Heavy Metal Index

data-gap-wishlist-2026-05-09

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Data-Gap Wishlist — 2026-05-09

External candidate papers identified for the HMTc Category 1 data-gap cells via PubMed E-utilities queries. Each entry shows the PMID, year, title, journal, OA status (PMC available or paywalled), and the (subcategory × analyte) cells the paper would address.

The PubMed query strategy targeted the most-acute data gaps from the Phase 5 master summary’s readiness roll-up: MeHg in any IandC subcategory, Cr-VI speciation in cereals/purees/snacks, second sample-level Pb/Cd/tAs source for infant rice cereal, Ni/Al/Sn rice-cereal-specific or puree-specific sample-level data, and Al in baby cereals.

Acquisition attempt status

The autonomous run made multiple attempts at PMC OA PDF fetch via different endpoints. Update after retry: the PMC IDs returned by my initial elink PMID→PMC mapping were partly citing or related PMCs rather than the originally-targeted papers’ PMCs. After reverse-verifying via PMC esummary, the actual papers behind those PMCs are different from what was first targeted. Specifically:

  • PMC11050093 is Toledo 2024 “Essential and Toxic Elements in Infant Cereal in Brazil: Exposure Risk Assessment” (Int J Environ Res Public Health 21(4):381) — not Mathebula 2019 as initially assumed. This is itself a high-value paper directly relevant to the rice cereal and non-rice cereal subcategories. License CC BY. Newly added to the wishlist.
  • PMC7065688 is Igweze 2020 “Public Health and Paediatric Risk Assessment of Aluminium, Arsenic and Mercury in Infant Formula Milks and Baby Foods” (Sultan Qaboos Univ Med J 20(1):e63-e70). This is the originally-targeted paper (PMID 32190371). License CC BY-ND.
  • PMC11125859 is Song 2024 “Development of a Fast Method Using ICP-MS Coupled with…” (Toxics 12(5):325) — methodology paper, lower direct value than originally hoped. Vacchina 2021 (PMID 33428550) does not appear to have its own PMC entry.

Acquisition still blocked. Both https://pmc.ncbi.nlm.nih.gov/articles/PMC<id>/pdf/ (returns 1.8 KB HTML interstitial “Preparing to download”) and the FTP-mirror HTTPS path https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/... (returns HTTP 404) failed from this autonomous environment. The PMC OA bulk API correctly returned tar.gz package URLs, but those URLs returned 404 when the ftp:// scheme was rewritten to https://. The next-session paths to try are: (a) actual FTP fetch via ftplib (autonomous environment may need DNS resolution to ftp.ncbi.nlm.nih.gov); (b) NCBI’s EFetch XML endpoint https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pmc&id=PMC<id>&retmode=xml for the JATS XML which contains the full text without a PDF; (c) Karen’s manual download via a logged-in browser session.

The Mathebula 2019 PubMed→PMC mapping needs to be redone — the first elink call surfaced PMC11050093 (Toledo 2024) as a citing paper, not Mathebula’s own PMC. If Mathebula 2019 has its own PMC entry it can be re-discovered with a tighter elink call (linkname=pubmed_pmc).

Highest-priority OA candidates (close direct gaps)

Newly-discovered: Toledo 2024 — infant cereal toxic elements (Brazil)

  • PMC11050093 (2024) “Essential and Toxic Elements in Infant Cereal in Brazil: Exposure Risk Assessment” — Int J Environ Res Public Health 21(4):381. Toledo MC et al. License: CC BY. Surfaced when verifying the PMC IDs returned by the original elink call.
    • Closes (potentially) sample-level Pb, Cd, tAs, possibly iAs cells for rice-based and non-rice infant cereal subcategories — depending on whether the paper splits by rice presence.
    • Brazilian market subset; would supply a second A-tier sample-level source for infant cereal cells currently at Path A thin.
    • Highest gap-filler value among confirmed-OA candidates given how many cells it could touch.

Cr-VI speciation gap — highest value

  • PMID 30931809 (2019) “Cr(VI) and Cr(III) in milk, dairy and cereal products and dietary exposure assessment” — Food Additives & Contaminants Part B: Surveillance. PMC11050093 (OA; download PDF and ingest as mathebula2019-crvi-criii-milk-dairy-cereal-products or per first-author derivation).

    • Closes Cr-VI cells for: infant-formula-powder-non-soy (currently n_a_tier=1 Soares 2000 only); infant-formula-powder-soy-based (currently n_a_tier=0); baby-cereals-dry-rice-based and baby-cereals-dry-non-rice (currently both n_a_tier=0).
    • Author scope per title: milk, dairy, and cereal products; dietary exposure assessment included. Apply two-axis row-fit on ingest.

  • PMID 33428550 (2021) “Chromium speciation analysis in raw and cooked milk and meat samples by species-specific isotope dilution and HPLC-ICP-MS” — Food Additives & Contaminants Part A. PMC11125859 (OA).

    • Closes Cr-VI/Cr-III cells for: milk-based formulae (raw milk subset extends to formula context), meat-and-poultry-purees.
    • Author scope: raw and cooked milk + meat samples; species-specific dilution methodology.

MeHg in baby foods — second priority

  • PMID 27507486 (2017) “Methylmercury varies more than one order of magnitude in commercial European rice” — Food Chemistry. Paywalled (no PMC link).

    • Closes MeHg cells for: rice-based subcategories (cereals, snacks, mixed meals) via ingredient cascade. Doesn’t fully close fish-containing baby foods MeHg gap (different matrix).
    • Wishlist for manual or institutional access.

  • PMID 41416855 (2026) “Toxic elements in baby and young children’s foods in the US and correlation to ingredient sourcing” — Food Additives & Contaminants Part B: Surveillance. Paywalled (no PMC link).

    • Recent (2026) US-specific multi-element baby-food study; potentially closes second-A-tier-source thinness for the Pb/Cd/tAs cells across multiple subcategories.
    • Wishlist for institutional access.

Multi-element infant diet — third priority

  • PMID 38196052 (2024) “Dietary Intake and Exposure Assessment of Trace Elements in Infants’ Diets: A Case Study in Spain” — Biological Trace Element Research. PMC link lookup errored (likely paywalled or behind Springer embargo).
    • Showed up in 4 of our queries (Ni, Al, Sn, infant-rice-cereal Pb/Cd) — multi-element multi-subcategory candidate.
    • Wishlist for manual fetch.

Al in baby cereal

  • PMID 32247442 (2020) “Aluminum content and effect of in vitro digestion on bioaccessible fraction in cereal-based baby foods” — Food Research International. Paywalled.

    • Closes Al-in-baby-cereal sample-level gap (rice + non-rice).
    • Wishlist.

  • PMID 32190371 (2020) “Public Health and Paediatric Risk Assessment of Aluminium, Arsenic and Mercury in Infant Formula Milks and Baby Foods” — Sultan Qaboos University Medical Journal. PMC7065688 (OA).

    • Closes Al-in-formula and Al-in-baby-food cells with regional (Oman) data.
    • Wishlist for OA fetch.

Lower-priority candidates surfaced by the queries

These candidates either (a) target a related but not directly-applicable matrix, (b) duplicate an already-ingested source, or (c) are exposure/biomarker context rather than direct occurrence concentrations.

  • PMID 30253364 (Gardener 2019) — already ingested.
  • PMID 36141460 (Almeida 2022) — already ingested.
  • PMID 30077707 (Chekri 2018, French TDS infants) — likely the Chekri 2019 source already ingested under a different DOI; verify.
  • PMID 30659630 (2019) — false-positive match; metapneumovirus paper, not chromium. Skip.
  • PMID 36841007 (2023) “Implementation of effect biomarkers in human biomonitoring” — methodological, not occurrence. Lower value.
  • PMID 39154470, 35384231, 35609844, 24819712 — Cr in rice/cereal plants (agronomic uptake studies), not finished baby cereal. Useful for ingredient cascade, not directly for product-row fit.
  • PMID 39154496, 16773731, 27782776 — rice or rice-grain Ni studies; ingredient context not finished product.
  • PMID 36565913 (2023) — Al/Sb/Li in breast milk, not formula or baby food.
  • PMID 1375091 (1992) — Cr in foods/diets; older than 2000 boundary used by HMTc Path A typically.
  • PMID 38787097 (2024) — Pb in Mexican foods generally, not infant-specific.
  • PMID 27747874 (2017) — aflatoxin in baby foods, not heavy metal.
  • PMID 23928037 (2013) — multimedia mercury exposure model, not measured occurrence.
  • PMID 7079739 (1982) — primate MeHg toxicology, way out of scope.

Search strategy used

PubMed E-utilities ESearch with query strings (executed 2026-05-09):

  1. (methylmercury OR MeHg) AND (infant formula OR baby formula) AND (concentration OR speciation) — 2 hits
  2. (methylmercury OR MeHg) AND (baby food OR infant cereal OR baby cereal OR weaning food) AND speciation — 2 hits
  3. (hexavalent chromium OR Cr(VI) OR chromium-VI) AND (baby food OR infant food OR infant formula OR weaning) — 5 hits
  4. hexavalent chromium AND rice AND (cereal OR product OR food) — 5 hits
  5. nickel AND (rice cereal OR infant rice OR baby cereal) AND concentration — 5 hits
  6. aluminum AND (baby cereal OR infant cereal) AND (concentration OR survey) — 5 hits
  7. tin AND (infant food OR baby food OR infant formula OR weaning) AND concentration — 5 hits
  8. (infant rice cereal OR baby rice cereal) AND (lead OR cadmium) AND (concentration OR distribution OR survey) AND (samples OR sample-level) — 3 hits

Total unique PMIDs surveyed: 30. After deduplication against already-ingested sources and false-positive filtering, 6 high-value candidates remain on the wishlist (3 OA, 3 paywalled).

  1. Manual PDF fetch of PMC11050093 (Mathebula 2019 Cr-VI/Cr-III milk/dairy/cereal) via logged-in PMC browser session. Highest gap-filler value — closes Cr-VI for all four formula subcategories and both cereal subcategories.
  2. Manual fetch of PMC7065688 (Al-Saleh 2020 Al/As/Hg infant formula) and PMC11125859 (Vacchina 2021 Cr speciation milk/meat).
  3. Institutional access for paywalled candidates 27507486, 32247442, 38196052, 41416855 if Karen has Sci-Hub-equivalent or library access.
  4. Per-paper ingest under current schema (no ## TL;DR heading; two-axis row-fit; frontmatter accurate to author scope; sample-level CSV extraction where feasible). Update relevant product-page CC blocks and the master summary.

PubMed query script

For reproducibility, the autonomous run’s PubMed E-utilities queries are saved at /tmp/pubmed_queries.json (esearch results) and /tmp/pubmed_metas.json (esummary metadata). Re-running the queries will surface any new papers indexed since 2026-05-09.