The acute and chronic effects of endosulfan pulse-exposure on Jordanella floridae (Florida flagfish) over one complete life-cycle

Overhauling the ecotoxicological impact of synthetic pesticides using plants' natural products: a focus on Zanthoxylum metabolites

The reduction in agricultural production due to the negative impact of insects and weeds, as well as the health and economic burden associated with vector-borne diseases, has promoted the wide use of chemicals that control these "enemies." However, the use of these synthetic chemicals has been recognized to elicit negative impacts on the environment as well as the health and wellbeing of man. In this study, we presented an overview of recent updates on the environmental and health impacts of synthetic pesticides against agro-pest and disease vectors while exhaustive reviewing the potentials of natural plant products from Zanthoxylum species (Rutaceae) as sustainable alternatives. This study is expected to spur further research on exploiting these plants and their chemicals as safe and effective pesticide entities to minimize the impact of their chemical and synthetic counterparts on health and the environment.

Effect of the coexistence of endosulfan on the lindane biodegradation by Novosphingobium barchaimii and microbial enrichment cultures

Organochlorine pesticides, especially lindane and endosulfan, have been demonstrated to be both biodegradable and frequently coexistent, but their inhibitory effect has never been studied. In this study, we investigated the effect of endosulfan coexistence on lindane degradation to a lindane-degrading isolate, Novosphingobium barchaimii strain LL02, and mixed enrichment cultures from two different inocula. Our results of the lindane degradation batch experiments demonstrated that endosulfan concentration above 20 mg L^-1 causes significant inhibition to the lindane degradation efficiency of the strain LL02. Besides, the acidic conditions at pH 5.0 to 6.0 further decreased its lindane degradation rate constants by 57% compared to the neutral and alkaline conditions. For the mixed microbial cultures, the lindane degradation efficiency in the lindane/endosulfan co-contamination conditions decreased by 35.7%-50.7% compared to the lindane alone conditions. From our 16S rRNA amplicon sequencing results through the PacBio platform, most of the predominant bacteria in the lindane-enriched cultures were depressed in the lindane/endosulfan-enriched cultures. Moreover, bacteria of Burkholderia australis, Chujaibacter soli, Flavitalea flava, and one Rhodanobacteraceae bacterium were relatively highly abundant in the co-contamination enrichment cultures, suggesting their potential for lindane degradation under the endosulfan stress. Our results demonstrated that endosulfan coexistence causes inhibitory impacts on lindane biodegradation toward both lindane-degrading bacteria and mixed microbial cultures. The coexistence of multiple organochlorine pesticides on the biodegradation efficiencies should be carefully considered when applying bioremediation to remove organochlorine pesticide contamination.

Isolation of lindane- and endosulfan-degrading bacteria and dominance analysis in the microbial communities by culture-dependent and independent methods

　　Bioremediation for lindane and endosulfan removal is a cost-effective approach, but its effectiveness depends on the ability to isolate degrading functionalized microorganisms. Researchers have isolated many lindane and endosulfan degrading bacteria from enrichment cultures based on culture-dependent methods during the past decades. However, it is unknown whether the isolated bacteria can reflect the indigenous predominant degraders in enriching cultures. In this study, we compared the culture-dependent method with selective medium isolation with culture-independent method (PacBio SMRT sequencing of full-length 16S rRNA amplicon) to analyze the bacterial communities from four distinct lindane (LA1 and LC1) and endosulfan (EA1 and EC1) enrichment cultures. From all the isolates we harvested from lindane (63 isolates) and endosulfan (61 isolates) enrichment cultures, their BLAST alignment can only match 5.49 % and 4.32 % of the bacterial operational taxonomic units (OTUs), respectively. Rhodanbacter lindaniclasticus and Pandoraea thiooxydans were the rarely seen potential degrading representatives that were simultaneously enriched and isolated. This study is the first comparative analysis of microbial communities from lindane and endosulfan enrichment culture using culture-dependent and culture-independent methods. Our results suggested that developing a target-specific and efficient microbial isolation method is necessary to harvest and study representative degrading bacteria in the community.

A pulsed-dose study evaluating chronic toxicity of chlorothalonil to fish: A case study for environmental risk assessment

Chlorothalonil is a fungicide which is highly toxic to aquatic organisms. However, in natural aquatic environments, it is very rapidly degraded, with a half-life typically in hours, reducing exposure of aquatic organisms and the potential for effects. In standard regulatory studies looking at the chronic toxicity of chlorothalonil to fathead minnow, the most sensitive endpoint was fecundity. A standard fish full-life cycle study, where chlorothalonil concentrations were maintained constant throughout, resulted in a no-observed-effect concentration (NOEC) of 1.4 µg/L. Comparing peak modeled exposure concentrations to this NOEC can result in the chronic risk to fish being considered unacceptable. The present study investigated the effect on fecundity in fathead minnow using a fish short-term reproduction assay. Five different exposure profiles were employed with time-varying concentrations based on realistic worst-case modeled environmental exposure profiles, multiplied by an assessment factor of 10, which resulted in maximum measured concentrations up to 15.5 µg/L. There were no effects on fecundity from any of the exposure profiles tested. Therefore, based on these more realistic exposure profiles, the chronic risk to fish could be considered acceptable if these exposures were deemed to be representative of the worst case. Environ Toxicol Chem 2019;38:1549-1559. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Life-cycle exposure to cadmium induced compensatory responses towards oxidative stress in the liver of female zebrafish

The current study examined effects of waterborne cadmium (Cd) at environmental relevant concentrations (0, 2.5 and 5 μg/L) on growth, survival, histology, ultrastructure, metal homeostasis, and antioxidant responses in female zebrafish from embryos to sexually maturity for 15 weeks. Growth and survival rate were not significantly affected by Cd exposure. There were no significant changes in ultrastructure of cellular organelles, reactive oxygen species (ROS) levels, lipid peroxidation (LPO) in liver. However, Cd exposure increased Cd and lipid accumulation, reduced contents of zinc, copper and reduced glutathione (GSH), and down-regulated activity of copper/zinc-superoxide dismutase (Cu/Zn-SOD) in liver of zebrafish. Contrarily, the mRNA and activity levels of catalase (CAT), the mRNA levels of Cu/Zn-SOD, and the mRNA and protein levels of metallothioneins (MTs) were up-regulated. The transcriptional regulation of Cu and Zn transporters might be a vital mechanism by which fish slow the Zn and Cu uptake. Taken together, our data demonstrated that long-term and low-dose Cd induced adaptive responses with interlinked compensatory mechanism, which may protect fish against oxidative stress.

Ecotoxicological assessment of oil-based paint using three-dimensional multi-species bio-testing model: pre- and post-bioremediation analysis

The present study validates the oil-based paint bioremediation potential of Bacillus subtilis NAP1 for ecotoxicological assessment using a three-dimensional multi-species bio-testing model. The model included bioassays to determine phytotoxic effect, cytotoxic effect, and antimicrobial effect of oil-based paint. Additionally, the antioxidant activity of pre- and post-bioremediation samples was also detected to confirm its detoxification. Although, the pre-bioremediation samples of oil-based paint displayed significant toxicity against all the life forms. However, post-bioremediation, the cytotoxic effect against Artemia salina revealed substantial detoxification of oil-based paint with LD₅₀ of 121 μl ml^-1 (without glucose) and > 400 μl ml^-1 (with glucose). Similarly, the reduction in toxicity against Raphanus raphanistrum seeds germination (%FG = 98 to 100%) was also evident of successful detoxification under experimental conditions. Moreover, the toxicity against test bacterial strains and fungal strains was completely removed after bioremediation. In addition, the post-bioremediation samples showed reduced antioxidant activities (% scavenging = 23.5 ± 0.35 and 28.9 ± 2.7) without and with glucose, respectively. Convincingly, the present multi-species bio-testing model in addition to antioxidant studies could be suggested as a validation tool for bioremediation experiments, especially for middle and low-income countries. Graphical abstract ᅟ.

Endosulfan Toxicity to Anabas testudineus and Histopathological Changes on Vital Organs

The toxicity of endosulfan, an organochlorine type insecticide to a commonly consumed freshwater fish species, A. testudineus (40.68±9.03 g; 13.49±0.99 cm), was investigated under static conditions. The nominal endosulfan concentrations ranging from 10 to 80 μg/L subjected to the fish population results in 96-hour median lethal concentration, LC50, of 35.2±3.99 μg/L. The toxicity is a function of both endosulfan concentration and exposure time (p>0.05). Histopathological analysis on vital organs exposed to sublethal concentrations indicates that structural changes started at sublethal dose and the effects aggravated with increasing endosulfan concentration. Gill was found to experience aneurism, hyperplasia in lamellar and autolysis of mast cell. Pyknotic nuclei and necrosis were observed in liver cell, while the lumen of renal tubule was found to narrow and haemorrhage was observed in cytoplasm cell. High LC50 compared to other fishes indicates that A. testudineus has high tolerant to endosulfan, however, endosulfan slowly alters the fish biochemistry and is potentially transferable to human

Impact of the composition of the bacterial population and additional carbon source on the pathway and kinetics of degradation of endosulfan isomers

Abiotic and bacterial degradation is presented for the two isomers α- and β- of the organochlorine pesticide endosulfan, denoted as ES-1 and ES-2, respectively. Biodegradation studies were conducted with two indigenous species Pseudomonas putida (P. putida) and Rhodococcus sp. Both ES isomers rapidly hydrolyzed in water at pH ≥ 7 but the hydrolysis was inhibited in the presence of biomass. The pesticide partitioned onto the biomass making it unavailable for abiotic hydrolytic reaction. Spontaneous temperature dependent abiotic conversion of ES-2 to ES-1 was reported in the presence of dual air-water phases but was not observed in the abiotic aqueous phase. Biodegradation experiments with pure isomers showed a small amount of interconversion (∼5%) in either direction and ruled out any preferential interconversion of the ES-2 isomer to ES-1 or vice versa. Both the species were shown to degrade ES-2 at a higher rate compared to ES-1 which may lead to enrichment of ES-1 in agricultural fields in short-term following application of the pesticide. P. putida degraded both the ES isomers through oxidative and hydrolytic pathways while the Rhodococcus sp. used only the hydrolytic pathway. Since ES-S (product of the oxidative pathway) is orders of magnitude more toxic than the parent isomers, the short term toxicity of a field following the application of the pesticide may increase if the composition of the indigenous bacterial population is such that the oxidative pathway is preferred over the hydrolytic one. The presence of an additional carbon source increased the rates of degradation of both the isomers but the enhancement was greater for the degradation rate of ES-2 than ES-1.

Immunosuppressive effects and associated compensatory responses in zebrafish after full life-cycle exposure to environmentally relevant concentrations of cadmium

In natural environments, fish survive in polluted water by cadmium (Cd) throughout their whole life cycle. However, little information is available on Cd toxicity considering a life cycle assessment. The present study investigated effects of environmental levels of cadmium (0, 2.5, and 5μg/L) on immune responses in liver and spleen of zebrafish for 15 weeks, from embryos to sexually maturity. Nitric oxide (NO) levels and iNOS activity declined in liver and spleen of zebrafish exposed to 5μg/L Cd, suggesting an immunosuppressive effect. The result was further supported by the decreased transcriptional levels of proinflammatory cytokines by Cd, such as interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-1β (IL-1β), and tumour necrosis factor-α (TNF-α) in liver. However, a sharp increase in the mRNA levels of these cytokines was observed in spleen of zebrafish exposed to Cd. The increased mRNA expression of these proinflammatory cytokines may be the secondary effect following immunosuppression and just reflect a compensatory mechanism for coping with the decreased immunity, which may explain an increase in mRNA levels and a decrease in iNOS activity in spleen of zebrafish exposed to Cd. In liver, the down-regulated mRNA levels of iNOS paralleled with the decreased iNOS activity, suggesting a synchronous response from a molecular level to a biochemical level. Positive correlations between mRNA expression levels of nuclear transcription factor κB (NF-κB) and proinflammatory cytokines were also observed, suggesting that NF-κB might be required for the protracted induction of inflammatory genes. The corresponding changes in the mRNA levels of the inhibitor of κBα (IκBαa and IκBαb) may form a feedback loop to restore transcriptional activity of NF-κB. Furthermore, splenic ROS levels were increased by 5μg/L Cd, possibly activating NF-κB pathway. Taken together, immunosuppressive effects and tissue-dependent compensatory responses were demonstrated in zebrafish after full life-cycle exposure to environmental levels of Cd, indicating a compromise between survival and immunity.

Reductive dechlorination of endosulfan isomers and its metabolites by zero-valent metals: reaction mechanism and degradation products

Degradation by-products of organochlorine pesticide endosulfan and metabolites by different zero valent metals.

Endosulfan isomers and sulfate metabolite induced reproductive toxicity in Caenorhabditis elegans involves genotoxic response genes

Endosulfan is enlisted as one of the persistent organic pollutants (POPs) and exists in the form of its α and β isomers in the environment as well as in the form of endosulfan sulfate, a toxic metabolite. General endosulfan toxicity has been investigated in various organisms, but the effect of the isomers and sulfate metabolites on reproductive function is unclear. This study was aimed at studying the reproductive dysfunction induced by endosulfan isomers and its sulfate metabolite in Caenorhabditis elegans (C. elegans). We also determined a role for the DNA-damage-checkpoint gene hus-1. Compared to β-endosulfan and its sulfate metabolite, α-endosulfan caused a dramatically higher level of germ cell apoptosis, which was regulated by DNA damage signal pathway. Both endosulfan isomers and the sulfate metabolite induced germ cell cycle arrest. Loss-of-function studies using hus-1, egl-1, and cep-1 mutants revealed that hus-1 specifically influenced the fecundity, hatchability, and sexual ratio after endosulfan exposure. Our data provide clear evidence that the DNA-checkpoint gene hus-1 has an essential role in endosulfan-induced reproductive dysfunction and that α-endosulfan exhibited the highest reproductive toxicity among the different forms of endosulfan.

Exposure and post-exposure effects of endosulfan on Bufo bufo tadpoles: morpho-histological and ultrastructural study on epidermis and iNOS localization

Endosulfan is a persistent organic pollutant (POP) that has lethal and sublethal effects on non-target organisms, including amphibians. In a laboratory study, we investigated direct and post-exposure effects of endosulfan on Bufo bufo tadpoles. For this purpose we exposed the tadpoles to a single short-term contamination event (96 h) at an environmentally-realistic concentration (200 μg endosulfan/L). This was followed by a recovery period of 10 days when the experimental animals were kept in pesticide-free water. The endpoints were assessed in terms of mortality, incidence of deformity, effects on behavior, and the morpho-functional features of the epidermis. We found that a short-term exposure to the tested concentration of endosulfan did not cause mortality but induced severe sublethal effects, such as hyperactivity, convulsions, and axis malformations. Following relocation to a pesticide-free environment, we noted two types of response within the experimental sample, in terms of morphological and behavioral traits. Moreover, by using both ultrastructural and a morpho-functional approach, we found that a short-term exposure to endosulfan negatively affected the amphibian epidermis. We also observed several histo-pathological alterations: increased mucous secretion, an increase in intercellular spaces and extensive cell degeneration, together with the induction of an inducible isoform of nitric oxide synthase (iNOS). Following the post-exposure period, we found large areas of epidermis in which degeneration phenomena were moderate or absent, as well as a further increase in iNOS immunoreactivity. Thus, after 10 days in a free-pesticide environment, the larval epidermis was able to partially replace elements that had been compromised due to a physiological and/or a pathological response to the pesticide. These results highlight the need for both exposure and post-exposure experiments, when attempting to assess pollutant effects.

Acute toxicity of agricultural pesticides to embryo-larval and juvenile African catfish Clarias gariepinus

Acute toxicities of Tihan 175 O-TEQ, as well as its active ingredients flubendiamide and spirotetramat, and of Thionex 350 EC (active compound endosulfan) were measured for embryo-larval and juvenile stages of the African catfish Clarias gariepinus to assess risks of pesticide use in the cotton basin in Benin (West Africa). For embryo-larval stages, Tihan was more toxic (LC5048h 20 ppm) than Thionex (LC5048h 56 ppm), and flubendiamide was more toxic (LC5048h 2.0 ppm) than spirotetramat (LC5048h 8.44 ppm). All decreased hatching rates. Tihan and spirotetramat disturbed larval swimming coordination; flubendiamide induced tail cleavage. For juvenile fish, Thionex was more toxic (LC5096h 0.22 ppm) than Tihan (LC5096h 8.8 ppm), and flubendiamide (LC5096h 4.7 ppm) was more toxic than spirotetramat (LC5096h 6.0 ppm). Eggs were more resistant than juvenile fish to all tested pesticides except flubendiamide. Although Thionex was more toxic to juvenile fish, replacing Thionex with Tihan may be undesirable for survival of eggs and larvae.

Endosulfan effects on Rana dalmatina tadpoles: quantitative developmental and behavioural analysis

Endosulfan is an organochlorine pesticide that was recently labeled as a persistent organic pollutant, but it is still widely employed, particularly in developing countries. The goal of this study is to evaluate the acute (LC(50)) and chronic effects (developmental and behavioural traits) of this insecticide on Rana dalmatina tadpoles after exposure to ecologically relevant concentrations (0.005, 0.01, and 0.05 mg/L) by applying video-tracking techniques to evaluate the quantitative effect of endosulfan on amphibian behavioural patterns. The 96 h LC(50) value was 0.074 mg endosulfan/L. Tadpoles chronically exposed to 0.01 and 0.05 mg endosulfan/L underwent high mortality rate, decreased larval growth, delayed development, and increased incidence of malformations, and they did not reach metamorphosis by the end of the experiment. Moreover, tadpoles exposed to these concentrations exhibited several abnormalities in swimming patterns, such as shorter distance moved, swirling, resting, and unusual use of space. The exposure to 0.005 mg endosulfan/L did not cause any significant effects on behaviour, larval growth, or development, but we observed a significant decrease in both survival and time to metamorphosis. We showed that developmental abnormalities are dose-dependent and that the pesticide effects could differ depending on the endosulfan concentration and the species tested. We also validated the hypothesis that behavioural analysis, along with the use of new analytical methods, could be a useful tool in amphibian ecotoxicological studies.