The effects of the insecticide lambda-Cyhalothrin on the earthworm Eisenia fetida under experimental conditions of tropical and temperate regions

Influence of soil organic matter content on the toxicity of pesticides to soil invertebrates: A review

A better understanding of how soil organic matter (OM) content influences pesticide toxicity to soil invertebrates is needed to improve the ecological relevance of risk assessment approaches. In the current study, soil invertebrate toxicity data (LC50 and EC50 values) were collected from studies determining the toxicity of organic chemicals in soils with varying OM content. Relevant studies were identified by performing a literature search and through the use of toxicity databases. The data were used to address the following questions: (1) Can the relationship between toxicity and soil OM content be quantified? (2) Does soil OM content influence different toxicity endpoints in a similar way? (3) Is the influence of soil OM content on sensitivity to pesticides different between species? The results indicate that toxicity-OM relationships are chemical dependent, differ between endpoints, and are species-specific. Hence, the grouping of chemicals based solely on their lipophilicity, as well as having only one correction factor for multiple species, may not be an appropriate approach to risk assessment. Integr Environ Assess Manag 2023;19:1457-1472. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Natural soils in OECD 222 testing - influence of soil water and soil properties on earthworm reproduction toxicity of carbendazim

Soil sorption properties can influence the bioavailability of substances and consequently the toxicity for soil organisms. Current standardised laboratory testing for the exposure assessment of pesticides to soil organisms uses OECD artificial soil that does not reflect the high variation in chemical-physical soil properties found in natural agroecosystems. According to guideline OECD 222, earthworm reproduction tests with Eisenia fetida and the pesticide carbendazim were performed in four natural soils and OECD artificial soil. By using pF 1.6, which ensures a uniformity in actual soil water availability, the control reproduction performance of E. fetida in all natural soils was at the same level as OECD artificial soil. In a principle component analysis, the variation in toxicity between the tested soils was attributable to a combination of two soil properties, namely total organic carbon content (TOC) and pH. The largest difference of 4.9-fold was found between the typical agricultural Luvisol with 1.03% TOC and pH 6.2 (EC₁₀: 0.17 (0.12-0.21) mg a.i. kg^-1 sdw, EC₅₀: 0.36 (0.31-0.40) mg a.i. kg^-1 sdw) and OECD artificial soil with 4.11% TOC and pH 5.6 (EC₁₀: 0.84 (0.72-0.92) mg a.i. kg^-1 sdw, EC₅₀: 1.07 (0.99-1.15) mg a.i. kg^-1 sdw). The use of typical agricultural soils in standardised laboratory earthworm testing was successfully established with using the measure pF for soil moisture adjustment. It provides a more application-oriented approach and could serve as a new tool to refine the environmental risk assessment at lower tier testing or in an intermediate tier based approach.

Arsenite and arsenate toxicity in the earthworm Eisenia andrei (Bouché 1972) in natural soil and tropical artificial soil

Inorganic forms of As (arsenite - As(III) and arsenate - As(V)) are prevalent in soil and recognized for their high toxicity. Once in the soil, these forms of As can compromise key organisms for ecological processes, such as earthworms. The aim of the study was to evaluate the toxicity of arsenite and arsenate in the Californian earthworm Eisenia andrei exposed in natural soil and tropical artificial soil (TAS). Adverse effects were evaluated using avoidance test, acute toxicity test, and a sublethal concentration test to assess biochemical parameters. LC50 values for arsenite were 21.27 mg/kg in natural soil and 19.0 mg/kg in TAS and for arsenate were 76.18 mg/kg in natural soil and above 120 mg/kg in TAS. In the avoidance test, this behavior was shown to be significantly higher in the natural soil and for earthworms exposed to arsenite, while total antioxidant capacity, glutathione levels, lipid damage, and DNA damage were significantly higher in animals exposed to arsenite, but without differences in relation to the two types of soil tested. Animals exposed to As(V) showed increased activity of enzymes related to glutathione metabolism. The results obtained in the present study show the impact of As exposure on the health of the Californian earthworm E. andrei, especially in the form of arsenite, and alert the public authorities that legal limits should, whenever possible, consider the soil properties and also the different chemical species of the contaminants.

Effect of temperature on the toxicity of imidacloprid to Eisenia andrei and Folsomia candida in tropical soils

The influence of temperature on the chronic toxicity and risk of imidacloprid to soil non-target species was assessed in tropical soils. Earthworms Eisenia andrei and collembolans Folsomia candida were exposed to a tropical artificial soil (TAS) and two natural tropical soils from Brazil (Entisol and Oxisol) with increasing concentrations of imidacloprid under atmospheric temperatures of 20, 25 and 28 °C. The effect of temperature on the reproduction of both species was assessed through the number of juveniles and earthworm's growth, and the risk associated was estimated through the Toxicity-Exposure Ratio (TER). Toxicity of imidacloprid increased with temperature in all tested soils, being generally lower in TAS soil (EC₅₀s of 1.48, 0.66 and 0.40 mg kg^-1 for E. andrei and 0.3, 0.2 and 0.06 mg kg^-1 for F. candida at 20, 25 and 28 °C, respectively) compared to Entisol (EC₅₀s of 0.19, 0.03 and 0.14 mg kg^-1 for E. andrei and 0.04, 0.02, 0.01 mg kg^-1 for F. candida at 20, 25 and 28 °C, respectively) and Oxisol (EC₅₀s of 0.21, 0.07, 0.06 mg kg^-1 for E. andrei and 0.16, 0.09, 0.06 mg kg^-1 for F. candida at 20, 25 and 28 °C, respectively) within each temperature for both species. These values indicate that properties of TAS may not be representative of natural/local soils to adequately estimate the toxicity of pesticides to non-target soil species. At higher temperatures, the variability of imidacloprid toxicity between soils was lower, which suggests that the influence of soil properties on imidacloprid toxicity was overshadowed by temperature. TER values revealed that risk is also greater at higher temperatures. Data reported enforce the need for the inclusion of more realistic conditions in single-species tests in prospective risk assessment of pesticides to avoid underestimation of risk to non-target species.

Acute and chronic toxicity of the fungicide carbendazim to the earthworm Eisenia fetida under tropical versus temperate laboratory conditions

Research efforts into the potential side-effects of pesticides on beneficial organisms have focused on temperate test species and conditions. There is thus a need for studies into the ecotoxicity of a vaster range of pesticides under tropical conditions. The present study therefore aimed to compare the acute and chronic toxicity of the fungicide carbendazim to the earthworm Eisenia fetida under tropical and temperate conditions. To this end, laboratory toxicity tests were conducted with a tropical and European strain of E. fetida, using different artificial (OECD and TAS) and natural (LUFA and TNS) soils, and under different test temperatures (20 °C and 28 °C). In the acute lethality tests with artificial soils, the tropical strain of E. fetida was three to four order of magnitude less sensitive than the European strain, which is ascribed to the higher test temperature and (hence) higher microbial activity/pesticide degradation. The tropical strain was particularly sensitive in the tropical natural soil, which was attributed to the low pH (3.9) of this soil. The chronic toxicity tests overall also showed a lower sensitivity of the tropical strain on reproduction. These findings thus support the use of toxicity data generated under temperate conditions in tropical pesticide effect assessments. However, intensive agricultural practices in the tropics may dictate that exposure levels (and hence potentially also risks) are higher.

Study of the effect of cypermethrin on the spider Polybetes phytagoricus in different energy states

Spiders are found among the most important predators of plague insects of numerous agricultural systems. They are the most numerous representatives of the Class Arachnid and are widely distributed in numerous ecosystems. Due to multiple variables, living beings are exposed to quantitative transitions of their energetic reserves, which affect their sensitivity before the different xenobiotics. In the present study we evaluate the effect of cypermethrin (pyrethroid) on different metabolic/energetic stages of the spider Polybetes pythagoricus (Sparassidae). We firstly studied LD₅₀ of cypermethrin on young, males and, pre-vitellogenic and post-vitellogenic females. The activity of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST) and acetylcholinesterase (AChE) was analyzed. Results indicate that young have a higher caloric content compared to adults, females have a higher caloric content than males and vitellogenesis generates a great calory decrease in females. The LD₅₀ was significantly lower in young (10%) (103 ng/g weight) in relation to the three models of adults (969-1108 ng/g weight). Vitellogenesis causes an increase of free radicals as a result of the different metabolic processes which manifest as an increase in the lipid peroxidation. Doses at the LD₃₀ and LD₄₀ levels of cypermethrin did not generate alterations in any of the enzymes analyzed in young, this fact may probably provoke an increase of lipid peroxidation (evaluated as a great MDA increase). The activity of the enzymes linked to oxidative stress was altered by this doses in the three adult models, the enzymatic activity CAT, GR, and GST was sex-dependent. Post-vitellogenic females showed a greater activity of CAT, SOD, GST and GR before the xenobiotics than pre-vitellogenic ones, probably as a consequence of metabolic stress generated during vitellogenesis.

World of earthworms with pesticides and insecticides

Earthworms are important organisms in soil communities and are known for sustaining the life of the soil. They are used as a model organism in environmental risk assessment of chemicals and soil toxicology. Soil provides physical and nutritive support to agriculture system by regulating biogeochemical cycles, nutrient cycle, waste degradation, organic matter degradation etc. The biggest threat to soil health are pesticides and synthetic chemicals including fertilizers. Earthworms are most severely hit by these xenobiotic compounds leading to a sizeable reduction of their population and adversely affecting soil fertility. Earthworms are incredible soil organisms playing a crucial role in maintaining soil health. Pesticides used in crop management are known to be most over-purchased and irrationally used soil toxicants, simultaneously, used insecticides contribute to a quantum of damage to earthworms and other non-target organisms. LC₅₀ and LD₅₀ studies revealed that earthworms are highly susceptible to insecticides causing immobility, rigidity and also show a significant effect on biomass reduction, growth and reproduction by disrupting various physiological activities leading to loss of earthworm population and soil biodiversity.

Effects of L-Glufosinate-ammonium and temperature on reproduction controlled by neuroendocrine system in lizard (Eremias argus)

In the context of global warming, an important issue is that many pesticides become more toxic, putting non-target organisms at higher risk of pesticide exposure. Eremias argus (a native Chinese lizard) was selected as animal model in this study. As a kind of poikilothermic vertebrate, E.argus is sensitive to temperature change. The experimental design [(with or without L-Glufosinate-ammonium (L-GLA) pollution × two temperatures (25 and 30 °C)] was used in this study for 90 days to identify the chronic effects of the pesticide-temperature interaction on the lizards' neuroendocrine-regulated reproduction. Survival rate, body weight, clutch characteristics, testicular histopathology, the content of neurotransmitters and related enzyme activity, the level of sex steroid, the expression of Heat shock protein 70 (HSP70), antioxidant system, the accumulation and degradation of L-GLA were examined. Results showed that L-GLA disrupt reproduction of lizards through hypothalamus-pituitary-gonad (HPG) axis. In addition, temperature can not only change the environmental behavior of pesticides, but also alter the physiological characteristics of lizards. Thus, our results emphasized that temperature is an essential abiotic factor that should not be overlooked in ecotoxicological studies.

Environmental risk assessment of pesticides in tropical terrestrial ecosystems: Test procedures, current status and future perspectives

Despite the increasing use of pesticides in tropical countries, research and legislative efforts have focused on their temperate counterparts. This paper presents a review of the literature on environmental risk assessment of pesticides for tropical terrestrial agroecosystems. It aims at evaluating potential differences in pesticide risk between temperate and tropical regions as well as to highlight research needs in the latter. Peculiarities of pesticide risks in tropical terrestrial agroecosystems are discussed in subsections 1) agricultural practices; 2) research efforts; 3) fate and exposure; 4) toxicity testing methods; and 5) sensitivity. The intensive and often inadequate pesticide application practices in tropical areas are likely to result in a relatively greater pesticide exposure in edge-of-field water bodies. Since pesticide fate may be different under tropical conditions, tropical scenarios for models estimating predicted environmental pesticide concentrations should be developed. Sensitivity comparisons do not indicate a consistent similar, greater or lower relative sensitivity of tropical soil organisms as compared to temperate organisms. However, several methods and procedures for application in the tropics need to be developed, which include: 1) identifying and collecting natural soils to be used as reference test substrates in tests; 2) identifying and discerning the range of sensitivity of native test species to soil contaminants; 3) developing test guidelines applicable to tropical/subtropical conditions; and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes.

Joint toxic effects of cadmium and four pesticides on the earthworm (Eisenia fetida)

The contaminants, instead of single contaminants, are usually found as chemical mixtures in terrestrial environment. However, little information is now available about the joint effects of heavy metals and farm chemicals on the soil organism. Our current study aimed to assess the combined toxicity of cadmium (Cd) and four pesticides (atrazine, chlorpyrifos, lambda-cyhalothrin and abamectin) to the earthworm (Eisenia fetida) with binary, ternary, quaternary and quinquenary mixtures. Two distinct kinds of bioassay systems were applied in this study, including contact filter paper test and artificial soil test. Synergistic effects were observed from two quaternary mixtures (Cd-Atrazine-Chlorpyrifos-Lambda-cyhalothrin and Cd-Chlorpyrifos-Lambda-cyhalothrin-Abamectin) and one quinquenary mixture (Cd-Atrazine-Chlorpyrifos-Lambda-cyhalothrin-Abamectin) in both bioassay systems. Besides, two binary mixtures (Cd-Atrazine and Cd-Lambda-cyhalothrin) and three ternary mixtures (Cd-Atrazine-Chlorpyrifos, Cd-Atrazine-Lambda-cyhalothrin and Cd-Chlorpyrifos-Lambda-cyhalothrin) also exhibited synergistic effects on E. fetida by the soil toxicity test. It is more practical to evaluate the contaminant toxicities to earthworm by soil toxicity test. Therefore, the effects of chemical mixtures on soil invertebrates might be underestimated by data obtained from single toxicant. Our findings would offer a better understanding of the complex effects of chemical mixtures on non-target living creatures, and these findings provided valuable insights into the interplay of different chemicals in natural environment.

Agrotóxicos e seus impactos na saúde humana e ambiental: uma revisão sistemática

RESUMO Atualmente, o Brasil é o maior consumidor de agrotóxicos do mundo. Diversos estudos comprovam os malefícios para a saúde humana e ambiental da exposição aos agrotóxicos. Realizou-se uma revisão sistemática no período de 2011 a 2017 acerca desse tema em bases de dados científicos. Foram incluídos 116 estudos que demonstraram o impacto negativo para a saúde humana e ambiental. É essencial a realização de estudos sobre os efeitos da exposição crônica e simultânea a diversos agrotóxicos, além de estudos sobre os nexos de determinação estrutural do uso dos venenos e suas consequências.

Effects of deltamethrin, dimethoate, and chlorpyrifos on survival and reproduction of the collembolan Folsomia candida and the predatory mite Hypoaspis aculeifer in two African and two European soils

Indiscriminate use of pesticides is rampant in most parts of Africa, but only scanty ecotoxicological data exist for the protection of soil organisms-and these data were usually obtained under temperate conditions, including the use of Organisation for Economic Co-operation and Development (OECD) standard test protocols. In order to assess the effects of 3 commonly used pesticides (deltamethrin, dimethoate, chlorpyrifos) on soil fauna in Africa, noncontaminated natural soils were collected from Nigeria and Tunisia. In addition, 2 common test soils, OECD artificial soil and European (Landwirtschaftliche Untersichungs- und Forschungsanstalt [LUFA]) 2.3 soil, were used in OECD standard reproduction tests. Two microarthropod species, the springtail Folsomia candida and the predatory mite Hypoaspis aculeifer, were exposed in these 4 soils spiked individually with the 3 insecticides. Results show that the collembolan F. candida was more sensitive than the mite H. aculeifer for all 3 insecticides. The toxicity of each insecticide in the 4 soils differed, with few exceptions, by less than an order of magnitude. However, the pattern of toxicity was not consistent, that is, the lowest toxicity was often but not always found in OECD artificial soil. Soil- and pesticide-specific patterns of toxicity to F. candida and H. aculeifer might be related to the physicochemical properties of the soils and thus the availability of the 3 pesticides. Following the rules laid down in the European Union for the registration of pesticides and using standard European exposure scenarios, neither an acute nor a chronic risk of dimethoate and chlorpyrifos can be excluded (with few exceptions) in all 4 soils. Lower risks were identified for deltamethrin. For pesticide used in Africa, an environmental risk assessment based on data gained in tests with at least 1 additional natural field soil, preferably of African origin, should be performed using the same risk assessment principles as in the European Union. Integr Environ Assess Manag 2018;14:92-104. © 2017 SETAC.

Soil ecotoxicology in Latin America: Current research and perspectives

Soils from some Latin American countries support the highest biodiversity levels on the planet and simultaneously have some of the most serious environmental impacts attributed to both historical and current agricultural practices and industrial activities. Soil contamination has resulted from intensive use of pesticides, extensive mining and other industrial activities, and uncontrolled management of waste within inappropriate regulatory frameworks. The present study presents an overview of the scientific research on soil ecotoxicology conducted in Latin America, summarizing the recent advances and highlighting the needs for further refinements in this research field. Most of the contributions to the scientific literature have been from Brazil. The most investigated issue is the ecotoxicity of pesticides and earthworms, which were the organisms most frequently used as test species. Needs identified by Latin American researchers include methods and procedures for: 1) identifying and collecting natural soils to be used as reference test-substrates in tests, 2) identifying and discerning the range of sensitivities of native test species to soil contaminants, 3) developing environmental guidelines applicable to tropical/subtropical conditions, and 4) developing methods and procedures for higher tier testing for full development and implementation of environmental risk assessment schemes. The protection of Latin American soils, including provision of goods and services, is currently framed in legislation and other regulations, but implementation requires significant improvement and additional training programs. Environ Toxicol Chem 2017;36:1795-1810. © 2017 SETAC.

Temperature influences the toxicity of deltamethrin, chlorpyrifos and dimethoate to the predatory mite Hypoaspis aculeifer (Acari) and the springtail Folsomia candida (Collembola)

In order to assess the influence of temperature on pesticide toxicity to soil fauna, specimens of the predatory mite Hypoaspis aculeifer and the springtail Folsomia candida were exposed in artificial soil spiked with different concentrations of three pesticides (dimethoate, chlorpyrifos and deltamethrin) at 20°C vs 28°C for the mites and 20°C vs 26°C for the springtails. All tests were carried out according to OECD guidelines. In the mite tests, the toxic effects of dimethoate and chlorpyrifos on survival was about two orders of magnitude more at 28°C than at 20°C. Mite reproduction decreased in the tests with chlorpyrifos and deltamethrin by about four to five orders of magnitude at 28°C than at 20°C. (EC50₂₈°_C =1.42 and 2.52mg/kg vs EC50₂₀°_C=6.18 and 10.09mg/kg) In the collembolan tests, the toxicity of dimethoate on survival was higher at 26°C than at 20°C (LC50₂₆°_C =0.17mg/kg vs LC50₂₀°_C =0.36mg/kg), while the opposite was detected for deltamethrin (LC50₂₆°_C =11.27mg/kg vs LC50₂₀°_C =6.84mg/kg). No difference was found in the test with chlorpyrifos. Effects of dimethoate and chlorpyrifos on reproduction were higher at 26°C than at 20°C (EC50₂₆°_C =0.11 and 0.018mg/kg vs EC50₂₀°_C =0.29 and 0.031mg/kg respectively), but in the case of deltamethrin the opposite was observed (EC50₂₆°_C =12.85mg/kg vs EC50₂₀°_C =2.77mg/kg). A preliminary risk assessment of the three pesticides at the two temperature regimes based on the Toxicity Exposure Ratio (TER) approach of the European Union, shows that in general there are few different outcomes when comparing data gained at different temperatures. However, in the light of the few comparisons made data gained in temperate regions should be used with caution in the tropics.

Mercury critical concentrations to Enchytraeus crypticus (Annelida: Oligochaeta) under normal and extreme conditions of moisture in tropical soils - Reproduction and survival

Soil provides many ecosystem services that are essential to maintain its quality and healthy development of the flora, fauna and human well-being. Environmental mercury levels may harm the survival and diversity of the soil fauna. In this respect, efforts have been made to establish limit values of mercury (Hg) in soils to terrestrial fauna. Soil organisms such as earthworms and enchytraeids have intimate contact with trace metals in soil by their oral and dermal routes, reflecting the potentially adverse effects of this contaminant. The main goal of this study was to obtain Hg critical concentrations under normal and extreme conditions of moisture in tropical soils to Enchytraeus crypticus to order to assess if climate change may potentiate their acute and chronic toxicity effects. Tropical soils were sampled from of two Forest Conservation Units of the Rio de Janeiro State - Brazil, which has been contaminated by Hg atmospheric depositions. Worms were exposed to three moisture conditions, at 20%, 50% and 80% of water holding capacity, respectively, and in combination with different Hg (HgCl₂) concentrations spiked in three types of tropical soil (two natural soils and one artificial soil). The tested concentrations ranged from 0 to 512mg Hg kg^-1 dry weight. Results indicate that the Hg toxicity is higher under increased conditions of moisture, significantly affecting survival and reproduction rate.

Combined toxicity of imidacloprid and three insecticides to the earthworm, Eisenia fetida (Annelida, Oligochaeta)

Although the earthworm Eisenia fetida has been used in many ecotoxicological studies in recent years, most of these studies have only focused on assessing the effects of individual insecticides. In the present study, we aimed to compare the individual and combined toxic effects of imidacloprid and three insecticides (phoxim, chlorpyrifos, and lambda-cyhalothrin) on E. fetida. We showed that imidacloprid had the highest intrinsic toxicity to the worms in filter paper contact test, followed by phoxim and lambda-cyhalothrin, while the least toxicity was found from chlorpyrifos. Moreover, 14-day soil toxicity test revealed that the highest toxicity was still detected for imidacloprid with an LC₅₀ value of 2.82 (2.61∼3.17) mg a.i. kg^-1 dry weight (DW), followed by chlorpyrifos with an LC₅₀ value of 384.9 (353.5∼440.3) mg a.i. kg^-1 DW. Meanwhile, a relatively less toxicity was found for lambda-cyhalothrin with an LC₅₀ value of 560.3 (475.9∼718.5) mg a.i. kg^-1 DW, while the lowest toxicity to E. fetida was observed for phoxim with an LC₅₀ value of 901.5 (821.3∼1017) mg a.i. kg^-1 DW. In addition, significant synergistic responses were found from the ternary mixture of imidacloprid-phoxim-lambda-cyhalothrin and quaternary mixture of imidacloprid-phoxim-chlorpyrifos-lambda-cyhalothrin in both bioassay systems. Therefore, our findings highlighted that the simultaneous presence of several insecticides in the soil environment might lead to increased toxicity, resulting in serious damage to the nontarget organisms compared with individual insecticides.

Soil ecotoxicology in Brazil is taking its course

Soil ecotoxicology has been motivated by the increasing global awareness on environmental issues. Northern Hemisphere has been the main driver of this science branch; however, the number and quality of contributions from the Southern Hemisphere are increasing quickly. In this case study, Brazil is taken as an example of how soil ecotoxicology has developed over the last 30 years. It starts with a brief historical overview depicting the main events on soil ecotoxicology in the country. Following, an overview on the Brazilian legislation related to soil ecotoxicology is given, covering regulations with prospective focus, mainly on the registration of pesticides. Regulations with retrospective focus in contaminated areas are also given. Then, an outline of the actors in soil ecotoxicology and examples of prospective ecotoxicological studies performed with soil organisms and plants are given by stressor groups: pesticides, pharmaceuticals, metals, and residues. Experiences from retrospective studies, mainly looking at the assessment of industrial sites, are also covered. Emphasis is given on methodological aspects, pointing to needed actions, mainly regarding the different biotic and abiotic conditions of a tropical country. Finally, the last session discusses how soil ecotoxicology could be improved in methodological adaptations as well as legal requirements.

Ecotoxicity of mercury to Folsomia candida and Proisotoma minuta (Collembola: Isotomidae) in tropical soils: Baseline for ecological risk assessment

Mercury (Hg) is a highly toxic nonessential trace metal. Despite its natural occurrence in the Earth's Crust, its concentrations have been steadily increasing in the environment due to anthropogenic sources. Recent studies have showed great concern about soil fauna, once the potential adverse effects of mercury concentrations in the environment of these invertebrates are still poorly understood, especially when linked to forest soils and tropical biota. Different collembolan species can show distinct toxicity effects to the contaminants, impairing its developing lifelong and affecting its diversity and abundance in the environment. Laboratory studies were performed to evaluate the ecotoxicity of Hg(II) to collembolan species collected in Brazil, Proisotoma minuta (autochthonous) and Folsomia candida (allochthonous), as a tool to predict effects in ecological risk assessment of tropical regions. Behavioral, acute and chronic tests were carried under temperatures of 20°C and 24°C using two test soils, natural and artificial, spiked with increasing mercury concentrations. F. candida was more sensitive to mercury contamination than P. minuta, presenting the most restrictive values of EC50 and LC50. Reproduction was a considerably more sensitive endpoint than avoidance and mortality. The 28-day lower EC50 values were found in chronic tests for F. candida in natural soil to 24°C (3.32mgHgkg(-1)), while for P. minuta was in tropical artificial soil to 20°C (4.43mgHgkg(-1)). There were similarity for each collembolan species to respond at the Hg(II) effects when exposed at 20°C and 24°C. F. candida can be suitable as a bioindicator species to mercury ecotoxicity tests in tropical forest soils.

Toxicity of mixtures of λ-cyhalothrin, imidacloprid and cadmium on the earthworm Eisenia fetida by combination index (CI)-isobologram method

Contaminants in the environment do not appear singly and usually occur as mixtures. We applied the combination index (CI)-isobologram method which allows computerized quantitation of synergism, additive effect and antagonism to determine the nature of toxicological interactions of two pesticides λ-cyhalothrin, imidacloprid, and heavy metal cadmium towards earthworm Eisenia fetida. In an artificial soil test, λ-cyhalothrin and Cd combination was slightly synergistic at low effect levels which turned into a slight antagonism above f(a) values of 0.6, while the binary mixtures containing imidacloprid exhibited antagonism. The presence of imidacloprid in the ternary mixture also resulted in an antagonistic effect to the earthworms. This behavior became more antagonistic in the ternary mixture in filter paper tests.

Comparative acute toxicity of twenty-four insecticides to earthworm, Eisenia fetida

In this study, we used two different types of bioassay, a contact filter paper toxicity bioassay and a soil toxicity bioassay, to compare the acute toxicity of twenty-four insecticides belonging to six chemical categories on earthworm species, Eisenia fetida. Results of the contact filter paper toxicity bioassay indicated that neonicotinoids were super toxic to E. fetida (48 h-LC(50) value ranged from 0.0088 to 0.45 μg cm(-2)), pyrethroids were very toxic (48 h-LC(50) values ranged from 10.55 to 25.7 μg cm(-2)) and insect growth regulators (IGRs) were moderately toxic (48 h-LC(50) values ranged from 117.6 to 564.6 μg cm(-2)) to the worms. However, antibiotics, carbamates and organophosphates induced variable toxicity responses in E. fetida, and were very to extremely toxic (48 h-LC(50) values ranged from 3.64 to 75.75 μg cm(-2)). Results of the soil toxicity bioassays showed a different pattern of toxicity except that neonicotinoids were the most toxic even under the soil toxicity bioassay system. The acute toxicity of neonicotinoids was higher than those of antibiotics, carbamates, IGRs and organophosphates. In contrast, pyrethroids were the least toxic to the worms under the soil toxicity bioassay system. It was concluded that irrespective of bioassay systems, earthworms were more susceptible to neonicotinoids than other modern synthetic insecticides.

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.