Bioaccumulation and acute toxicity of As(III) and As(V) in Nile tilapia (Oreochromis niloticus)

Abstract

The distribution of arsenic in the different tissues of tilapia fish is determined by the exposure time and the depuration rate. The mechanisms of toxicity/carcinogenicity depend on the arsenic species involved in the biotransformation processes. After a 7-day exposure period, the accumulation of inorganic arsenic (iAs) in the tilapia tissues studied was in the order: liver > stomach > gills > muscles. In bioaccumulation assays, the values of the organ uptake constant (ka) ranged from 0.06 to 0.51 mL g−1 d−1, while the depuration rate constant (kd) values were in the range 0.03–1.15 d−1. Higher iAs bioaccumulation factor (BCF) values were observed for the stomach (3.1 mL g−1) and the liver (1.6 mL g−1), reflecting their high capacity to accumulate iAs species. These organs act as long-term storage sites for iAs, following chronic exposure. The LC50 values were determined considering the average iAs concentration and the cumulative fish mortality. For As(III), the LC50 values indicated fish mortality at concentrations above 30 mg L−1. The fish showed greater tolerance to exposure to As(V), compared to As(III), with fish mortality after the second day of exposure requiring an As(V) concentration 7-fold higher than As(III).