We studied chemical speciation of arsenic compounds in urine samples b
y using HPLC with inductively coupled plasma mass spectrometry detecti
on. We examined urinary arsenic excretion patterns and the arsenic spe
cies excreted from nine human subjects who ingested seaweed products a
nd crab (or shrimp). Fast urinary excretion of unchanged arsenobetaine
was seen after ingestion of crab and shrimp, which contain arsenobeta
ine as the major arsenic species. In contrast, the arsenosugars, which
comprise the major arsenic species in seaweed, are metabolized and ha
ve a longer retention time in the human body. When nine volunteers ing
ested the commercial seaweed product nori, both the urinary arsenic ex
cretion pattern and the excreted arsenic species varied from individua
l to individual, and as many as six metabolites could be detected. It
seems that arsenosugars are not decomposed by stomach acid and that re
actions involving enzymatic and (or) microbial activity in the human b
ody may be responsible for the metabolism of arsenosugars.