[Kinetics of arsenic in human blood after a fish meal]

It is well known that fish contains high amounts of arsenic (As) compounds (mean values per wet weight [mg x kg-1] Ballin [1]: 41; Falconer et al. [2]: 14; Staveland et al. [3]: 5.2), which are mainly represented by organic As compounds, especially by arsenobetaine. It is generally assumed that arsenobetaine is rapidly eliminated via the urine and therefore seems to be non-toxic for humans. However, the kinetics of arsenobetaine in human blood are unknown to date. Therefore, the following experiments were performed: 14 women of 24 to 32 years of age voluntarily ingested 179 to 292 g of cooked plaice fillet containing 44 (minimum) to 276 (maximum) mg As x kg-1 dry weight. Hence, the volunteers ingested 2.5 (minimum) to 20 (maximum) mg As per person, equivalent to 0.04 to 0.35 mg As x kg-1 body weight. The element As was measured by atomic absorption spectrometry using the graphite furnace technique in order to detect the total amount of As including that of the stable arsenobetaine. In the blood, the highest As values of 55 +/- 5.8 micrograms x L-1 (median) were found 2 hours after fish ingestion. Subsequently the As concentrations declined reaching 16 +/- 0.69 micrograms x L-1 (median) 48 hours after fish ingestion. In respect of the As values in blood recorded between 2 and 10 hours after fish ingestion, rapid elimination could be observed leading to a half-life of 7.1 hours (first value) recorded by linear regression analysis. With regard to the As values in blood between 10 and 48 hours after fish ingestion, a lower elimination rate was estimated with a longer half-life of 63 hours (second value). The reason for this delayed elimination of As is not known. The results indicate that As mainly absorbed as arsenonetaine due to ingestion of fish is not eliminated as fast as had been expected on the basis of published data. As long as it is not known what happens to arsenobetaine remaining for longer periods in the blood with a half-life of 63 hours, caution is advised regarding the general opinion that arsenobetaine is rapidly eliminated and non-toxic for human consumption.