Ecotoxicity of doped zinc oxide nanoparticles: Perspectives on environmental safety.

Studies on the ecotoxicity of doped zinc oxide nanoparticles (ZnO NPs) are recent, with the first publications starting in 2010. In this sense, this is the first study that comprehensively reviews the ecotoxicological effects of ZnO NPs doped with lanthanide elements to fill this literature gap. This research explores a multifaceted question at the intersection of nanotechnology, toxicology, and environmental science. Different types of dopants commonly used for ZnO doping were investigated in this review, focusing on the ecotoxicological effects of lanthanides as dopants. Bacteria were the main class of organisms used in ecotoxicological studies, since antimicrobial activity of these nanomaterials is extensively explored to combat the imminent problem of resistant bacteria, in addition to enabling the safe use of these nanomaterials for biomedical applications. Doping appears to exhibit greater efficacy when compared to undoped ZnO NPs in terms of antimicrobial effects; however, it cannot be said that it has no impact on non-target organisms. An extensive examination of the literature also establishes the importance and need to evaluate the effects of doped ZnO NPs on organisms from different environmental compartments in order to identify their potential impacts. We underscore the dearth of research information regarding the environmental toxicity/ecotoxicity of doped ZnO nanoparticles across various ecological levels, thereby limiting the extrapolation of findings to humans or other complex models. Therefore, we emphasize the urgency of a multi-parameter assessment for the development of sanitary and environmentally safe nanotechnologies.

Biomarkers activity in Oreochromis niloticus under sub-chronic exposure to a UV filters ternary mixture.

The behavior of organic UV filters in aquatic ecosystems and living organisms raises concern. For the first time, biochemical biomarkers were evaluated in the liver and brain of juvenile Oreochromis niloticus exposed to 0.001 and 0.5 mg L-1 of a benzophenone-3 (BP-3), octyl methoxycinnamate (EHMC), and octocrylene (OC) mixture for 29 days. Before the exposure, the stability of these UV filters was investigated using liquid chromatography. The experiment with aeration in the aquarium showed a high percentage of concentration reduction (%) after 24 h: 62 ± 2 for BP-3, 96 ± 6 for EHMC, and 88 ± 2 for OC versus 5 ± 4 for BP-3, 8 ± 7 for EHMC, and 2 ± 3 for OC when without aeration. These results defined the bioassay protocol. The stability of the filters concentrations after being stored in PET flasks and subjected to freezing and thawing cycles was also verified. In PET bottles, the BP-3, EHMC, and OC presented concentration reductions of 8 ± 1, 28 ± 7 and 25 ± 5 respectively, after 96 h storage and four freezing cycles. In falcon tubes the concentration reductions observed were 47 ± 2 for BP-3, >95 ± 1 for EHMC and 86 ± 2 for OC after 48 h and two cycles. The 29 days of sub-chronic exposure indicated the occurrence of oxidative stress through the enhanced lipid peroxidation (LPO) levels for the groups exposed to both bioassay concentrations. The catalase (CAT), glutathione-S-transferase (GST), and acetylcholinesterase (AChE) activities did not show significant alterations. The genetic adverse effects were analyzed in erythrocytes of fish exposed to 0.001 mg L-1 of the mixture by comet and micronucleus biomarkers and no significant damage was observed.

Sublethal effects of the herbicides atrazine and glyphosate at environmentally relevant concentrations on South American catfish (Rhamdia quelen) embryos.

The objective of this work was to evaluate the effects following exposure (96 h) of South American catfish (R. quelen) embryos to active ingredients and commercial formulations from atrazine and glyphosate, isolated and in mixtures, at environmentally relevant concentrations. While the survival rates were not affected, sublethal effects were evidenced after exposure. The most frequent deformities were fin damage and axial and thoracic damage. The mixture of active ingredients caused an increase in SOD and GST, differing from the treatment with the mixture of commercial formulations. The activity of AChE was significantly reduced following the treatment with the active ingredient atrazine and in the mixture of active ingredients. In general, herbicide mixtures were responsible for causing more toxic effects to R. quelen embryos. Therefore, these responses showed to be suitable biomarkers of herbicides' exposure, in addition to generating more environmentally relevant baseline data for re-stablishing safety levels of these substances in aquatic bodies.

Effects of environmentally relevant concentrations of atrazine and glyphosate herbicides, isolated and in mixture, on two generation of the freshwater microcrustacean Daphnia magna.

The herbicides atrazine and glyphosate are used worldwide and their excessive usage results in the frequent presence of these pesticides in environmental compartments. We evaluated the effects of environmentally relevant concentrations of analytical standards and commercial formulations of atrazine (2 µg L-1) and glyphosate (65 µg L-1), isolated and in mixture (2 + 65 µg L-1) on the microcrustacean Daphnia magna. Through chronic exposure (21 days) of two generations, we observed effects on survival, reproductive capacity and responses of the antioxidant defense system (catalase) and biotransformation system (glutathione S-transferase). The survival of organisms was affected in the second generation (F1) with a mortality of 17% in the mixture of commercial formulations treatments. In the evaluation of the first generation (F0) we observed only effects on sexual maturation of organisms, while in the F1, changes were observed in all parameters evaluated. A statistical difference (p < 0.05) was also observed between the analytical standards and the commercial formulations for all parameters evaluated, indicating that other components present in the formulations can change the toxicity of products. We suggest that atrazine can modulate toxicity when mixed with glyphosate, as the standard analytical atrazine and mixture of analytical standards results were similar in most parameters. Given the difficulty in estimating effects of mixtures and considering that various stressors are found in the environment, our results support the need to carry out long-term studies and, above all, to verify what are the impacts across generations, so that the toxicity of products is not underestimated. Graphical abstract.

Removal of micropollutants by UASB reactor and post-treatment by Fenton and photo-Fenton: Matrix effect and toxicity responses.

Literature is scarce on the performance of Fenton-based processes as post-treatment of municipal wastewater treated by upflow anaerobic sludge blanket (UASB) reactor. This study aims to perform Fenton and photo-Fenton from UASB influent and effluent matrices to remove micropollutants (MPs) models: atrazine (ATZ), rifampicin (RIF), and 17α-ethynylestradiol (EE2). A UASB reactor at bench-scale (14 L) was operated with these MPs, and the AOPs experiments at bench-scale were performed on a conventional photochemical reactor (1 L). A high-pressure vapor mercury lamp was used for photo-Fenton process (UVA-Vis) as a radiation source. Microcrustacean Daphnia magna (acute toxicity) and seeds of Lactuca sativa (phytotoxicity) were indicator organisms for toxicity monitoring. The UASB reactor showed stability removing 90% of the mean chemical oxygen demand, and removal efficiencies for ATZ, RIF, and EE2 were 16.5%, 45.9%, and 15.7%, respectively. A matrix effect was noted regarding the application of both Fenton and photo-Fenton in UASB influent and effluent to remove MPs and toxicity responses. The pesticide ATZ was the most recalcitrant compound, yet the processes carried out from UASB effluent achieved removal >99.99%. The post-treatment of the UASB reactor by photo-Fenton removed acute toxicity in D. magna for all treatment times. However, only the photo-Fenton conducted for 90 min did not result in a phytotoxic effect in L. sativa.

Ecotoxicity of losartan potassium in aquatic organisms of different trophic levels.

The intensive use of the antihypertensive losartan potassium (LOS) has culminated in its high occurrence in aquatic environments. However, insufficient studies had investigated its effects in non-target organisms. In this study, ecotoxicity of LOS was assessed in aquatic organisms from distinct trophic levels (Desmodesmus subspicatus, Daphnia magna, and Astyanax altiparanae). Genotoxicity was assessed by the comet assay in D. magna and A. altiparanae, and biochemical biomarkers for the fish. LOS was more toxic to D. subspicatus (EC50(72h) = 27.93 mg L-1) than D. magna (EC50 = 303.69 mg L-1). Subsequently, this drug showed to induce more DNA damage in D. magna than A. altiparanae, when exposed to 2.5 mg L-1. No significant stress responses were observed by the fish biomarkers, suggesting that higher trophic levels organisms are more tolerant to LOS toxicity. LOS showed relatively low toxic potential for a short period of exposure, but with different patterns of toxicity for the organisms from distinct trophic levels, contributing to further risk assessment of LOS.

Effects of trophic 2,2', 4,4'-tetrabromodiphenyl ether (BDE-47) exposure in Oreochromis niloticus: A multiple biomarkers analysis.

Polybrominated diphenyl esters are emerging environmental contaminants with few toxicological data, being a concern for the scientific community. This study evaluated the effects of BDE-47 on the health of Oreochromis niloticus fish. The animals were exposed to three doses of BDE-47 (0, 0.253, 2.53, 25.3 ng g-1) every 10 days, for 80 days. The BDE-47 affected the hepatosomatic and gonadosomatic index in female and the condition factor by intermediate dose in both sexes. The levels of estradiol decreased and the T4 are increased, but the vitellogenin production was not modulated in male individuals. Changes in AChE, GST, LPO and histopathology were observed while the integrated biomarker response index suggests that the lowest dose of BDE-47 compromised the activity of antioxidant enzymes. The oral exposure to BDE-47 in environmental concentrations is toxic to O. niloticus and the use of multiple biomarkers is an attribution in ecotoxicology studies and biomonitoring programs.

Ecotoxicity and genotoxicity assessment of losartan after UV/H2O2 and UVC/photolysis treatments.

Losartan potassium (LOS) is one of the most antihypertensives used in the world, and its presence in environmental matrices can cause impacts to biota. In this study, the ecotoxicity and genotoxicity of LOS was assessed before and after treatment by UVC/photolysis and UV/H2O2. The photodegradations were carried out at LOS solutions (2.5 mg L-1; 4.6 µM) for 30, 60, 90, 120, 240, and 480 min of treatment. For chromatographic analysis, the samples were submitted to solid-phase extraction (SPE) and analyzed by HPLC-DAD. Ecotoxicity bioassays were conducted using Daphnia magna (acute) and Desmodesmus subspicatus (chronic) for all the degradation times. To evaluate the genotoxicity, the comet assay was performed with a D. magna whole organism cell suspension applying the alkaline gel electrophoresis technique. For both process, the degradation rate was over 99% at 30 min, which reduced the acute toxicity of LOS to D. magna. In addition, only the sample treated at 240 min by UV/H2O2 showed significant chronic and acute toxicity. However, the genotoxicity effect was observed for samples treated LOS before treatment and at 480 min by UV/H2O2. Therefore, even reaching high LOS degradation rates, for both processes, the bioassays demonstrated the importance of ecotoxicological analyses by AOPs treatment.

Ecotoxicity of malathion pesticide and its genotoxic effects over the biomarker comet assay in Daphnia magna.

Malathion is a highly toxic organophosphate insecticide, being one of the most widely used in the world and is generally used for insect control in food production. Thus, ecotoxicological studies have been used to verify its toxic effects on aquatic organisms, such as Daphnia magna and biomarkers, as the comet assay. The comet assay is a microgel electrophoresis method for the detection and quantification of DNA strand breaks in individual cells. Cells were obtained from Daphnia magna after disaggregation of newborn organisms, exposed at concentrations of 0.23 µg L-1 and 0.47 µg L-1 for 48 h. Malathion has shown to cause damage to DNA of the exposed organisms. It was also observed the need of further studies to standardize the comet assay technique for Daphnia magna, once methodologies used present several differences.

The evaluation of the potential ecotoxicity of pyroligneous acid obtained from fast pyrolysis.

Pyroligneous acid (PA) is a by-product of bio-oil, which is obtained by pyrolysis of the wood. This product has been tested for use in several areas, such as agriculture, as a promising green herbicide; however, there are few scientific data regarding its environmental impacts. For this study, an ecotoxicity testing battery, composed of Daphnia magna acute toxicity test, Allium cepa test and in vitro Comet assay with the rainbow trout gonad-2 cell fish line (RTG-2) were used to evaluate the acute toxicity and genotoxicity of PA obtained from fast pyrolysis of eucalyptus wood fines. The PA presented acute toxicity to D. magna (microcrustacea) with EC50 of 26.12 mg/L, and inhibited the seed germination (EC50 5.556 g/L) and root development (EC50 3.436 g/L) of A. cepa (higher plant). No signs of genotoxicity (chromosomal aberrations and micronuclei in A. cepa and primary DNA lesions in RTG-2 cells) were detected to this product. The acute toxicity and absence of genotoxicity may relate to the molecules found in the PA, being the phenolic fraction the key chemical candidate responsible for the toxicity observed. In addition, daphnids seem to be more sensitivity to the toxicity of PA than higher plants based on their EC50 values. This first ecotoxicological evaluation of PA from fast pyrolysis pointed out the need of determining environmental exposure limits to promote the safer agriculture use of this product, avoiding impacts to living organisms.

Antioxidant imbalance and genotoxicity detected in fish induced by titanium dioxide nanoparticles (NpTiO2) and inorganic lead (PbII).

Titanium dioxide nanoparticles (NpTiO2) are the most widely-used nanoparticle type and the adsorption of metals such as lead (PbII) onto their surface is a major source of concern to scientists. This study evaluated the effects of the associated exposure to both types of contaminant, i.e., lead (a known genotoxic metal) and NpTiO2, in a freshwater fish (Astyanax serratus) through intraperitoneal injection for an acute assay of 96 h. The effects of this exposure were evaluated using the comet assay, DNA diffusion assay and piscine micronucleus test, as well as the quantification of antioxidant enzymes (SOD, CAT, and GST) and metallothioneins. Our findings indicate that co-exposure of PbII with NpTiO2 can provoke ROS imbalances, leading to DNA damage in the blood and liver tissue of A. serratus, as well as modifying erythropoiesis in this species, inducing necrosis and changing the nuclear morphology of the erythrocytes.

Ecotoxicity response of chlorpyrifos in Aedes aegypti larvae and Lactuca sativa seeds after UV/H2O2 and UVC oxidation.

Chlorpyrifos (CP) is an organophosphate pesticide widely used in agriculture known to cause neurological and immunological effects in addition to interfering in the reproduction and development of organisms. In this study, CP degradation by UV/H2O2 process and UVC radiation was investigated, and the ecotoxicity and phytotoxicity was evaluated using bioassays of Aedes aegypti larvae and Lactuca sativa seeds. CP degradation was monitored by HPLC-DAD, and kinetic parameters were calculated for all processes evaluated. Results demonstrated that both processes are efficient, showing a reduction of over 97% of initial CP after 20 and 60 min of UV/H2O2 and UVC radiation, respectively. However, samples treated by UV/H2O2 process demonstrated increase of toxicity, leading to larvae mortality (>90% of organisms) and inhibition effects in seed root growth. The relationship between increased toxicity and the CP byproducts formed was not confirmed due to its low concentration. However, the direct influence of acetonitrile solvent, specifically their toxic byproducts, was observed. This study provides insights into parent compound abatement using oxidative treatment and the changes in toxicity due to the transformation of CP byproducts and complex mixtures (acetonitrile as solvent and hydrogen peroxide).

Evaluation of multiwalled carbon nanotubes toxicity in two fish species.

Carbon Nanotubes are among the most promising materials for the technology industry. Their unique physical and chemical proprieties may reduce the production costs and improve the efficiency of a large range of products. However, the same characteristics that have made nanomaterials interesting for industry may be responsible for inducing toxic effects on the aquatic organisms. Since the carbon nanotubes toxicity is still a controversial issue, we performed tests of acute and subchronic exposure to a commercial sample of multiwalled carbon nanotubes in two fish species, an exotic model (Danio rerio) and a native one (Astyanax altiparanae). Using the alkaline version of the comet assay on erythrocytes and the piscine micronucleous, also performed on erythrocytes, it was verified that the tested carbon nanotubes sample did not generate apparent genotoxicity by means of single/double DNA strand break or clastogenic/aneugenic effects over any of the species, independently of the exposure period. Although, our findings indicate the possibility of the occurrence of CNTs-DNA crosslinks. Apparently, the sample tested induces oxidative stress after subchronic exposure as shown by activity of superoxide dismutase and catalase. The data obtained by the activity levels of acetylcholinesterase suggests acute neurotoxicity in Astyanax altiparanae and subchronic neurotoxicity in Danio rerio.

Saxitoxins induce cytotoxicity, genotoxicity and oxidative stress in teleost neurons in vitro.

The aim of this study was establish a protocol for isolation and primary culture of neurons from tropical freshwater fish species Hoplias malabaricus for assessment of the effects of neurotoxic substances as saxitoxins (STXs). Cells from brain of H. malabaricus were treated with different concentrations of trypsin, dispase and papain for tissue dissociation. Cells type was separated by cellular gradient and basic fibroblast growth factor (bFGF) supplement nutrition media were added. The dissociated cells were plated with medium and different STXs concentrations and the toxic cellular effects such as oxidative stress, neurotoxicity, and genotoxicity and apoptosis process were evaluated. Cultures treated with bFGF showed the greatest adherence, survival and cellular development. STXs increased specific activity of glutathione peroxidase and lipoperoxidation levels, were cytotoxic and genotoxic indicated by the comet assay. Although the STXs effects due the blockage of sodium channels is reported to be reversible, the time exposure and concentration of STXs suggested cellular injuries which can lead to neuropathology. The establishment of primary neuronal culture protocol enables new applications for neurotoxicological assessments.

Hematologic and hepatic responses of the freshwater fish Hoplias malabaricus after saxitoxin exposure.

The bioaccumulation of saxitoxins (STX) in the trophic chain, mainly in freshwater, are not completely known. This work aimed to elucidate the effects of STX on Hoplias malabaricus through trophic bioassay. The fish were fed once every five days with Astyanax sp. before being subjected to an intraperitoneal inoculation with the lysate of Cylindrospermopsis raciborskii culture containing 97% STX and 3% by neosaxitoxin and gonyautoxin during 20 days. The animal's liver was assessed using biomarkers as activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPx), and concentrations of reduced glutathione (GSH) and lipoperoxidation (LPO) and protein carbonylation (PCO). In the blood was analyzed the genotoxic and hematological parameters. The hepatosomatic index and the relative condition factor did not show a significant difference between the exposed and control groups. The values of mean corpuscular hemoglobin concentration and mean corpuscular hemoglobin increased in the STX group. The hepatic tissue from both groups exhibited a typical pattern that have been already described for most teleost fish. The results suggested the generation of reactive oxygen species, with increased activity of GPx and concentrations of LPO and GSH; whereas the specific activity of SOD decreased. However, no changes were observed in the CAT, PCO, and DNA damage. Although the STX effects are known as neurotoxic, this cyanotoxin caused liver biochemical alterations that can be considered ecologically relevant.

Handling of Astyanax sp. for biomonitoring in Cangüiri Farm within a fountainhead (Iraí River Environment Preservation Area) through the use of genetic biomarkers.

Aquatic environmental pollution may cause biodiversity loss. Thus, monitoring studies are very important because fish health reflects both quality and sustainability of the environment, as well as of the individuals that live there. In the present report, genetic biomarkers (piscine micronucleus test; comet assay with blood, liver, and kidney cells) were used in specimens of Astyanax sp. to analyze the contamination level of the Cangüiri Farm through biomonitoring. The Cangüiri Farm, the old school farm of the Federal University of Paraná, is inside the Iraí River Environment Preservation Area, created in 1996 to preserve the sources of public water supply in Curitiba and metropolitan area. We verified that the fishes collected within the Cangüiri Farm area presented high damage levels, showing more environment contamination when compared to the specimens collected in the Costa Ecologic Park, used as reference in the present report. The results indicate that the Cangüiri Farm, which is inside an environment protection area, created especially for the protection of the fountainhead for water supply, may be contaminated. These toxic residues, which were remarkably persistent in the environment, are possibly derived from agricultural activities in the wider area. Thus, we suggest the analysis of the area with other biomarkers and for a longer time period.

Genotoxic evaluation of different doses of methylmercury (CH3Hg⁺) in Hoplias malabaricus.

The survey of the effects of toxic metals and its organic compounds are of critical importance because these compounds tend to accumulate in aquatic environments. In the present work, the genotoxic potential of methylmercury, an organomercurial compound with high toxicity and present in large amounts in fish of the Amazon due to the mining process, was evaluated using the piscine micronucleus test and comet assay in fish. Specimens of Hoplias malabaricus (popularly known as traira), a neotropical specie, was exposed to methylmercury via food web, over 70 days, in two different concentrations: two groups of fifteen fish were tested with 0.075 µg CH(3)Hg(+)/g and 0.75 µg CH(3)Hg(+)/g of methylmercury per gram of fish, at 5-day intervals and over 14 successive intervals whereas control group, composed by nine fish, was fed by uncontaminated prey fish (Astyanax sp). One of the aims of this study was to reproduce the contamination found in nature in an attempt to increase our biological knowledge on the neotropical species. Hoplias malabaricus specimens were then anesthetized for removal of blood samples and dissected, for cephalic kidney removal. As a result, it was observed that the piscine micronucleus test showed no significant differences between exposed groups and control group. The comet assay performed on erythrocyte system cells, showed a significant difference between controls and contaminated, but there was no difference between doses. In contrast, the kidney cells comet assay showed no significant difference between groups, probably due to the type of damage caused by xenobiotics to be related to the tissues of most contact with it, as well as its mode of action and the chain of bioaccumulation within bodies.

Chronic genetic damages in Geophagus brasiliensis exposed to anthropic impact in estuarine lakes at Santa Catarina coast--southern of Brazil.

Biological monitoring through animals exposed to pollutants using biomarkers provides a promising tool for the identification of pollutants that may cause damage to human health and/or to sustainability of ecosystems. The effects of pollutants in fish tissues are important tools to understand the impact of human activities in natural ecosystems. The aim of this work was to study the water quality of two estuarine lakes in Santa Catarina, Brazil (Camacho Lake and Santa Marta Lake). Geophagus brasiliensis is a species widely distributed in Brazil and was used in this work. Comet assays in peripheral red blood and kidney cells, micronucleus tests in peripheral red blood cells, measurements of acetylcholinesterase activity in axial muscle and histopathological analysis of liver were used as biomarkers. Three sampling campaigns were undertaken in November 2004, June 2005 and November 2005. Thirty adult animals were sampled from each of three different sites (P1--Santa Marta Lake, P2 and P3--Camacho Lake). A negative control was sampled in a non-polluted site at Costa Ecological Park, Paraná. The positive control for genotoxicity was obtained by treating animals with copper sulphate. The results showed that both studied lakes are impacted by potential genotoxic substances. Severe lesions in liver of G. brasiliensis were also observed. The inhibition of acetylcholinesterase activity suggests the presence of pesticides or metals in the studied sites. This work shows that the water quality of Santa Marta and Camacho Lakes have been compromised and further control source of pollutants into these ecosystems is required.

First report about saxitoxins in freshwater fish Hoplias malabaricus through trophic exposure.

Cyanobacterial waterblooms, such as the saxitoxin (STX) producer Cylindrospermopsis raciborskii, have been a worldwide concern in environmental health. However, the bioaccumulation of this neurotoxin in the trophic chain is not completely known. The aim of the present work was to evaluate STX bioaccumulation through chemical analyses and the toxic and trophic effects using biomarkers in the tropical freshwater fish Hoplias malabaricus. They were fed once every five days with Astyanax sp. before being subjected to intraperitoneal inoculation with STX extract (0.08 µg/100 g) obtained by lysis of toxic C. raciborskii strain (T3). After 20 days the brain was collected for acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione (GSH), lipoperoxidation (LPO), protein carbonylation (PCO), and comet assay analysis. The muscle was collected for STX chemical analysis. The activities of SOD and concentrations of PCO and LPO increased. The CAT, GST, and GPx activities decreased. Genotoxicity was observed in the experimental group. STX was not detected in muscle samples. Thus, an oxidative stress was observed in the brain, leading to the damage of lipids, proteins, and DNA. The mechanism of action of the neurotoxin in this subchronic exposure suggests an apoptotic cellular process.

Evaluation of genotoxicity in Rhamdia quelen (Pisces, Siluriformes) after sub-chronic contamination with Fipronil.

Diverse genetic biomarkers have been used to evaluate the effects of pollution by mutagenic agents such as metals and pesticides, as well as a large variety of chemical substances derived from human activities. This work researched the effects that an exposure of 60 days to the insecticide Fipronil (concentrations of 0.05, 0.10 and 0.23 µg/L) can cause in the fish Rhamdia quelen using Comet assay with gills, histopathological analysis of gills and the Piscine Micronucleus test and Nuclear Morphological Alterations. The results for the Comet assay and for gills histopathological injuries showed no difference between the control group and the contaminated groups. In the Piscine Micronucleus test, the smallest concentration of Fipronil (0.05 µg/L) was similar as the control group, while concentrations of 0.10 and 0.23 µg/L caused more damage to the DNA. These results suggested that only the highest concentrations of Fipronil tested cause damage in erythrocytes, but none of these concentrations was sufficient to alter the DNA in the gill cells. R. quelen may be a less sensitive bioindicator than other fish that have been tested. On the other hand, the concentrations used may not have been sufficient to detect alterations in the DNA of R. quelen with the chosen tests. Works like this take on great importance given the enormous quantity of substances that are thrown daily into the environment in an uncontrolled way, without evaluation of the consequences. The application of these tests with other concentrations, tissues and exposure times is suggested for future works.