FSANZ 2012 — Inorganic arsenic in seaweed and seaweed products on the Australian market

Food Standards Australia New Zealand surveyed inorganic arsenic in 38 dried seaweed and seaweed-containing product samples collected from Australian retail in April–May 2010, undertaken to review the 2004 FSANZ consumer advice to avoid hijiki. Inorganic arsenic in dried seaweed ranged from below the 0.05 mg/kg limit of reporting to 7.80 mg/kg in a single hijiki composite, with all samples below the Australia New Zealand Food Standards Code maximum level of 1 mg/kg (calculated at 85% hydration) except that one hijiki composite, which at 7.80 mg/kg dried equated to 1.4 mg/kg at 85% hydration and was referred to the relevant jurisdiction. Inorganic arsenic was consistently higher in hijiki/Sargassum fusiforme than in wakame, kombu, or nori; among seaweed-containing products only two seaweed-chip samples exceeded the limit of reporting. The survey reproduces the cross-national pattern that hijiki is the inorganic-arsenic outlier among edible seaweeds.

Key numbers

Method limits: limit of reporting (LOR) 0.05 mg/kg; practical quantitation limit (PQL/LOQ) 0.03 mg/kg. Inorganic arsenic defined as arsenite (As³⁺) + arsenate (As⁵⁺), conservatively including any co-extracted MMA. All values dried-seaweed basis unless noted; non-detects assigned 0.05 mg/kg (upper bound) for means.

Table 1 — inorganic arsenic (mg/kg) in dried seaweed (individual and composite samples):

Table 2 — inorganic arsenic (mg/kg) in seaweed-containing products:

Additional source-reported facts:

• All dried-seaweed samples were below the Code ML of 1 mg/kg iAs except the one hijiki composite at 7.80 mg/kg dried (= 1.4 mg/kg at 85% hydration; hijiki composite moisture 14.6%), which exceeded the ML and was referred to the relevant jurisdiction.
• In this survey hijiki inorganic arsenic was at least 23-fold higher than other brown seaweeds and approximately 48-fold higher than nori.
• Samples labelled hijiki versus Sargassum fusiforme differed by at least 20-fold (7.80 vs 0.32 mg/kg), attributed to harvest-region/season variation rather than necessarily different species.
• Cross-national comparison (the survey’s Table 3) reported the dried-seaweed inorganic-arsenic ranges as: wakame 0.16–0.20, kombu 0.16–0.33, hijiki/Sargassum 0.32–7.8, nori 0.09–0.16, sea vegetable 0.10 mg/kg (FSANZ 2012, n=38), with hijiki the highest across all countries compared.
• Dietary exposure (Appendix 1, 23rd ATDS baseline + assumed 10 g/day dried seaweed): best-case scenario 0.3–0.7 µg/kg bw/day across population groups; worst-case 2.2–7.6 µg/kg bw/day; for children aged 2–5 the range across scenarios was 0.7–7.6 µg/kg bw/day. Exposure is far more sensitive to high seaweed arsenic concentrations than to background diet.
• Hazard context: JECFA (2011) BMDL₀.₅ for inorganic arsenic = 3 µg/kg bw/day (range 2–7); the prior PTWI of 15 µg/kg bw/week was withdrawn.

Methods (brief)

Samples were drawn from those already collected for the companion FSANZ iodine survey (retail outlets, all Australian states/territories, April–May 2010): 22 individual samples plus composites (three 3-purchase composites of different brands, one 3-purchase composite of the same brand, two 2-purchase composites of the same brand). Dried seaweed was analysed directly from packaging; seaweed-containing products (soup, tea, etc.) were analysed as purchased. The National Measurement Institute (NMI) performed analysis using a NATA-accredited method of acid extraction followed by hydride-generation inductively coupled plasma mass spectrometry (HG-ICP-MS; Holak and Specchio 1991), LOR 0.05 mg/kg, PQL 0.03 mg/kg. Inorganic arsenic was reported as arsenite + arsenate; because the extraction may co-extract MMA, the conservative total-inorganic figure may slightly overestimate true inorganic arsenic. Concentrations are for dried seaweed except where the 85%-hydration basis is stated (used only for the ML comparison on the exceeding hijiki sample). The report rates occurrence-data uncertainty as low (accredited, validated method) and overall dietary-exposure uncertainty as medium-to-high (driven by sparse Australian seaweed-consumption data).

Implications

• Certification (HMTc): a direct-evidence, government-survey occurrence source for the Category 6 seaweed-kelp-foods row (iAs platform), reporting inorganic arsenic on the dried, as-sold basis — the row’s native basis. It independently confirms the category’s central structure: inorganic arsenic in wakame, kombu, nori, and sea vegetable clusters tightly at 0.09–0.33 mg/kg, while hijiki is a categorical outlier (up to 7.80 mg/kg dried), directly supporting the within-row hijiki/Hizikia/Sargassum fusiforme species sub-split flagged in the Category 6 Step 0 lock. Seaweed-containing products (chips, soup, sauce, tea, desserts) sit at or near the LOR, indicating the contamination tracks seaweed content.
• Courses: a teachable regulatory case study linking survey occurrence data, an existing ML (ANZ Code, 1 mg/kg at 85% hydration), border risk-categorisation of hijiki, and consumer-advice review.
• App: contributes to the seaweed ingredient contamination_profile for inorganic arsenic, with the species-specific hijiki caveat.

Verification notes

• raw_handle MFK_survey-of-inorganic-arsenic-in-seaweed-and-seaweed derived from the PDF filename (slugified, truncated); raw_path under “raw/Manual Fetch Kimi /June 8 Inorganic Arsenic Seaweed/” preserving the trailing space before “.pdf”. No DOI (agency report); access_url left null.
• Evidence tier A: government surveillance report, NATA-accredited validated method (HG-ICP-MS), documented QC and uncertainty analysis.
• source_type gov-report per corpus convention for agency surveillance reports (cf. efsa2014-dietary-exposure-iAs).
• Speciation: the survey measures inorganic arsenic only (arsenite + arsenate); recorded as iAs. Total arsenic was not measured in these samples (tAs context in the report is drawn from the separate Australian Total Diet Study), so tAs is not lifted to frontmatter. The conservative possible-MMA inclusion is noted in Methods, not treated as a separate species.
• Units/basis preserved exactly (mg/kg dried seaweed; the single 85%-hydration figure of 1.4 mg/kg for the exceeding hijiki sample is labelled). Non-detects recorded as “<0.05” (the LOR), with the report’s upper-bound (0.05 mg/kg) convention noted where it computes means; numeric value columns left censored for non-detects.
• Censoring: many product samples and one seaweed sample are <0.05 mg/kg (below_lod, LOR 0.05 mg/kg).
• Brand firewall: not engaged. The report describes composites by “same brand”/“different brands” as a sampling-design detail but names no commercial brands; no brand-by-brand values appear.
• Jurisdictions [AU, NZ]: FSANZ is the binational agency and the maximum level is the Australia New Zealand Food Standards Code; the occurrence samples were collected in Australia. sampling_year_range 2010.
• matrices [edible-seaweed, macroalgae, kelp, dry-weight] kept broad per corpus convention; kombu (Laminaria) supports kelp. Seaweed-containing products are covered in the body and routed via the seaweed-kelp-foods product link rather than by overspecifying matrices.
• Instrument/lab names (National Measurement Institute; HG-ICP-MS) retained in Methods as permitted scientific reporting.
• This is the FSANZ survey report, distinct from the cited FSANZ companion iodine survey and from Almela 2002/2006, Rose 2007, NSWFA 2010, and Smith 2010, which appear only as comparison references in the report’s Table 3.

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