Environmental biomonitoring of toxic and essential metals in amazonian ecosystems using animal tissues

Abstract

The Tapajós River basin is one of the prominent regions for mercury contamination from mining activities. It is worth mentioning that the element mercury is not the only heavy metal with potential harm to the health of Amazonian populations. Arsenic, cadmium, and lead are toxic metals known to be present in the region, either by anthropogenic or natural action. In addition to toxic forests, the risks of excessive consumption of even metals considered essential must be warned. This thesis presents four chapters that deal with the monitoring of toxic and essential metals in the Lower Amazon mesoregion. In chapter I, a review was carried out on the four toxic elements addressed in the thesis, namely Mercury, Arsenic, Lead and Cadmium. In chapter II, we determined the sensitivity and specificity of Hg detection performed with DMA-80 and whether these results are reliable compared to those obtained with the Inductively Coupled Plasma Mass Spectrometer (ICP-MS), which is the gold standard. The Bland-Altman analysis showed that DMA-80 showed a positive bias of 6.5% in relation to ICP-MS, which is more evident in samples with high Hg concentrations. DMA-80 was efficient in determining whether Hg levels exceeded the maximum allowable levels required by the European Union, USA and Brazil, with specificity and sensitivity above 95%. In chapter III, we considered the evaluation of the concentration of toxic metals, such as mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As), in muscle tissue samples from cattle belonging to six municipalities in the Lower Amazon region. In this study, the results of the calculation of daily intake of toxic metals (EDI), which represents the daily intake of toxic metals through the daily consumption of beef (71 g per person), in general, indicated that the concentrations of metals were slightly below the reference values (RfDo).The results of the analysis of the target risk quotient (THQ) and the multiple contaminant exposure data (TTHQ) revealed that the values of the four toxic elements were not associated with risks by isolated exposure (THQ<1). The city of Monte Alegre presented the highest concentrations of THQ and TTHQ for the metals As and Pb. However, in Itaituba and Oriximiná, the concentrations of toxic elements resulted in the highest THQ values of Hg and Cd, leading to a TTHQ of 0.06 to 0.02, respectively. The results of the present research indicate that beef from animals raised in the region is safe for consumption. In Chapter IV, we determined the concentrations of essential elements such as cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se) and zinc (Zn) in liver tissue of cattle consumed in municipalities of the western region of Pará. We also assessed the risks arising from the daily consumption of these elements. The daily intake of bovine liver tissue calculations were higher than those established for the copper element in all municipalities evaluated. The EDI of Se and Zn remained above the values when the hepatic tissues from Oriximiná were evaluated The total target risk quotient (TTHQ) revealed that all municipalities, were exposed to the risks of excessive consumption of these minerals, indicating that the degree of accumulation of essential elements in cattle in the Amazon region presents a significant risk for the consumption of the local population.