Why short-term bioassays are not meaningful--effects of a pesticide (Imidacloprid) and a metal (cadmium) on pea aphids (Acyrthosiphon pisum Harris)

Uptake, accumulation and elimination of cadmium in a soil - Faba bean (Vicia faba) - Aphid (Aphis fabae) - Ladybird (Coccinella transversalis) food chain

Cadmium is a highly mobile toxic heavy metal and a serious hazard to the biosphere. We studied uptake, accumulation and elimination of cadmium in a soil - faba bean - aphid - ladybird food chain. The soil in the study was amended with Cd at concentrations 0, 5, 10, 20 and, 30 mg kg^-1 (w/w). We noted significant Cd transfer in a dose-dependent manner. Cadmium biomagnified in faba bean roots and aphids while biominimized in ladybirds as revealed by their respective transfer coefficients. The concentration-dependent removal of Cd from aphids through excretion via honeydew as well as through pupal exuviae of ladybirds during metamorphosis links to possible mechanisms of Cd detoxification at these trophic levels, which regulates the bioaccumulation of Cd along the food chain. These findings press for the advance studies to find and understand the physiological pathways and mechanisms leading to bio-minimization of Cd across the food chain.

Different effects of Zn nanoparticles and ions on growth and cellular respiration in the earthworm Eisenia andrei after long-term exposure

In this study, the effects of zinc nanoparticles (ZnO-NPs) and ions (ZnCl₂) on the mortality, growth, maturation, and cellular respiration of the earthworm Eisenia andrei were assessed. Earthworms were individually exposed for 98 days, starting from the juvenile stage, to soils contaminated with either ZnO-NPs or ZnCl₂ (125, 250, 500 and 1000 mg Zn kg^-1 dry weight (dw)). Exposure to the highest-concentration ionic treatments (500 and 1000 mg kg^-1) caused 100% mortality, while for other treatments, mortality did not exceed 15% at the end of exposure. Compared to the control treatment, both 125-1000 mg kg^-1 ZnO-NPs and 125 or 250 mg kg^-1 ZnCl₂ stimulated earthworm growth, which might be due to a hormetic effect. ZnO-NPs and ZnCl₂ caused different responses at medium Zn concentrations (250 and 500 mg kg^-1): earthworms exposed to ionic treatment at 250 mg kg^-1 were characterized by a significantly lower growth constant, lower cellular respiration rate, later inflection point, and higher final body weight than those exposed to ZnO-NPs treatments at the same (250 mg kg^-1) or twice as high (500 mg kg^-1) nominal Zn concentrations. However, differences were not observed in all examined parameters between the studied forms when the highest-concentration ZnO-NPs treatment was compared with the lowest-concentration ionic treatment, which was likely due to the same levels of available Zn concentrations in those treatments. Overall, different growth and maturation strategies accompanied by pronounced differences in cellular respiration were adopted by earthworms exposed to low and medium levels of either ZnO-NPs or ZnCl₂.

Analysis of vitellogenin by histochemical method as an indicator of estrogenic effect in male Danio rerio exposed to metals

Several chemicals present in the aquatic environment have the ability to alter the endocrine system of aquatic organisms, including the metals cadmium (Cd) and zinc (Zn). In males, a tool to analyze this effect is the vitellogenin (VTG) detection, a protein with defined function in the yolk production and subsequent aid to embryo-larval development. This protein is produced just by females and can be detected by simple and cheap methods such as histochemical method. Thus, this study aimed to analyze the capacity of Cd and Zn to induce VTG production in Danio rerio males and determine whether the histochemical labeling method is efficient to study estrogenic effects in this species. For this, D. rerio adult males were exposed chronically (21 days) to 0.25 and 1 μg/L of Cd and 120 and 180 μg/L of Zn, values allowed by the Brazilian and American legislation to aquatic life protection. After which, the organisms were submitted to a histological process as preparation to liver VTG marking by histochemical method and subsequent qualitative analysis of this protein in zebrafish's liver. After analyzes, it was possible observed that Cd and Zn are capable of inducing VTG production in D. rerio males and that the histochemistry method is efficient for detection of estrogenic effects in this species.

Cerium chloride heptahydrate (CeCl3 · 7H2O) induces muscle paralysis in the generalist herbivore, Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae), fed contaminated plant tissues

Of increasing economic importance are the rare earth elements (REEs). Pollution from mining and processing activity is expected to rise with industrial demand. Plants are known to accumulate REEs, although levels vary with species and soil content. However, the effect on wildlife of ingesting REE contaminated vegetation is not well understood. Here we examined the effect of consuming vegetation with elevated levels of cerium on the generalist grasshopper, Melanoplus sanguinipes (Fabricius). Adults excreted a substantial portion of ingested contamination. However, after only four-days of feeding, accumulation in the body occurred at all doses and paralysis of appendages resulted at the highest doses. Short-term toxicity studies may underestimate the impact of ingesting REE contamination. Metals tend to be low in toxicity; however, their persistence in the environment may be better represented by exposure over longer portions of the life cycle.

Combined effect of nickel and chlorpyrifos on the ground beetle Pterostichus oblongopunctatus

Although terrestrial invertebrates are often exposed to mixtures of chemicals in the field, little is known about their combined effects on metabolism. We studied the effects of nickel (Ni), chlorpyrifos (CPF) and their mixtures on the respiration rate of the ground beetle Pterostichus oblongopunctatus in a toxicokinetics experiment. The respiration rate was measured six times in the uptake phase (64 days) and four times in the decontamination phase (32 days), and internal Ni concentrations were measured in parallel. The beetles׳ respiration rate in the uptake phase was especially affected by CPF. Moreover, the significant interaction of Ni with the time of exposure indicated that at certain dates Ni also affected respiration rates. Respiration rates changed significantly with time, and the most pronounced increase was observed after 2 days of exposure to a high concentration of CPF. Increased respiration rates in CPF-exposed beetles compared with controls were still observed after switching the beetles to uncontaminated food, whereas the effect of Ni disappeared in the decontamination phase altogether. In the beetles exposed to both Ni alone and Ni mixed with CPF at a low concentration, Ni reached high internal concentrations by the second day of exposure. Two days later, the internal concentrations dropped significantly, indicating efficient decontamination, even if the beetles were still exposed to Ni-contaminated food. High-concentration CPF decreased the accumulation of Ni. No effect of CPF was found in the decontamination phase. The importance of accounting for time in the mixture toxicity testing and ecological risk assessment is discussed.

More ecological ERA: incorporating natural environmental factors and animal behavior

We discuss the importance of selected natural abiotic and biotic factors in ecological risk assessment based on simplistic laboratory bioassays. Although it is impossible to include all possible natural factors in standard lower-tier ecotoxicological testing, neglecting them is not an option. Therefore, we try to identify the most important factors and advocate redesigning standard testing procedures to include theoretically most potent interactions. We also point out a few potentially important factors that have not been studied enough so far. The available data allowed us to identify temperature and O2 depletion as the most critical factors that should be included in ecotoxicity testing as soon as possible. Temporal limitations and fluctuations in food availability also appear important, but at this point more fundamental research in this area is necessary before making decisions on their inclusion in risk assessment procedures. We propose using specific experimental designs, such as Box-Behnken or Central Composite, which allow for simultaneous testing of 3 or more factors for their individual and interactive effects with greater precision and without increasing the effort and costs of tests dramatically. Factorial design can lead to more powerful tests and help to extend the validity of conclusions. Finally, ecological risk assessment procedures should include information on animal behavior, especially feeding patterns. This requires more basic studies, but already at this point adequate mechanistic effect models can be developed for some species.

Decomposition analysis of LTREs may facilitate the design of short-term ecotoxicological tests

This study compared two methods, based on re-analyzed data from a partly published life table response experiment (LTRE), to help determine the optimal approach for designing ecotoxicological assessments. The 36-day LTRE data recorded the toxic effects of cadmium (Cd) and imidacloprid, alone and in combination, on the reproduction and survivorship of aphids (Acyrthosiphon pisum Harris). We used this data to construct an age-classified matrix model (six age classes, each 6 days long) to estimate aphid population growth rate (λ) under each treatment. For each treatment, an elasticity analysis and a demographic decomposition analysis were performed, and results were compared. Despite different results expected from the two toxicants, the elasticity values were very similar. The elasticity of λ with respect to survival was highest in the first age class, and that with respect to fertility was highest in the second age class. The demographic decomposition analysis examined how changes in life-history traits contributed to differences in λ between control and treated populations (Δλ). This indicated that the most important contributors to Δλ were the differences in survival (resulting from both demographic sensitivity and toxicity) in the first and the second age classes of aphids and differences in fertility in the third and the fourth age classes. Additionally, the toxicants acted differently. Cd reduced Δλ by impairing fertility at third age class and reducing survivorship from the second to the third age class. Imidacloprid mostly reduced survivorship at the first and second age classes. The elasticity and decomposition analyses showed different results, because these methods addressed different questions about the interaction of organism life history and sensitivity to toxicants. This study indicated that the LTRE may be useful for designing individual-level ecotoxicological experiments that account for both the effects of the toxicant and the demographic sensitivity of the organism.

Chlorpyrifos reduces nickel-induced growth retardation of the soil dwelling Collembolan Folsomia candida

For 7 weeks, we studied the effects on body size and growth rate of Folsomia candida exposed to nickel and chlorpyrifos and their mixtures in a natural Lufa 2.2 soil. Nickel significantly reduced the development of body size of the springtails, although no complete dose-response curve was obtained. Chlorpyrifos did not influence the springtail growth when applied alone, but significantly reduced the growth retardation induced by nickel. We showed that by monitoring the development of toxicity in time for both the single compounds and the mixtures it was possible to determine mixture interactions even when no complete dose-response curves were available for all mixture components.

Chemical contamination and the ecological quality of surface water

In the assessment of the quality of surface waters, the typical procedure is that the concentration of contaminants in the surface water is monitored and subsequently compared with their respective Maximum Permissible Concentrations (MPCs). If the MPCs are not exceeded the water quality is considered to be safe. But can we be certain that this is true? We compared MPCs to observed and calculated effects of measured contaminants in Dutch surface waters and showed that effects of mixtures can cause a daphnid population to go extinct within 30h of exposure even when MPCs are not exceeded. We conclude that there are shortcomings underlying the concepts of the MPCs. And that the MPCs aim to protect 95% of all species is not met.

The effects of cadmium on the life history traits of Lymantria dispar L

Gypsy moth (Lymantria dispar L.) females and males were chronically exposed to three sublethal cadmium concentrations (10, 30 and 50 mg/g dry food mass) in order to assess the effects of cadmium on larval and pupal duration, pupal mass and longevity. On average, the presence of cadmium in food did not affect larval duration while shortened pupal duration and reduced pupal mass and longevity were recorded. The most significant effects were obtained at the highest cadmium concentration. Females and males did not differ in sensitivity of life history traits to cadmium exposure. It is concluded that (1) cadmium exerts a strong adverse impact on the growth and development of gypsy moths, and (2) the significance of the cadmium effects depends on the dose.

Effects of nickel and temperature on the ground beetle Pterostichus oblongopunctatus (Coleoptera: Carabidae)

In natural ecosystems it is not unusual for an organism to be exposed both to chemical and physical stressful factors at the same time. Herein we present results of the study on nickel toxicity to the carabid beetle, Pterostichus oblongopunctatus, and effect of Ni and temperature on the beetles respiration rates. In the first part of the study (Experiment I) we measured the survival, respiration rates and internal Ni concentrations in animals exposed for 245 d at constant temperature (20 degrees C) to food contaminated with Ni at nominal concentrations 0; 600; 1,200; 2,400; 4,800; and 9,600 mg kg(-1) dry weigh (dw). The LC(50) was estimated at 8,351 mg Ni kg(-1), with no effect on fertility. We found a significant positive correlation between Ni concentration in food and internal body concentration of Ni, and a negative correlation between Ni exposure and the respiration rate. Based on these results, the concentration of 2,400 mg kg(-1) (LOEC for the respiration rate) was selected for the second part of the study (Experiment II) in which field-collected males of P. oblongopunctatus were exposed to Ni-contaminated food for 64 d and then to uncontaminated food for the next 64 d at three temperatures: 10, 15 and 20 degrees C. In this part of the study we found that the temperature under which the beetles were kept affected their respiration rates, and that effect of Ni on the respiration was significant only in animals originating from 20 degrees C. The results from both experiments indicate that negative effects of nickel appear only after relatively long exposure.

Sulfamethoxazole abatement by photo-Fenton toxicity, inhibition and biodegradability assessment of intermediates

The objective of this work was to study the abatement of 200mgL(-1) sulfamethoxazole (SMX) solution by means of photo-Fenton process. Biodegradability of the treated solutions was followed by the ratio biochemical oxygen demand at five days/chemical oxygen demand (BOD(5)/COD) and toxicity by Microtox and inhibition tests. Experiments with different initial concentration of H(2)O(2) were carried out. The initial amount of Fe(2+) and pH of the solution were set at 10mgL(-1) and 2.8 respectively. The temperature of the reactor was kept constant in all the experiments (25+/-0.8 degrees C). Photo-Fenton process is thought to be a successful treatment step to improve the biodegradability of wastewater containing SMX. The complete antibiotic removal was achieved for a H(2)O(2) dose over 300mgL(-1). Biodegradability (BOD(5)/COD) rose from zero (SMX solution) to values higher than 0.3 (treated solutions). Toxicity and inhibition tests pointed out in the same direction: oxidized intermediates for initial H(2)O(2) dose over 300mgL(-1) showed no toxicity effects on pure bacteria and no inhibition on activated sludge activity.

Nonylphenol stimulates fecundity but not population growth rate (lambda) of Folsomia candida

The toxicity of nonylphenol (NP) to springtails was pronounced at 40 mg/kg dry weight soil, at which no animals survived. Body length and fecundity were the individual life-history traits significantly stimulated by sublethal concentrations of NP during a 64-day experiment. However, the effects of NP on these traits did not result in a statistically significant increase in population growth rate (lambda). Decomposition analysis indicated that fecundity was the main contributor to the (non-significant) changes observed in lambda. However, since the elasticity of fecundity was very low, large changes in fecundity resulted in a minimal effect on lambda. Juvenile survival had the highest elasticity of all traits, but was not affected by NP, and therefore did not contribute to effects on lambda. This study confirms previous studies showing that effects of chemicals on individual life-history traits are attenuated at the population level and that lambda is an appropriate endpoint for ecotoxicological studies.

Excretion and ecotoxicity of pharmaceutical and personal care products in the environment

The presence and fate of pharmaceutical and personal care products (PPCPs) in the environment is undergoing increasing scrutiny. The existing clinical pharmacokinetics and pharmacodynamics data for 81 common compounds were examined for cues of ecotoxicity. Of these the proportions excreted were available for 60 compounds (i.e., 74%). The compounds had a low (< or =0.5%), a moderately low (6-39%), a relatively high (40-69%), or a high (> or =70%) proportion of the parent compound excreted. More than half of the compounds evaluated have low or moderately low proportions of the parent compound excreted. However, the proportions excreted were negatively but moderately correlated (r = -0.50; n = 13; P = 0.08) with the concentrations of the compounds in the aquatic environment, suggesting that the compounds that have low proportions excreted may also have inherently low degradability in the environment. Solubility, logK(ow), and pKa work well in predicting the behavior of PPCPs under clinical conditions and have been used in the environmental assessment of PPCPs prior to approval. However, these parameters did not correlate with the proportion of PPCPs excreted in the environment or their concentration in the environment, underscoring the need for research into the behavior of PPCPs in the environment. PPCPs occur in low concentrations in the environment and are unlikely to elicit acute toxicity. An ecotoxicity potential that is based on chronic toxicity, bioavailability, and duration of exposure to nontarget organisms is described as a guide in assessing the potency of these compounds in the environment.

Vitellogenesis inhibition in Oncopeltus fasciatus females (Heteroptera: Lygaeidae) exposed to cadmium

Newly moulted females of the insect Oncopeltus fasciatus were exposed to cadmium (Cd) dissolved in the drinking water (50-400 mg l(-1) Cd) for 5 days. Cd exposure delayed ovarian maturation and inhibited egg production. Exposure to Cd, moreover, decreased hemolymph levels of the two major vitellogenin polypeptides of O. fasciatus, VG1 and VG2, in a concentration-dependent way, probably by a reduction in their synthesis. The ovarian levels of VG1 and VG2 were also decreased in Cd-exposed females. It was next investigated whether Cd effects might be a consequence of the endocrine disruption of vitellogenin synthesis, which is controlled by juvenile hormone (JH). JH replacement therapy did not restore VG1 or VG2 levels in Cd-exposed females, but did so in starved females. Our results do not therefore support a disturbance of JH production or a reduction in feeding as the cause of the reduced vitellogenin polypeptide levels, but rather point to the site of action of JH, the JH receptor, as the target of Cd effects.

Bio-monitoring the genotoxicity of populations of Scots pine in the vicinity of a radioactive waste storage facility

Results of a long-term (1997-2002) study of the Scots pine populations growing in the vicinity of the radioactive waste storage facility ('Radon' LWPE) are presented. Cytogenetic disturbances in reproductive (seeds) and vegetative (needles) tissues sampled from Scots pine populations were studied to examine whether Scots pine trees have experienced environmental stress in areas with relatively low levels of pollution. The data clearly indicate the presence of mutagenic contaminants in the environment of the pine trees. An increased number of mitotic abnormalities, especially multipolar mitoses was found in the pine tree populations submitted to man-made exposure, which suggests that the cytogenetic damage is mainly caused by chemical contamination. A higher radioresistance of the Scots pine seeds from the impacted populations was shown by use of acute gamma-irradiation. During the observation period 1997-2002, pine trees exposed to anthropogenic pollution showed a steady increase of cytogenetic alterations in the root meristem cells.

The effects of fungicide benomyl (benlate) on growth and mitosis in onion (Allium cepa L.) root apical meristem

In this study, the effects of benomyl, a systemic fungicide were investigated in the mitotic cell division in onion (Allium cepa) root tip cells during germination. For this aim, different concentrations (1, 2, 5, 10 and 20 mM) of benomyl solutions were used. All the concentrations used caused several abnormalities in mitotic cell divisions and the mitotic frequency in the onion root tip cells decreased as the concentration of benomyl solution increased. Based on our findings, it is reported that benomyl has some negative effects on mitotic divisions in onion root tip cells.

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.

Ecotoxicological impact of pharmaceuticals found in treated wastewaters: study of carbamazepine, clofibric acid, and diclofenac

In four countries (France, Greece, Italy, and Sweden) occurrence in sewage treatment plant (STP) effluents and ecotoxicity of the pharmaceuticals carbamazepine, clofibric acid, and diclofenac were investigated. Bioassays were performed on bacteria, algae, microcrustaceans, and fishes in order to calculate their predicted no-effect concentrations (PNEC) and to perform a first approach of risk characterization. For this aim, risk has been estimated by the predicted environmental concentration/PNEC ratio and the measured environmental concentration/PNEC ratio. First, regarding the PNEC, carbamazepine appears to be the more hazardous compound. Second, even though it is demonstrated that carbamazepine, clofibric acid, and diclofenac have been detected in effluents, only carbamazepine have been detected in all sewage treatment plants with the greatest concentrations. Third, risk quotients greater than unity were calculated only for carbamazepine, suggesting that risk for the water compartment is expected.