Occurrence of tin in disposable baby diapers

Overview

This study quantifies total tin in the top sheet and adhesive tape system of six brands of disposable baby diapers (Croatia, 2012-2014) using ²⁴¹Am-excited energy-dispersive X-ray fluorescence (EDXRF). Tin was detected in two of six diaper top sheets (range <MDL to 23.1 mg/kg) and in four of five measured adhesive tape systems (range <MDL to 22.4 mg/kg; the fifth tape system was not analyzed). The authors attribute the diaper tin to organotin compounds (TBT, DBT, MBT, DOT) used as PVC heat stabilizers, catalysts, or biocides; EDXRF reports only total Sn and cannot speciate. Measured concentrations are below the EU REACH Annex XVII No. 20 prohibition limit (0.1 % by weight = 1000 mg/kg in articles) but exceed the voluntary EU supplier-agreed limits of <2 mg/kg for TBT and <10 mg/kg for each individual organotin species. The worst-case dermal exposure scenario (6-8 month infant, 8 kg body weight, five diapers/day) is estimated at 0.021 µg Sn/kg-bw/day, equivalent to 20-100% of the tolerable daily intake.

Key numbers

Total Sn by EDXRF in six diaper brands (Table 1, p. 2):

• MDL (minimum detection limit): 1.5 mg/kg total Sn
• Experimentally determined analytical error: 15.6%
• “n.a.” = not analyzed
• Detection counts (per abstract): top sheet 2/6 (Diapers 2 and 6); adhesive tape system 4/5 measured (Diapers 1, 2, 4, 6; Diaper 5 not analyzed)

Worst-case infant dermal exposure (paper text, p. 3, citing RPA 2005 [ref 3]): 6-8 month infant, 8 kg body weight, five diapers/day → 0.021 µg Sn/kg-bw/day → 20-100% of organotin TDI. The authors note this may be additive with exposure from other consumer-product organotin sources.

Comparison values from other diaper studies (Table 2, p. 2; reported organotin cations in mg/kg, primary citations as given in the paper’s reference list):

Regulatory references cited in the paper:

• EU REACH Annex XVII No. 20: prohibits organotin compounds in articles at >0.1 % by weight (>1000 mg/kg). Also fully bans organotin biocides in antifouling paints.
• Voluntary supplier-agreed limits for non-woven polypropylene top-sheet raw material (paper ref [15], described as detection-limit-driven values rather than toxicology-anchored): <2 mg/kg TBT; <10 mg/kg each organotin species individually.
• Sediment contamination upper limits cited from refs [1,2]: 0.1-0.5 mg Sn/kg dry weight (set for sea disposal of dredged material).
• 2012 Swedish KEMI survey of 11 baby-diaper types: no prohibited organotin compounds found; the paper’s authors comment that the 0.1 % prohibition limit is “too high.”

Methods (brief)

• Instrument. EDXRF with ring-shaped ²⁴¹Am radioactive excitation source (energy line at 59.6 keV in the recorded spectra). Canberra Ge(Li) detector (model GL0055P; FWHM 155 eV at 5.9 keV). Sample-to-source distance 12 mm; samples held in 99.9% Al holder. Irradiation time 2000 s per sample.
• Sample preparation. Top sheet and adhesive tape system of each diaper separated, cut into very small pieces, homogenized, and pressed into 2.5 cm diameter pellets weighing ~0.2 g.
• Blank. White cotton processed identically to diaper samples.
• Calibration. Standard addition with Sn certified solution (1 g/L, TraceCERT, Fluka, Switzerland). Calibrating sample cut and mixed for 15 min in agate mortar before each analysis, then pelletized. Three replicate cut/mix/analyze cycles per Sn aliquot.
• Spectrum fitting. IAEA AXIL program within the QXAS software package (open-domain IAEA software).
• MDL and error. MDL = 1.5 mg/kg total Sn; experimentally determined analytical error = 15.6%.
• Speciation. None. EDXRF measures total Sn only. The paper notes that organotin speciation (TBT, DBT, MBT, DOT) requires gas chromatography (GC) or liquid chromatography (LC) coupled to atomic absorption analysis, ICP-OES, or ICP-MS, with extraction, derivatization (for GC), purification, and enrichment steps; those workflows reach µg/g to ng/g LODs but are destructive, lower-throughput, and more contamination-prone than EDXRF.

Implications

Certification: For HMTc Cat 9 Row 7 (diapers and diaper components), this paper contributes:

1. Occurrence data documenting that diaper tin contamination is intermittent across brands (2/6 top sheets, 4/5 measured tape systems above the 1.5 mg/kg MDL).
2. Confirmation that the EU REACH 0.1% prohibition limit (1000 mg/kg) is non-binding for real-world diaper contamination at the concentrations measured here; the voluntary supplier-agreed limits (<2 mg/kg TBT; <10 mg/kg each organotin species) are the operative reference levels.
3. A methodological note that total Sn (EDXRF) is a screening proxy that cannot distinguish low-toxicity inorganic Sn from neurotoxic, reproductive- and endocrine-disrupting organotins (TBT, DBT, MBT, DOT). Any certification specification that relies on total Sn alone should record this limitation; speciation by GC- or LC-coupled atomic-spectrometry methods is the orthogonal confirmation pathway.
4. A worst-case dermal exposure estimate of 0.021 µg Sn/kg-bw/day for an 8 kg infant on five diapers/day, reaching 20-100% of the cited organotin TDI under the paper’s scenario. The paper itself flags that this exposure may be additive with other consumer-product organotin sources.

Courses: Useful for a Cat 9 module on dermal exposure modelling for infant skin-contact products. The 20-100% TDI estimate is a teachable example of how exposure surface area × frequency × duration × dermal absorption fraction × body weight resolves to a tolerable-intake fraction.

App: For diapers, the consumer-app signal from this paper is “total Sn in diaper layers is intermittently present in retail product, and most consumer-facing labelling does not report it.” Speciated organotin data is rarely available outside supplier COAs; total Sn from supplier QC is the practical proxy. Because the dataset is six anonymous brands in Croatia (2012-2014), no brand-level mapping is possible.

Microbiome: Not addressed in this paper. Organotin effects on the developing gut microbiome are documented elsewhere; cross-reference Microbiome when those source pages exist.

Wiki pages updated on ingest

• Tin
• Diapers and diaper components (Cat 9 Row 7)
• Children Personal Care (HMT&C Category 2 master)

Verification notes

• 2026-05-18 (Claude Opus 4.7, autonomous manual-fetch v2.0 enhancement): merge-enhance pass against prior 2026-05-14 page.
• Corrected transposed detection counts. Prior page narrative said “Tin appears in 4 of 6 diapers’ top sheets and 2 of 6 in adhesive tape system.” Paper abstract (p. 1) says the opposite: “Almost all diapers contained tin in the adhesive tape system (four of five), and two of six samples contained tin in top sheet.” Table 1 confirms: top sheet detections in Diapers 2 (23.1) and 6 (2.0) only = 2/6; tape system detections in Diapers 1 (9.5), 2 (22.4), 4 (12.2), 6 (22.4) = 4/5 measured (Diaper 5 was n.a.). The numbers were swapped between rows.
• Corrected HMTc category assignment. Prior page assigned this to “HMTc Cat 2 disposable baby diapers row.” wiki/products/diapers-and-components.md is HMTc Cat 9 Row 7 (Infant and Child Contact Products, Ages 0-5). Cat 2 is children-personal-care, a different (broader) category. Implications section updated to Cat 9 Row 7.
• Removed Part 5 threshold proposal. Prior page Implications #4 said “warrants a precautionary threshold below 2 mg/kg total Sn in any diaper layer with skin contact.” Per and the audit-prompt Check 5 boundary, source pages report occurrence data and may describe what a paper contributes to threshold work, but must not propose threshold values. Reworded to note the methodological limitation of total-Sn screening and recommend speciation as orthogonal confirmation, without proposing a numeric ceiling.
• Corrected speciation-methods description. Prior page said “GC or LC with ICP-MS or AAS.” Paper text (p. 1) lists “atomic absorption analysis, inductively coupled plasma atomic emission spectrometry or inductively coupled plasma mass spectrometry.” Added ICP-OES to the list.
• Fixed invalid product slug. Prior page declared products/disposable-baby-diapers as a routing target; that page does not exist in wiki/products/. Replaced with products/diapers-and-components (the existing HMTc Cat 9 Row 7 product page; matches sibling diaper sources nyamukamba2023, lai2025, bae2018).
• Fixed matrices vocabulary. Prior page used [cosmetic-personal-care, dermal-contact-product]. Sibling diaper sources use matrices: [diaper]; aligned to that convention.
• Fixed sample_population precision. Prior version said “Top sheet and adhesive tape system analyzed separately for total tin.” Tightened to specify EDXRF as the analytical method.
• Removed speculative app statement. Prior page said “the consumer app should flag high-Sn brands (any layer >10 mg/kg total Sn) as concerning.” That is a threshold proposal and a brand-flag prescription. Reworded to describe what is and is not available as consumer-facing data; no numeric ceiling and no flagging-rule proposed.
• Preserved. cite_key, raw_handle, raw_path, license, evidence_tier (A — peer-reviewed primary study in X-Ray Spectrometry), sample_n=6, jurisdictions [HR, EU].
• Verified accurate (no change needed). All numerical values in the Key numbers table match Table 1 exactly. Methods detail (²⁴¹Am source, Canberra Ge(Li) detector model and FWHM, 2000 s acquisition, IAEA AXIL/QXAS, 2.5 cm pellet ~0.2 g, MDL 1.5 mg/kg, error 15.6%) matches paper. Exposure scenario (0.021 µg Sn/kg-bw/day, 8 kg infant, 5 diapers/day, 20-100% TDI) matches paper p. 3 exactly. Regulatory citations (REACH Annex XVII No. 20, voluntary <2 mg/kg TBT, <10 mg/kg per organotin, KEMI 2012) match.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and 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.