Influence of aging on copper bioavailability in soils

Because of long-term chemical processes, metal bioavailability in field soils decreases with time. Metal toxicity may, therefore, be overestimated if toxicity data with freshly spiked soils are used to derive soil quality criteria, a current practice. In the present study, effects of the long-term processes, called aging, on copper partitioning and ecotoxicity are investigated. Twenty-five field soils contaminated by copper runoff from bronze statues and 25 uncontaminated control soils sampled at 5-m distance from these statues were collected in Flanders (Belgium). The soils were selected so that parameters affecting copper bioavailability (pH, cation-exchange capacity, organic matter content, etc.) varied considerably. To assess the effect of aging on copper toxicity, control soils were spiked at total copper concentrations comparable to those of historically contaminated soils. Pore-water copper concentrations and 0.01 M CaCl2-extracted copper concentrations were significantly higher in freshly spiked soils compared to contaminated field soils. However, this could be a pH effect, because pH decreased after spiking. Acute toxicity to Enchytraeus albidus (14 d) as well as chronic toxicity to Folsomia candida (28-d reproduction) and Trifolium pratense (14-d growth) indicated a dose-response relationship between copper toxicity and pore-water copper concentration or the CaCl2-extracted copper fraction.     

Increased alanine concentration is associated with exposure to fenitrothion but not carbamates in Chironomus riparius larvae

The polychlorinated insecticide toxaphene belonged to the most used pesticides in the 20th century. Even recently, significant residues have been found in soils at various sites in the world. However, knowledge on toxicity to soil organisms is limited. In this study, the effects of toxaphene on soil invertebrates Folsomia candida, Eisenia fetida, Enchytraeus albidus, Enchytraeus crypticus, Caenorhabditis elegans, and microorganisms were investigated. Among the organisms tested, F. candida was the most sensitive. The 50% effect on survival and reproduction output (LC50 and EC50) was found at concentrations of 10.4 and 3.6 mg/kg, respectively. Sensitivity of other organisms was significantly lower with effective concentrations at tens or hundreds of mg/kg. Our data on soil toxicity were recalculated to soil pore-water concentrations and good accordance with available data reported for aquatic toxicity was found. Since soil concentrations at some sites are comparable to concentrations effective in our tests, toxaphene may negatively affect soil communities at these sites.     

Comparison of toxicity of zinc for soil microbial processes between laboratory-contamined and polluted field soils

Soil microbial processes are readily disturbed by added zinc (Zn) in laboratory ecotoxicity tests. This study compares Zn toxicity between freshly spiked soils and soils that have been contaminated with Zn in the field. Soils were sampled in three transects (< 80 m) toward galvanized electricity transmission towers (pylons). The soil total Zn concentrations gradually increased in each transect from background values (25-82 mg Zn/kg) to elevated Zn concentrations near the pylon (226-595 mg Zn/kg). Soil samples taken at the furthest distance from the Zn source were spiked with ZnCl2 to a range of total Zn concentrations similar to those in the transect. Nitrification, respiration, and N-mineralization rates were significantly reduced by added Zn in laboratory-spiked soils and were 9 to 95% (mean 32%) of the control values at largest doses depending on soil type and the microbial process. In contrast, these processes were either unaffected by soil Zn (p > 0.05) or increased significantly with soil Zn concentrations in the transect soils. These increases could not be explained by soil pH or % soil organic carbon. Leaching soils after spiking significantly lowered the toxic effects of Zn on nitrification or on substrate-induced respiration. The soil solution Zn concentrations of field soils were always smaller than in spiked soils at equivalent total Zn. Highest soil solution Zn concentrations were always lower than the soil-solution EC50s of spiked soils. It is concluded that there is a large discrepancy in microbial responses to elevated Zn between spiked soils (unleached) and field-contaminated soils and there is a need to explain this discrepancy in terms of Zn availability, adaptation processes, and additional soil factors controlling the microbial processes.     

Influence of soil properties on copper toxicity for two soil invertebrates

Although a large body of evidence indicates that metal toxicity to soil organisms is affected by physicochemical soil properties, use of this knowledge in ecological risk assessments is limited because of the lack of a model applicable to a wide range of soils. To study the effect of soil characteristics on the toxicity of copper to terrestrial invertebrates, chronic toxicity tests with Eisenia fetida and Folsomia candida were performed in 19 European field soils. These soils were carefully selected to cover the range of toxicity-influencing parameters encountered in the European Union. Toxicity values varied greatly among soils, with 28-d median effect concentrations ranging from 72.0 to 781 mg Cu/kg dry weight for E. fetida and from 45.4 to 2,270 mg Cu/kg dry weight for F. candida. For both species, variation in copper toxicity values was best explained by differences in the actual cation-exchange capacity (CEC) at soil pH. Using the obtained regression algorithms, the observed toxicity could, in most cases, be predicted within a factor of two for E. fetida and within a factor of three for F. candida. The developed models were validated in three additional European field soils, a standard artificial soil and a standard field soil. The presented regression equations, based on the actual CEC, offer an easy-to-apply method for taking the influence of soil properties on metal toxicity into account.     

Effects of insect growth regulators on the nontarget soil arthropod Folsomia candida (Collembola)

The aim of this study was to assess the effect of several insect growth regulators (IGRs) on the nontarget soil arthropod Folsomia candida (Collembola). The survival and reproduction rates of F. candida were evaluated after 28 days of exposure to six IGRs (methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) and to one herbicide (diuron) in artificial soil. The differences in the sensitivity of F. candida to these different substances are high. The chitin synthesis inhibitors teflubenzuron and hexaflumuron were the most toxic compounds with an EC50 of 0.05 mg/kg (dry weight) for teflubenzuron and an EC50 of 0.6mg/kg for hexaflumuron. Teflubenzuron is toxic for F. candida at concentrations that are probably close to environmental levels of this insecticide. Inhibition of reproduction is strongly related to adult survival for the juvenile hormone agonist methoprene and for the antijuvenile hormone precocene II, with an EC50 of 173 mg/kg and a LC50 of 178mg/kg for methoprene and an EC50 of 15 mg/kg and a LC50 of 26 mg/kg for precocene II. Fenoxycarb, another juvenile hormone analog, showed a dose-response curve for mortality different from that of methoprene; at concentrations such as 3052 mg/kg no effect on adult survival was observed. However, the EC50 value of 113mg/kg is of the same order of magnitude as that obtained for methoprene. A test with compressed soil contaminated with fenoxycarb was conducted to observe parameters such as numbers of eggs laid and juveniles hatched. No differences were observed between these two endpoints for fenoxycarb. An EC50 of 109 mg/kg was obtained for the ecdysone agonist tebufenozide. The herbicide diuron showed a relatively high toxicity for F. candida with an EC50 of 20 mg/kg. Our results show that some of the tested IGRs can have effects on Collembola at environmentally relevant concentrations (toxicity/exposure ratios < 5 for teflubenzuron, hexaflumuron, and diuron).     

The influence of soil properties on the toxicity of molybdenum to three species of soil invertebrates

Mo toxicity to earthworms (Eisenia andrei), Collembola (Folsomia candida) and enchytraeids (Enchytraeus crypticus) was determined in 10 European soils and a standard artificial soil, freshly spiked with Na₂MoO₄, after 28 days exposure. Mo affected survival only in three low pH sandy soils; in all other soils LC50 was >3200 mg Mo/kg dry soil. EC50 values for the reproduction toxicity of Mo were 129-2378 mg/kg for earthworms, 72->3396 mg/kg for Collembola, and 301->2820 mg/kg for enchytraeids. Variation in toxicity among soils could not be explained by differences in available (pore water, water and 0.01 M CaCl₂ extractable) Mo concentrations. Clay content best predicted the EC50 for Mo toxicity to earthworms, while toxicity of Mo for enchytraeids was best described by soil pH. For Collembola no relationships could be derived due to the absence of toxicity in most soils. Soil properties had a strong but species-specific effect on Mo toxicity to soil invertebrates.     

Effect of soil properties on lead bioavailability and toxicity to earthworms

Soil properties are important factors modifying metal bioavailability to ecological receptors. Twenty-one soils with a wide range of soil properties (USA; http://soils.usda.gov/technical/classification/taxonomy/) were amended with a single concentration of Pb (2,000 mg/kg) to determine the effects of soil properties on Pb bioavailability and toxicity to earthworms. Earthworm mortality ranged from 0 to 100% acute mortality following exposure to the same total concentration of Pb (2,000 mg/kg) in amended field soils. Internal Pb concentrations in earthworms ranged from 28.7 to 782 mg/kg, with a mean of 271 mg/kg. Path analysis was used to partition correlations in an attempt to discern the relative contribution of each soil property. Results of path analysis indicated that pH was the most important soil property affecting earthworm mortality (p < 0.01) and internal Pb (p < 0.05). Soil pH was related inversely to mortality and internal Pb, soil solution Pb, and Pb bioavailability. The most important soil property modifying reproduction was amorphous iron and aluminum oxides (FEAL). Because FEAL is rich in pH-dependent cation-exchange sites, several soil properties, including pH, FEAL, and cation-exchange capacity, have a causal effect on Pb adsorption and soluble Pb. Path analysis is useful for assessing contaminated soils with a wide range of soil properties and can assist in ecological risk assessment and remediation decisions for contaminated sites. Soil properties are important factors modifying metal bioavailability and toxicity and should be considered during the ecological risk assessment of metals in contaminated soils.     

Unexpected reduction in reproduction of Collembola exposed to an arsenic-contaminated soil

To assess the problems posed by ecological testing of the toxicity of polluted soils, we applied the Collembola reproduction test to the soil from a mining site polluted by metals. Our aim was to quantify the chronic toxicity of contaminated soil using the Folsomia candida reproduction test. Briefly, the polluted soil, which contains in particular large quantities of arsenic, is mixed in various proportions with a reference soil, and the number of juveniles is counted five weeks later. The results were quite unexpected in that a stronger effect was observed on reproduction with dilute contaminated soil, 0.78 to 3.1%, than with much higher concentrations. The pure contaminated soil is not highly toxic. Arsenic (As) dosage in pore water shows that a change in its bioavailability occurs that may explain the surprising toxicity results. As the main contaminant of the soil was arsenic, we showed that the lowest-observed-effect concentration and the median effective concentration of this metal for the reproduction of F. candida in International Organization for Standardization (Geneva, Switzerland) soil experimentally contaminated with arsenic were low (2.22 and 2.19 microg/g, respectively). Likewise, we showed that pH modifies the bioavailability and the toxicity of As, but we do not think that this parameter explains the test results. These results show that this bioassay should be used cautiously to test toxicity of polluted soils.     

Toxicity of copper to the collembolan Folsomia fimetaria in relation to the age of soil contamination

The toxicity of copper to the collembolan Folsomia fimetaria L. was studied in soil incubated with copper sulfate for different periods before the introduction of collembolans, to assess the effect of aging of contamination on the toxicity of copper. Adult survival, reproduction, and juvenile size were assessed. No clear influence of differences in contamination age was detected. The data were compared with results from a study performed in soil sampled at an old copper-contaminated site. Large differences in effects existed between spiked soil and field soil when concentrations were expressed on the basis of total soil copper concentrations. EC(10) and EC(50) values for reproduction in spiked soil were ca. 700 and 1400 mg Cu/kg soil, whereas no effects were found in field soil at copper concentrations up to 2500 mg/kg. Most of the differences disappeared when effects were expressed as a function of 0.01 M CaCl(2)-extractable soil copper. the lack of effects in field soil could be explained from the fact that in this field soil the CaCl(2)-extractable concentration was never higher than one-third of the EC(50) estimated for tests in the laboratory spiked soils.     

Tungsten effects on survival, growth, and reproduction in the earthworm, Eisenia fetida

To provide basic toxicity data for formulating risk characterization benchmarks, the effects of tungsten on survival, growth, and reproduction were investigated in the earthworm Eisenia fetida. Parallel studies with lead as a reference toxicant also were conducted. Although sodium tungstate (Na2WO4) was less acutely toxic than lead nitrate (Pb(NO3)2) in 14-d spiked field soil acute toxicity assays (lethal concentrations for 50% of organisms: W, 6,250 mg/kg; Pb, 2,490 mg/kg), tungstate completely inhibited reproduction in 28- and 56-d assays at all tested tungsten concentrations (> or = 704 mg/kg). By comparison, cocoon production was not significantly reduced for lead concentrations until concentrations reached 766 mg/kg, and cocoon production was still observed at the highest concentration tested (1,650 mg/kg). These data indicate that tungsten is a reproductive toxicant for earthworms and that, by comparison, its sublethal toxicity is greater than that of lead. Toxicity data for other soil invertebrate species are required to fully establish benchmark levels/ecological soil screening levels for tungsten.     

Ecotoxicity of a polycyclic aromatic hydrocarbon (PAH)-contaminated soil

Soil samples from a former cokery site polluted with polycyclic aromatic hydrocarbons (PAHs) were assessed for their toxicity to terrestrial and aquatic organisms and for their mutagenicity. The total concentration of the 16 PAHs listed as priority pollutants by the US Environmental Protection Agency (US-EPA) was 2634+/-241 mg/kgdw in soil samples. The toxicity of water-extractable pollutants from the contaminated soil samples was evaluated using acute (Vibrio fischeri; Microtox test, Daphnia magna) and chronic (Pseudokirchneriella subcapitata, Ceriodaphnia dubia) bioassays and the EC values were expressed as percentage water extract in the test media (v/v). Algal growth (EC50-3d=2.4+/-0.2% of the water extracts) and reproduction of C. dubia (EC50-7d=4.3+/-0.6%) were the most severely affected, compared to bacterial luminescence (EC50-30 min=12+/-3%) and daphnid viability (EC50-48 h=30+/-3%). The Ames and Mutatox tests indicated mutagenicity of water extracts, while no response was found with the umu test. The toxicity of the soil samples was assessed on the survival and reproduction of earthworms (Eisenia fetida) and collembolae (Folsomia candida), and on the germination and growth of higher plants (Lactuca sativa L.: lettuce and Brassica chinensis J.: Chinese cabbage). The EC50 values were expressed as percentage contaminated soil in ISO soil test medium (weight per weight-w/w) and indicated severe effects on reproduction of the collembola F. candida (EC50-28 d=5.7%) and the earthworm E. fetida (EC50-28 d=18% and EC50-56 d=8%, based on cocoon and juvenile production, respectively). Survival of collembolae was already affected at a low concentration of the contaminated soil (EC50-28 d=11%). The viability of juvenile earthworms was inhibited at much lower concentrations of the cokery soil (EC50-14 d=28%) than the viability of adults (EC50-14 d=74%). Only plant growth was inhibited (EC50-17d=26%) while germination was not. Chemical analyses of water extracts allowed us to identify inorganic water-extractable pollutants as responsible for toxicity on aquatic species, especially copper for effects on D. magna and C. dubia. The soil toxicity on collembolae and earthworms could be explained by 4 PAH congeners-fluorene, phenanthrene, pyrene, and fluoranthene. Yet, toxicity of the cokery soil as a whole was much lower than toxicity that could be deduced from the concentration of each congener in spiked soils, indicating that pollutants in the soil became less bioavailable with ageing.     

Effect of soil properties and aging on the toxicity of copper for Enchytraeus albidus, Enchytraeus luxuriosus, and Folsomia candida

In the present study, the effect of the heavy-metal salt copper chloride (CuCl2.2H2O) in soils freshly spiked (3 d) and aged (70 +/- 10 d; mean +/- SD) was studied in the test species Enchytraeus albidus, E. luxuriosus, and Folsomia candida. Up to nine soils were used: Besides the Organisation for Economic Co-operation and Development (OECD) artificial soil and the Agricultural Testing and Research Agency (Landwirtschaftliche Untersuchungs- und Forschungsanstalt, Speyer, Germany) 2.2 natural standard soils, the others were selected based on the EURO Soil approach, taking into account the effect of different soil parameters (pH, organic matter, grain size distribution, and carbon to nitrogen ratio). Additionally, the effect of the chloride ions was studied separately. The results revealed the following: First, a soil effect was observed; for example, in F. candida, median effective concentrations (EC50s) varied between 262 mg/kg in a sample from the same site as the original EURO Soil 5 soil and greater than 1,000 mg/kg in OECD soil. Second, an aging effect was observed, mainly in F. candida. For example, toxicity of offspring survival was increased twofold in the OECD soil and approximately eightfold with aging in the EURO Soil 7 soil, whereas the enchytraeid species did not react differently after aging. Third, an effect of chloride ions on reproduction of the animals was found; however, this effect was independent of the aging period. Fourth, species variation was seen in terms of sensitivity (EC50), decreasing in the following order: E. luxuriosus > E. albidus > F. candida. Differences in toxicity of offspring survival between enchytraeids and F. candida might be explained by the different routes of uptake.     

Amendment of sediments with a carbonaceous resin reduces bioavailability of polycyclic aromatic hydrocarbons

We evaluated the effectiveness of Ambersorb, a carbonaceous resin, in reducing bioavailability of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediments collected from the field. In laboratory studies, sediment pore-water concentrations of eight unsubstituted PAHs were significantly decreased after resin addition. Reduced PAH concentrations in oligochaete tissues from a laboratory bioaccumulation test, along with increased survival/reproduction and reduced photo-enhanced toxicity and sediment avoidance, also resulted from sediment treatment with Ambersorb. Resin amendment also decreased pore-water PAH concentrations in field deployed sediments but did not improve benthic invertebrate colonization. Prediction of partitioning of PAHs between solid and aqueous phases in the test sediments was complicated by the presence of coal and soot. However, accurate predictions of bioavailability were achieved based on pore-water chemistry. Overall, these studies show that the addition of high affinity sorbents effectively reduces pore-water PAH concentrations and bioavailability and suggests that sorbent addition may serve as an option for in situ remediation of some contaminated sediments.     

Toxicity of the pesticide alpha-cypermethrin to four soil nontarget invertebrates and implications for risk assessment

Alpha-cypermethrin, a synthetic pyrethroid, is used as an insecticide in agricultural settings and is increasingly replacing organophosphates and carbamates because of lower application rates and lower toxicity to mammals. Because very little is known about the acute and chronic toxicity of this compound for soil-living organisms, the present study investigated acute and sublethal toxicity of alpha-cypermethrin for four terrestrial invertebrate species in an agricultural soil from Norway. Bioassays with the earthworm Eisenia fetida, the potworm Enchytraeus crypticus, the springtail Folsomia candida, and the land snail Helix aspersa were performed according to slightly modified versions of Organization for Economic Cooperation and Development (Paris, France) or International Organization for Standardization (Geneva, Switzerland) guidelines and resulted in median lethal concentrations of greater than >1,000 to 31.4 mg/kg and sublethal no-observed-effect concentrations of 2.51 to 82 mg/kg. A high acute to chronic ratio was found, especially in the earthworms. Interspecies differences in sensitivity may be explained by differences in exposure and differences in metabolization rate. When based on measured pore-water concentrations, terrestrial species overall appear to be approximately one order of magnitude less sensitive than aquatic species. Effect assessments conducted according to European guideline for risk assessment of pesticides reveal that assessments based on acute toxicity tests are not always conservative enough to determine environmentally safe concentrations in soil. Mandatory incorporation of sublethal toxicity data will ensure that in regions with temperate climate, the effects of pesticides on populations of soil-living organisms are unlikely.     

Toxic effects of nine polycyclic aromatic compounds on Enchytraeus crypticus in artificial soil in relation to their properties

The aim of this study was to compare the toxic effects of selected two- and three-ringed PAHs (naphthalene, phenanthrene, and anthracene) and their N-heterocyclic analogs with one (quinoline, acridine, and phenanthridine) or two (quinoxaline, phenazine, and 1,10-phenanthroline) nitrogen atoms on the survival and reproduction of Enchytraeus crypticus in artificial soil. Toxicity of compounds was recalculated to soil pore-water concentrations using the data of chemical analyses of 0.01 M CaCl₂ extracts of spiked soils. When toxicity was based on molar concentrations in pore water (μmol/L), it significantly increased with increasing K_ow value. This relationship indicates nonpolar narcosis as the general toxicity mechanism of the tested compounds. In addition, significant correlation between the toxicity of PACs and their ionization potential has been identified by multidimensional QSAR models.     

Ecotoxicity of chromium (III) to Eisenia fetida, Enchytraeus albidus, and Folsomia candida

Despite growing concerns about the potential adverse effects of elevated chromium concentrations in the environment, only a few terrestrial toxicity data are available. Therefore, chronic toxicity of chromium(III) was assessed for Eisenia fetida, Enchytraeus albidus, and Folsomia candida, the three invertebrates for which standard test protocols are available. The 21-day EC(50) for the cocoon production of E. fetida was 892 (679-1110) mg Cr/kg dry weight. Based on the reproduction, a 42-days EC(50) of 637 (355-791) mg Cr/kg dry weight was observed for E. albidus, while for F. candida a 28-day EC(50) of 604 (254-3380) mg Cr/kg dry weight was noted. Although the presented data can be considered a step forward in the assessment of the potential risks of chromium(III) in terrestrial environments, further research is needed to evaluate the influence of soil parameters on the toxicity of chromium and to quantify the effect of aging on bioavailability.     

Chronic toxicity of polycyclic aromatic compounds to the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus

An urgent need exists for incorporating heterocyclic compounds and (bio)transformation products in ecotoxicological test schemes and risk assessment of polycyclic aromatic compounds (PACs). The aim of the present study therefore was to determine the chronic effects of (heterocyclic) PACs on two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. The effects of 11 PACs were determined in chronic experiments using reproduction and survival as endpoints. The results demonstrated that as far as narcosis-induced mortality is concerned, effects of both homocyclic and heterocyclic PACs are well described by the relationship between estimated pore-water 50% lethal concentrations and log Kow. In contrast, specific effects on reproduction varied between species and between compounds as closely related as isomers, showing up as deviations from the relationship between pore-water 50% effect concentrations and log Kow. These unpredictable specific effects on reproduction force one to test the toxicity of these PACs to populations of soil invertebrates to obtain reliable effect concentrations for use in risk assessment of PACs.     

Accumulation and toxicity of metals (copper, zinc, cadmium, and lead) and organic compounds (geraniol and benzo[a]pyrene) in the oribatid mite Oppia nitens

The oribatid mite Oppia nitens has been suggested as a test species for ecotoxicological assessment of contaminated boreal soils. Knowledge of the ecotoxicity of pollutants of different modes of action to this species is necessary to assess its relative sensitivity in comparison with other invertebrates. The toxicity of four metals and two organic chemicals to O. nitens was evaluated over a 28- or 35-d period. Mite survival, reproduction, and tissue accumulation were assessed at the end of the test. Reproduction was a more sensitive endpoint than survival for all of the compounds except geraniol. The reproduction median inhibitory concentration (IC50) values for Cu, Zn, Cd, and Pb were 2,896, 1,562, 137, and 1,678 mg/kg, respectively, whereas those for benzo[a]pyrene and geraniol were greater than 1,600 and 283 mg/kg. The median lethal concentration (LC50) values for Cu, Zn, Cd, and Pb were 3,311, 2,291, 603, and 6,761 mg/kg, respectively, whereas those for benzo[a]pyrene and geraniol were greater than 1,600 and 251 mg/kg. When effects on reproduction are compared with those of other soil invertebrates, O. nitens appears less sensitive to Cu and Zn but within the same order of magnitude of sensitivity as that for Cd and Pb. Despite its lower sensitivity to Cu and Zn, O. nitens is a member of a group underrepresented in ecotoxicological evaluations and should therefore be included in test battery for risk assessment of contaminated boreal and other northern soils.     

TNT,RDX, and HMX decrease earthworm (Eisenia andrei) life-cycle responses in a spiked natural forest soil

Sublethal and chronic toxicities of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) on earthworm Eisenia andrei in a sandy forest soil were assessed. Various reproduction parameters of fecundity (total and hatched number of cocoons, number of juveniles, and their biomass) were significantly decreased by TNT (> or = 58.8 +/- 5.1 mg/kg dry soil), RDX (> or = 46.7 +/- 2.6 mg/kg), and HMX (> or = 15.6 +/- 4.6 mg/kg). These effects occurred at much lower concentrations than those reported earlier using artificial soil preparations. Growth of adults was significantly decreased in the TNT-spiked natural soils at 136.2 +/- 25.6 mg/kg dry soil, the highest concentration having no significant mortality. In contrast, survival and growth were not significantly reduced at relatively high measured concentrations of RDX (167.3 mg/kg) and HMX (711.0 mg/kg). Although TNT, RDX, and HMX share a common life-cycle response ( i.e., decreased juvenile counts), a number of differences related to other reproduction parameters (e.g., productivity of cocoons) was observed. These results indicate that the tested explosives do not support a common mechanism of toxicity, at least in the earthworm, probably due to differences in their physical-chemical properties as well as metabolites formed during exposure.