Spatial-temporal dynamics of Cr in fish from Puruzinho Lake (Western Amazon) and dietary risk assessment

Cr contamination is a growing concern in the Amazon. Along with the rise of cattle farming in the region, tanneries are becoming more common and threatening environmental quality, since the effluents from this activity are rich in Cr. The objective of this study was to evaluate the seasonal and spatial dynamics of Cr in fish with different feeding habits from Puruzinho Lake, located in the Madeira River basin, also determining the daily intake of Cr associated with the consumption of these fish by the population that lives around the lake. Seasonality and feeding habits directly affected Cr dynamics in fish (p < 0.0001), with medians of Cr concentration ranging between 0.07 mg kg^-1 in the species Cichla pleiozona, a carnivorous fish, and 0.62 mg kg^-1 in Mylossoma duriventre, a herbivorous fish. The high Cr concentrations in M. duriventre were related to the biodilution effect of Cr in the trophic chain (R² = 0.14, p < 0.0001). The consumption of M. duriventre by the population was associated with the highest daily intake of Cr (55.5 μg∙day^-1), exceeding the recommended limits of Cr intake (35 μg∙day^-1). However, no harmful effects on health are expected due to the ingestion of Cr through the consumption of fish from Puruzinho Lake. Spatial analysis showed an increasing trend in Cr concentrations along the Madeira River, suggesting that contaminants present in the river are being carried over long distances and are reaching preserved areas of the Amazon.