O’Connor et al. 2026 — U.S. infant biomonitoring for toxic elements from human milk and infant formula
This systematic review evaluates whether infant biospecimens in the United States show exposure to arsenic, cadmium, lead, mercury, or PFAS in relation to human milk and/or infant formula feeding. The paper is an a4 exposure source, not a product-occurrence paper: it synthesizes infant urine and blood biomonitoring evidence rather than measuring contaminants in formula products directly. Its main contribution is to document how thin the U.S. infant biomonitoring evidence base still is despite longstanding concern about toxic elements in infant feeding.
Key numbers
- The review identified 7 articles from 4 studies out of 6799 unique records screened through 2025.
- The New Hampshire Birth Cohort contributed infant urinary arsenic in 4 articles, cadmium in 2, lead in 1, and mercury in 1, with data collected between 2009 and 2019.
- Three additional studies reported infant blood lead concentrations between 1975 and 1994.
- One NHBC article reported a geometric mean urinary total arsenic concentration minus arsenobetaine of 0.23 ug/L (95% CI: 0.21, 0.25) for 462 infants between 2012 and 2019.
- Another NHBC article reported mean urinary total arsenic including arsenobetaine of 0.6 ug/L (range: ⇐0.05-4.8) for 204 infants in 2009.
- In 187 infants from 2014 to 2019, median urinary arsenic concentrations increased 14.8-fold from 6 weeks to 1 year (P < 0.001).
- Across the NHBC feeding comparisons, urinary arsenic was highest in infants exclusively fed formula, intermediate in mixed-fed infants, and lowest in infants exclusively fed human milk (P < 0.0001).
Methods (brief)
The authors conducted a registered series of systematic reviews with database searches through 2 April 2025 across CAB Abstracts, CENTRAL, CINAHL, Embase, and MEDLINE, plus targeted manual searching. Included studies had to report infant biospecimen contaminant concentrations in relation to human milk only, infant formula only, or mixed feeding. Risk of bias was assessed with ROBINS-E, and a technical expert panel reviewed sample collection and contaminant assessment methods.
Evidence Fitness
Evidence Fitness is strong for a4 exposure and biomonitoring context and weak for a1 product occurrence. The paper does not provide routeable product concentrations for formula rows, but it is directly useful for the health/exposure layer because it ties feeding mode to infant urinary arsenic and summarizes the much thinner cadmium, lead, and mercury infant biomonitoring record in the United States.
Implications
Certification: This review does not set formula occurrence values, but it strengthens the vulnerable-population case for keeping infant-feeding evidence separate from adult exposure framing and for tracking biomonitoring literature alongside occurrence papers.
Health: The review supports infant exposure pages by showing that existing U.S. biomonitoring evidence is sparse, geographically narrow, and dominated by one cohort, leaving a surveillance gap rather than a settled exposure picture.
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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.
| Commit | Date | Description |
|---|---|---|
| ae6c129 | 2026-07-01 | feat(auth): large login + role-based signup screens (design, burgundy) |