Arsenic Bioaccumulation and Biotransformation in Clams (Asaphis violascens) Exposed to Inorganic Arsenic: Effects of Species and Concentrations.

High arsenic (As) concentrations are found in marine clams, usually as less-toxic arsenobetaine (AsB). However, when clams were exposed to elevated As concentrations in the environments, As species distribution within them may be altered. This study aimed to determine As bioaccumulation and biotransformation in marine clams (Asaphis violascens) along As concentration gradients for 10 days. Nine treatments of dissolved As exposure [control, 1, 3 (low), 10, 20 (high) mg/L As(III) and As(V)] were performed. Clams could biotransform low-levels of inorganic As efficiently, while they had lower biotransformation efficiencies when exposed to high As concentrations. AsB decreased with increasing As(III) and As(V) concentrations, while dimethylarsinic acid exhibited as a predominant As species in 3 mg/L exposure treatments. These results suggested that As methylation, synthesis and/or degradation of AsB should be affected by exposure concentrations. Therefore, these toxic As species within clams may cause a potential toxicological hazard to human beings.