Ingestion of Hijiki seaweed and risk of arsenic poisoning

Abstract The major route of human exposure to arsenic is via ingestion. Seafoods contain large amounts of various arsenic compounds. Recently, people have been advised not to eat Hijiki seaweed (Hijikia fusiforme) in the UK because of its high content of inorganic arsenic (iAs). To clarify the risks of Hijiki ingestion, a 42‐year‐old male volunteer ingested 825 µg of iAs compounds contained in eight servings of commercial Hijiki food, after refraining from eating seafood for 3 months. In order to determine the distribution of arsenic species in his urine, arsenic compounds were analyzed using HPLC‐ICP‐MS. The maximum concentrations of arsenate (AsV), arsenite (AsIII), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were found at 4, 6.5, 13 and 17.5 h after ingestion, respectively. Arsenobetaine concentration was very low, and almost constant throughout the observation period. A total of 28% of ingested arsenic was excreted in urine. The total amounts of AsV, AsIII, MMA and DMA excreted in urine over 50 h were 11.2, 31.8, 40.9 and 104.0 µg, respectively. After eating one serving of Hijiki, arsenic intake and urinary excretion were at levels similar to those in individuals affected by arsenic poisoning. Long‐term ingestion of Hijiki might thus have the potential to cause arsenic poisoning. Copyright © 2006 John Wiley & Sons, Ltd.