Ecological impacts of pesticides on Astyanax jacuhiensis (Characiformes: Characidae) from the Uruguay river, Brazil

Organic contamination and multi-biomarker assessment in watersheds of the southern Brazil: an integrated approach using fish from the Astyanax genus

We aimed to examine the responses of pollution biomarkers in feral fish from Astyanax genus collected at three hydrographic regions in southern Brazil and the capacity of these tools to differentiate between various levels of contamination. To achieve this, levels of organochlorine pesticides (liver), as well as the biomarkers AChE (muscle and brain), TBARS (liver), and EROD (liver) were assessed. Collections were conducted in four municipalities (Alegrete, Caraá, Lavras, and Santa Vitória) during 1 year, encompassing winter and summer. Fish from Alegrete were the most contaminated overall, but animals sampled in Caraá, and Lavras also displayed elevated levels of current-use pesticides. Elevated levels of endosulfans, DDTs, HCHs, and current-use pesticides were accompanied by elevated levels of TBARS in the liver. Conversely, fish from Santa Vitória exhibited the highest levels of PAHs, accompanied by elevated levels of EROD in the liver and reduced levels of AChE in muscle and brain. TBARS proved to be a reliable biomarker for assessing impacts arising from pesticide accumulation, while EROD and AChE served as valuable indicators of impacts resulting from PAHs accumulation. Ultimately, the results obtained in this study demonstrate the reliable use of the proposed biomarkers for tracking biological impacts stemming from aquatic pollution using feral Astyanax as biomonitoring species.

Occurrence of contaminants of emerging concern and their risks to the Pantanal Sul-Mato-Grossense aquatic biota, Brazil

The Aquidauana River is an important ecological corridor in the Pantanal biome. However, the growth of agricultural and urban areas along its banks has contributed to the deterioration of its water quality, consequently putting the aquatic biota at risk. Our objectives were to evaluate: 1) the composition of the landscape around six sampling sites located in the Aquidauana River middle section; and 2) the quality of its water by determining limnological parameters, concentrations of contaminants of emerging concern (CECs), and the risks to native aquatic biota. Water samples were collected in November 2020. We observed the conversion of native riparian vegetation to extensive pasture areas and anthropic occupation around the sampling sites. We observed that the chlorophyll and total ammoniacal nitrogen values were above the standards established by Brazilian legislation in all samples. Studies focused on the quantification of CECs in the Pantanal waters are scarce, and to the best of our knowledge, this is the first study that investigated the presence of pharmaceuticals in the Aquidauana River. All 30 C ECs analyzed were detected in at least one water sample. Eleven CECs were quantified with eight pesticides (atrazine, diuron, hexazinone, tebuthiuron, azoxystrobin, carbendazim, tebuconazole, and fipronil) and one atrazine degradation product (atrazine-2-hydroxy), caffeine, and bisphenol A. The concentrations of atrazine herbicide observed in the water samples pose risks for protecting aquatic biota (RQs >1). Therefore, the native biota of the Pantanal biome is vulnerable to several types of toxic contaminants observed in the water, which can cause the disappearance of native and endemic species in this region. Establishing a monitoring program, improving sanitation infrastructure, and intensifying good agricultural practices are essential for reducing and controlling the entry of CECs into the Aquidauana River and the Pantanal water system.

Atrazine characterization: An update on uses, monitoring, effects, and environmental impact, for the development of regulatory policies in Argentina

Atrazine (ATZ) is the third most widely used herbicide in Argentina (10 000 t year^-1 ) and is approved for sugar cane, flax, corn, sorghum, and tea. An assessment of the ATZ environmental impacts was conducted at the request of the Ministry of Environment and Sustainable Development of Argentina. A review of 541 national and international technical and scientific reports and a survey among agricultural technicians, applicators, and producers was done. The survey revealed that 94% of ATZ applications are terrestrial and use diversion exists, associated mainly with soybean cultivation. Atrazine was reported at high frequencies (50%-100%) in surface and groundwater, sediments, and soils, sometimes exceeding permitted limits. Several sublethal effects induced by ATZ on invertebrate and vertebrate species were found, sometimes at concentrations lower than those in water quality guidelines (<3 µg L^-1 ) or the environmental concentrations found in Argentina. Available epidemiological or human health studies of local populations are extremely scarce. This assessment also demonstrated that herbicides are ubiquitous in the environment. The investigation highlights the need for further studies assessing the adverse effects of ATZ on local species, ecosystems, and human health. Therefore, the precautionary principle is recommended to promote better application standards and product traceability to reduce volumes entering the environment and to avoid use deviation. In addition, this work concluded that there is a need for reviewing the toxicological classification, establishing buffer zones for ATZ application, introducing specific management guidelines, and expanding local studies of toxicity, ecotoxicity, and human epidemiology for environmental and health risk assessments. This study could also serve as a preliminary risk evaluation for establishing a final regulatory action and for considering ATZ inclusion in Annex III of the Rotterdam Convention. Finally, the requirements to consider its inclusion in Annex A (Elimination) or B (Restriction) of the Stockholm Convention were evaluated and discussed, and information on the potential of long-range transport was the only criterion with no information to consider. Integr Environ Assess Manag 2023;19:684-697. © 2022 SETAC.

Fish liver damage related to the wastewater treatment plant effluents

Wastewater treatment plants (WWTPs) continuously release a complex mixture of municipal, hospital, industrial, and runoff chemicals into the aquatic environment. These contaminants are both legacy contaminants and emerging-concern contaminants, affecting all tissues in a fish body, particularly the liver. The fish liver is the principal detoxifying organ and effects of consistent pollutant exposure can be evident on its cellular and tissue level. The objective of this paper is thus to provide an in-depth analysis of the WWTP contaminants' impact on the fish liver structure, physiology, and metabolism. The paper also gives an overview of the fish liver biotransformation enzymes, antioxidant enzymes, and non-enzymatic antioxidants, their role in metabolizing xenobiotic compounds and coping with oxidative damage. Emphasis has been placed on highlighting the vulnerability of fish to xenobiotic compounds, and on biomonitoring of exposed fish, generally involving observation of biomarkers in caged or native fish. Furthermore, the paper systematically assesses the most common contaminants with the potential to affect fish liver tissue.

Biotransformation and oxidative stress responses in fish (Astyanax aeneus) inhabiting a Caribbean estuary contaminated with pesticide residues from agricultural runoff

The estuarine ecosystem of Madre de Dios Lagoon (MDL), in the Caribbean Coast of Costa Rica, is exposed to contamination with pesticide residues coming from the upstream agricultural areas. Biomarkers can provide a better indication of the fitness of biota in real mixture exposure scenarios than traditional lethal dose toxicity measurements. Here, we measured biomarkers of biotransformation, oxidative stress, and neurotoxicity on Astyanax aeneus, an abundant fish species in MDL. Glutathione S-transferase activity (GST), catalase activity (CAT), lipid peroxidation (LPO), and cholinesterase activity (ChE) were measured in fish collected during seven sampling campaigns, carried out between 2016 and 2018. Pesticide residues were analyzed in surface water samples collected every time fish were sampled. Residues of 25 pesticides, including fungicides, insecticides, and herbicides, were detected. The biomarkers measured in A. aeneus varied along the sampling moments, with biotransformation and oxidative stress signals showing a coupled response throughout the assessment. Furthermore, significant correlations were established between three biomarkers (GST, LPO, and CAT) and individual pesticides, as well as between GST and LPO with groups of pesticides with shared biocide action. Among pesticides, insecticide residues had a major influence on the responses observed in fish. This work demonstrates the chronic exposure to pesticide residues in MDL and how such exposure is related to physiological responses in fish that can affect their health and potentially, the trophic networks. This early warning information should be considered to improve the protection of estuarine ecosystems in the tropics.

Mapping Plant Bioaccumulation Potentials of Pesticides from Soil Using Satellite-Based Canopy Transpiration Rates

The transpiration rate is an important factor that determines the bioaccumulation potential of pesticides from soil and can present a spatiotemporal pattern. In the present study, we proposed a satellite-based approach to map the bioaccumulation potential of pesticides from soil using the Global Land Evaporation Amsterdam Model (GLEAM). In the proposed model, the spatiotemporal variable (i.e., plant transpiration rate) was separately analyzed from the plant- and chemical-specific variables. The simulated bioaccumulation factors (BAFs; steady-state concentration ratios between plants and soil) of atrazine and lindane for the United States indicated that the proposed model can better predict the spatiotemporal pattern of bioaccumulation potentials of pesticides from soil than a previous weather-based model. The proposed approach using GLEAM's satellite data avoids the overestimation of plant transpiration rate in regions with a dry and warm climate. The comparison of BAFs between the proposed and weather-based models indicated that the satellite-based simulation was consistent with the weather-based simulation for most states and was more effective for the southwest region. Furthermore, plant- and chemical-specific variables were simulated for over 700 pesticides, which could be multiplied by satellite-based canopy transpiration rates to map the bioaccumulation potentials of chemicals from soil. Further evaluation of plant-specific variables, partitioning behaviors of ionizable compounds, and multiple uptake routes (e.g., airborne residue deposition) will aid in the evaluation of the spatiotemporal patterns of pesticide BAFs in plants in future research. Environ Toxicol Chem 2023;42:117-129. © 2022 SETAC.

Ecological risk of imidacloprid on the Brazilian non-target freshwater organisms Chironomus sancticaroli and Poecilia reticulata

Imidacloprid (IMI) is a neonicotinoid insecticide widely used in agriculture worldwide. This pesticide has been found in freshwater ecosystems, including Brazilian freshwaters. For this reason, studies are being conducted to detect the presence of IMI in freshwater and understand its effects on the aquatic biota. In the present study, the acute toxic effect of the imidacloprid commercial formulation (ICF) Galeão^® on the Brazilian non-target aquatic organisms Chironomus sancticaroli and Poecilia reticulata was evaluated. Enzymatic activities (glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX)) were also determined. Moreover, we considered 11 studies that detected IMI concentrations up to 3.65 µg.L^-1 in 28 different Brazilian freshwaters to evaluate the acute ecological risk of IMI in these environments. From the ecotoxicological assays, we determined the LC₅₀ values for C. sancticaroli (LC_50-48 h 1.52 µg.L^-1) and P. reticulata (LC_50-96 h 122.65 mg.L^-1). The high sensitivity of C. sancticaroli demonstrates that this species could be used as a bioindicator in studies investigating the contamination of freshwater by IMI. Enzymatic activity changes were observed in both organisms and offered sublethal responses to the effects of the pollution by IMI on aquatic biota. Our results suggest that the presence of IMI in Brazilian aquatic ecosystems can represent a potential ecological risk for the aquatic insect populations and, consequently, cause an imbalance in these ecosystems. The present study provides relevant and comparable toxicity information that may be useful to develop public policies to protect the Brazilian aquatic ecosystem from IMI contamination.

Neuro-hepatopathological changes in juvenile Oreochromis niloticus exposed to sublethal concentrations of commercial herbicides

The current study estimates the impact of different common herbicides on antioxidant defenses and histological structure of liver and spinal cord of juvenile tilapia. Eighty-four fish were divided into seven groups: group 1 fish acted as controls and the remaining fish were exposed to sublethal concentrations of acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, or quinclorac at sublethal concentrations 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l, respectively, for 96 h. Antioxidant parameters changed in response to some test herbicides and the greatest effects were caused by exposure to acetochlor and quinelorac for all antioxidant measurements. Prominent histological changes in liver tissue included loss of liver architecture and the appearance of fatty liver cells, necrotic areas, foci of leukocytic infiltration and many apoptotic cells. The most obvious changes in the spinal cord in all treated fish were degradation of myelinated white matter fibers with the emergence of empty spaces, large aggregation of pyknotic neuroglial nuclei, and damaged areas in the dorsal horn of gray matter. Collectively, the harmful effect of tested herbicides on antioxidant capacity and significant alterations in histological structures of liver and spinal cord of Oreochromis niloticus.

Pesticides in surface freshwater: a critical review

The objective of this study was to critically review studies published up to November 2021 that investigated the presence of pesticides in surface freshwater to answer three questions: (1) in which countries were the studies conducted? (2) which pesticides are most evaluated and detected? and (3) which pesticides have the highest concentrations? Using the Prisma protocol, 146 articles published from 1976 to November 2021 were included in this analysis: 127 studies used grab sampling, 10 used passive sampling, and 9 used both sampling techniques. In the 45-year historical series, the USA, China, and Spain were the countries that conducted the highest number of studies. Atrazine was the most evaluated pesticide (56% of the studies), detected in 43% of the studies using grab sampling, and the most detected in passive sampling studies (68%). The compounds with the highest maximum and mean concentrations in the grab sampling were molinate (211.38 µg/L) and bentazone (53 µg/L), respectively, and in passive sampling, they were oxyfluorfen (16.8 µg/L) and atrazine (4.8 μg/L), respectively. The levels found for atrazine, p,p'-DDD, and heptachlor in Brazil were higher than the regulatory levels for superficial water in the country. The concentrations exceeded the toxicological endpoint for at least 11 pesticides, including atrazine (Daphnia LC₅₀ and fish NOAEC), cypermethrin (algae EC50, Daphnia and fish LC₅₀; fish NOAEC), and chlorpyrifos (Daphnia and fish LC₅₀; fish NOAEC). These results can be used for planning pesticide monitoring programs in surface freshwater, at regional and global levels, and for establishing or updating water quality regulations.

Quantifying exposure source allocation factors of pesticides in support of regulatory human health risk assessment

One of the challenges while assessing the aggregate exposure risk of pesticides is quantifying exposure doses from various exposure pathways. To address this issue, a regulatory screening approach is proposed for evaluating pesticide allocation factors (AFs) for major exposure pathways for rural and urban residents. This was achieved by integrating dynamiCrop and other screening models to estimate the potential human intake of residues from major crops at harvest, livestock products, and main environmental media (air, water, and soil). The AFs were calculated from the average daily dose factors (ADDFs) of pesticides via major exposure pathways, where a large AF of an exposure pathway indicates that a greater margin of exposure should be given to that exposure pathway. The simulated results for many current-use pesticides showed that the ingestion of crops had pesticide AFs close to 1.0, which indicated that the crop exposure pathway contributed to a significant portion of the total exposure to pesticides. In contrast, for legacy pesticides with high lipophilicity and low degradability in the environment, the simulated AFs for major environmental compartments (air, freshwater, and soil) accounted for relatively large exposures. As legacy pesticides have been banned globally, exposure pathways via the food web and environmental media cannot be neglected because of their high lipophilicity and environmental persistence. Although other factors such as geographical conditions and living habits should be considered to improve the spatial resolution of the model, the method proposed in this study can serve as a preliminary tool to conduct screening-level risk assessments for populations by considering the allocated exposure to pesticides via major exposure pathways.

Organophosphorus Pesticides as Modulating Substances of Inflammation through the Cholinergic Pathway

Organophosphorus pesticides (OPs) are widespread insecticides used for pest control in agricultural activities and the control of the vectors of human and animal diseases. However, OPs’ neurotoxic mechanism involves cholinergic components, which, beyond being involved in the transmission of neuronal signals, also influence the activity of cytokines and other pro-inflammatory molecules; thus, acute and chronic exposure to OPs may be related to the development of chronic degenerative pathologies and other inflammatory diseases. The present article reviews and discusses the experimental evidence linking inflammatory process with OP-induced cholinergic dysregulation, emphasizing the molecular mechanisms related to the role of cytokines and cellular alterations in humans and other animal models, and possible therapeutic targets to inhibit inflammation.

Concentration of current-use pesticides in frogs from the Pampa region and correlation of a mixture toxicity index with biological effects

Contamination with current-use pesticides is frequently mentioned as a key factor in global amphibian declines although a limited number of studies have examined the mixture of pesticides accumulated by free-living frogs. This study examined the presence of 46 different pesticide residues in the muscle and kidney tissues of two frog species living in close association with row crops in the Pampa region of Argentina: The terrestrial Leptodactylus latinasus and the semi-aquatic Leptodactylus latrans. A total of 20 different pesticides were identified in frog tissues; chlorpyrifos-methyl, pirimiphos-methyl and acetochlor being the most frequently detected molecules. Overall, one or more pesticide residues (up to 12 in a single frog) were detected in 40-57 % of L. latrans. L. latinasus was found to present more pesticide detections than L. latrans. Interestingly, frog sampled in a natural reserve where no pesticides are applied presented an equivalent frequency of detections as frogs living near a crop. In L. latrans, the calculation of a pesticide toxicity index (PTI) permitted to highlight the existence of a strong positive correlation between PTI and liver GSH contents of females whereas, in males, PTI was negatively correlated with the perimeter of testicular seminiferous tubules. Males also presented near significant negative correlations between PTI and both body condition and the scaled fat index. These results indicate that frogs inhabiting agricultural regions are exposed to a complex and diffuse contamination by pesticide mixtures which is likely responsible for a number of biological effects that may be relevant at the population level.

Biochemical and Behavioral Responses in Zebrafish Exposed to Imidacloprid Oxidative Damage and Antioxidant Responses

Imidacloprid (IMI) is an insecticide used worldwide, a neonicotinoid that could cause toxicity in non-target organisms. Zebrafish (Danio rerio) is a model organism widely used in different fields of research such as behavioral studies, biochemical parameters as well as neurotoxicity research. Here, we investigate whether the exposure to three concentrations (0.15, 15, and 45 μg/L) of IMI for 96 h alters responses in zebrafish. Oxidative stress parameters and acetylcholinesterase activity (AChE) as well as the behavioral responses of locomotion were measured. IMI exposure decreased distance traveled in fish exposed to the 45 μg/L. In the exploratory activity, time spent and transitions to the top area of the water column decreased in fish exposed to all concentrations of IMI. In addition, exposures to 45 and 15 μg/L of IMI decreased episodes of erratic movement in the zebrafish. Exposures to IMI at a concentration of 45 μg/L decreased the time spent in erratic movements and increased the time spent with no movement (i.e., "freezing"). Glutathione S-transferase (GST) activity was increased in the brain of zebrafish exposed for 96 h to concentrations of 0.15 and 45 μg/L. Brain AChE activity was reduced and the levels of carbonyl protein (CP) increased in brain of zebrafish at concentrations of 15 and 45 μg/L. Lipid peroxidation measured by TBARS and, also non-protein thiols (NPSH) did not show any variation in the brain of zebrafish exposed to IMI. Changes in the activity of cholinergic neurotransmitters in the brain tissues of zebrafish indicate IMI toxicity. Exposures of fish over 96 h to IMI at a nominal concentration of 45 μg/L caused more extensive sublethal responses in zebrafish, but this concentration is well above those expected in the aquatic environment. Studies are warranted to evaluate the effects on behavior and biomarker responses in fish exposed over longer periods to IMI at environmentally relevant concentrations.

Ecotoxicological assessment of Uruguay River and affluents pre- and post-pesticides' application using Caenorhabditis elegans for biomonitoring

Uruguay River is the most important river in western Rio Grande do Sul, separating Brazil from Argentina and Uruguay. However, its pollution is of great concern due to agricultural activities in the region and the extensive use of pesticides. In a long term, this practice leads to environmental pollution, especially to the aquatic system. The objective of this study was to analyze the physicochemical characteristics, metals and pesticides levels in water samples obtained before and after the planting and pesticides' application season from three sites: Uruguay River and two minor affluents, Mezomo Dam and Salso Stream. For biomonitoring, the free-living nematode Caenorhabditis elegans was used, which were exposed for 24 h. We did not find any significant alteration in physicochemical parameters. In the pre- and post-pesticides' samples we observed a residual presence of three pesticides (tebuconazole, imazethapyr, and clomazone) and metals which levels were above the recommended (As, Hg, Fe, and Mn). Exposure to both pre- and post-pesticides' samples impaired C. elegans reproduction and post-pesticides samples reduced worms' survival rate and lifespan. PCA analysis indicated that the presence of metals and pesticides are important variables that impacted C. elegans biological endpoints. Our data demonstrates that Uruguay River and two affluents are contaminated independent whether before or after pesticides' application season. In addition, it reinforces the usefulness of biological indicators, since simple physicochemical analyses are not sufficient to attest water quality and ecological safety.

A mixture of pesticides at environmental concentrations induces oxidative stress and cholinergic effects in the neotropical fish Rhamdia quelen

The insecticides imidacloprid (IMI), a neonicotinoid, and propoxur (PRO), an N-methylcarbamate compound, are pesticides widely used throughout the world. Although they are not used together to combat pests, both are often found in freshwater near agricultural areas. Thereby, the goal of this study was to evaluate the additive effects of IMI and PRO mixtures at environmental concentrations in relation to isolated compounds on Rhamdia quelen, a neotropical fish. The fish was exposed to IMI (0.11 µg/L), PRO (0.039 µg/L), or Mix (0.11 µg/L IMI plus 0.039 µg/L PRO) during 96 h. Glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), acetylcholinesterase (AChE) activities were determined. To verify oxidative damage thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC), reactive oxygen species contents (ROS), antioxidant capacity against peroxides (ACAP) were determined in gills, liver, brain and muscle. The results shows that a mixture of these pesticides at environmental concentrations inhibited acetylcholinesterase activity in the brain and induced oxidative damage in all analyzed tissues. These results reinforce the hypothesis that mixture of contaminants present in environment could induce additive or synergistic effects on fish species.