JECFA 33rd Meeting (1988) — Tin Re-evaluation (WHO Food Additives Series 24)

The 33rd meeting of the Joint FAO/WHO Expert Committee on Food Additives (Geneva, 21-30 March 1988) re-examined the human acute-toxicity literature for inorganic tin in canned foods and beverages, in response to a request from the 18th session of the Codex Committee on Food Additives (The Hague, November 1985) for clarification of the 26th JECFA report’s findings on the chemical forms of tin that cause gastric disturbances. The Committee left the underlying tolerable intake unchanged and instead converted the previously established provisional maximum tolerable daily intake of 2 mg inorganic tin per kg body weight (set at JECFA’s 14th meeting, 1971, and reaffirmed in 1975, 1978, and 1982) into a provisional tolerable weekly intake of 14 mg inorganic tin per kg body weight, applicable to chronic exposure. For acute effects, the monograph concludes that gastric irritation can occur at tin concentrations as low as 150 µg/g in canned beverages and 250 µg/g in other canned foods, while some canned products containing up to 700 µg/g produced no detectable effects, and recommends that tin in canned foods be kept as low as practicable consistent with good manufacturing practice.

Key numbers

Tolerable intake (chronic):

Acute symptomatic thresholds in humans (committee’s evaluation conclusion):

Background dietary-exposure estimates compiled in the monograph (general population):

Illustrative single-portion intakes the monograph provides for a 100 µg/g canned juice:

Published case-series and controlled-trial findings the monograph synthesizes:

Methods (brief)

The Committee’s task was a literature reassessment, not new experimental work. The monograph compiled published human case-series and controlled-feeding studies on inorganic tin in canned foods and beverages from 1887 to 1975, weighted toward the better-characterized incidents and the 1971 Benoy et al. controlled-dose human trials, and noted that “no very recent studies are available” at the time of the 33rd meeting. Background exposure estimates from air, drinking water, and unprocessed foods were taken from Friberg, Nordberg and Vouk (1986) Handbook on the toxicology of metals (2nd ed.), the WHO (1980) Environmental Health Criteria 15 monograph on tin and organotin compounds, the UK Ministry of Agriculture, Fisheries and Food (1985) 15th Food Surveillance Report on aluminium, antimony, chromium, cobalt, indium, nickel, thallium, and tin in food, and Reilly (1980) Metal contamination in food. The monograph identifies several confounders that complicate interpretation of acute-outbreak case series — co-occurring nitrate from over-fertilized tomatoes, container corrosion linked to product acidity and oxygen headspace, indigestible tin-protein complex formation, and unreplicated symptom reports on month-later re-challenge in the Benoy controlled trial — but does not quantitatively model them.

The PTWI of 14 mg Sn/kg body weight per week is a direct numerical conversion of the prior PMTDI of 2 mg/kg body weight per day (2 × 7 = 14) and reflects a change in the averaging window the Committee used to express the tolerable intake, not a re-derivation of the underlying toxicological basis.

Implications

• Certification: This monograph is the JECFA-side reference value for the inorganic-tin PTWI of 14 mg Sn/kg body weight per week. It does not by itself derive a maximum level for tin in food; the corresponding Codex maximum levels for inorganic tin in canned foods live in codex-cxs-193-1995-tin-canned-foods and the operative EU maximum levels in eu2023-contaminants-maximum-levels. HMTc tin thresholds for canned-product rows should cite this monograph for the chronic PTWI baseline and the acute symptomatic-threshold findings (150 µg/g beverages, 250 µg/g other canned foods, up to 700 µg/g no-effect).
• Courses: Useful teaching case for the distinction between chronic tolerable intake (PMTDI/PTWI, set on systemic-toxicity grounds) and acute symptomatic threshold (set on local gastrointestinal irritation grounds). Tin is one of the few heavy metals where the acute threshold from local irritation is operationally tighter than the chronic systemic threshold expressed as a single-meal intake at the PTWI.
• App: Supports per-product caution context for canned juices and canned solids stored in unlacquered or aged tinplate containers. The 100 µg/g threshold separating lacquered from unlacquered cans, and the 25 µg/g typical level inside lacquered cans, is a useful field-level anchor.
• Microbiome: Not addressed in this monograph.

Provenance notes

License CC-BY-NC-SA-3.0-IGO (WHO/IPCS standard publication terms). Redistribution permitted non-commercially with attribution and under the same or equivalent license. Heavy Metal Index extracts numerical findings and Committee conclusions as facts and paraphrases narrative content; no verbatim passages of substantial length are reproduced.

The PDF as held in raw/ (SHA-256 15b6d319bd5f923fc297ead2c5c635bff298837eb352e8283ad6950bd0846833) is a print-rendered capture of the INCHEM HTML at https://www.inchem.org/documents/jecfa/jecmono/v024je13.htm, dated 6/3/2026 in the footer.

The monograph carries one phrasing artifact worth noting: the “Comments and evaluation” section reads “the Committee converted the previously established tolerable daily intake of 14 mg of inorganic tin per kg of body weight into a PTWI.” Read literally this is internally inconsistent with the same monograph’s “Explanation” section, which states the prior PMTDI as 2 mg/kg body weight per day; the arithmetically consistent reading is that the Committee converted the prior 2 mg/kg/day PMTDI (equivalent to 14 mg/kg/week) into a PTWI of 14 mg/kg body weight per week. Subsequent JECFA documents (FAS 46, 2001; FAS 55, 2005) and the Codex CCFAC literature cite the JECFA 33rd PTWI as 14 mg/kg body weight per week, consistent with this reading.

The 33rd-meeting Codex committee request that triggered the re-examination is cited in the monograph as “Report of the Eighteenth Session of the Codex Committee on Food Additives, The Hague, 5-11 November 1985, FAO ALINORM 87/12.”

The 33rd-meeting tin monograph is referenced in its “See Also” footer alongside a successor, “Tin (WHO Food Additives Series 46),” which is the 55th-meeting (2000) tin re-evaluation. The successor monograph is not yet in the wiki corpus and is queued for separate ingest; on its ingest, this page’s superseded_by should be updated and the relationship between the 33rd-meeting PTWI of 14 mg/kg body weight per week and the 55th-meeting tin guidance value should be cross-linked.

Verification notes

Fresh-context audit subagent (Claude Opus 4.7, 2026-06-03) returned verdict REVISE with two actionable items, plus several ⚠️ concerns and one false positive.

• Applied: corrected the “Source meeting” cell in the chronic-intake table. The original draft cited “JECFA 14th (1971), reaffirmed 17th (1973), 19th (1975), 22nd (1978), 26th (1982)” — but the monograph’s “Explanation” section enumerates only years (1966, 1970, 1971, 1975, 1978, 1982) with no meeting numbers, and “17th (1973)” specifically is not in the PDF. Replaced with the PDF’s verbatim year-only enumeration to avoid claiming structure the monograph does not provide. Verified against PDF p. 1 paragraph 1.
• Rejected as false positive: audit Check 2 ❌ flagged [[products/canned-foods-general]] as a non-snapshot slug. The taxonomy snapshot at docs/gpt-collaboration/taxonomy-snapshot.md is stale on this point — wiki/products/canned-foods-general.md exists on disk and the routing audit accepted the slug, generating one of the three routing rows for this source page (canned-foods-general,locked_hmtc_row,jecfa-33rd-tin-1989,...,direct_evidence,...). The operational source of truth is the routing audit’s resolution against the live wiki tree, not the snapshot. Slug retained.
• Documented but not changed: audit Check 2 ⚠️ noted that the PDF does not explicitly enumerate Sn2+ and Sn4+ as analyte forms. The species: field is structural metadata defining the chemistry scope of “inorganic tin” rather than a claim about the source’s analytical speciation, and the precedent pages benoy1971-tin-toxicity-canned-fruit-juices and eu-scf-2002-acute-tin-canned-foods both use the same species: [Sn2+, Sn4+] convention for analogous inorganic-tin documents. Retained for cross-source comparability.
• Documented but not changed: audit Check 1 noted minor losses in the case-series table (Barker & Runte 1972 corroded-can range 381-477 ppm summarized as mean 418 only; Calloway & McMullen 1966 daily-average 163 mg/day omitted; Nehring 1972 nitrite 1.7 ppm omitted from “trace Zn/Cd/Pb/Cu/Cl” summary). These are condensations that preserve the values used in the Committee’s evaluation; the omitted values are secondary and do not change the symptomatic-threshold finding. Retained as written.

Otherwise PROMOTE per audit Checks 3, 4, 5 (speciation/methods, brand firewall, wiki/HMTc firewall all ✅).

Wiki pages this source may touch

• tin
• tin-inorganic
• codex-cxs-193-1995-tin-canned-foods
• canned-foods-general
• canned-fruit
• canned-vegetables
• canned-fish
• fruit-juices-non-apple
• fruit-juices-apple-containing

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.