Occurrence of Acetamiprid Residues in Water Reservoirs in the Cotton Basin of Northern Benin

Effective removal of acetamiprid and eosin Y by adsorption on pristine and modified MIL-101(Fe)

In this work, the efficacy of two metal-organic frameworks (MIL-101(Fe) and NH2-MIL-101(Fe)) in eliminating acetamiprid (ATP) insecticide and eosin Y (EY) dye from aqueous solution is tested. An analysis was conducted on the developed nanocomposite's optical, morphological, and structural characteristics. The adsorption isotherm, kinetics, thermodynamics, reusability, and mechanisms for ATP and EY dye removal were assessed. NH2-MIL-101(Fe) adsorbed 76% and 90% of ATP pesticide and EY dye, respectively after 10 to 15 min in optimum conditions. For both adsorbents, with regard to explaining the isotherm data, the Langmuir model offered the most accurate description. Moreover, the adsorption of ATP and EY dye is described by the pseudo-second-order kinetic model. The maximum adsorption capacities of ATP and EY dye on MIL-101(Fe) were 57.6 and 48.9 mg/g compared to 70.5 and 97.8 mg/g using NH2-MIL-101(Fe). The greatest amount of ATP and EY dye clearance was obtained at a neutral medium for both adsorbents. The results of this investigation demonstrate the effectiveness of MIL-101(Fe) and NH2-MIL-101(Fe) as effective substances in the adsorption process for removing pesticides and dyes from aqueous solution.

Toxicological approaches as tool to assess the effects of a mixture of photocatalytic degradation products originated from the unregulated neonicotinoid acetamiprid employing a terrestrial organism (Eisenia andrei)

Acetamiprid (ACT) has been detected in several water sources in Latin America. The presence of its degradation products in the environment is not negligible and transformation products (TPs) significantly contribute to environmental health risks. Although advanced oxidative processes are promising for the treatment of this neocotinoid, effects of these are still unknown. In this context, the effects of a mixture of photocatalytic degradation products resulting from an ACT treatment for 90 min employing TiO2/UV on cytotoxicity and oxidative stress parameters in Eisenia andrei earthworms in acute and chronic experiments using typical Latin American soil were assessed. Acute contact tests were performed (72 h) using a filter paper moistened with an ACT solution and a chronic test was performed using Oxisoil (200 g) moistened with an ACT solution for 45 days. Catalase (CAT) and glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and cytotoxicity (cellular eleocyte and amoebocyte assessments) were investigated. Over 75 % of ACT was degraded within the first 15 min of treatment, with levels below the limit of detection after 60 min. The acute test revealed greater cytotoxic effects associated with the effluents treated for T0 and T15 min, with decreased cell density noted after 48 h of exposure, in addition to CAT induction (in all treatments) and GST induction following T0, T15 and T90 min exposures. Concerning the chronic assay, decreases in cell density (T0, T15, T60 and T90 min) and viability (T0, T60 and T90 min) were observed after 45 days, in addition to induced CAT activity following T0, T15 and T60 exposures and GST induction following the T60 min exposure. Reduced glutathione levels were unaltered, comprising the least sensitive biomarker among the investigated parameters to the treated effluent exposures. The mixture of ACT degradation products can cause toxic effects to non-target organisms, despite parent compound degradation, alerting for the need for ecotoxicological tests to prove decreased effluent toxicity, in addition to the improvement of degradation techniques.

Neuroprotective potential of berberine against acetamiprid induced toxicity in rats: Implication of oxidative stress, mitochondrial alterations, and structural changes in brain regions

Acetamiprid (ACMP) is an extensively used neonicotinoid pesticide to control sucking and chewing insects and is known to cause nontarget toxicity. The present study aimed to evaluate the ameliorative potential of berberine (BBR)-a polyphenolic alkaloid- on ACMP-induced oxidative stress, mitochondrial dysfunctioning, and structural changes in different rat brain regions. The male Wistar rats were divided into four groups, that is, control, BBR-treated (150 mg/kg b.wt), ACMP-exposed (21.7 mg/kg b.wt) and BBR + ACMP co-treated; and were dosed intragastrically for 21 consecutive days. Results of the biochemical analysis showed that BBR significantly ameliorated ACMP-induced oxidative stress by decreasing lipid peroxidation and protein oxidation along with a marked increase in endogenous antioxidants and lowered AChE activity in rat brain regions. Inside mitochondria, BBR significantly attenuated the toxic effects of ACMP by increasing the activity of mitochondrial complexes. Findings of polymerase chain reaction also demonstrated the modulatory effects of BBR against ACMP-mediated downregulation of ND1, ND2, COX1, and COX4 subunits of mitochondrial complexes. The histopathological and ultrastructural examination also validated the biochemical and transcriptional alterations following toxicity of ACMP exposure and the protective potential of BBR against ACMP-induced neurotoxicity. Thus, the present study indicates the promising ameliorative potential of BBR against ACMP-induced neurotoxicity via its antioxidative and modulatory activities.

Berberine mitigates acetamiprid-induced hepatotoxicity and inflammation via regulating endogenous antioxidants and NF-κB/TNF-α signaling in rats

Acetamiprid is a neonicotinoid insecticide used on a large scale and has been reported for oxidative stress-mediated toxicity and physiological alterations in mammals. The plant-derived natural antioxidant berberine (BBR) possesses protective potential against inflammation, structural changes, and cellular toxicity. The current study aimed to investigate the toxic effects of acetamiprid exposure and the antioxidative and anti-inflammatory efficacy of BBR in rat liver tissue. The results showed that intragastric exposure of acetamiprid (21.7 mg/kg b.wt, i.e., 1/10 of LD50) for 21 days significantly elicited oxidative stress as evidenced by lipid peroxidation, protein oxidation, and depletion of endogenous antioxidants. Furthermore, acetamiprid exposure elevated NF-κB, TNF-α, IL-1β, IL-6, and IL-12 expression and caused structural alterations in liver tissue. Biochemical results showed that 2-h pre-treatment of BBR (150 mg/kg b.wt; 21 days) reduced damage to lipids and proteins, replenished GSH, enhanced SOD and catalase activities, and offered antioxidative effects against acetamiprid toxicity. Also, BBR suppressed inflammation by regulating NF-κB/TNF-α signaling in hepatic tissue of acetamiprid-intoxicated rats. Histopathological examination confirmed the hepatoprotective effects of BBR. Our findings indicate that BBR might be a potential ameliorative agent against oxidative stress-mediated hepatotoxicity.

Effects of a Neonicotinoid on Indigenous Earthworm Perionyx excavatus Biochemical and Histopathological Alterations

Acetamiprid is a broad-spectrum insecticide, belonging to the neonicotinoid compounds group, which has been extensively applied throughout the globe. Recently, indiscriminate use of these compounds was reported to cause fatal impacts on non-targeted soil organisms. Hence, the present study aimed to examine the impact of acetamiprid on Indian indigenous earthworm, Perionyx excavatus. Acute toxicity revealed an LC₅₀ concentration of 0.25 µg/cm² for filter paper test/72 h and 400 µg/kg for artificial soil test/14 days. Oxidative stress (ROS) and various biomarkers including superoxide dismutase, catalase, glutathione S-transferase, malondialdehyde content and DNA damage were measured. The results of the biomarker responses confirmed the acetamiprid exposure can cause toxicity to P. excavatus. In addition, cell density (20 × 10² cell mL/mg) and cell viability (40%) were significantly (p < 0.05) reduced. Further, the ecotoxicological assessment made through this study can be utilized as good evidence to toxicity of neonicotinoids to non-targeted indigenous organisms.

Biodegradation of neonicotinoid insecticide acetamiprid by earthworm gut bacteria Brucella intermedium PDB13 and its ecotoxicity

Extensive use of neonicotinoid insecticides in recent decade had contaminated water and soil systems and poses serious environmental and health risk. Microbial degradation of toxic contaminants in the environment has been established as a sustainable tool towards its remediation. Under this context, the present study focused on the biodegradation of neonicotinoid insecticide acetamiprid, by bacterial strain Brucella intermedia PDB13 isolated from the gut of the acetamiprid exposed earthworms. To enhance acetamiprid biodegradation, suitable parameters such as pH, temperature, inoculum size and acetamiprid concentration range were optimised using Response Surface Methodology (RSM). The experimental results showed that the Brucella intermedium PDB13 can tolerate and degrade relatively high concentrations of acetamiprid (50 - 350 mg L^-1). The results confirmed that maximum degradation of about 89.72% was achieved under optimized conditions. Further, confirmation of acetamiprid biodegradation was assessed through the occurrence of its degraded metabolites through HPLC, FTIR, and LCMS analysis. Based on this analysis, possible acetamiprid biodegradation pathway by Brucella intermedia PDB13 was proposed. Additionally, cytotoxicity, earthworm acute toxicity, and zebrafish embryo toxicity studies were also performed to assess the toxicity variations between the parent compound and its metabolites. The acetamiprid treated group resulted in cytotoxic effects apparently, with the increase in aberrant cells frequency (22.5 ± 3.3), when compared with its metabolites (2.3 ± 4.3) and control (1.9 ± 5.6) respectively. All these results evidently reported the degradation potential of Brucella intermedia PDB13, thereby establishing the scope for further advanced biodegradation studies towards mitigating the pesticide pollution.

The Effect of Neonicotinoids Exposure on Oreochromis niloticus Histopathological Alterations and Genotoxicity

This study aimed to examine the side effects of selected neonicotinoids (Acetamiprid, Aceta, and Imidacloprid, Imid) on Oreochromis niloticus juveniles. The acute toxicity, Probit method, revealed an LC₅₀ of 195.81 and 150.76 ppm for Aceta/96 h and Imid/72 h respectively. The fish were divided into three groups that were exposed, for 21 days (n = 5/replicate), to 1/10 of the LC₅₀ of either neonicotinoids, however, the third was an unexposed control group. Results of erythrocytic micronucleus (MN), and nuclear abnormalities (NA) showed that Aceta and Imid exposure caused a significant (p < 0.05) increase in MN by ~ 2.2 and ~ 10 folds, respectively relative to control. NAs occurred at the order of kidney-shaped > budding > binucleated in Aceta, however, budding > binucleated > kidney-shaped was noticed in the Imid group. Histopathological changes in gills, liver, and muscles were observed significantly in both exposed groups with more severity in the Imid group. Collectively, Aceta and Imid have potential genotoxicity and histopathological alterations in O. niloticus.

Integrated biomarker response to assess the effects of pesticide residues on Nile Tilapia in aquatic ecosystems contaminated by cotton-field effluents

An in-situ study combined with an integrated biomarker response was used to evaluate the impact of agricultural effluents in the physiological responses of Nile tilapia reared in cages and enclosures of water reservoirs in North Benin. Fish were distributed in fish farming systems at two sites: Songhai located outside the cotton basin and Batran located in the most productive commune. They were sampled for blood and organs before (BST), during (DST) and after (AST) pesticide treatment. Pesticide residues were analysed in water, sediments and fish muscles. Several biomarkers were investigated related to the immune (peroxidase, lysozyme and complement activities, superoxide anion production) and reproductive (sex steroids and vitellogenin levels) responses as well as neurotoxicity (cholinesterase activity) and tissue alterations. Biomarkers were assessed and analysed via the integrated biomarker response (IBR). The results showed that Batran water reservoir was a more harmful ecosystem for fish than Songhai one, especially by depressing some immune and reproductive functions in relation to a higher-level of pesticide contamination. They also demonstrated that the contact of fish to sediments in enclosures aggravated the pesticide burden on fish. Therefore, using males as bioindicators would improve the sensitivity of the used biomarkers since males seemed more affected than females especially due to pesticide estrogenic induction impacting their reproductive system.

Aqueous Acetamiprid Degradation Using Combined Ultrasonication and Photocatalysis Under Visible Light

Acetamiprid (ACE), a neonicotinoid pesticide widely used in pest control, was found in high concentrations in soils, rivers, and lakes. In the present study, ACE degradation was investigated using visible light driven photocatalysis over nitrogen-graphene oxide (N-GO) and palladium-graphene oxide (Pd-GO)-doped ZnO photocatalysts combined with ultrasonication implemented either as a pretreatment (sonolysis) or operated simultaneously with photocatalysis (sonophocatalysis). The effectiveness of the two ACE degradation processes was determined separately. The sonolysis pretreatment allowed reaching almost 40% acetamiprid conversion within 30 min of reaction. Pursuing with the photodegradation reaction in the presence of N-GO-ZnO and Pd-GO-ZnO resulted in a maximum conversion of 98% of ACE within 5 h. As for the sonophotocatalysis process, the reaction time was shortened from 5 to 2 h with 100% acetamiprid conversion. In addition, the photocatalysts were shown to keep their activity even after 5 sonophotocatalytic cycles, thus proving their reusability.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11270-022-05867-4.

Palladium and Graphene Oxide Doped ZnO for Aqueous Acetamiprid Degradation under Visible Light

Acetamiprid is a neonicotinoid insecticide widely used in pest control. In recent years, it has been considered as a contaminant in groundwater, lakes, and rivers. Photocatalysis under visible light radiation proved to be an effective process for getting rid of several organic pollutants. In the present work, photodegradation of aqueous acetamiprid was investigated over bare zinc oxide (ZnO) photocatalyst as well as ZnO doped with either palladium or palladium combined with graphene oxide. Both ZnO and doped-ZnO were synthesized via a microwave-assisted hydrothermal procedure. The obtained photocatalysts were characterized using different techniques. After 5 h of reaction at ambient temperature under visible light irradiation, acetamiprid conversions attained ca. 38, 82, and 98% in the presence of bare ZnO, Pd-doped ZnO and Pd-GO-doped ZnO photocatalysts, respectively, thus demonstrating the positive effect of Pd- and GO-doping on the photocatalytic activity of ZnO. In addition, Pd-GO-doped ZnO was shown to keep its activity even when it is recycled five times, thus proving its stability in the reaction medium.

Adsorption Kinetics of Imidacloprid, Acetamiprid and Methomyl Pesticides in Aqueous Solution onto Eucalyptus Woodchip Derived Biochar

This work reports the application of a biochar (BC) derived from eucalyptus wood chips to remove pesticides (imidacloprid, acetamiprid and methomyl) from water. The pseudo-second order kinetic adsorption model is the best fit describing the adsorption of pesticides on BC. Furthermore, the Langmuir model correlated well with the adsorption isotherm data for acetamiprid and methomyl, while the Freundlich model was selected to explain the adsorption of imidacloprid on BC. The maximum adsorption capacities for methomyl, imidacloprid and acetamiprid on the BC material are 32.42, 14.75 and 4.87 mg g−1, respectively. The highest adsorption capacity of methomyl on the BC surface could be the result of multilayer adsorption suggested by the adsorption isotherm studies, with imidacloprid (or acetamiprid) monolayer being adsorbed on the BC surface. The structure, functional groups of pesticides, including their polarity, all played an important role contributing to the performance of biochar sorbent. Preferable interactions between the studied pesticides and the BC surface may include π-π interactions and hydrogen bonding. The steric aromatic entity in adsorbed imidacloprid and acetamiprid on the BC surface may hinder the possibility of other pesticide molecules approaching the available sorption sites on the surface.

Behavioural Responses and Mortality of Mozambique Tilapia Oreochromis mossambicus to Three Commonly Used Macadamia Plantation Pesticides

The use of pesticides in agricultural systems may have deleterious effects on surrounding environments. Aquatic systems are no exception and are increasingly polluted through the leaching of pesticides from agricultural activities. However, the pesticide pollution effects on key aquatic species have not been studied in many regions. In southern Africa, increasing pesticide use associated with macadamia tree Macadamia integrifolia farming presents a growing risk to surrounding aquatic ecosystems. This study assessed behavioural responses of an important and widely-distributed freshwater fish, Mozambique tilapia Oreochromis mossambicus, following exposure to three commonly used macadamia pesticides (i.e., Karate Zeon 10 CS, Mulan 20 SP, Pyrinex 250 CS) at different concentrations (0.7–200 µL, 0.3–1000 mg, and 0.7–8750 µL, respectively) over 24 h. Behavioural responses, i.e., swimming erratically, surfacing, vertical positioning, loss of equilibrium, being motionless and mortality were observed after pesticides exposure. Lethal dose 50 (LD50) values of Karate Zeon 10 CS, Mulan 20 SP and Pyrinex 250 CS were 2.1 µL (per water litre dilution—WLD), 5.2 mg (WLD) and 21.5 µL (WLD), respectively. These concentrations are therefore expressed as a maximal threshold usage in the environment around macadamia farms and a minimum distance of the plantations to water systems should be considered. Further studies should examine effects on other fish species and aquatic invertebrates to inform on pesticide pollution threats and mitigation plans for the region.

Ameliorative role of ascorbic acid on the oxidative stress and genotoxicity induced by acetamiprid in Nile tilapia (Oreochromis niloticus)

On juveniles of Oreochromis niloticus, the protective potential of ascorbic acid (Asc) against oxidative stress and genotoxicity induced by acetamiprid (Aceta) sub-lethal concentrations was investigated in this study. Fishes were divided into six groups and exposed to either Asc (50 ppm), 10 and 20 ppm Aceta, 10 ppm (Aceta)+Asc, 20 ppm (Aceta)+Asc, or the unexposed control group. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities and their transcripts were assessed. DNA damage in erythrocytes, hepatocytes, and gill cells, in addition to the mitotic index (MI), and the existence of erythrocytic nuclear abnormalities (ENAs) were performed. The results showed that concentrations of Aceta (10 and 20 ppm) induced oxidative stress by altering the antioxidant enzyme activities and transcripts. There were genotoxic effects of Aceta exposure showed by the significant (P < 0.05) increase in DNA-damaged cells and ENA, meanwhile a decrease in MI. Co-exposure with Asc showed significant alleviations of oxidative status and genotoxicity. Thus, results suggest that Asc-combined exposure could be the effective treatment against Aceta-induced oxidative stress accompanied with genotoxicity in O. niloticus.

Contamination of Water, Sediment and Fish with Residues of Pesticides Used in Cotton Production in Northern Benin

In Northern Benin, insecticides are used for cotton production. These insecticides can be easily transferred to water ponds close to cotton fields. To monitor insecticides levels in water, sediments and fish samples from water ponds, a GC-MS analytical method was developed to detect residues of endosulfan, DDT and its parent compounds, isomers of HCH, pyrethroids and chlorpyrifos. In addition, the influence of storage conditions of water sample on pesticides determination performance has been studied. The limits of quantification were between 0.16 and 0.32 µg/L in water, 0.5 and 1 μg/kg in sediment and 1 and 2 μg/kg in fish. Twenty samples of water, twenty of sediments and forty of fish were taken in four different water reservoirs at five different times. Alpha-endosulfan, lambda-cyhalothrin and permethrin were identified in sediment while p,p'-DDE, α- and β-HCH, chlorpyrifos, lambda-cyhalothrin and permethrin were detected in fish. Only organochlorines were determined in water because of the lack of recovery of pyrethroids from water stored in glass. Concentrations of insecticide residues in sediment for all water ponds ranged from non-detected to 101 µg/kg and from non-detected to 36 µg/kg in fish. Preliminary risk assessment for consumers of the North of Benin showed that the Estimated Daily Intakes were lower than the Acceptable Daily Intakes and Acute Reference Doses for all consumers. However, as one fish can be contaminated by five pesticide residues at the same time, it is not possible to exclude a risk for the consumer due to his exposure to mixtures of pesticides.

Chronic effects of a binary insecticide Acer 35 EC on Nile tilapia Oreochromis niloticus through a multi-biomarker approach

Acer 35 EC is a widely used insecticide (a binary mixture of lambda-cyhalothrin and acetamiprid) in pest control in many West African countries, particularly in the cotton culture in north Benin. The aim of this study was to investigate the chronic effects of Acer 35 EC on Nile tilapia Oreochromis niloticus juveniles using a multi-biomarker approach under laboratory conditions. For this purpose, fish were exposed to sublethal concentrations of Acer 35 EC (0, 1 and 10% of LC₅₀- 96 h value). After 28 and 56 days of exposure, several biomarkers were measured in males and females including enzymatic activities related to detoxification and oxidative stress, neurotoxicity and immune responses, sex steroid hormones (testosterone, 17β-estradiol and 11-keto-testosterone) and histological alterations of liver, kidney and gonads. An Integrated Biomarker Response (IBR) was then calculated. The results showed a reduction of cholinesterase activity in muscles, and intercellular superoxide anion production in both sexes. Female steroidogenesis and gametogenesis were affected, especially testosterone levels and oocyte growth. More alterations were observed in liver after exposure to Acer 35 EC. In both sexes, IBR values were higher after 56 days than after 28 days of exposure. In conclusion, based on a large set of biomarkers and IBR values, the chronic exposure to low doses of insecticide Acer 35 EC seems to impair different physiological functions in Nile tilapia juveniles on a time-dependent manner, with a stronger impact on females than on males.

Magnetic Solid Phase Extraction Based on Nanostructured Magnetic Porous Porphyrin Organic Polymer for Simultaneous Extraction and Preconcentration of Neonicotinoid Insecticides From Surface Water

In this study, a magnetic porphyrin-based porous organic polymer (MP-POP) nanocomposite was successfully synthesized according previous studies and applied as an adsorbent for simultaneous extraction and preconcentration of four neonicotinoid insecticides from surface river water. The MP-POP was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDS), N₂-adsorption/desorption analysis, Fourier Transform infrared spectroscopy (FTIR). The neonicotinoid insecticides were quantified using high performance chromatography coupled with diode array detector (HPLC-DAD). The MP-POP shown to have a high surface area, highly porous structure and strong affinity toward the investigated analytes. The adsorption capacities were 99.0, 85.5, 90.0, and 79.4 mg g⁻¹ for acetamiprid, clothiandin, thiacloprid and imidacloprid, respectively. The influential parameters affecting the magmatic μ-solid phase extraction (M-μ-SPE) procedure were investigated using fractional factorial design and surface response methodology (RSM). Under optimum conditions, the method exhibited relatively low limit of detection in the range of 1.3–3.2 ng L⁻¹, limit of quantification in the range of 4.3–11 ng L⁻¹ and wide linearity (up to 600 μg L⁻¹). The intraday and interday precision, expressed as the relative standard deviation (RSD) were <5%. The percentage recoveries for the four target analytes ranged from 91 to 99.3% for the spiked river water samples. The method was applied for determination of neonicotinoids in river water samples and concentrations ranged from 0 to 190 ng L⁻¹.

Resolution of the spectra of acetamiprid, flutolanil and etofenprox residues for their analysis in tomato fruits

This study involves spectroscopic analysis of pesticide residues extracted from tomato, one of the most freshly eaten fruit all over the world. In Egypt, tomato can be protected against pests infection by concomitantly spraying three pesticides namely, acetamiprid (AC), flutolanil (FL) and etofenprox (ET). The three pesticides have been simply and efficiently extracted from the fruits and analyzed by applying the following methods: Differential dual wavelength method, where AC, FL and ET were determined by amplitudes subtraction at 264.8-277 nm, 229-241 nm and 225.6 and 243 nm, respectively after obtaining their first derivative spectra. Modified ratio difference method, where the difference in amplitude values at 261.2 and 241 nm, 273.4 and 236.8 nm and 269.8 and 232 nm was used for determination of AC, FL and ET, respectively. The third method includes recording the amplitudes at 284, 293 and 224 nm for AC, FL and ET, respectively, after mean centering of their spectra. The linear ranges were 1-11, 0.2-2.5 and 0.2-2.5 μg mL^-1 for AC, FL and ET, respectively. The methods were proven to be green regarding the Eco-Scale calculations. The methods were efficiently applied for determination of AC, FL and ET in their commercial forms and field trials, where the residues were approximately equal to or below their specified maximum residue limits.

Joint toxicity of two phytosanitary molecules, lambda-cyhalothrin and acetamiprid, on African catfish (Clarias gariepinus) juveniles

This study was designed to evaluate the acute toxicity of acetamiprid (neonicotinoid) and lambda-cyhalothrin (pyrethroid), individually and mixtures (Act-LCh mixture and Acer 35 EC®, 15 g/L of acetamiprid and 20 g/L of lambda-cyhalothrin) in African catfish juveniles (3.35 ± 0.75 g). The tests were conducted in the laboratory under semi-static conditions according to OECD Guideline 203. Mixture toxicity effects as a function of lethal concentrations were assessed using the additive index (AI) method. Acetamiprid with 96 h-LC₅₀ = 265.7 ppm can be considered to be nontoxic for this species. However, lambda-cyhalothrin was highly toxic to C. gariepinus with 96 h-LC₅₀ = 0.00083 ppm. Acer 35 EC^® was less toxic (96 h-LC₅₀ = 0.21 ppm) than the Act-LCh mixture (96 h-LC₅₀ = 0.043 ppm). Marked changes indicating nervous system damage were also recorded. An antagonistic effect was shown for lethal concentrations leading to 5 to 15% mortality in 96 hours (96 h-LC_5-15) while an additive effect was obtained for the 96 h-LC_20-50. The results indicate that ecological risk assessment of these molecules in aquatic environments should consider their contamination levels. Moreover, particular attention to behavior changes related to their neurotoxicity is recommended for additional monitoring of the negative effects of these insecticides.

Comparative acute toxicity of two phytosanitary molecules, lambda-cyhalothrin and acetamiprid, on Nile Tilapia (Oreochromis Niloticus) juveniles

This study aimed to compare the toxicity for fish of two active ingredients (lambda-cyhalothrin-20 g L^-1, a pyrethroid, and acetamiprid-15 g L^-1, a neonicotinoid) which are components of a commercial insecticide (Acer 35 EC) used in cotton crop in many West African countries. The juveniles of Oreochromis niloticus (4.01 ± 0.34 g, mean body weight) were exposed for 96 h to increasing concentrations of active ingredients (lambda-cyhalothrin and acetamiprid) or a mixture similar to Acer 35 EC (composed by 20 g of chemical compound lambda-cyhalothrin and 15 g of acetamiprid dissolved in 1 L of acetone). The experiments were carried out under controlled conditions in aquaria according to OECD Guidelines. During the experiments, the behavioral responses (loss of balance, color change, hyperactivity, etc.) that usually precede death were observed in exposed fish. Mortalities were recorded in each aquarium and the LC₅₀-96h of each chemical was determined. The LC₅₀-96h obtained were respectively 0.1268, 0.0029, 182.9 and 0.5685 ppm for Acer 35 EC, lambda-cyhalothrin, acetamiprid and mixture. All insecticides used in this study had profound impact on Nile tilapia behavior which may confirm the neurotoxicity of each single active compound as well as of their mixture.