SPECIATION AND HEALTH RISK CONSIDERATIONS OF ARSENIC IN THE EDIBLE MUSHROOM LACCARIA AMETHYSTINA COLLECTED FROM CONTAMINATED AND UNCONTAMINATED LOCATIONS

Samples of the edible mushroom Laccaria amethystina, which is known to accumulate arsenic, were collected from two uncontaminated beech fore sts and an arsenic-contaminated one in Denmark, The total arsenic conc entration was 23 and 77 mu g As g(-1) (dry weight) in the two uncontam inated samples and 1420 mu g As g(-1) in the contaminated sample. The arsenic species were liberated from the samples using focused microwav e-assisted extraction, and were separated and detected by anion- and c ation-exchange high-performance liquid chromatography with an inductiv ely coupled plasma mass spectrometer as arsenic-selective detector. Di methylarsinic acid accounted for 68-74%, methylarsonic acid for 0.3-2. 9%, trimethylarsine oxide for 0.6-2.0% and arsenic acid for 0.1-6.1% o f the total arsenic. The unextractable fraction of arsenic ranged betw een 15 and 32%, The results also showed that when growing in the highl y arsenate-contaminated soil (500-800 mu g As g(-1)) the mushrooms or their associated bacteria were able to biosynthesize dimethylarsinic a cid from arsinic acid in the soil. Furthermore, arsenobetaine and trim ethylarsine oxide were detected for the first time in Laccaria amethys tina. Additionally, unidentified arsenic species were detected in the mushroom, The finding of arsenobetaine and trimethylarsine oxide in lo w amounts in the mushrooms showed that synthesis of this arsenical in nature is not restricted to marine biota. In order to minimize the tox icological risk of arsenic to humans it is recommended not to consume Laccaria amethystina mushrooms collected from the highly contaminated soil, because of a genotoxic effect of dimethylarsinic acid observed a t high doses in animal experiments. (C) 1998 John Wiley & Sons, Ltd.