Assessment of reproductive toxicity of carbofuran and copper sulfate in male Nile tilapia (Oreochromis niloticus).

This study's hypothesis is that carbofuran and copper sulfate have a synergistic harmful impact on the fertility of male Nile tilapia. Hence, this study was designed to assess the toxic reproductive outcome of carbofuran, copper sulfate, and their mixture in male Nile tilapia. Sixty male Nile tilapia fishes were separated into four groups (15 fish/group). The control group; carbofuran group, was given dechlorinated tap water containing 0.02 mg/L (1/10 dose of LC50) carbofuran; copper group was given dechlorinated tap water containing 4.0 mg/L (1/10 dose of LC50) copper sulfate; carbofuran + copper sulfate group received dechlorinated tap water containing 0.02 mg/L carbofuran plus 4.0 mg/L copper sulfate. After 6 weeks, results revealed a significant rise in testicular malondialdehyde levels and a significant decrease in testicular reduced glutathione contents among all experimental groups compared to the control group. Testicular testosterone levels were significantly declined in copper and combined groups compared to the control. The seminal evaluation using computer-assisted sperm analysis showed a significant decline in the progressive motility percentage, motile ratio percentage, sperm concentration, curvilinear velocity, straight-line velocity, average path velocity, and wobble in all intoxicated groups, particularly, the combined group. The histopathology of testes in all intoxicated groups revealed a detachment of the basal membrane of some seminiferous tubules, and others were free from spermatogonia and spermatozoa with interstitial eosinophilic granular cell infiltration. Testicular lesions were more severe in the combined group. Finally, it was concluded that carbofuran and copper sulfate exerted a negative effect on the reproductive function of male Nile tilapia, and they have a synergistic harmful impact on the fertility of male Nile tilapia.

Assessment of acute toxicity of carbofuran in Macrobrachium olfersii (Wiegmann, 1836) at different temperature levels.

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate; C12H15NO3) is one of the most toxic carbamate pesticides. For acute toxicity of carbofuran, juveniles of Macrobrachium olfersii were exposed to different concentrations of carbofuran using the static renewal method at different temperature levels (15, 20 and 25°C) at pH 7.0. The main purpose of the present study was to detect the acute toxicity of carbofuran to M. olfersii and investigate its effects on oxygen consumption and ammonium excretion; these tests have not been carried out in this species before. First, the acute toxicity - median lethal concentration - of carbofuran to M. olfersii for 24, 48, 72 and 96 h was examined, which resulted in the following values: 1.64, 1.22, 0.86 and 0.42 mg L(-1), respectively. Furthermore, we also found that carbofuran caused an inhibition in oxygen consumption of 60.6, 65.3 and 66.2% with respect to the control. In addition, after separate exposures to carbofuran, elevations in ammonium excretion were more than 500% with respect to the control.

Integrated ecological risk assessment of pesticides in tropical ecosystems: a case study with carbofuran in Brazil.

The aim of the present study is to contribute an ecologically relevant assessment of the ecotoxicological effects of pesticide applications in agricultural areas in the tropics, using an integrated approach with information gathered from soil and aquatic compartments. Carbofuran, an insecticide/nematicide used widely on sugarcane crops, was selected as a model substance. To evaluate the toxic effects of pesticide spraying for soil biota, as well as the potential indirect effects on aquatic biota resulting from surface runoff and/or leaching, field and laboratory (using a cost-effective simulator of pesticide applications) trials were performed. Standard ecotoxicological tests were performed with soil (Eisenia andrei, Folsomia candida, and Enchytraeus crypticus) and aquatic (Ceriodaphnia silvestrii) organisms, using serial dilutions of soil, eluate, leachate, and runoff samples. Among soil organisms, sensitivity was found to be E. crypticus < E. andrei < F. candida. Among the aqueous extracts, mortality of C. silvestrii was extreme in runoff samples, whereas eluates were by far the least toxic samples. A generally higher toxicity was found in the bioassays performed with samples from the field trial, indicating the need for improvements in the laboratory simulator. However, the tool developed proved to be valuable in evaluating the toxic effects of pesticide spraying in soils and the potential risks for aquatic compartments.

Carbofuran occupational dermal toxicity, exposure and risk assessment.

BACKGROUND: Carbofuran is a carbamate insecticide that inhibits AChE. Although toxic by ingestion in mammals, it has low dermal toxicity, with relatively few confirmed worker illnesses. This risk assessment describes its time of onset, time to peak effect and time to recovery in rats using brain AChE inhibition in acute and 21 day dermal studies; in vitro rat/human relative dermal absorption for granular (5G) and liquid (4F) formulations; occupational exposure estimates using the Pesticide Handlers' Exposure Database and Agricultural Handlers' Exposure Database (PHED/AHED). RESULTS: The point of departure for acute risk calculation (BMDL(10)) was 6.7 mg kg(-1) day(-1) for brain AChE inhibition after 6 h exposure. In a 21 day study, the BMDL(10) was 6.8 mg kg(-1) day(-1), indicating reversibility. At 75 mg kg(-1) day(-1), time of onset was ≤ 30 min and time to peak effect was 6-12 h. Rat skin had ca tenfold greater dermal absorption of carbofuran (Furadan(®) 5G or 4F) than human skin. Exposure estimates for 5G in rice and 4F in ten crops had adequate margins of exposure (>100). CONCLUSION: Rat dermal carbofuran toxicity was assessed in terms of dose and time-related inhibition of AChE. Comparative dermal absorption in rats was greater than in humans. Worker exposure estimates indicated acceptable risk for granular and liquid formulations of carbofuran.

Evaluación del riesgo ambiental de carbofurano en bioensayos con organismos no blanco / Environmental risk assessment of carbofuran in bioassays with non-target organisms

El carbofurano es uno de los plaguicidas más empleado en la agricultura peruana. El objetivo de este trabajo fue evaluar el riesgo ambiental del carbofurano en bioensayos de toxicidad, sobre once especies no destinatarias. La siguiente secuencia relativa de mayor a menor cocientes de riesgo (CR) del carbofurano para los 19 puntos finales de efecto en once especies fue encontrada: Daphnia magna (mortalidad) > Lemna minor (inhibición de formación de las hojas) > Paracheirodon innesi (nado extraño) = P. innesi (incremento del movimiento opercular) > Chironomus calligraphus (mortalidad) > L. minor (necrosis) > P. innesi (mortalidad) > L. minor (clorosis) > Tetrapygus niger (inhibición de la fecundación) > Coturnix japonica (mortalidad) > Oncorhynchus mykiss (incremento de coloración) > Ceraeochrysa cincta (no eclosión de huevos) > O. mykiss (mortalidad con oxígeno) > O. mykiss (mortalidad sin oxígeno) > Trichogramma pretiosum (mortalidad) > C. cincta (mortalidad) > T. pretiosum (no emergencia de adultos) > Trichogramma pintoi (mortalidad) > Beauveria bassiana (inhibición del crecimiento). Los cocientes de riesgo (CR) indicaron en todos los casos un alto riesgo del carbofurano principalmente en el ambiente acuático en comparación con el terrestre.

Carbofuran is one of the most employed pesticides in Peruvian agriculture. This research aimed to evaluate the risk assessment in bioassays of carbofuran on eleven non-target species. The following relative sequence in decreasing ecotoxicity order in terms of RQ (Risk quotient) to carbofuran to 19 end points on 11 species was found: Daphnia magna (mortality) > Lemna minor (inhibition of new fronds) > Paracheirodon innesi (strange swim) = P. innesi (increase of opercula movement) > Chironomus calligraphus (mortality) > L. minor (necrosis) > P. innesi (mortality) > L. minor (chlorosis) > Tetrapygus niger (inhibition of fertilization)> Coturnix japonica (mortality) > Oncorhynchus mykiss (increase of coloration) > Ceraeochrysa cincta (not hatch of eggs) > O. mykiss (mortality without oxygen) > O. mykiss (mortality with oxygen) > Trichogramma pretiosum (mortality) > C. cincta (mortality) > T. pretiosum (not emergence of adults) > Trichogramma pintoi (mortality) > Beauveria bassiana (inhibition of growth). Risk quotient (RQ) indicated that carbofuran is highly risky mainly to aquatic environment than terrestrial.

Natural impacted freshwaters: in situ use of alginate immobilized algae to the assessment of algal response.

The objective of this study was to investigate the feasibility of an in situ phytotoxicity test using alginate-immobilized algae for 60 days, in the assessment of water quality in an impacted small peri-urban stream. After laboratory optimization of algae immobilization/de-immobilization processes, the performance of immobilized/de-immobilized algae was compared to the performance of free algae in terms of specific algal growth and sensitivity. This was done by comparing 72 h EC50 values obtained with zinc and the pesticides clomazone and carbofuran. The results showed a similar performance, which allow us to conclude that immobilization for 60 days do not cause any significant alteration in algae physiology. In the field, immobilized algae were exposed at different times (2, 4 and 7 days) to water samples in both disturbed and undisturbed sites. Both laboratory and field experiments indicated that alginate-immobilized algae for 60 days were sufficiently sensitive for use in the in situ assessment of water quality.

Assessment of biochemical markers of carbofuran toxicity and recovery response in tissues of the freshwater teleost, Clarias batrachus (Linn).

The effects of a sublethal concentration (7.66 mg/L) of carbofuran, were assessed on Clarias batrachus. The fish were exposed to 7.66 mg of carbofuran/L for 6 days. After 6 days, fish were released into carbofuran-free water in order to study the recovery pattern. Proteins were decreased in gill and kidney and recovery was greater in gill than in kidney. Total amino acids were increased in both tissues. Ammonia level declined in gill and enhanced in kidney throughout the study period. The activities of all enzymes measured were induced in both tissues, except for aspartate aminotransaminase, which was inhibited in gill tissues.

A physiologically based pharmacokinetic/pharmacodynamic model for carbofuran in Sprague-Dawley rats using the exposure-related dose estimating model.

Carbofuran (2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methylcarbamate), a broad spectrum N-methyl carbamate insecticide, and its metabolite, 3-hydroxycarbofuran, exert their toxicity by reversibly inhibiting acetylcholinesterase (AChE). To characterize AChE inhibition from carbofuran exposure, a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model was developed in the Exposure-Related Dose Estimating Model (ERDEM) platform for the Sprague-Dawley (SD) rat. Experimental estimates of physiological, biochemical, and physicochemical model parameters were obtained or based on data from the open literature. The PBPK/PD model structure included carbofuran metabolism in the liver to 16 known metabolites, enterohepatic circulation of glucuronic acid conjugates, and excretion in urine and feces. Bolus doses by ingestion of 50 microg/kg and 0.5 mg/kg carbofuran were simulated for the blood and brain AChE activity. The carbofuran ERDEM simulated a half-life of 5.2 h for urinary clearance, and the experimental AChE activity data were reproduced for the blood and brain. Thirty model parameters were found influential to the model outputs and were chosen for perturbation in Monte Carlo simulations to evaluate the impact of their variability on the model predictions. Results of the simulation runs indicated that the minimum AChE activity in the blood ranged from 29.3 to 79.0% (as 5th and 95th percentiles) of the control level with a mean of 55.9% (standard deviation = 15.1%) compared to an experimental value of 63%. The constructed PBPK/PD model for carbofuran in the SD rat provides a foundation for extrapolating to a human model that can be used for future risk assessment.

Physiological basis in the assessment of ecotoxicity of pesticides to soil organisms.

Earthworms are universally accepted as one of the most suitable and representative soil animals to be used for assessing chemical pollution in soils. Therefore, in this work earthworm species diverse in habitat and life-pattern are used and the effects of sublethal concentrations of terbuthylazine and carbofuran on the reproductive processes, respiration and excretion are investigated. The results show that even low and moderate concentrations of the pesticides can induce measurable physiological effects. Species-specific and substance-specific effects are noticeable in the worms.

A new sensitive cell culture test for the assessment of pesticide toxicity.

A new, simple and sensitive cell culture test for the determination of cytotoxicity of pesticides is described. This test is based on assessment of the growth inhibitory effect of pesticides on the rapidly growing mouse hybridoma cell line 1E6 cultivated in a defined serum-free medium (RPMI-SR3). In addition the cytotoxicity in serum-containing medium was investigated. The results showed that the sensitivity of 1E6 cell towards the toxicity of the pesticides; carbofuran, cypermethrin, lindane, glyphosate and 2,4-D was considerably higher in the serum-free medium than in serum-containing medium. Also IC50 values of these pesticides were compared with LD50 values obtained from the literature. The ratio between the in vitro IC50 and the in vivo LD50 showed that the present cell culture test determine the toxicity of low levels of pesticides with much higher sensitivity than tests based on using animals.

A sensitive sperm-motility test for the assessment of cytotoxic effect of pesticides.

A sensitive sperm-motility test for the evaluation of cytotoxic effects of carbofuran and glyphosate in a defined protein-free culture medium is described. The sperm motility was compared to that obtained with a protein-containing medium. The use of protein-free medium considerably increased the sensitivity of sperm cells from rabbit and human to the toxic effects of the pesticide. The respective IC50 values (the concentration needed to cause 50% inhibition of sperm motility) in protein-free medium of carbofuran and glyphosate were 321 and 48.2 microM with human sperm, and 116 and 23.5 microM with rabbit sperm. Whereas, the corresponding values in protein-containing medium were 920 and 740 microM, and 910 and 500 microM with human and rabbit sperm, respectively. Our results show that testing human and rabbit sperm in protein-free medium proves to be a more sensitive method than that in protein-containing medium. Additionally, the use of rabbit sperm is a more sensitive test system than human sperm. This study suggests that the rabbit sperm test appears to have a potential for the assessment of toxicity on human reproduction.

Assessment of the genotoxicity potential of the nematicide insecticide carbofuran in wheat cells

Carbofuran (Furadan), an insecticide-nematicide, is widely used for seed treatment in Brazil, against pests in crops such as wheat, rice and corn. It was assessed for its cytotoxic and or clastogenic potential in root meristems of Triticum aestivum (tested in vivo). Seed samples (1OO grams each) were individually treated with one, two, four and eight liters of the pure commercial product/lOO kg seed and germinated on three substrates: virgin soil, sterilized soil and growth chamber (on paper). For all treatments, no cytotoxic or clastogenic effects were observed in the meristem root cells.

Toxicity assessment of atrazine, alachlor, and carbofuran and their respective environmental metabolites using Microtox.

Using the Microtox method of toxicity assessment designed by Microbics Corporation, the relative toxicities of alachlor, atrazine, and carbofuran, three pesticides commonly used in agricultural production, were determined. Generally, carbofuran was found to be most acutely toxic, followed closely by atrazine. Alachlor was least toxic of the three pesticides tested. Selected environmental metabolites of these three agri-chemicals were also tested using the same method. Hydroxyalachlor, deethylatrazine, deisopropylatrazine, 3-hydroxycarbofuran, and 3-ketocarbofuran were selected for analysis because previous studies determined their presence in surface and ground-water supplies along with their parents. Results showed that often the metabolites were at least as acutely toxic as their parents, particularly in the case of 3-ketocarbofuran and hydroxyalachlor, which demonstrated toxicities higher or not significantly different than their parents. Hydroxycarbofuran was assessed as the least toxic of all substances tested. The atrazine environmental metabolites were less toxic than their parent.

Methods for the assessment of the toxicity of environmental chemicals to earthworms.

In view of the impending publication of standards for earthworm toxicity testing by the Commission of the European Communities, a review has been made of the recent literature on earthworm toxicology. Relevant studies are reviewed from the standpoints of methods used, reproducibility of results, and ability to extrapolate laboratory results to field situations. Eisenia foetida, a commonly used test species, is much less sensitive to agricultural chemicals than other, native earthworms and is of doubtful utility for extrapolating laboratory data to field conditions, but when native soil organisms are used, such extrapolations show good general agreement. Standardization of test conditions and broadening of the data base are encouraged.