Rapid Communication: oxidative stress induced by mixed exposure to glyphosate and silver nanoparticles.

The aim of this study was to examine oxidative stress induced by the binary mixture of silver nanoparticles (AgNP) and glyphosate (Gly) in Daphnia magna by measurement of reactive oxygen species (ROS) production, glutathione (GSH) levels, enzyme activities of catalase (CAT) and superoxide dismutase (SOD) as well as malondialdehyde (MDA) content. Acute exposure of Daphnia magna to binary mixture of AgNP and Gly resulted in significant biochemical responses indicative of oxidative damage. This response seemed to be related to imbalance in enzymatic/non-enzymatic antioxidant enzymes associated with intracellular overproduction of ROS and significant increase in MDA levels, indicating that the integrity and function of the cell membrane was damaged. These changes adversely affected the fitness and survival of Daphnia magna and negatively influenced offspring growth and reproduction.

Multigenerational Toxic Effects on Daphnia magna Induced by Silver Nanoparticles and Glyphosate Mixture.

Multigenerational toxicological effects of a binary mixture of silver nanoparticles (AgNPs) with glyphosate were identified in Daphnia magna using acute and chronic toxicity tests. Acute toxicity interactions were analyzed with the Abbott method. In the chronic tests, the survival, growth, reproduction, and age at first brood were evaluated for the parents and the exposed (F1E) and non-exposed (F1NE) descendants. The scales tested for binary mixture, at the acute level, presented antagonistic and additive interactions, possibly associated with the complexation of the AgNPs by glyphosate. Multigenerational chronic effects related to the parameters, reproduction, and age at first brood were observed in the descendants tested with the individual compounds, with no recovery for F1E and F1NE. In organisms exposed to binary mixture, there was a delay in the age at first brood and also a significant change in the reproduction parameter, with a strong reduction for the parents, F1E, and F1NE, indicating a higher toxicity than the compounds tested individually. Although the results for acute interactions between AgNP and glyphosate did not provide clear evidence, multigenerational chronic binary mixture trials have resulted in unexpected toxicity compared with individual treatments, increasing the concerns associated with this co-exposure in other scenarios. Therefore, the interaction of binary mixture with the organisms merits further investigation and the results reported in the present study will be useful in this regard. Environ Toxicol Chem 2021;40:1123-1131. © 2020 SETAC.

Study of phenol biodegradation in different agitation systems and fixed bed column: experimental, mathematical modeling, and numerical simulation.

Phenol degradation was studied in two different agitation systems in a batc h reactor (mechanical agitation and orbital agitation) and the support of the most efficient system was used for fixed bed bioreactor studies. The support used was coconut shell charcoal. The results showed that the mechanical agitation bioreactor was more effective in phenol removal, due to the amount of biomass adhered to the support (8.56 mg gsupport-1), running at approximately 100% of the phenol biodegradation in 300 min. The toxicity analysis of the waters was moderate, because the EC50,48h values in the analyzed samples are higher than 50%. Within the experimental data obtained from the batch system, it was possible to find the parameters of the kinetic model of Michaelis-Menten, which was used to simulate the bioreactor in a fixed bed. A mathematical model of a one-equation, which considers the effects of dispersion, convection, and reaction in the liquid phase, and diffusion and reaction inside the biofilm was used and the results obtained through numerical simulation were compared with the experimental results of the bioreactor in a fixed bed, and new operational conditions in the bed were simulated with good accuracy.

Oxidative stress and hypermethylation induced by exposure of Oreochromis niloticus to complex environmental mixtures of river water from Cubatão do Sul, Brazil.

In this study, we investigated the effects of oxidative stress and hypermethylation through lipid peroxidation and DNA methylation, respectively, in erythrocytes of Oreochromis niloticus exposed to environmental complex mixture of water from Cubatão do Sul River throughout the year. This river is the source of drinking water for the region of Florianópolis, the capital of Santa Catarina State, Brazil. Lipid peroxidation was quantified by the rate of malondialdehyde (MDA) formation, and DNA methylation was quantified by the rate of 5-methyldeoxycytosine (m(5)dC) formation. In all studied sites, the river water samples caused metabolic changes in O. niloticus. MDA formation rates were significantly different when compared to the negative control (except for samples from Site 1 during spring 2010, summer 2011 and fall 2011). All samples (except Site 1, spring 2010) induced increases in the m(5)dC formation rates, and at the end of the study, the values were near the values found in the positive control (potassium dichromate 2.5mg/L). The results showed that samples of environmental complex mixtures of water from Cubatão do Sul River are capable of inducing high levels of oxidative damage and hypermethylation in O. niloticus.

Effects of exposure to soluble fraction of industrial solid waste on lipid peroxidation and DNA methylation in erythrocytes of Oreochromis niloticus, as assessed by quantification of MDA and m5dC rates.

In this study, lipid peroxidation and DNA methylation were observed in erythrocytes of Oreochromis niloticus exposed to soluble fractions of textile, metal-mechanic and pulp and paper industrial waste, after a period of 48 h. Lipid peroxidation was quantified by the rate of malondialdehyde (MDA) and DNA methylation was quantified by the rate of 5-methyldeoxycytosine (m5dC). Soluble fractions of textile industrial waste caused metabolic changes for all studied samples. In organisms exposed to samples TX1 and TX2 (textile waste) MDA rates were 132.36 and 140.28 nM MDA/mg protein, respectively, while in control organism the MDA rates were 27.5 nM MDA/mg protein. All samples from soluble fractions of textile industrial waste induced increases in m5dC rates, increases varied between 300 percent and 700 percent when compared to the control organism. All the organisms exposed to soluble fractions of metal-mechanic industrial waste presented increases between 360 percent and 600 percent in the rates of MDA, and one of them (sample MM3) induced an increase of 180 percent in the rate of m5dC, when compared to control. Although a significant increase was not observed in the MDA rate of fish exposed to the soluble fractions of pulp and paper industrial waste, there was an increase of 460 percent in the rate of m5dC in one of the samples (sample PP2), when compared to control. The results showed that the soluble fractions of these industrial wastes are capable of inducing oxidative damage and altering the DNA methylation of O. niloticus. Thus, the MDA and m5dC rates demonstrated to be effective biomarkers of exposure, which could be used to evaluate the toxicity of soluble fractions of industrial solid waste.