Responses of the aquatic midge Chironomus riparius to DEET exposure

Models for the No-Observed-Effect Concentration (NOEC) and Maximal Half-Effective Concentration (EC50)

Typical in silico models for ecotoxicology focus on a few endpoints, but there is a need to increase the diversity of these models. This study proposes models using the NOEC for the harlequin fly (Chironomus riparius) and EC50 for swollen duckweed (Lemna gibba) for the first time. The data were derived from the EFSA OpenFoodTox database. The models were based on the correlation weights of molecular features used to calculate the 2D descriptor in CORAL software. The Monte Carlo method was used to calculate the correlation weights of the algorithms. The determination coefficients of the best models for the external validation set were 0.74 (NOAEC) and 0.85 (EC50).

Recent advances in degradation of N,N-diethyl-3-toluamide (DEET)-an emerging environmental contaminant: a review

N,N-Diethyl-3-toluamide (DEET) is a commonly used insect repellent, which acts as an organic chemical contaminant in water and considered as an emerging contaminant which has been observed worldwide. It gets discharged into the environment through sewage waste. The various methods have been used to degrade DEET, such as UV based, ozonation, photocatalytic degradation, and biodegradation (based on the metabolic activity of fungi and bacteria). However, less research has been done on the degradation of DEET by deploying nanoparticles. Therefore, biodegradation and nanotechnology-based methods can be the potential solution to remediate DEET from the environment. This review is an attempt to analyze the routes of entry of DEET into the atmosphere and its environmental health consequences and to explore physical, chemical, and biological methods of degradation. Furthermore, it focuses on the various methods used for the biodegradation of the DEET, including their environmental consequences. Future research is needed with the application of biological methods for the degradation of DEET. Metabolic pathway for biodegradation was explored for the new potent microbial strains by the application of physical, chemical, and microbial genomics; molecular biology; genetic engineering; and genome sequencing methods.

Physiological impact of personal care product constituents on non-target aquatic organisms

Personal care products (PCPs) are products used in cleaning, beautification, grooming, and personal hygiene. The rise in diversity, usage, and availability of PCPs has resulted in their higher accumulation in the environment. Thus, these constitute an emerging category of environmental contaminants due to the potential of its constituents (chemical and non-chemical) to induce various physiological effects even at lower concentrations (ng/L). For analyzing the impact of the PCPs constituents on the non-target organism about 300 article including research articles, review articles and guidelines were studied from 2000 to 2023. This review aims to firstly discuss the fate and accumulation of PCPs in the aquatic environment and organisms; secondly provides overview of environmental risks that are linked to PCPs; thirdly review the trends, current status of regulations and risks associated with PCPs and finally discuss the knowledge gaps and future perspectives for future research. The article discusses important constituents of PCPs such as antimicrobials, cleansing agents and disinfectants, fragrances, insect repellent, moisturizers, plasticizers, preservatives, surfactants, UV filters, and UV stabilizers. Each of them has been found to display certain toxic impact on the aquatic organisms especially the plasticizers and UV filters. These continuously and persistently release biologically active and inactive components which interferes with the physiological system of the non-target organism such as fish, corals, shrimps, bivalves, algae, etc. With a rise in the number of toxicity reports, concerns are being raised over the potential impacts of these contaminant on aquatic organism and humans. The rate of adoption of nanotechnology in PCPs is greater than the evaluation of the safety risk associated with the nano-additives. Hence, this review article presents the current state of knowledge on PCPs in aquatic ecosystems.

Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT-mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT-mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT-mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT-mag diminished PW toxicity. Therefore, using VMT-mag to treat PW may be the key to reducing the PW effects on aquatic organisms.

Bioconcentration and cellular effects of emerging contaminants in sponges from Maldivian coral reefs: A managing tool for sustainable tourism

Tourism is the main income source for the Maldives, but concurrently, it represents a growing threat to its marine ecosystem. Here, we monitored the bioaccumulation of 15 emerging contaminants (ECs) in the Maldivian reef sponges Spheciospongia vagabunda collected in two resort islands (Athuruga and Thudufushi, Ari Atoll) and an inhabited island (Magoodhoo, Faafu Atoll), and we analysed their impact on different sponge cellular stress biomarkers. Caffeine and the insect repellent DEET were detected in sponges of all the islands, whereas the antibiotic erythromycin and the UV filter 4-methylbenzylidene camphor were found in resort islands only. Although concentrations were approximately a few ng/g d.w., we quantified various induced cellular effects, in particular an increase of the levels of the enzyme glutathione S-transferase involved in cell detoxification. Our results highlight the importance to increase awareness on ECs pollution, promoting the use of more environmental friendly products to achieving the sustainable development goals.

Transcriptomic and metabolomic integration to assess the response of gilthead sea bream (Sparus aurata) exposed to the most used insect repellent: DEET

DEET is one of the most frequently detected insect repellents in the environment reaching concentrations of several μg L^-1 in surface water. There is scarce information available regarding its mode of action in non-target organisms. Here, we have used an integrated metabolomic and transcriptomic approach to elucidate the possible adverse effects of DEET exposure in the marine fish gilthead sea bream (Sparus aurata). Individuals were exposed at an environmentally relevant concentration of DEET (10 μg L^-1) for 22 days in a continuous flow-through system. Transcriptomic analysis revealed 250 differentially expressed genes in liver, while metabolomic analysis identified 190 differentially modulated features in liver and 98 in plasma. Multi-omic data integration and visualization allowed elucidation of the modes of action of DEET exposure, including: energy depletion through the disruption of carbohydrate and amino acids metabolisms, oxidative stress leading to DNA damage, lipid peroxidation, and damage to cell membrane and apoptosis. Activation of xenobiotic pathway as well as the inmune-inflammatory reaction was evidenced in the present work.

Environmental quality and ecotoxicity of sediments from the lower Salado River basin (Santa Fe, Argentina) on amphibian larvae

The lower Salado River basin receive agricultural, industrial and domestic waste water. So, the aim was to evaluate the quality of three sampling sites that belong to the Salado River basin (S1: Cululú stream; S2: Salado River, at Esperanza City, S3: Salado River at Santo Tomé City) based on physicochemical parameters, metals and pesticides analyses and ecotoxicity on Rhinella arenarum larvae. R. arenarum larvae (Gosner Stage -GS- 25) were chronically exposed (504h) to complex matrixes of surface water and sediment samples of each site for the determination of the survival rate. Biomarkers of oxidative stress, neurotoxicity and genotoxicity were analyzed in R. arenarum larvae (GS. 25) after exposure (96h) to the complex matrix of water and sediment. The water quality index showed a marginal quality for all sites, influenced mainly by low dissolved oxygen, high total suspended solid, phosphate, nitrite, conductivity, Pb, Cr and Cu levels. Metal concentrations were higher in sediment than in water samples (˜34-35000 times). In total, thirty different pesticides were detected in all water and sediment samples, S1 presented the greatest variety (26). Glyphosate and AMPA were detected in sediments from all sites, being higher in S3. N,N-Diethyl-meta-toluamide (DEET) and atrazine were detected in all water samples. Greatest mortality was observed in larvae exposed to samples from S1 from 288h (43.3%), reaching a maximum value of 50% at 408h. Oxidative stress and genotoxicity were observed in larvae exposed to S1 and S3 matrix samples. Neurotoxicity was observed in larvae exposed to all matrix samples. The integrated biomarker response index showed that larvae exposed to S1 and S3 were the most affected. According to the physicochemical data and the ecotoxicity assessment, this important river basin is significantly degraded and may represent a risk to aquatic biota, especially for R. arenarum larvae.

The screening of emerging micropollutants in wastewater in Sol Plaatje Municipality, Northern Cape, South Africa

Although pollutants pose environmental and human health risks, the majority are not routinely monitored and regulated. Organic pollutants emanate from a variety of sources, and can be classified depending on their chemistry and environmental fate. Classification of pollutants is important because it informs fate processes and apposite removal technologies. The occurrence of emerging contaminants (ECs) in water bodies is a source of environmental and human health concern globally. Despite being widely reported, data on the occurrence of ECs in South Africa are scarce. Specifically, ECS in wastewater in the Northern Cape in South Africa are understudied. In this study, various ECs were screened in water samples collected from three wastewater treatment plants (WWTPs) in the province. The ECs were detected using liquid chromatography coupled to high resolution Orbitrap mass spectrometry following Oasis HLB solid-phase extraction. The main findings were: (1) there is a wide variety of ECs in the WWTPs, (2) physico-chemical properties such as pH, total dissolved solids, conductivity, and dissolved organic content showed reduced values in the outlet compared to the inlet which confirms the presence of less contaminants in the treated wastewater, (3) specific ultraviolet absorbance of less than 2 was observed in the WWTPs samples, suggesting the presence of natural organic matter (NOM) that is predominantly non-humic in nature, (4) most of the ECs were recalcitrant to the treatment processes, (5) pesticides, recreational drugs, and analgesics constitute a significant proportion of pollutants in wastewater, and (6) NOM removal ranged between 35 and 90%. Consequently, a comprehensive database of ECs in wastewater in Sol Plaatje Municipality was created. Since the detected ECs pose ecotoxicological risks, there is a need to monitor and quantify ECs in WWTPs. These data are useful in selecting suitable monitoring and control strategies at WWTPs.

Functionalized magnetic nanostructured composites and hybrids for photocatalytic elimination of pharmaceuticals and personal care products

Due to rapid urbanization and globalization, an enormous use of pharmaceuticals and personal care products (PPCPs) has resulted their excessive release in water bodies leading to several environmental issues. This release into the environment takes place via household sewage, hospital effluents, manufacturing units and landfill sites etc. The pharmaceuticals and personal care products (PPCPs) are recently listed as emerging contaminants having many adverse effects towards aquatic life, human beings, and the whole ecosystem. The alarming threats of PPCPs demand efficient methods to cope up their hazardous impacts. The conventional wastewater remediations are not specifically designed for the removal of PPCPs and hence, they require advanced technologies and materials for their elimination to ensure water safety. Among various methods employed so far, photocatalysis is considered to be one of the most cost effective and eco-friendly method but it requires a suitable candidate as a photocatalyst. Thanks to the magnetic nanocomposites which have improved the limitations (poor stability, agglomeration, and difficult separation, etc.) of classically used nanomaterials. Magnetic nanocomposites contain at least one component having magnetic properties making their separation easy from the aqueous media after the photodegradation phenomenon. These can be further functionalized with other materials to obtain maximum advantage as photocatalyst. Few examples of such functionalized nanocomposites are inorganic material based magnetic nanocomposites, carbon based magnetic nanocomposites, biomaterial based magnetic nanocomposites, metal-organic framework based magnetic nanocomposites and polymer based magnetic nanocomposites etc. This review covers the global environmental issue of water pollution especially with respect to the PPCPs, their occurrence in aqueous environment and toxic effects on living beings. A comprehensive discussion of the recently reported functionalized magnetic nanocomposites for the photocatalytic removal of PPCPs from water is the main aim of this review. The synthetic/morphological approaches of various functionalized magnetic composites and their mechanism of action are also elaborated. The possible research challenges in the field of magnetic nanocomposites and future research directions are discussed to apply magnetic nanocomposites for wastewater treatment in near future.

Combined effects of polyethylene microplastics and natural stressors on Chironomus riparius life-history traits

Several studies have shown that ingestion of microplastics causes adverse effects in aquatic organisms, including sediment-dwelling invertebrates. Most studies focus on evaluating the effects of plastic particles alone without testing the mediating effects of different natural stressors and thus lacking realistic exposure scenarios. The present study addresses the interactive effects of exposure to polyethylene microplastics (PE-MPs; 2.5 g/kg) in the midge Chironomus riparius life history traits under different temperatures (15, 20 and 25 °C), a salinity gradient (0, 1 and 3 g L^-1 sodium chloride - NaCl) and different levels of food (0.5, 0.25 and 0.125 mg macerated fish food larva^-1day^-1). By the analyses of linear models and independent action models applied to different life-history traits, such as larval growth, development time and imagoes body weight, the present work reveals that under temperatures lower than 20 °C or severe food shortage (<0.25 mg macerated fish food larva^-1day^-1), microplastics' effects can be stronger than those observed at standard toxicity test conditions (20 °C and 0.5 mg food larva^-1day^-1). Additionally, we also found that, in general, toxicity induced by PE-MPs to C. riparius larvae was reduced under warmer temperature (25 °C) and salinity. As observed, MPs toxicity can be mediated by natural stressors, which underlines the importance of co-exposure studies. In this sense, these results contribute to a more accurate risk assessment of microplastics. Despite the complex interactions between microplastics and natural factors here tested, were not found evidence that the deleterious effects of PE-MPs on C. riparius life cycle history are aggravated under increased temperature, food shortage, or salinisation of freshwaters.

Can the toxicity of polyethylene microplastics and engineered nanoclays on flatfish (Solea senegalensis) be influenced by the presence of each other?

Microplastics and nanomaterials are applied in a myriad of commercial and industrial applications. When leaked to natural environments, such small particles might threaten living organisms' health, particularly when considering their potential combination that remains poorly investigated. This study investigated the physiological and biochemical effects of polyethylene (PE; 64-125 μm in size, 0.1, 1.0, and 10.0 mg·L^-1) single and combined with an engineered nanomaterial applied in antifouling coatings, the copper-aluminium layered double hydroxides (Cu-Al LDH; 0.33, 1.0, and 3.33 mg·L^-1) in the flatfish Solea senegalensis larvae (8 dph) after 3 h exposure, in a full factorial design. Particles ingestion, histopathology, and biochemical biomarkers were assessed. Fish larvae presented <1 PE particles in their gut, independently of their concentration in the medium. The histological health index showed minimal pathological alterations at PE combined exposure, with a higher value observed at 1 mg LDH·L^-1 × 0.1 mg PE·L^-1. Gut deformity and increased antioxidant defences (catalase), neurotransmission (acetylcholinesterase), and aerobic energy production (electron transport system) were observed at PE ≥ 1.0 mg·L^-1. No oxidative damage (lipid peroxidation) or alterations in the detoxification capacity (glutathione-S-transferase) was observed on single and combined exposures. PE, combined or not with Cu-Al LDH, does not seem to compromise larvae's homeostasis considering levels reported so far in the marine and aquaculture environments. However, harsh effects are expected with MP contamination rise, as projections suggest.

Ecotoxicological effects, environmental fate and risks of pharmaceutical and personal care products in the water environment: A review

Due to the extensive use and incomplete removal, pharmaceutical and personal care products (PPCPs) are introduced into the water continuously. It has been proved that the unique properties of PPCPs are influential to organisms and the environment, and gradually affect human health. In this paper, the toxicological effects of typical PPCPs, and the environmental behavior of PPCPs in aquatic are reviewed. The risk assessments of PPCPs in the water are summarized. The research directions of environmental toxicology research of PPCPs in the future are proposed. Many PPCPs were found to be toxic or even highly toxic toward aquatic organisms, and have the potential for bioaccumulation. It is essential to study the acute and long-term toxicity of PPCPs and their metabolites, evaluate the environmental behaviors and make a reasonable assessment of ecotoxicology and human health risks of PPCPs.

Persistent pesticides: effects of endosulfan at the molecular level on the aquatic invertebrate Chironomus riparius

Although banned in multiple areas, due to its persistence in the environment, endosulfan constitutes a significant environmental concern. In this work, fourth instar Chironomus riparius larvae were exposed at environmentally relevant endosulfan concentrations of 0.1, 1, and 10 μg/L for 24 h to analyze the possible effects of this acaricide on gene expression and enzymatic activity. Transcriptional changes were studied through the implementation of a real-time polymerase chain reaction array with 42 genes related to several metabolic pathways (endocrine system, detoxification response, stress response, DNA reparation, and immune system). Moreover, glutathione-S-transferase (GST), phenoloxidase (PO), and acetylcholinesterase (AChE) activities were assessed. The five pathways were differentially altered by endosulfan exposure with significant changes in the E93, Dis, MAPR, Met, InR, GSTd3, GSTt3, MRP1, hsp70, hsp40, hsp24, ATM, PARP, Proph, and Def genes. Besides, all of the measured enzymatic activities were modified, with increased activity of GST, followed by PO and AChE. In summary, the results reflected the effects provoked in C. riparius at molecular level despite the absence of lethality. These data raise concerns about the strong alteration on different metabolic routes despite the low concentrations used. Therefore, new risk assessment strategies should consider include the effects at the sub-organismal level as endpoints in addition to the classical ecologically relevant parameters (such as survival). This endeavor will facilitate a comprehensive evaluation of toxicants in the environment.

Are Microplastics Impairing Marine Fish Larviculture?—Preliminary Results with Argyrosomus regius

The presence of small-sized (<300 µm) microplastics (MPs) in aquaculture facilities may threaten finfish hatchery, as their (in)voluntary ingestion by fish larvae may compromise nutritional requirements during early ontogeny, and consequently larval health and performance. Thus, we addressed the short-term effects (7 h) of polyethylene microplastics (0.1, 1.0, 10 mg/L, PE-MPs) in meagre larvae Argyrosomus regius (15 dph) in the presence/absence of food. Larval feeding behavior, oxidative stress status, neurotoxicity, and metabolic requirements were evaluated. Results showed that meagre larvae ingested PE-MPs regardless of their concentration, decreasing in the presence of food (Artemia metanauplii). The presence of PE-MPs compromised larval feeding activity at the highest concentration. Under starvation, exposed larvae activated the antioxidant defenses by increasing the total glutathione levels and inhibiting catalase activity, which seemed efficient to prevent oxidative damage. Such larvae also presented increased energy consumption potentially related to oxidative damage prevention and decreased neurotransmission. Biochemical responses of fed larvae showed a similar trend, except for LPO, which remained unaffected, except at 0.1 mg/PE-MPs/L. Our results suggest that small-sized MPs in finfish hatcheries may compromise larvae nutritional requirements, but at considerably higher levels than those reported in marine environments. Nevertheless, cumulative adverse effects due to lower MPs concentrations may occur.

Strategies of cellular energy allocation to cope with paraquat-induced oxidative stress: Chironomids vs Planarians and the importance of using different species

Paraquat (PQ) is still used in several countries worldwide as an herbicide for weed control in agricultural production, ponds, reservoirs and irrigation canals. Thus, PQ is frequently found in surface water systems and is potentially toxic to aquatic organisms, since it can cause mitochondrial dysfunction altering in the redox state of cells. This study aimed to investigate the chronic effects of PQ to Chironomus riparius and Girardia tigrina, and compare their physiological strategies to cope with environmental stress. The mean emergence time was the most sensitive endpoint for Chironomids, with the lowest observed effect concentrations (LOEC) being 0.02 for males and 0.1 mg PQ L^-1 for females. Moreover, PQ reduced the body weight of male and female imagoes, with LOECs of 0.5 and 2.5 mg PQ L^-1, respectively. Paraquat also decreased the respiration rate (LOEC = 2.5 mg PQ L^-1) and total glutathione (tGSH) content (LOEC = 0.5 mg PQ L^-1). Thus, the aerobic production of energy was not affected and allowed chironomids to cope with oxidative stress induced by PQ, but with consequent physiological costs in terms of development rates and weight of adults. In planarians, PQ decreased the locomotion and feeding activity, and delayed photoreceptor regeneration (LOECs = 2.5 mg PQ L^-1 for all endpoints). Despite increased aerobic energy production (LOEC = 0.5 mg PQ L^-1), planarians were not able to cope with oxidative stress induced by the highest PQ concentrations, since lipid peroxidation levels were significantly increased (LOEC = 2.5 mg PQ L^-1) concomitantly with a significant decrease of tGSH (LOEC = 2.5 mg PQ L^-1). These results showed that planarians were unable to cope with oxidative stress induced by PQ with consequent impairments of behavior and regeneration despite an increased aerobic energy production.

Effects of lethal and sublethal concentrations of peracetic acid and active chlorine of calcium hypochlorite on Chironomus xanthus

Freshwater ecosystems are vulnerable to residual concentrations of chemical agents from anthropogenic activities, and the real impacts of such compounds can only be evaluated accurately using ecotoxicological tests. The assessment of ecotoxicological effects of peracetic acid (PAA) and the active chlorine of calcium hypochlorite (Ca(ClO)₂) on the insect Chironomus xanthus Meigen (Diptera: Chironomidae) is highly relevant as there are few reports on its effects in fresh water ecosystems. To our best knowledge, this is the first study to assess the chronic toxicity of the compounds to C. xanthus. The toxicity bioassays for C. xanthus included the acute effect (CL₅₀) and the chronic effects based on body length, head width, and cumulative emergence. The results obtained in the acute effect tests indicated that the active chlorine of Ca(ClO)₂ is 14 fold more toxic than PAA to C. xanthus. In sublethal evaluations, the active chlorine of Ca(ClO)₂ presented higher toxicity than PAA in terms of percentage emergence, body development, and head width. In general, the results showed lower PAA toxicity relative to the active chlorine of Ca(ClO)₂, demonstrating that PAA is a promising substitute for chlorinated disinfectants. In addition, the study facilitates the establishment of reference values for the safe release of effluents treated with PAA into water bodies.

Genotoxic, metabolic, and biological responses of Chironomus sancticaroli Strixino & Strixino, 1981 (Diptera: Chironomidae) after exposure to BBP

Benzyl butyl phthalate (BBP), which is widely used in industrial production, reaches the aquatic environment, mainly owing to improper disposal of plastic products. In the water, it remains adsorbed to sedimentary particles causing toxic effects in aquatic invertebrates such as Chironomidae, which are important in maintaining ecosystem dynamics and are an important link in the food chain. However, the effects of BBP on Chironomidae are still poorly known. Thus, the toxic effects of BBP on Chironomus sancticaroli at acute (48 h), subchronic (8 d), and chronic (25 d) exposures of concentrations between 0.1 and 2000 μg·L^-1 were determined. Genotoxicity effects, changes in the oxidative stress pathway, and development and emergence of organisms were evaluated. Biochemical markers showed a reduction in cholinesterase (ChE) activity, indicating a neurotoxic effect on acute exposure (1-1000 μg·L^-1). The antioxidant pathway, glutathione S-transferase (GST) activity showed reduction on acute (0.1; 1-2000 μg·L^-1) and subchronic (1-2000 μg·L^-1) exposures and reduction in superoxide dismutase (SOD) activity at all evaluated concentrations, suggesting oxidative stress. In contrast, lipid peroxidation was not observed. DNA damage occurred on acute (10 μg·L^-1) and subchronic (10-2000 μg·L^-1) exposures, indicating genotoxic effects. At concentrations above 10 μg·L^-1, no emergence of adults occurred, while lower concentrations (0.1 and 1 μg·L^-1) showed a reduction in the number of adults, mainly males. The observed effects indicate that BBP is genotoxic and causes biochemical alterations presenting high toxicity at the population level.

Toxicity of microbial insecticides toward the non-target freshwater insect Chironomus xanthus

BACKGROUND

Commercial formulations based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) are commonly used microbial insecticides in Brazil and other tropical regions. However, and despite being considered environmentally friendly, their use generates concerns regarding possible adverse ecological effects in freshwater ecosystems. Here, we evaluate the effects of these bioinsecticides on the tropical aquatic dipteran Chironomus xanthus under laboratory conditions.

RESULTS

After laboratory exposures to these compounds 48-h median lethal concentration (LC₅₀ ) values of 1534 μg a.i./L for Btk and of 6.35 μg a.i./L for Bb were estimated. Chronic assays revealed different sublethal effects: Btk-based bioinsecticide exposure reduced C. xanthus growth [lowest observed effect concentration (LOEC) was 126 μg a.i./L for head width], decreased emergence rate (LOEC = 8 μg a.i./L) and increased immunological response (LOEC = 50 μg a.i./L) measured as total hemocyte count in larvae hemolymph. Exposure to low concentrations of Bb-based insecticide also reduced C. xanthus growth (LOEC = 0.07 μg a.i./L for larvae body length measurements), and emergence rate (LOEC = 0.28 μg a.i./L), despite no clear effects on the total hemocyte counts.

CONCLUSION

Our results suggest that low concentrations of Btk and Bb bioinsecticides are toxic to C. xanthus. Given their widespread use and occurrence in tropical freshwater systems, research is needed to evaluate the potential effects of these compounds concerning natural freshwater insect communities and ecosystem functioning. © 2019 Society of Chemical Industry.

Aquatic life criteria derivation and ecological risk assessment of DEET in China

N,N-diethyl-meta-toluamide (DEET) is the most widely used active ingredient in commercial insect repellents. In addition to its adverse effects in insects, DEET can affect non-target organisms in surface water systems. Nevertheless, the aquatic life criteria of DEET are not available. This study conducted both acute and chronic toxicity tests on DEET in native Chinese aquatic species, and derived its criterion maximum concentration (CMC) and criterion continuous concentration (CCC). The determined CMC and CCC of DEET were 21.53 and 0.52 mg/L, respectively. The toxicity data indicated that DEET exposure posed a higher toxicity to some algae than other aquatic species. Compared with other insect repellents, DEET exposure posed a moderate toxicity to aquatic species. Therefore, the exposure concentration of DEET in Chinese surface water was collected to assess the potential ecological risk. The preliminary ecological risk assessment showed that DEET posed negligible risk to aquatic ecosystems in China. However, considering its toxic effects on the growth and reproduction to aquatic organisms, the ecological risk posed by DEET is worth further concern.

Combined effects of benzophenone-3 and temperature on gene expression and enzymatic activity in the aquatic larvae Chironomus riparius

Climate change and pollution are two of the main environmental problems living organisms currently face. Temperature can modify a toxicant's effects and the organism's response to it. Global warming is expected to increase the temperature of freshwater ecosystems. In this work, we analyzed the effect of a mild temperature increase on the acute response of the aquatic larvae Chironomus riparius to the ultraviolet filter benzophenone-3 (BP3). This substance is commonly used in sunscreens and other commercial products and can reach the environment in different ways. We exposed larvae to BP3 at 18.5 or 23 °C for 8 or 24 h and analyzed the acute response at the molecular level. By quantitative real-time polymerase chain reaction (q-PCR), we studied altered messenger RNA (mRNA) levels of genes related to the endocrine system (EcR, InR and Met), detoxification mechanisms (Cyp4d2, Cyp6b7, GST d6, GST o1 and MRP-1) and stress response (Hsp22, Hsp27, Hsp70, HYOU and Gp93). Moreover, enzyme activity was evaluated, with a focus on glutathione-S-transferase (GST), phenoloxidase (PO) and acetylcholinesterase (AChE). Results showed that temperature affected the acute response of this organism by modifying the expression of EcR, Cyp6b7, GST d6, GST o1, MRP-1, Hsp22, Hsp27 and Hsp70 genes. These results suggest that even mild temperature change can affect the response of this organism to BP3 influencing short-term progress of the population. Although longer exposures are required to determine the ability of C. riparius to manage the pollutants in this novel environmental conditions, in order to know the possible mechanisms of detoxification or adaptation that may develop. This research represents a first step in the analysis of multi-stress response in this animal, and opens new possibilities in the toxicity evaluation of this organism in line with the real scenario that organisms face today.

Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responses

Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels. At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 μg L^-1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 μg L^-1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC₅₀ = 0.084 μg L^-1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and non-exposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level. Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.

Biological, biochemical and genotoxic effects of Sb in the midge Chironomus sancticaroli Strixino and Strixino, 1981 (Diptera: Chironomidae)

In aquatic systems, antimony (Sb) is found in the water column and associated with sediment particles being bioavailable to organisms. Consequently, toxic effects have been detected in benthic invertebrates, but the toxicity after Sb exposure in Chironomidae have not been investigated. Were investigated DNA damage, activities of cholinesterase (ChE), alpha and beta esterase (EST-α, EST-β), glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) and lipid peroxidation after acute (48 h) and subchronic exposure (8 d). We also investigated the effects of subchronic (8 d) on development of larvae and chronic (25 d) Sb exposure on emergence and size of adults of Chironomus sancticaroli. Were analyze Sb nominal concentrations ranged from 0.5 to 800 μg.L^-1. Genotoxic effects occurred at higher concentrations upon acute (50, 800 μg.L^-1) and subchronic exposure (50 μg.L^-1). Acute exposure increased ChE, EST-α, EST-β, and GST activities. Subchronic Sb exposure increased EST-α activity at 0.2 μg.L^-1 and GST activity at 5 μg.L^-1. CAT activity increased at all concentrations while increasing lipid peroxidation levels were observed (1 μg.L^-1, 5 μg.L^-1 and 50 μg.L^-1), indicating oxidative stress. All concentrations of Sb delayed larval development and decreased the number of emerging adults. At high concentrations (50, 500, 800 μg.L^-1), the emerging adults were smaller. In conclusion, these varying genotoxic, biochemical and biological effects of Sb make a notable impact on the reproduction and population dynamics of C. sancticaroli.

Bioaccumulation and risks of 24 personal care products in plasma of wild fish from the Yangtze River, China

We used a hybrid precipitation method to simultaneously extract and analyze 24 personal care products (PCPs), including 16 biocides, 4 synthetic musks, and 4 benzotriazoles, in the plasma of fish. The method's performance was validated for plasma samples with and without β-glucuronidase/aryl-sulfatase hydrolysis. The recoveries were in the range of 70-120% for most of the PCPs, except N,N-diethyl-3-methylbenzamide (DEET), clotrimazole (CTZ), miconazole and itraconazole at spiking concentration of 20 and 5 ng/mL. The quantification limits ranged between 0.89 and 17.9 ng/mL (hydrolyzed plasma) and 0.85-18.5 ng/mL (non-hydrolyzed plasma), except CTZ at 77.5 ng/mL and 76.3 ng/mL. Totally, 13 PCPs were detected in plasma samples of fish collected from the Yangtze River, with a maximum concentration of 58.4 ng/mL (galaxolide). Compounds with the phenol hydroxyl groups of parabens or triclosan in hydrolyzed plasma showed higher concentrations than those in unhydrolyzed plasma with the ratio of conjugation (glucuronides + sulfates) forms up to 86%. The median values for the logarithm of bioaccumulation factors were between 1.39 and 4.15, which were 2-3 orders of magnitude higher than the theoretical logarithm of bioconcentration factors. Using the fish plasma model, the effect ratios (effect concentration/measured plasma concentration ratios) of tonalide, galaxolide, benzotriazole, triclosan, and DEET reached 0.35, 4.15, 3.78, 7.52, and 9.24, respectively. These are recognized as priority chemicals for further risk assessment.

Amitraz toxicity to the midge Chironomus riparius: Life-history and biochemical responses

Acute and chronic toxicity of the formamidine pesticide amitraz to the midge Chironomus riparius was assessed using conventional ecotoxicological tests and biochemical approaches (biomarkers). Amitraz is mainly used as an ectoparasiticide in veterinary medicine, but also in agriculture and apiculture. However, information of amitraz toxicity to non-target invertebrates is limited. Besides the impairment of developmental and emergence rates (reduced larval growth, emergence, and delayed development time) caused by chronic exposure to amitraz, acute exposures induced alterations in the antioxidant enzymes glutathione peroxidase (GPx) and catalase (CAT), and in energetic metabolism biomarkers, lactate dehydrogenase (LDH) and electron transport system (ETS) activities. Moreover, lipid peroxidation (LPO) increased by amitraz exposure. Our results reveal potential secondary effects of amitraz to invertebrates and biomarkers that may aid in the interpretation of sub-lethal toxic responses to amitraz. These results add information concerning the potential outcomes of amitraz exposure to freshwater invertebrates underlining the importance of risk assessment studies of formamidine pesticides.

Mixed-chemical exposure and predicted effects potential in wadeable southeastern USA streams

Complex chemical mixtures have been widely reported in larger streams but relatively little work has been done to characterize them and assess their potential effects in headwater streams. In 2014, the United States Geological Survey (USGS) sampled 54 Piedmont streams over ten weeks and measured 475 unique organic compounds using five analytical methods. Maximum and median exposure conditions were evaluated in relation to watershed characteristics and for potential biological effects using multiple lines of evidence. Results demonstrate that mixed-contaminant exposures are ubiquitous and varied in sampled headwater streams. Approximately 56% (264) of the 475 compounds were detected at least once across all sites. Cumulative maximum concentrations ranged 1,922-162,346ngL^-1 per site. Chemical occurrence significantly correlated to urban land use but was not related to presence/absence of wastewater treatment facility discharges. Designed bioactive chemicals represent about 2/3rd of chemicals detected, notably pharmaceuticals and pesticides, qualitative evidence for possible adverse biological effects. Comparative Toxicogenomics Database chemical-gene associations applied to maximum exposure conditions indicate >12,000 and 2,900 potential gene targets were predicted at least once across all sites for fish and invertebrates, respectively. Analysis of cumulative exposure-activity ratios provided additional evidence that, at a minimum, transient exposures with high probability of molecular effects to vertebrates were common. Finally, cumulative detections and concentrations correlated inversely with invertebrate metrics from in-stream surveys. The results demonstrate widespread instream exposure to extensive contaminant mixtures and compelling multiple lines of evidence for adverse effects on aquatic communities.

Bioconcentration and ecotoxicity of sulfadiazine in the aquatic midge Chironomus riparius

Although sulfadiazine (SDZ) is widespread in aquatic environments, information regarding the effects of SDZ on aquatic insects is still limited. In the present study, the bioconcentration and the effects of SDZ on the antioxidant system and the expression of endocrine and stress-related genes in Chironomus riparius larvae were investigated. The larvae were exposed to SDZ at the nominal concentrations of 2, 20 and 200 μg/L for 48 h. The results showed that SDZ was taken up by C. riparius despite presenting low bioconcentration factor values (0.99-3.92). In addition, superoxide dismutase activity was markedly reduced compared with the control group, whereas the levels of malondialdehyde were not significantly affected by SDZ. Moreover, the mRNA expression of genes related to heat shock proteins (Hsp70 and Hsp27) and ecdysone pathway (EcR and E74) were significantly up-regulated following all SDZ treatments. In aggregate, our work provides novel and interesting results regarding the potential biochemical and genetic effects of SDZ on freshwater insects.

Response of detoxification system genes on Chironomus riparius aquatic larvae after antibacterial agent triclosan exposures

Triclosan (TCS) is an antimicrobial agent used in a range of personal care and consumer products and is commonly detected in aquatic ecosystems. In the present study, the effects of TCS at the molecular level on the detoxification system of Chironomus riparius aquatic larvae, a test organism widely used for the assessment of aquatic toxicology, were evaluated. The obtained results show that this xenobiotic was able to induce significant changes in transcripts from different cytochrome P450s and glutathione s-transferases genes, involved in phase I and phase II of detoxification system, respectively. In contrast, TCS did not affect the glutathione S-transferase enzyme activity nor the expression pattern of multidrug resistance-associated protein 1, which belongs to phase III of detoxification system. These results provide information about the effects of TCS on the detoxification mechanism of C. riparius and offers different biomarker genes that could be useful in ecotoxicological studies, risk assessment and bioremediation.

Lethal and sublethal effects of metal-polluted sediments on Chironomus sancticaroli Strixino and Strixino, 1981

The Cantareira Complex is one of the most important water supplies of the metropolitan region of São Paulo, Brazil. Previously, it was demonstrated that the sediments in this complex were polluted with metals and that Paiva Castro Reservoir-the last reservoir in the sequence, which receives water from the five previous reservoirs-was the reservoir with the greatest concentration of pollutants. Based on field data, it was noticed that copper concentrations in sediments were related to morphological alterations in chironomids. The present study provides novel monitoring methods and results for the complex by isolating the environmental and biological sources of variation. An adaptation of the in situ assay proposed by Soares et al. (Arch Environ Contam Toxicol 49:163-172, 2005), which uses a native tropical Chironomus species and low-cost materials, is also provided. The aim of this study was to isolate the effects of sediments from Paiva Castro on controlled populations of C. sancticaroli larvae using an in situ assay. A seven-day experiment was performed in triplicate. Third instar larvae were inoculated in chambers containing sediments from two distinct regions of Paiva Castro reservoir and a control site with sand. Five biological responses were considered: mouthpart alterations, larval length, width of cephalic capsule, mortality and total damage. The results suggest the effects of sediment toxicity on larvae include a reduction in length and a higher occurrence of total damage.

Toxicity of organic UV-filters to the aquatic midge Chironomus riparius

Despite the frequent detection of organic ultraviolet-filters (UV-filters) in freshwater sediments, there is a lack of ecotoxicological data undermining a correct risk assessment for these emerging contaminants. The present study assessed the effects of three of the most commonly used UV-filters (benzophenone-3 - BP3; 3-(4-methylbenzylidene)camphor - 4-MBC and octocrylene - OC) on Chironomus riparius life history and biochemical responses. Standard ecotoxicological assays confirmed that all compounds impaired growth of C. riparius larvae and induced developmental effects such as delayed emergence and a reduction of imagoes weight. Concerning the biochemical responses analysed no evidences of oxidative damage in lipids or neurotoxicity (tested assessing acetylcholinesterase activity) were observed for any of the tested compounds. However, 4-MBC exposure induced a decrease in catalase activity and an increase in glutathione-S-transferase activity at 14.13mg/Kg while OC exposure caused an increase in total glutathione levels at 0.23 and 18.23mg/Kg. Exposure to all UV-filters tested, increased energy consumption on C. riparius with significant differences above 1.00mg/Kg for BP3, 0.09mg/Kg for 4-MBC and 2.13mg/Kg for OC. These results suggest that environmental relevant concentrations of UV-filters can cause deleterious effects to aquatic benthic species, such as C. riparius, and call for further research concerning effects of organic UV-filters on natural invertebrate communities and ecosystem functioning.

Evolutionary consequences of historical metal contamination for natural populations of Chironomus riparius (Diptera: Chironomidae)

Populations inhabiting metal-impacted freshwater systems located nearby industrial and urban areas may be under intense selection. The present study aims to address two fundamental microevolutionary aspects of metal contamination in the midge Chironomus riparius (Meigen): Are populations inhabiting historically metal contaminated sites genetically adapted to metals? And, are populations from these sites genetically eroded? To answer these questions, C. riparius populations were sampled from three sites with well-known histories of metal contamination and three nearby-located references. Genetic adaptation to metals was investigated through acute and chronic exposures to cadmium (Cd), after rearing all populations for at least six generations under laboratory clean conditions. Genetic diversity was estimated based on the allelic variation of seven microsatellite markers. Results showed higher acute tolerance to Cd in populations originating from metal contaminated sites compared to their respective references and significant differences in two out of three pairwise comparisons. However, there was a mismatch between acute and chronic tolerance to Cd with results of the partial life-cycle tests suggesting fitness costs under control clean conditions in two metal-adapted populations. Despite no evidences of genetic erosion in populations sampled from metal contaminated sites, our results suggest genetically inherited tolerance to Cd in populations inhabiting historically contaminated sites. These findings lend support to the use of C. riparius as a model organism in evolutionary toxicology and highlight the importance of coupling measures of neutral genetic diversity with assessments of chemical tolerance of populations for a better understanding of contaminant-induced adaptation and evolutionary processes.

Molecular Characterization and Expression Analysis of P38 MAPK Gene and Protein in Aquatic Midge, Chironomus riparius (Diptera: Chironomidae), Exposed to Environmental Contaminants

P38 Mitogen-activated protein kinase (MAPK), an important signaling protein involved in various cellular processes, including stress responses, has been well characterized in model organisms. P38 has been identified in a number of insects, including the genus Drosophila; however, its homologue in Chironomus riparius has not yet been identified. In this study, we identified and characterized p38 MAPK (Crp38) gene in C. riparius using a transcriptome database that was previously generated 454 GS-FLX pyrosequencing. Comparative and phylogenetic analyses were performed using the p38 homologue of other species, such as Drosophila melanogaster, Aedes aegypti, Bombyx mori, Caenorhabditis elegans, Homo sapiens, etc. Furthermore, to test its potential as a biomarker of environmental contamination, Crp38 gene expression was analyzed upon exposure to nonylphenol (NP), silver nanoparticles (AgNPs), and cadmium (Cd). Crp38 gene expression was up- or down-regulated depending on the concentration and exposure duration of chemicals. These results show the role of Crp38 gene in defense against environmental stresses, as well as its potential use as a biomarker for various environmental pollutants. We further synthesized p38 antibody based on the predicted amino acid sequence deduced from Crp38 cDNA and, using this customized antibody, examined p38 protein expression in Cd exposed C. riparius. Although transcriptional alteration was not translated to the protein level, this result showed the possible application of a protein level functional study using cDNA sequence information from next-generation sequencing database in nonmodel organisms.

The insect repellents: A silent environmental chemical toxicant to the health

In recent years, a large number of insect repellents have been developed with the idea of consumer benefits. In addition to already known advantageous application of insect repellents, there is increasing concern about the potential toxicity in environment leading to health caused by random use of these compounds. An increasing number of evidence suggests that insect repellents may trigger undesirable hazardous interactions with biological systems with a potential to generate harmful effects including intermediate metabolites. Biotransformation followed by bioaccumulation (vice e versa) may be an important phenomenon for toxic response of this chemicals. In this review, we have summarized the current state of knowledge on the insect repellent toxicity, including biochemical pathway alteration under in vitro and in vivo conditions considering different classes of organisms, from lower to higher vertebrate. Furthermore, we have tried to incorporate the effects of insect repellent in light of some clinical reports. We hope this review would provide useful information on potential side effects of uncontrolled use of insect repellents.

Assessment of thiamethoxam toxicity to Chironomus riparius

The insecticide thiamethoxam (TMX) is a systemic neonicotinoid widely used for pest control in several agricultural crops. TMX mimics the action of acetylcholine causing uncontrolled muscular contraction eventually leading to insect death. TMX is being found in freshwater ecosystems at concentrations of up to 225µg/L. Still, chronic toxicity data for freshwater invertebrates is limited. Therefore, the aim of this study was to evaluate the acute and chronic effects (at organismal and biochemical levels) of TMX on the freshwater insect Chironomus riparius. C. riparius life history responses were significantly affected by TMX exposure, namely with a decrease in growth and delay in emergence. Concerning the biochemical responses, after a short exposure (48h) to TMX, our results showed that low concentrations of TMX significantly reduced CAT activity and LPO levels of C. riparius. No effects were observed in AChE, GST and ETS activities. Effects in terms of survival, development rates and biochemical responses of C. riparius exposed to low concentrations of TMX observed in this study suggest potential deleterious effects of this neonicotinoid on aquatic insects inhabiting freshwaters environments near agricultural areas.

Are insect repellents toxic to freshwater insects? A case study using caddisflies exposed to DEET

Stream ecosystems face ever-increasing pressures by the presence of emergent contaminants, such as, personal care products. N, N-diethyl-3-methylbenzamide (DEET) is a synthetic insect repellent that is being found in surface waters environments in concentrations up to 33.4 μg/L. Information concerning DEET's toxicity in the aquatic environment is still limited and focused only on its acute effects on model species. Our main objective was to assess the effects of DEET exposure to a caddisfly non-target species using sub-lethal endpoints. For that, we chose Sericostoma vittatum, an important shredder in Portuguese freshwaters that has been already used in different ecotoxicological assays. Besides acute tests, S. vittatum were exposed during 6 days to a gradient of DEET concentrations (8, 18 and 40.5 mg/L) to assess effects on feeding behaviour and biochemical responses, such as, lipid peroxidation levels (LPO), catalase and acetylcholinesterase (AChE) activities, and also assess effects on energy reserves and consumption. Acute tests revealed a 48 h-LC50 of 80.12 mg/L and DEET exposure caused feeding inhibition with a LOEC of 36.80 mg/L. Concerning the biochemical responses, DEET caused no effects in LPO nor on catalase activity. A non-significant decrease in AChE activity was observed. Regarding energetic reserves, exposure to DEET caused a significant reduction in S. vittatum carbohydrates levels. These results add important information for the risk assessment of insect repellents in the aquatic environment and suggest that reported environmental concentrations of DEET are not toxic to non-target freshwater insects.