Teores de mercúrio e parâmetros físico-químicos em peixes comercializados no mercado municipal de Humaitá – AM

Abstract

This work aimed to investigate the total mercury contents, physical parameters (size, weight and temperature) and physico-chemical quality (pH and Total Volatile Bases - BVT) in different species of fish collected in the municipal market of Humaitá - AM between 2021 and 2022, in two seasons of the year (full and dry), namely: Matrinxã (Brycon falcatus), Pacu (Mylossoma duriventre), Tambaqui (Colossoma macropomum), Jatuarana (Brycon amazonicus) and Pescada (Plagioscion squamosissimus). Total mercury was determined by atomic absorption spectrometry after thermal decomposition and gold amalgamation; pH and BVT by official methodology. In general, total mercury levels ranged from nd (not detected, < 0.050 mg/kg) in samples from Jatuarana, Matrinxã and Tambaqui, to 0.852 mg/kg in Pescada, and 77% of the total samples contained detected levels of mercury. The median mercury contents were significantly higher (Kruskal-Wallis test, p≤0.05) in Pescada (0.592 mg/kg), followed by Jatuarana (0.124 mg/kg), Matrinxã (0.083 mg/kg), Pacu (0.051 mg/kg) and Tambaqui (0. 003 mg/kg). It is possible to establish a positive correlation between mercury contents and trophic chain of fish. All samples met the quality criteria, with respect to pH < 7.0. On the other hand, as for the BVT, 4.2% of the Matrinxã samples and 33.3% of the Pescada samples were unfit for consumption. The average mercury levels identified were used to assess the risk for the Brazilian population in general, for the northern region and for the riverine population. Mercury intake for the Brazilian population and in northern Brazil met the provisional tolerable weekly intake (PTWI) of 1.6 μg/kg/week determined by Joint FAO/WHO Expert Committee on Food Additives (JECFA). However, due to the high consumption, the ingestion of these fish by the ribeirinhos dwellers of the Madeira river - AM, exceeded the PTWI, contributing significantly to the increased risk of neurological pathologies in these peoples, because they are being chronically exposed to this element. The results obtained suggest that in the current scenario it is sought to choose to consume fish that belong to low trophic level (herbivores and omnivores) among those marketed in the municipality of Humaitá and in the Amazon, in general, and also demonstrates the need for biomonitoring of the aquatic ecosystem vulnerable to anthropogenic sources of mercury, to assist in the development of better preventive strategies and actions for the issue of exposure to Hg in this region.