Sitarik et al. 2020 — Fetal and early postnatal lead exposure in teeth and infant gut microbiota

Sitarik and colleagues used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on shed deciduous teeth to retrospectively quantify lead exposure across three developmental windows (2nd trimester, 3rd trimester, and postnatal birth-to-~1-year), then tested those exposure measures against bacterial (16S rRNA) and fungal (ITS2) gut microbiome composition in stool collected at 1 month and 6 months of age in 146 maternal-child pairs from the Detroit-area WHEALS birth cohort. In utero tooth lead levels were significantly associated with infant gut fungal community composition at 1 month — higher 2nd-trimester lead with lower abundances of Candida and Aspergillus and higher abundances of Malassezia and Saccharomyces — and 3rd-trimester lead with lower Candida. Lead did not significantly alter overall bacterial community structure, but specific bacterial taxa associated with lead exposure: higher Collinsella (at 1 month) and Bilophila (at 6 months), and lower Bacteroides at both time points.

Key numbers

Tooth lead quantification by LA-ICP-MS, expressed as ²⁰⁸Pb:⁴³Ca ratios (calibrated against NIST SRM 612). LOD: 0.05 µg/g; ~2–7% of lead measurements were below LOD across time points and were excluded from analysis (Methods §2.6). Lead levels were standardized to one-standard-deviation increases for regression modelling. All associations below are adjusted for tooth type, attrition, batch, exact age at stool sample collection, and child race; reported p-values are FDR-corrected (Benjamini-Hochberg).

Cohort flow: 1,258 maternal-child pairs in WHEALS → 512 teeth donated → 203 children with teeth → 180 children with both quality-controlled metal measurements and either birth-outcome or 2-year-clinic-visit data → 146 with both tooth metals and early-life microbiome data. Of the 146, 35 had 1-month bacterial microbiota only, 35 had 6-month only, and 68 had bacterial data at both time points; for fungal data the subset sizes were 33 / 29 / 19, respectively (a 53% ITS2 amplification failure rate is reported by the authors as the cause of the smaller fungal subset). Mean (SD) stool collection age: 1-month visit 38 ± 16 days (range 16-107); 6-month visit 205 ± 27 days (range 172-290).

Fungal genera significantly associated with tooth lead (FDR-corrected; from text §3.3 and Fig. 1):

The positive Malassezia signal was attributable to Malassezia restricta and Malassezia globosa OTUs; the negative Candida signal was attributable to a Candida parapsilosis OTU (Supplemental Table 1).

Bacterial genera significantly associated with tooth lead (FDR-corrected; from text §3.2 and Fig. 1):

The Collinsella signal was driven by four Collinsella aerofaciens OTUs.

Beta diversity (PERMANOVA, Table 3): In utero and postnatal lead did not significantly explain overall bacterial beta diversity by any of unweighted UniFrac, weighted UniFrac, Bray-Curtis, or Canberra distances at 1 or 6 months. Fungal beta diversity by Bray-Curtis was significantly associated with 2nd-trimester lead (p=0.048 at 1 month) and 3rd-trimester lead (p=0.049 at 1 month), explaining approximately 4% of variability in community composition.

Alpha diversity (Table 2): No significant associations between any lead exposure window and bacterial or fungal alpha diversity metrics (richness, evenness, Faith’s phylogenetic diversity, Shannon’s diversity) at either time point after covariate adjustment.

Cohort lead-level predictors (Table 1): Among the 146-pair analysis subset, higher tooth lead levels at all three time points were significantly associated with Black race (all p < 0.001), urban residence (p = 0.024, 0.005, 0.003 for 2nd trimester, 3rd trimester, and postnatal respectively), and lower birthweight z-score (p = 0.021, 0.019, 0.036). Absence of a household pet during pregnancy was associated with higher 3rd-trimester lead (p = 0.019) and trended for 2nd-trimester lead (p = 0.058); the postnatal-window association was not significant (p = 0.19). After adjustment for race, the residence and prenatal-pet associations were attenuated (all p ≥ 0.067). Birthweight z-score remained associated and is flagged by the authors as a potential mediator rather than a confounder.

Methods (brief)

Tooth lead by LA-ICP-MS on sectioned deciduous teeth using an ArF excimer laser ablation system (ESI, USA) coupled to an Agilent Technologies 8800 triple-quadrupole ICP-MS. The neonatal line — a histological feature formed in enamel and dentine at the time of birth — and incremental growth markings were used to assign 2nd-trimester, 3rd-trimester, and postnatal (birth–~1 year) exposure points along the ablation path, per Arora et al. 2012/2014. Data are reported as ²⁰⁸Pb:⁴³Ca ratios to correct for mineral-content variation within and between teeth. NIST SRM 612 was used for calibration and quality control. LOD = 0.05 µg/g; ~2-7% of measurements below LOD were excluded. Tooth-attrition wear was quantified and adjusted for. Within-child quality control on N = 17 children with two teeth gave second-trimester ICC = 0.55, third-trimester ICC = 0.74, and postnatal ICC = 0.87.

Stool collected at home visits at approximately 1 month and 6 months of age, banked at –80 °C. Bacterial 16S rRNA V4 region amplified using F515/R806 primers and sequenced on Illumina NextSeq (40% PhiX, 12.5 pM, 5 pM loading per cartridge). Fungal internal transcribed spacer 2 (ITS2) region amplified using fITS7/ITS4 primers and sequenced on Illumina MiSeq (25% PhiX, 10 pM). Reads quality-filtered (USEARCH v8.0.1623, > 2 expected errors removed), dereplicated, clustered at 97% identity into OTUs (UPARSE), taxonomy assigned via Greengenes (16S) and UNITE v7.0 (ITS). Rarefaction depth 60,000 reads/sample for 16S; multiply-rarefying to 1,000 reads for ITS to maximize sample inclusion given lower amplification success (53% ITS amplification failure rate, common for early-life cohorts).

Statistical analysis: Kruskal-Wallis (categorical) and Spearman (continuous) for tooth-lead-by-covariate associations. Covariate-adjusted linear regression for alpha diversity; covariate-adjusted PERMANOVA for beta diversity (vegan R package); covariate-adjusted zero-inflated negative binomial regression (pscl) — or negative binomial (MASS) where ZINB failed to converge — for differential genus/OTU abundance, restricted to taxa found in ≥ 10% of samples. FDR correction (Benjamini-Hochberg) applied at p < 0.05. Models adjusted for tooth type, attrition, batch, exact age at stool sample, and child race. Software: SAS 9.4 and R 3.6.1.

Limitations stated by authors: small analytical sample (n = 146), particularly for fungal microbiota (n ≈ 48 at 1 month, ~45 at 6 months); residual confounding plausible (race adjustment alone may be insufficient; birthweight z-score plausibly a mediator); no metagenomic sequencing so functional capacity not assessed; observational design so causality not established; reverse causation cannot be fully ruled out for fetal-microbiota mechanism.

Implications

Certification: Does not directly measure food contamination and therefore does not contribute numerical inputs to HMT&C threshold-setting. Provides mechanistic biomarker evidence linking in utero and early postnatal lead exposure to early-life gut microbiome composition, relevant to vulnerable-population framing (pregnancy and infancy) used in the wiki’s lead exposure discussion.

Courses: Methodological exemplar for retrospective exposure-window reconstruction via LA-ICP-MS on deciduous teeth, with concrete reporting of ICCs (0.55–0.87) across developmental windows that illustrates how reliability varies with tooth-developmental chronology. The fungal-microbiome finding is unusual in the lead-exposure literature, which has overwhelmingly focused on bacterial communities; useful as a case study of how mycobiome work expands the “metals and microbiome” frame.

App: Not directly applicable to food-contamination profiling. Provides exposure-source context: the WHEALS cohort lead exposures captured here are integrated biomarker measures, not food-specific.

Microbiome: Single-paper evidence for lead → mycobiome and lead → specific bacterial taxa axes. Fungal genera affected by fetal Pb (relative to controls): Candida (−), Aspergillus (−), Penicillium (− postnatally at 6 months), Malassezia restricta and M. globosa (+), Saccharomyces (+ at 1 month / − at 6 months). Bacterial genera affected: Collinsella aerofaciens (+ at 1 month), Bilophila (+ at 6 months), and several Bacteroides OTUs (−). Candidate for WikiBiome federation as a primary source on lead-mycobiome interactions in human infants.

Wiki pages updated on ingest

• lead
• la-icp-ms

Verification notes

Enhanced 2026-05-18 from the source PDF (raw/Papers Cube Manual Fetch/article (1).pdf) under skill v2.0 merge-enhance path. The prior revision (dated 2026-05-14) carried several defects against the source:

• Authors list was hallucinated. Prior frontmatter listed [Sitarik AR, Bobbitt KR, Havstad SL, Fujimura KE, Levin AM, Zoratti EM, Kim H, Johnson CC, Lynch SV, Ownby DR, Wegienka GR], which appears to be a WHEALS-cohort author roster from a different publication. The actual author list per the PDF title page is the one now in frontmatter: Sitarik AR, Arora M, Austin C, Bielak LF, Eggers S, Johnson CC, Lynch SV, Park SK, Wu KH, Yong GJM, Cassidy-Bushrow AE. Manish Arora and Christine Austin (Mount Sinai/Lautenberg) ran the LA-ICP-MS work; Bielak (U-Michigan epidemiology) provided cohort statistical input; Park (U-Michigan environmental health) co-authored.
• Title corrected from “Fetal and early postnatal lead exposure and the infant gut microbiota in a birth cohort” to the published title “Fetal and early postnatal lead exposure measured in teeth associates with infant gut microbiota” (Environment International 144 (2020) 106062, DOI 10.1016/j.envint.2020.106062).
• Sequencing platform reversed. Prior version stated 16S was run on Illumina MiSeq; the paper states the 16S V4 amplicon library was loaded onto the Illumina NextSeq cartridge (Methods §2.3), while ITS2 was run on Illumina MiSeq. Corrected.
• ITS region misidentified. Prior version said “ITS1 sequencing (fungal)”; the paper states “The internal transcribed spacer region (ITS) 2 of the rRNA gene was amplified using the primer pair fITS7 … and ITS4” (Methods §2.3). Corrected to ITS2.
• Key numbers expanded and made specific. Prior table reported generic “pFDR<0.05” for most findings; the paper reports specific p-values (0.006, 0.003, 0.002, etc.) that have been transcribed. Bilophila timing clarified to 6-month sample (prior table left it ambiguous; the paper specifies 6 months for both 2nd- and 3rd-trimester exposure). Added Penicillium → 6-month postnatal-window decrease (pFDR = 0.002) and the dual Saccharomyces signal (1-month increase, 6-month decrease) that were missing from the prior key-numbers table.
• Cohort-flow numbers added. Prior page reported only n=146; the paper details a more nuanced cohort-flow (1,258 → 512 → 203 → 180 → 146) and gives subset sizes by time point and assay that matter for interpreting fungal-arm statistical power. Added.
• Implications softened toward observation, away from synthesis. The prior Certification subsection asserted that the paper “supports the rationale for precautionary lead limits in foods consumed during pregnancy and early infancy” — a synthesis-toward-HMT&C claim that the wiki/HMT&C firewall (CLAUDE.md Part 2) prohibits in source pages. Replaced with a neutral statement that the paper informs vulnerable-population framing but does not provide threshold-setting inputs.
• Wiki pages updated on ingest pruned. Prior list referenced [[microbiome/lead-gut-mycobiome]] and [[health/vulnerable-populations]] — pages that do not exist as wiki targets. Routing audit would otherwise mark these as unresolved. Retained only the two extant targets (metals/lead, testing/la-icp-ms); the microbiome federation candidate is mentioned in Implications prose instead.

Preserved per v2 skill rule: cite_key, raw_handle: papers-cube, raw_path, license: CC BY-NC-ND 4.0, source_type: peer-reviewed, evidence_tier: A, jurisdictions: [US], metals: [Pb], ingredients: [], products: [], matrices: [tooth-dentin, stool, infant-gut-microbiome], near_duplicates: [], sample_n: 146.

Audit subagent (2026-05-18) — REVISE verdict, two findings applied:

• Audit flagged the bacterial-subset breakdown as “81 / 35 / 68” being inconsistent with the source. Verified against PDF p. 3 §2.7, which reads: “Of these 146 children, 35 had 1-month bacterial microbiota only, 35 had 6-month bacterial microbiota only, and 68 had bacterial microbiota at both time points.” The “81” was a transcription error introduced in the merge-enhance pass. Corrected to “35 / 35 / 68.”
• Audit flagged the Prenatal-indoor-pets p-values reported as “0.058, 0.038, 0.213 — 3rd trimester reaching p = 0.019” as both internally inconsistent and not matching Table 1. Verified against PDF p. 5 Table 1 row “Prenatal indoor pets”: the across-time-point p-values are 0.058 (2nd trim), 0.019 (3rd trim, bolded as significant), and 0.19 (postnatal). The “0.038” and “0.213” values are not in the source. The wiki now reads “p = 0.019” for the 3rd-trimester significant association, “p = 0.058” trend for 2nd trimester, and “p = 0.19” non-significant for postnatal — matching the source exactly.
• Audit Check 2 raised an advisory observation that tooth-dentin, stool, and infant-gut-microbiome are biological/biomarker matrices outside the food-matrices vocabulary. Not applied as a change: these matrix slugs are consistent with the established convention across sibling biomarker source pages (per a grep matrices: wiki/sources/*.md survey at the time of ingest) and are not a defect.
• All other audit checks: PROMOTE (numerical fidelity on tables, speciation/methods, brand firewall, wiki/HMTc firewall). No false-positive findings to record.

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.