A comprehensive evaluation of inorganic arsenic in food and considerations for dietary intake analyses

Overview

Lynch and colleagues compiled 134 studies into a >6500-data-point database to estimate mean speciated-arsenic concentrations across food groups, focused on inorganic arsenic (inAs). This is a secondary source (literature meta-analysis), not a primary measurement study; its values are aggregates of the underlying primary studies and so are recorded here as literature-wide context, not as poolable occurrence data (pooling them would double-count the primary sources). Its central finding for the Category 6 seaweed row: seaweed/algae had the highest mean total inorganic arsenic of any food group, 11,000 µg/kg (n=312, range <14–120,000), with seaweed-containing products far lower at 260 µg/kg (n=30). The review also documents extensive data-quality caveats (extraction efficiencies often <80% for algae, high non-detect fractions, combined dry/wet-weight reporting) that bear on how seaweed arsenic data should be interpreted.

Key numbers

Meta-analytic means (µg/kg unless noted); these are literature aggregates, NOT new measurements and NOT poolable.

Seaweed (the row-relevant group; Table 3.3):

• Total inorganic arsenic (As): mean 11,000 µg/kg, n=312, range <14–120,000 — the highest mean inAs of any food group analysed.
• inAs³⁺: 1200 (range <0.1–6700), n=37; inAs⁵⁺: 21,000 (range <17–110,000), n=105.
• MMA: 2200 (n=58); DMA: 2200 (range <7–46,000), n=103; Total As: 39,000 (range 31–150,000), n=421.
• Seaweed products (foods with seaweed as an ingredient): total inAs mean 260 µg/kg, n=30, range <14–1700; % inAs of total ranged 1–91%.
• % inorganic As of total in seaweed/algae samples ranged 0–86%; 18 of 312 inAs values were non-detect (6%) (Table 3.5).

For cross-food context (Table 3.3, same meta-analysis):

• Rice: total inAs mean 130 µg/kg, n=1126; rice products 760 µg/kg, n=151.
• Seafood: total inAs 130 µg/kg, n=835 (total As 10,000 µg/kg, n=2417); Fish total inAs 45 µg/kg.
• Infant rice cakes/cereal: total inAs ~92 µg/kg (range 8–220), n=65 — highest among infant foods.

Additional source-reported facts:

• The review contrasts its seaweed mean (11,000 µg/kg inAs, ≈25% of total As) with JECFA (2011), which assumed inAs = 50% of total As in hijiki and <15% in other seaweed; the meta-analysis mean is “much lower than the assumption used in the EFSA analysis.”
• The maximum compiled total inAs across all foods was ~120,000 µg/kg, in dried seaweed/algae.
• Sensitivity analysis (Table 4.1): restricting to dry-weight-only seaweed values changed the seaweed inAs mean by −38% vs the combined dry/wet main analysis (wet-weight-only: no change; seaweed products dry-only: +8%). This reflects which studies reported on which basis (a data-availability artifact across studies), not a within-sample dry/wet conversion, so it does not by itself indicate the dry basis runs higher for seaweed. (The +77% dry-weight figure in Table 4.1 is the seafood row, not seaweed.)
• Cooking/preparation: traditional washing and soaking of Hizikia (hijiki) can reduce total As by up to ~60% (citing EFSA 2009); cooking rice in high water volumes can reduce inAs.
• Data-quality caveats specific to algae: extraction efficiencies are often <80% (one study spanned 20.7–97% across species), which may underestimate total As; varying LODs and combined dry/wet-weight reporting add uncertainty; the authors stress speciation-based, study-quality-weighted, population-tailored intake calculations.

Methods (brief)

Comprehensive literature search (PubMed, Scopus, Toxline, Agricola) for studies measuring speciated arsenic in food intended for human consumption, 1995–July 2013; 134 studies retained after excluding anthropogenically-contaminated-site and laboratory-uptake studies. Each food was categorised into food groups; for each group the authors computed mean (mean-of-study-means or arithmetic mean of raw data, weighted by sample size), minimum and maximum for inAs³⁺, inAs⁵⁺, total inAs, MMA, DMA, and total As. Values below LOD were substituted with half the LOD (with sensitivity analyses using 0, minimum LOD, and minimum detected value); dry- and wet-weight values were combined in the main analysis (with dry-vs-wet sensitivity analysis). No primary sampling or measurement was performed. Funded by the Electric Power Research Institute (EPRI); authors affiliated with Gradient (a scientific consulting firm) — disclosure recorded for transparency.

Update history

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