What question did this study set out to answer?

The aim is to evaluate the levels of toxic and essential elements and related enzymatic responses in native fish.

March 10, 2026Open Access

Bioaccumulation of toxic and essential elements and enzymatic responses in native fish from the middle Tocantins River

Key Points

The aim is to evaluate the levels of toxic and essential elements and related enzymatic responses in native fish.
Collected specimens from urban and rural zones of the middle Tocantins River.
Measured concentrations of toxic and essential elements in liver and muscle tissues.
Assessed biochemical biomarkers including AChE, AST, ALT, and ALP.
Evaluated human health risks using bioconcentration factor, risk quotient, and estimated daily intake.
P. amazonica showed arsenic levels exceeding safety limits by up to 266% in muscle and 220% in liver.
Lead levels in liver were found to exceed limits by as much as 1850%.
C. labyrhinthicus exhibited arsenic and selenium levels far exceeding safety thresholds.
Moderate bioaccumulation of sulfur and iron was observed.
Risk assessment revealed a high level of concern, particularly for selenium.

Abstract

This study provides the first ecotoxicological evaluation of potentially toxic elements (PTEs), essential elements (EEs), and enzymatic biomarkers in two native fish species, Branquinha (Psectrogaster amazonica) and Branquinha-cascuda (Caenotropus labyrhinthicus), from the middle Tocantins River, Brazil. Specimens were collected from the urban riverside zone of Beira Rio (P1) and a fluvial beach near the rural community of Embiral (P2). PTEs and EEs concentrations were measured in liver and muscle tissues, and biochemical biomarkers included acetylcholinesterase (AChE), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP). Human health risks associated with fish consumption were assessed using the bioconcentration factor (BCF), risk quotient (RQ), and estimated daily intake (EDI). In P. amazonica (urban zone), arsenic (As) exceeded limits by 83–266% in muscle and 60–220% in liver, lead (Pb) in liver by 95–1850%, and selenium (Se) by up to 4537%. In C. labyrhinthicus (rural zone), As and Se in muscle exceeded limits by 185–470% and 5–200%, respectively, while Pb and zinc (Zn) were not detected. BCF values indicated moderate bioaccumulation of sulfur (S) (2867.29) and iron (Fe) (2641.30). Risk assessment revealed a high level of concern, with an RQ for Se reaching 53.13 and As intake exceeding child safety thresholds sevenfold, highlighting significant food safety risks.

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