EFSA 2023 - Heavy metals in seaweeds and halophytes

EFSA assessed occurrence and dietary exposure for cadmium, lead, total arsenic, inorganic arsenic, total mercury, and iodine in seaweeds, halophytes, and products based on or containing seaweed in Europe. The report used sampling years 2011-2021 and separates total arsenic from inorganic arsenic, and total mercury from the few reported methylmercury and inorganic-mercury records. The PDF-visible tables provide aggregate occurrence means by FoodEx-style seaweed group and exposure estimates for current seaweed consumers and replacement-scenario products.

Key numbers

The abstract and summary report the following food occurrence result counts: Cd 2,093 analytical data, Pb 1,988, tAs 1,934, iAs 920, tHg 1,499, and iodine 1,002. The final data set also contained 254 analytical results on feed from 76 samples, but the key occurrence tables below are food-focused.

Selected mean food occurrence concentrations from Tables 3-7 are in µg/kg; Table 3 explicitly states whole weight, while Tables 4-7 use the same occurrence-table format:

Section 3.1.4 states that the highest mean iAs levels were reported for dried Kombu at 2,723-2,758 µg/kg, while Table 6 also lists dried brown algae, unspecified, at 3,402-3,404 µg/kg. Section 3.1.5 states that the highest mean tHg levels were reported for dried Rockweed at 123-127 µg/kg, with N=5 and one sample at 540 µg/kg strongly affecting the mean.

Table 23 summarizes the highest exposure estimates in current seaweed/halophyte consumers:

Table 23 also reports replacement-scenario highest mean exposures for Toddlers: Cd 1.59 µg/kg bw per week, tAs 5.1-5.2 µg/kg bw per day, iAs 0.090-0.11 µg/kg bw per day, Pb 0.15-0.16 µg/kg bw per day, and tHg 0.028-0.081 µg/kg bw per week.

Methods (brief)

EFSA compiled occurrence records submitted by European countries and food consumption records from the EFSA Comprehensive European Food Consumption Database. Occurrence results were classified for arsenic as arsenic derivatives, total arsenic, inorganic arsenic, As(V), As(III), arsenobetaine, and other arsenic compounds; for mercury as mercury derivatives, mercury compounds, total mercury, methylmercury, and inorganic mercury; and for cadmium and lead as the element or derivatives. The assessment used lower-bound and upper-bound treatment for left-censored results and linked occurrence groups to current seaweed/halophyte consumption plus a replacement scenario using seaweed pasta, seaweed snacks, seaweed salad, and seaweed condiments. The PDF reports exposure estimates from aggregate occurrence data; the detailed Annex D spreadsheets are referenced externally and were not embedded in the PDF text.

Implications

This A-tier EFSA report contributes occurrence and exposure context for seaweed-kelp foods and algae/seaweed-based supplements. It is especially useful for keeping arsenic and mercury species separate in seaweed evidence: EFSA reports both tAs and iAs tables, but mercury exposure is primarily based on tHg data and not a measured MeHg occurrence pool. The source also documents missing product coverage for halophytes, seaweed snacks, seaweed pasta, seaweed tea, and seaweed condiments where the closed product vocabulary is not yet specific.

Verification notes

• PDF text extracted with pdftotext -layout; abstract, summary, occurrence Tables 3-7, and exposure Table 23 were readable.
• DOI 10.2903/j.efsa.2023.7798 matched this existing source page, so this edit is a merge-enhancement from the manual-fetch PDF rather than a new duplicate source page.
• Occurrence result counts, selected Table 3-7 means, and Table 23 exposure estimates were checked against /tmp/ingest.txt.
• Units are preserved as µg/kg, µg/kg bw per week, and µg/kg bw per day; no conversion was performed. The PDF extraction renders the micro sign as l in some places, but the table headings are EFSA microgram units.
• Speciation is preserved: total arsenic and inorganic arsenic are separate EFSA occurrence tables; total mercury is not treated as methylmercury. The summary notes that only a few methylmercury and arsenobetaine data were available.
• Brand firewall: no brand-level values were reported in the PDF-visible tables.
• Frontmatter ingredient and product slugs were checked against docs/gpt-collaboration/taxonomy-snapshot.md; no new slug was invented. Missing closed slugs noted for halophytes, seaweed snacks, seaweed pasta, seaweed tea, and seaweed condiments/relishes.
• LC% cells shown as 0 in the occurrence table reflect source cells printed as – in Tables 3, 5, and 6 (Brown algae unspecified Cd/tAs, Snacks Cd, Relishes tAs). In every such cell the source reports LB = UB, so 0% left-censored is the correct semantic; the wiki normalizes the dash for readability.
• 2026-06-09 audit pass (autonomous QA subagent) verified all Table 3-7 occurrence values, all Table 23 exposure values, and the Cd/Pb/tAs/iAs/tHg occurrence-count totals against the PDF; verdict PROMOTE with the LC%-dash normalization above as the only adjusted item.

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.