Rupture of dam B-1 at the Córrego do Feijão mine in Brumadinho, state of Minas Gerais, Brazil (25/Jan/2019) contaminated the Paraopeba River with mine waste. To identify the adverse effects of this event on public and environmental health, we conducted the Fish Embryo Acute Toxicity (FET) test (OECD No. 236). During the tests, zebrafish embryos were exposed for 144 hours to solutions containing realistic concentrations of dissolved iron and aluminum and total manganese at the following analysis points upstream or downstream of the dam: 10 km, upstream; 19.7 km, downstream, at the point where water for consumption is collected; 24.5 km, downstream, in the city of Mário Franco; and 59 km, downstream, on the border between the towns of Juatuba and Betim. Metal concentrations were taken from September 2019 report No. 53 released by IGAM. Mortality was high at all exposure points and reached 93% at the Juatuba/Betim point. We also detected lethal, sublethal and teratogenic effects, such as non-hatching, non-inflation of the swim bladder, pericardial edema and scoliosis, affecting up to 25% of embryos at the other analysis points. The results highlight the need for continuous monitoring of the water quality of the Paraopeba River.

Cosmetic residues have been found in water resources, especially trace elements of precursors, couplers, and pigments of hair dyes, which are indiscriminately disposed of in the sewage system. These contaminants are persistent, bioactive, and bioaccumulative, and may pose risks to living beings. Thus, the present study assessed the ecotoxicity of two types of effluents generated in beauty salons after the hair dyeing process. The toxicity of effluent derived from capillary washing with water, shampoo, and conditioner (complete effluent—CE) and effluent not associated with these products (dye effluent—DE) was evaluated by tests carried out with the aquatic organisms Artemia salina, Daphnia similis, and Danio rerio. The bioindicators were exposed to pure samples and different dilutions of both effluents. The results showed toxicity in D. similis (CE₅₀ of 3.43% and 0.54% for CE and DE, respectively); A. salina (LC₅₀ 8.327% and 3.874% for CE and DE, respectively); and D. rerio (LC₅₀ of 4.25–4.59% and 7.33–8.18% for CE and DE, respectively). Given these results, we can infer that hair dyes, even at low concentrations, have a high toxic potential for aquatic biota, as they induced deleterious effects in all tested bioindicators.

Triclopyr, an auxin-like herbicide that is widely employed for managing weeds in food crops and pastures, has been identified in various environmental settings, particularly aquatic ecosystems. Limited understanding of the environmental fate of this herbicide, its potential repercussions for both the environment and human health, and its insufficient monitoring in diverse environmental compartments has caused it to be recognized as an emerging contaminant of concern. In this study, we have investigated how triclopyr affects zebrafish, considering a new alternative methodology. We focused on the endpoints of developmental toxicity, neurotoxicity, and behavior of zebrafish embryos and larvae. We determined that triclopyr has a 96 h median lethal concentration of 87.46 mg/L (341.01 µM). When we exposed zebrafish embryos to sublethal triclopyr concentrations (0.5, 1, 5, 10, and 50 μM) for up to 144 h, we found that 50 µM triclopyr delayed zebrafish egg hatchability. Yolk sac malabsorption was significant at 0.5, 1, 5, and 10 µM triclopyr. In zebrafish larvae, uninflated swim bladder was significant only at 50 µM triclopyr. Furthermore, zebrafish larvae had altered swimming activity after exposure to 10 µM triclopyr for 144 h. In summary, these comprehensive results indicate that even low triclopyr concentrations can elicit adverse effects during early zebrafish development.

Oxidative stress is involved in pathophysiological mechanisms associated with a myriad of liver diseases. Bergamot (Citrus bergamia) leaves yield a high level of antioxidant polyphenolic compounds that may hinder the development of liver diseases, while their potential is yet to be fully explored. Thus, the aim of the study was to test the effects of bergamot leaf extract (BLE) on hepatic and mitochondrial oxidative stress in different models. In vivo study: Wistar rats were distributed into two groups: control diet (C) and high-sugar–fat diet (HSF) for twenty weeks. Afterward, the animals were redivided to initiate a ten-week treatment with BLE: C, HSF, and HSF+BLE. In vitro study: Rat hepatic mitochondria were isolated by differential centrifugation and used to assess safety and efficacy of the BLE. Hepatocyte monolayer and spheroids were applied to evaluate the safety of physiologically plausible BLE concentrations and their effects on hydrogen peroxide-induced cytotoxicity. The results showed that BLE improved metabolic parameters, reduced hepatic triglyceride levels, malondialdehyde, and increased catalase activity in vivo. In vitro, BLE decreased lipid peroxidation and increased the ratio of reduced and oxidized glutathione in chemically challenged mitochondria. BLE did not exert cytotoxicity in the hepatocyte monolayer and spheroids, while attenuated oxidative stress-induced cytotoxicity. Data indicate that in vivo and in vitro hepatic oxidative stress is modulated by BLE, reinforcing that BLE may act as an agent against chronic liver diseases.

This chapter provides an overview of the zebrafish (Danio rerio) as a model organism for studies of mitochondrial dysfunction. Zebrafish possess a genetic similarity with humans and have conserved mitochondrial genomes, rendering them a valuable research tool for examining the intricate mechanisms that govern mitochondrial processes at diverse developmental stages. The chapter explores several methods for evaluating mitochondrial health and function. Examples include in vitro cell culture and in vivo analysis in embryos, larvae, and adults. The chapter discusses the use of zebrafish models in toxicological research to investigate mitochondrial reactions to environmental stressors and xenobiotics. The importance of implementing standardized protocols, validating marker, integrating different omics data, and using in vivo and in vitro approaches to advance mitochondrial research will be highlighted. In summary, zebrafish are suitable for analyzing both mitochondrial function and dysfunction, as well as their impact on human health.

The objective of this present study was to evaluate the sub-lethal effects of 2,4-D herbicide and its commercial formula in zebrafish (Danio rerio) adults chronically exposed in relevant environmental concentrations. The fish were exposed to 0.1, 5, and 30 µM of 2,4-D and DMA 806 for 3 months, with solution renewals every 7 days. We analyzed genotoxicity and mutagenicity through the micronucleus (MN) assay, chromosomal instability by quantifying nuclear abnormalities and histopathological alterations of the kidney and liver using H&E staining. We found no significant difference in the relative frequency of MN, which means both 2,4-D and DMA 806 are not mutagenic for zebrafish chronically exposed to these substances. However, there was a significant difference in the relative frequency of total nucleus abnormalities to both substances’ treatments. Lobed nuclei (LN) were the most found, even in relevant environmental concentrations to the commercial formula DMA 806. For histopathological analysis, it was also found a significant difference in kidney and liver index alterations for both 2,4-D acid and DMA 806 treatments compared to the negative control. The commercial formula treatments showed the highest index results, also indicating that it is more toxic than the active ingredient. It can be concluded that in this case, the commercial formula DMA 806, in the salt form of 2,4-D acid, has more potential to be genotoxic and to cause injuries to liver and kidney tissues.