL in the source); Zn detected in 55% of samples at ~2.09 mg/L (range 0.95–4.18; units as reported); Ba 18%, Cd 14%; Se and Sr detected in over 82% of samples.
• Motas 2021 (Spain): Zn, As, Pb, Hg, and Ni were highest in industrial-zone mothers; Mg, Cr, and Fe were highest in agricultural-zone mothers.

Notes on the source: the review reproduces values from the constituent papers without re-normalizing units; ng/mL versus mg/L versus µg/L appear inconsistently and in a few places (Castro Zn and Mg, Tratnik means) the units in the table column do not align with the units in the body text. These are flagged here rather than silently corrected because the original studies are the authoritative source for each number; this page reports what the review states.

Methods (brief)

Systematic review following PRISMA 2020 (PROSPERO ID CRD42024545030). Databases: PubMed, Scopus, Science Direct. Search string combined (“Heavy metals” OR “metals”) AND (“Human Milk” OR “Breast Milk”) AND (“Associated Factor” OR “Influenced Factor”). Inclusion: full-text English-language primary research articles 2013–2023 reporting quantitative heavy-metal concentrations in human breast milk plus maternal/environmental factors. Exclusion: review articles, animal studies, full-text-inaccessible articles, and articles lacking measurable heavy-metal data. Two independent reviewers screened with third-reviewer arbitration. Quality appraisal used the JBI critical-appraisal checklist (results tabulated in the paper’s Table 1; most included studies received “Yes” on most criteria). 355 records screened → 22 full-text assessed → 9 included. Narrative synthesis; no meta-analysis.

Implications

Certification: Synthesizes cross-national data on Pb, Cd, tHg, tAs, Al, Cr, Cu, and Ni in breast milk, including biomonitoring detections in industrial/urban versus rural/agricultural zones and in diabetic versus non-diabetic mothers. The Taiwan colostrum Pb values (~13 ng/mL) and the Palestine urban/rural adjusted odds ratio (aOR 4.96) provide biomonitoring context for maternal-infant exposure, not product-occurrence data for threshold setting.

Courses: Useful for teaching how review authors connect diet (seafood, canned food, fruit), water consumption, smoking, and regional environment (industrial versus agricultural zones; urban versus rural) to breast-milk heavy-metal concentrations. Keep the associated factors as source-reported exposure context rather than as wiki-side dietary guidance.

App: Breast milk is not in the app’s ingredient-list model but the biomonitoring data from this review supports the health-effects sections on infant exposure pathways.

Microbiome: Al, Pb, and Cd exposure via breast milk during infant gut colonization may be relevant to metal-microbiome teaching context, but this review does not directly study microbiome outcomes.

Wiki pages this source may touch

• breastmilk
• lead
• cadmium
• mercury-total
• arsenic-total
• aluminum
• chromium
• copper
• nickel

Verification notes

• 2026-05-19 (manual-fetch-kimi merge-enhance, Claude Opus 4.7 v2 skill): rebuilt the page from the source PDF. Fixes: (a) raw_handle replaced with the MFK_ form per current convention; (b) jurisdictions corrected from [TW, ES, PL, CN, PS, SL] to [TW, ES, CN, PS, NG, EG, SI] — the 9 included studies cover Taiwan, Spain, China, Palestine, Nigeria, Egypt, and Slovenia; the prior list misidentified Slovenia as Sierra Leone (SL) and added Poland (PL), which is only cited in the discussion via Szukalska 2021 as a non-included reference; (c) sample_population rewritten to reflect the actual 7 countries; (d) Pb attribution corrected — 13.22 ± 3.58 ng/mL colostrum is Chao 2014 (n=34), not n=228, while 6.49 ± 5.23 ng/mL mature-milk Pb is Lin 2023 (n=228); (e) Hg attribution corrected — GM 14 ng/mL (195/197) is Li 2014 China, while 0.76 ± 0.98 ng/mL in n=228 is Lin 2023 Taiwan; the prior page conflated these; (f) Cr / Zn transposition removed — the prior page wrote that Cr was “approximately 4× higher than Hg at 2.09 mg/L,” but Castro 2021 actually reports Cr ≤ 0.5 ng/mL in all samples and the 2.09 mg/L value belongs to Zn; (g) Palestine aOR 4.96 (95% CI 1.10–22.38) re-attributed cleanly to Shawahna 2021 (the source paper has an ambiguous in-text citation but Table 2 confirms the attribution); (h) metals expanded to include Cu and Ni, both of which the review reports findings on; (i) added access_url from DOI; license normalized to CC BY-SA 4.0; updated advanced to 2026-05-19; (j) added unit-inconsistency flag for Castro 2021 Zn and Mg, where the review carries mixed mg/L and ng/mL labels — flagged here rather than silently corrected because the constituent studies are the authoritative source.
• Brand firewall (Part 12): no sampled-product brand naming in this source; methods-section vendor naming not applicable to a narrative review.
• Wiki/HMTc firewall (Part 2): no synthesis claims, threshold proposals, or consumer guidance in this page; biomonitoring detection numbers are reported as source-stated and not converted into wiki-side dietary or certification recommendations.
• Prior verification note (2026-05-17 cross-vendor strict Part 12 recheck) is superseded by this 2026-05-19 pass.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.