Assessing the relevance of environmental exposure data sets.

Environmental exposure data are used by decision-makers to assess environmental risks and implement actions to mitigate risks from contaminants. The first article in this series summarized the available evaluation schemes for environmental exposure data, of which there are few compared to those available for environmental hazard data. The second article covered the assessment of the reliability of environmental exposure data sets under the Criteria for the Reporting and Evaluation of Exposure Data (CREED). The aim of this article is to provide an overview and practical guidance on the relevance assessment in the context of the CREED approach for evaluating exposure monitoring data sets. Systematically considering relevance is critical for both evaluating existing data sets and for optimizing the design of new monitoring studies. Relevance is defined here as the degree of suitability or appropriateness of a data set to address a specific purpose or to answer the questions that have been defined by the assessor or for those generating exposure data. The purpose definition will be the foundation for the relevance assessment, to clarify how the assessor should rate the assessment criteria (fully met, partly met, not met/inappropriate, not reported, not applicable). This will provide transparency for anyone reviewing the outcomes. An explicit gap analysis (i.e., an articulation of the data set limitations for the stated purpose) is an important outcome of the relevance assessment. The relevance evaluation approach is demonstrated with three case studies, all relating to the freshwater aquatic environment, where the data sets are scored as relevant with or without restrictions, not relevant, or not assignable. The case studies represent both organic and inorganic constituents, and have different data characteristics (e.g., percentage of censored data, sampling frequencies, relation to supporting parameters). Integr Environ Assess Manag 2024;00:1-15. © 2023 SETAC.

Are standard aquatic test species and methods adequate surrogates for use in environmental risk assessment of pesticides in tropical environments?

In regulatory risk assessment, surrogate species of fish, aquatic invertebrates, and primary producers are tested to assess toxicity and subsequently the risk of pesticides to freshwater biota. This study evaluates whether the standard, surrogate test species (mostly temperate in latitudinal distribution) used in many parts of the world are suitable surrogates for first-tier risk assessments involving tropical freshwater biota. Data for the toxicity of pesticides to tropical fish, invertebrates, and primary producer species were extracted from the USEPA ECOTOX database and peer-reviewed literature. For each pesticide, the most sensitive regulatory endpoint extracted from the US Environmental Protection Agency (USEPA) and European Food Safety Authority (EFSA) dossiers for freshwater fish, invertebrates, and primary producers was selected. The ratios of the endpoint for tropical species and for the most sensitive regulatory endpoint for the appropriate taxonomic group were determined. A value >1 indicates that the tropical species is less sensitive than the respective standard regulatory species. Tropical fish species were less sensitive than standard fish species in 84% of the comparisons, and in 93.5% of the comparisons, tropical fish were less or similarly sensitive (within a factor of 5). For aquatic invertebrates, 78.1% of the evaluated tropical species were less sensitive than standard species and 93.3% of tropical invertebrates species were less or similarly sensitive. For primary producers, 96% of tropical species were less sensitive than standard test species. Overall, standard species used globally were more sensitive or similarly sensitive compared to tropical species in more than 93% of the cases. In conclusion, the data show that freshwater toxicity data for pesticides from tests using standard test species, tested according to international accepted guidelines, are appropriate for use in first-tier risk assessments for tropical environments. Integr Environ Assess Manag 2023;19:202-212. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

A pulsed-dose study evaluating chronic toxicity of chlorothalonil to fish: A case study for environmental risk assessment.

Chlorothalonil is a fungicide which is highly toxic to aquatic organisms. However, in natural aquatic environments, it is very rapidly degraded, with a half-life typically in hours, reducing exposure of aquatic organisms and the potential for effects. In standard regulatory studies looking at the chronic toxicity of chlorothalonil to fathead minnow, the most sensitive endpoint was fecundity. A standard fish full-life cycle study, where chlorothalonil concentrations were maintained constant throughout, resulted in a no-observed-effect concentration (NOEC) of 1.4 µg/L. Comparing peak modeled exposure concentrations to this NOEC can result in the chronic risk to fish being considered unacceptable. The present study investigated the effect on fecundity in fathead minnow using a fish short-term reproduction assay. Five different exposure profiles were employed with time-varying concentrations based on realistic worst-case modeled environmental exposure profiles, multiplied by an assessment factor of 10, which resulted in maximum measured concentrations up to 15.5 µg/L. There were no effects on fecundity from any of the exposure profiles tested. Therefore, based on these more realistic exposure profiles, the chronic risk to fish could be considered acceptable if these exposures were deemed to be representative of the worst case. Environ Toxicol Chem 2019;38:1549-1559. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

A freshwater mesocosm study into the effects of the neonicotinoid insecticide thiamethoxam at multiple trophic levels.

Thiamethoxam is a neonicotinoid insecticide used widely in agriculture to control a broad spectrum of insect pests. To assess potential risks from this compound to non-target aquatic organisms, an outdoor mesocosm study was performed. Mesocosms (1300 L) were treated once with a formulated product with the active substance (a.s.) thiamethoxam at nominal concentrations of 1 (n = 3), 3 (n = 3), 10 (n = 4), 30 (n = 4), and 100 (n = 2) µg a.s./L, plus untreated controls (n = 4). Primary producers (phytoplankton), zooplankton, and macroinvertebrates were monitored for up to 93 days following treatment. Thiamethoxam was observed to have a water column dissipation half-life (DT50) of ≤1.6-5.2 days in the mesocosms. Community-based principal response curve analysis detected no treatment effects for phytoplankton, zooplankton, emergent insects, and macroinvertebrates, indicating a lack of direct and indirect effects. A number of statistically significant differences from controls were detected for individual phytoplankton and zooplankton species abundances, but these were not considered to be treatment-related due to their transient nature and lack of concentration-response. After application of 30 µg a.s./L, slight temporary effects on Asellus aquaticus could not be excluded. At 100 µg a.s./L, there was an effect with no clear recovery of Asellus observed, likely due to their inability to recolonize these isolated test systems. A statistically significant but transient reduction in the emergence of chironomids by day 23 at the 100 µg a.s./L treatment was observed and possibly related to direct toxicity from thiamethoxam on larval stages. Therefore, a conservative study specific No Observed Ecological Adverse Effect Concentration (NOEAEC) is proposed to be 30 µg a.s./L. Overall, based on current concentrations of thiamethoxam detected in North American surface waters (typically <0.4 µg/L), there is low likelihood of direct or indirect effects from a pulsed exposure on primary producers, zooplankton, and macroinvertebrates, including insects, as monitored in this study.

Risk assessment considerations for plant protection products and terrestrial life-stages of amphibians.

Some amphibians occur in agricultural landscapes during certain periods of their life cycle and consequently might be exposed to plant protection products (PPPs). While the sensitivity of aquatic life-stages is considered to be covered by the standard assessment for aquatic organisms (especially fish), the situation is less clear for terrestrial amphibian life-stages. In this paper, considerations are presented on how a risk assessment for PPPs and terrestrial life-stages of amphibians could be conducted. It discusses available information concerning the toxicity of PPPs to terrestrial amphibians, and their potential exposure to PPPs in consideration of aspects of amphibian biology. The emphasis is on avoiding additional vertebrate testing as much as possible by using exposure-driven approaches and by making use of existing vertebrate toxicity data, where appropriate. Options for toxicity testing and risk assessment are presented in a flowchart as a tiered approach, progressing from a non-testing approach, to simple worst-case laboratory testing, to extended laboratory testing, to semi-field enclosure tests and ultimately to full-scale field testing and monitoring. Suggestions are made for triggers to progress to higher tiers. Also, mitigation options to reduce the potential for exposure of terrestrial life-stages of amphibians to PPPs, if a risk were identified, are discussed. Finally, remaining uncertainties and research needs are considered by proposing a way forward (road map) for generating additional information to inform terrestrial amphibian risk assessment.

Exposure and effects of sediment-spiked fludioxonil on macroinvertebrates and zooplankton in outdoor aquatic microcosms.

Information from effects of pesticides in sediments at an ecosystem level, to validate current and proposed risk assessment procedures, is scarce. A sediment-spiked outdoor freshwater microcosm experiment was conducted with fludioxonil (lipophilic, non-systemic fungicide) to study exposure dynamics and treatment-related responses of benthic and pelagic macroinvertebrates and zooplankton. Besides blank control and solvent control systems the experiment had six different treatment levels (1.7-614mga.s./kg dry sediment) based around the reported 28-d No Observed Effect Concentration (NOEC) for Chironomus riparius (40mga.s./kg dry sediment). Twelve systems were available per treatment of which four were sacrificed on each of days 28, 56 and 84 after microcosm construction. Fludioxonil persisted in the sediment and mean measured concentrations were 53-82% of the initial concentration after 84days. The dissipation rate increased with the treatment level. Also exposure concentrations in overlying water were long-term, with highest concentrations 28days after initiation of the experiment. Sediment-dwelling Oligochaeta and pelagic Rotifera and Cladocera showed the most pronounced treatment-related declines. The most sensitive sediment-dwelling oligochaete was Dero digitata (population NOEC 14.2mga.s./kg dry sediment). The same NOEC was calculated for the sediment-dwelling macroinvertebrate community. The most sensitive zooplankton species was the cladoceran Diaphanosoma brachyurum (NOEC of 1.6µga.s./L in overlying water corresponding to 5.0mga.s./kg dry sediment). At the two highest treatments several rotifer taxa showed a pronounced decrease, while the zooplankton community-level NOEC was 5.6µga.s./L (corresponding to 14.2mga.s./kg dry sediment). Zooplankton taxa calanoid Copepoda and Daphnia gr. longispina showed a pronounced treatment-related increase (indirect effects). Consequently, an assessment factor of 10 to the chronic laboratory NOECs of Chironomus riparius (sediment) and Daphnia magna (water) results in a regulatory acceptable concentration that is sufficiently protective for both the sediment-dwelling and pelagic organisms in the microcosms.

Prospective aquatic risk assessment for chemical mixtures in agricultural landscapes.

Environmental risk assessment of chemical mixtures is challenging because of the multitude of possible combinations that may occur. Aquatic risk from chemical mixtures in an agricultural landscape was evaluated prospectively in 2 exposure scenario case studies: at field scale for a program of 13 plant-protection products applied annually for 20 yr and at a watershed scale for a mixed land-use scenario over 30 yr with 12 plant-protection products and 2 veterinary pharmaceuticals used for beef cattle. Risk quotients were calculated from regulatory exposure models with typical real-world use patterns and regulatory acceptable concentrations for individual chemicals. The results could differentiate situations when there was concern associated with single chemicals from those when concern was associated with a mixture (based on concentration addition) with no single chemical triggering concern. Potential mixture risk was identified on 0.02 to 7.07% of the total days modeled, depending on the scenario, the taxa, and whether considering acute or chronic risk. Taxa at risk were influenced by receiving water body characteristics along with chemical use profiles and associated properties. The present study demonstrates that a scenario-based approach can be used to determine whether mixtures of chemicals pose risks over and above any identified using existing approaches for single chemicals, how often and to what magnitude, and ultimately which mixtures (and dominant chemicals) cause greatest concern. Environ Toxicol Chem 2018;37:674-689. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Response of the mayfly (Cloeon dipterum) to chronic exposure to thiamethoxam in outdoor mesocosms.

Thiamethoxam is a widely used neonicotinoid insecticide that has been detected in surface water monitoring programs in North America and Europe. This has led to questions about its toxicity to nontarget insects, specifically those with an aquatic life stage. To address the uncertainty associated with possible impacts from environmental exposures, a chronic (35-d) outdoor mesocosm study with a formulated product containing thiamethoxam was conducted. The specific focus of the study was the response of mayflies (Ephemeroptera), which have been reported to be particularly sensitive in laboratory studies. A range of concentrations (nominally 0.1, 0.3, 1.0, 3.0, and 10.0 µg/L thiamethoxam), plus untreated controls were tested, and the abundance and emergence of mayflies (Cloeon dipterum) were assessed weekly for 35 d. Mean measured time-weighted average exposures were within 6% of nominal over the duration of the study, with the mean half-life of thiamethoxam in each treatment ranging from 7 to 13 d. Statistically significant reductions in both larval abundance and adult emergence were observed at 10.0, 3.0, and 1.0 µg/L following 1, 2, and 3 wk of exposure, respectively. Exposure to 0.1 and 0.3 µg/L thiamethoxam had no statistically significant effect on larval mayfly abundance or adult emergence at any point in the study. These findings support a 35-d no-observed-effect concentration (NOEC) of 0.3 µg thiamethoxam/L for mayflies (C. dipterum) under chronic conditions. Furthermore, because the 95th percentile of environmental concentrations has been reported to be 0.054 µg/L, these results indicate that populations of C. dipterum and similarly sensitive aquatic insects are unlikely to be significantly impacted by thiamethoxam exposure in natural systems represented by the conditions in our study. Environ Toxicol Chem 2018;37:1040-1050. © 2017 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Toward the definition of specific protection goals for the environmental risk assessment of chemicals: A perspective on environmental regulation in Europe.

This critical review examines the definition and implementation of environmental protection goals for chemicals in current European Union (EU) legislation, guidelines, and international agreements to which EU countries are party. The European chemical industry is highly regulated, and prospective environmental risk assessments (ERAs) are tailored for different classes of chemical, according to their specific hazards, uses, and environmental exposure profiles. However, environmental protection goals are often highly generic, requiring the prevention of "unacceptable" or "adverse" impacts on "biodiversity" and "ecosystems" or the "environment as a whole." This review aims to highlight working examples, challenges, solutions, and best practices for defining specific protection goals (SPGs), which are seen to be essential for refining and improving ERA. Specific protection goals hinge on discerning acceptable versus unacceptable adverse effects on the key attributes of relevant, sensitive ecological entities (ranging from organisms to ecosystems). Some isolated examples of SPGs for terrestrial and aquatic biota can be found in prospective ERA guidance for plant protection products (PPPs). However, SPGs are generally limited to environmental or nature legislation that requires environmental monitoring and retrospective ERA. This limitation is due mainly to the availability of baselines, which define acceptable versus unacceptable environmental effects on the key attributes of sentinel species, populations and/or communities, such as reproductive status, abundance, or diversity. Nevertheless, very few regulatory case examples exist in which SPGs incorporate effect magnitude, spatial extent, and temporal duration. We conclude that more holistic approaches are needed for defining SPGs, particularly with respect to protecting population sustainability, ecosystem function, and integrity, which are implicit in generic protection goals and explicit in the International Programme for Chemical Safety (IPCS) definition of "adverse effect." A possible solution, which the chemical industry is currently assessing, is wider application of the ecosystem services approach proposed by the European Food Safety Authority (EFSA) for the risk assessment of PPPs. Integr Environ Assess Manag 2017;13:17-37. © 2016 SETAC.

Is an ecosystem services-based approach developed for setting specific protection goals for plant protection products applicable to other chemicals?

Clearly defined protection goals specifying what to protect, where and when, are required for designing scientifically sound risk assessments and effective risk management of chemicals. Environmental protection goals specified in EU legislation are defined in general terms, resulting in uncertainty in how to achieve them. In 2010, the European Food Safety Authority (EFSA) published a framework to identify more specific protection goals based on ecosystem services potentially affected by plant protection products. But how applicable is this framework to chemicals with different emission scenarios and receptor ecosystems? Four case studies used to address this question were: (i) oil refinery waste water exposure in estuarine environments; (ii) oil dispersant exposure in aquatic environments; (iii) down the drain chemicals exposure in a wide range of ecosystems (terrestrial and aquatic); (iv) persistent organic pollutant exposure in remote (pristine) Arctic environments. A four-step process was followed to identify ecosystems and services potentially impacted by chemical emissions and to define specific protection goals. Case studies demonstrated that, in principle, the ecosystem services concept and the EFSA framework can be applied to derive specific protection goals for a broad range of chemical exposure scenarios. By identifying key habitats and ecosystem services of concern, the approach offers the potential for greater spatial and temporal resolution, together with increased environmental relevance, in chemical risk assessments. With modifications including improved clarity on terminology/definitions and further development/refinement of the key concepts, we believe the principles of the EFSA framework could provide a methodical approach to the identification and prioritization of ecosystems, ecosystem services and the service providing units that are most at risk from chemical exposure.

Future needs and recommendations in the development of species sensitivity distributions: Estimating toxicity thresholds for aquatic ecological communities and assessing impacts of chemical exposures.

A species sensitivity distribution (SSD) is a probability model of the variation of species sensitivities to a stressor, in particular chemical exposure. The SSD approach has been used as a decision support tool in environmental protection and management since the 1980s, and the ecotoxicological, statistical, and regulatory basis and applications continue to evolve. This article summarizes the findings of a 2014 workshop held by the European Centre for Toxicology and Ecotoxicology of Chemicals and the UK Environment Agency in Amsterdam, The Netherlands, on the ecological relevance, statistical basis, and regulatory applications of SSDs. An array of research recommendations categorized under the topical areas of use of SSDs, ecological considerations, guideline considerations, method development and validation, toxicity data, mechanistic understanding, and uncertainty were identified and prioritized. A rationale for the most critical research needs identified in the workshop is provided. The workshop reviewed the technical basis and historical development and application of SSDs, described approaches to estimating generic and scenario-specific SSD-based thresholds, evaluated utility and application of SSDs as diagnostic tools, and presented new statistical approaches to formulate SSDs. Collectively, these address many of the research needs to expand and improve their application. The highest priority work, from a pragmatic regulatory point of view, is to develop a guidance of best practices that could act as a basis for global harmonization and discussions regarding the SSD methodology and tools. Integr Environ Assess Manag 2017;13:664-674. © 2016 SETAC.

Population-level effects and recovery of aquatic invertebrates after multiple applications of an insecticide.

Standard risk assessment of plant protection products (PPP) combines "worst-case" exposure scenarios with effect thresholds using assessment (safety) factors to account for uncertainties. If needed, risks can be addressed applying more realistic conditions at higher tiers, which refine exposure and/or effect assessments using additional data. However, it is not possible to investigate the wide range of potential scenarios experimentally. In contrast, ecotoxicological mechanistic effect models do allow for addressing a multitude of scenarios. Furthermore, they may aid the interpretation of experiments such as mesocosm studies, allowing extrapolation to conditions not covered in experiments. Here, we explore how to use mechanistic effect models in the aquatic risk assessment of a model insecticide (Modelmethrin), applied several times per season but rapidly dissipating between applications. The case study focuses on potential effects on aquatic arthropods, the most sensitive group for this substance. The models provide information on the impact of a number of short exposure pulses on sensitive and/or vulnerable populations and, when impacted, assess recovery. The species to model were selected based on their sensitivity in laboratory and field (mesocosm) studies. The general unified threshold model for survival (GUTS) model, which describes the toxicokinetics and toxicodynamics of chemicals in individuals, was linked to 3 individual-based models (IBM), translating individual survival of sensitive organisms into population-level effects. The impact of pulsed insecticide exposures on populations were modeled using the spatially explicit IBM metapopulation model for assessing spatial and temporal effects of pesticides (MASTEP) for Gammarus pulex, the Chaoborus IBM for populations of Chaoborus crystallinus, and the "IdamP" model for populations of Daphnia magna. The different models were able to predict the potential effects of Modelmethrin applications to key arthropod species inhabiting different aquatic ecosystems; the most sensitive species were significantly impacted unless respective mitigation measures were implemented (buffer zones resulting in reduced exposure). As expected the impact was stronger in shallow ditches as compared to deeper pond scenarios. Furthermore, as expected, recovery depended on factors such as temperature (affecting population growth rate and number of generations) and the occurence of nonimpacted aquatic ecosystems (their frequency and connectivity). These model predictions were largely in line with field observations and/or the results of a mesocosm study, providing additional evidence on the suitability and reliability of the models for risk assessment purposes. Because of their flexibility, models may predict the likelihood of unacceptable effects-based on previously defined protection goals-for a range of insecticide exposure scenarios and freshwater habitats.

High concentrations of protein test substances may have non-toxic effects on Daphnia magna: implications for regulatory study designs and ecological risk assessments for GM crops.

Laboratory testing for possible adverse effects of insecticidal proteins on non-target organisms (NTOs) is an important part of many ecological risk assessments for regulatory decision-making about the cultivation of insect-resistant genetically modified (IRGM) crops. To increase confidence in the risk assessments, regulatory guidelines for effects testing specify that representative surrogate species for NTOs are exposed to concentrations of insecticidal proteins that are in excess of worst-case predicted exposures in the field. High concentrations in effects tests are achieved by using protein test substances produced in microbes, such as Escherichia coli. In a study that exposed Daphnia magna to a single high concentration of a microbial test substance containing Vip3Aa20, the insecticidal protein in MIR162 maize, small reductions in growth were observed. These effects were surprising as many other studies strongly suggest that the activity of Vip3Aa20 is limited to Lepidoptera. A plausible explanation for the effect on growth is that high concentrations of test substance have a non-toxic effect on Daphnia, perhaps by reducing its feeding rate. A follow-up study tested that hypothesis by exposing D. magna to several concentrations of Vip3Aa20, and a high concentration of a non-toxic protein, bovine serum albumin (BSA). Vip3Aa20 and BSA had sporadic effects on the reproduction and growth of D. magna. The pattern of the effects suggests that they result from non-toxic effects of high concentrations of protein, and not from toxicity. The implications of these results for regulatory NTO effects testing and ERA of IRGM crops are discussed.

Pairing behavior and reproduction in Hyalella azteca as sensitive endpoints for detecting long-term consequences of pesticide pulses.

The aim of the present study was to examine acute and delayed effects of pulse exposure of the pyrethroid pesticide, permethrin, on precopulatory pairs of Hyalella azteca. Pairs of H. azteca were exposed to a single 1h pulse of different nominal concentrations of permethrin: 0, 0.3, 0.9 or 2.7 µg/L. During exposure, pairing behavior was observed, and during a 56 day post-exposure period the treatments were monitored for pairing behavior, survival and reproductive output. All permethrin-exposed pairs separated within minutes during exposure and shortly thereafter became immobile; however they regained mobility after transfer to clean water. The time to re-form pairs was significantly longer in all tested concentrations compared to the control, although all surviving pairs re-formed within the 56 day test period. Nevertheless not all pairs exposed to 0.9 and 2.7 µg/L reproduced. Furthermore the numbers of juveniles produced by pairs exposed to 0.9 and 2.7 µg/L, but not 0.3 µg/L, were lower throughout the entire post-exposure period compared to the control groups, and the total numbers of juveniles produced during 56 days were significantly lower in organisms exposed to 0.9 and 2.7 µg/L, but not 0.3 µg/L, compared to the control groups. The long-term effects of short-term exposure on reproductive behavior of pairs could potentially have consequences for the population dynamics of H. azteca. However, since individual-level responses can both overestimate and underestimate effects at the population level, appropriate population models are needed to reduce the uncertainty in extrapolating between these levels of biological organization.

Genetically modified crops and aquatic ecosystems: considerations for environmental risk assessment and non-target organism testing.

Environmental risk assessments (ERA) support regulatory decisions for the commercial cultivation of genetically modified (GM) crops. The ERA for terrestrial agroecosystems is well-developed, whereas guidance for ERA of GM crops in aquatic ecosystems is not as well-defined. The purpose of this document is to demonstrate how comprehensive problem formulation can be used to develop a conceptual model and to identify potential exposure pathways, using Bacillus thuringiensis (Bt) maize as a case study. Within problem formulation, the insecticidal trait, the crop, the receiving environment, and protection goals were characterized, and a conceptual model was developed to identify routes through which aquatic organisms may be exposed to insecticidal proteins in maize tissue. Following a tiered approach for exposure assessment, worst-case exposures were estimated using standardized models, and factors mitigating exposure were described. Based on exposure estimates, shredders were identified as the functional group most likely to be exposed to insecticidal proteins. However, even using worst-case assumptions, the exposure of shredders to Bt maize was low and studies supporting the current risk assessments were deemed adequate. Determining if early tier toxicity studies are necessary to inform the risk assessment for a specific GM crop should be done on a case by case basis, and should be guided by thorough problem formulation and exposure assessment. The processes used to develop the Bt maize case study are intended to serve as a model for performing risk assessments on future traits and crops.

Framework for traits-based assessment in ecotoxicology.

A key challenge in ecotoxicology is to assess the potential risks of chemicals to the wide range of species in the environment on the basis of laboratory toxicity data derived from a limited number of species. These species are then assumed to be suitable surrogates for a wider class of related taxa. For example, Daphnia spp. are used as the indicator species for freshwater aquatic invertebrates. Extrapolation from these datasets to natural communities poses a challenge because the extent to which test species are representative of their various taxonomic groups is often largely unknown, and different taxonomic groups and chemicals are variously represented in the available datasets. Moreover, it has been recognized that physiological and ecological factors can each be powerful determinants of vulnerability to chemical stress, thus differentially influencing toxicant effects at the population and community level. Recently it was proposed that detailed study of species traits might eventually permit better understanding, and thus prediction, of the potential for adverse effects of chemicals to a wider range of organisms than those amenable for study in the laboratory. This line of inquiry stems in part from the ecology literature, in which species traits are being used for improved understanding of how communities are constructed, as well as how communities might respond to, and recover from, disturbance (see other articles in this issue). In the present work, we develop a framework for the application of traits-based assessment. The framework is based on the population vulnerability conceptual model of Van Straalen in which vulnerability is determined by traits that can be grouped into 3 major categories, i.e., external exposure, intrinsic sensitivity, and population sustainability. Within each of these major categories, we evaluate specific traits as well as how they could contribute to the assessment of the potential effects of a toxicant on an organism. We then develop an example considering bioavailability to explore how traits could be used mechanistically to estimate vulnerability. A preliminary inventory of traits for use in ecotoxicology is included; this also identifies the availability of data to quantify those traits, in addition to an indication of the strength of linkage between the trait and the affected process. Finally, we propose a way forward for the further development of traits-based approaches in ecotoxicology.

A microcosm system to evaluate the toxicity of the triazine herbicide simazine on aquatic macrophytes.

This study evaluates the effects of the triazine herbicide simazine in an outdoor pond microcosm test system that contained two submerged rooted species (Myriophyllum spicatum and Elodea canadensis) and two emergent rooted species (Persicaria amphibia and Glyceria maxima) over a period of 84 days. Simazine was applied to the microcosms at nominal concentrations of 0.05, 0.5 and 5 mg/L. General biological endpoints and physiological endpoints were used to evaluate herbicide toxicity on macrophytes and the algae developing naturally in the system. Concentration-related responses of macrophytes and algae were obtained for the endpoints selected, resulting in a no observed ecologically adverse effect concentration (NOEAEC) at simazine concentrations of 0.05 mg active ingredient/L after 84 days. E. canadensis was the most negatively affected species based on length increase, which was consistently a very sensitive parameter for all macrophytes. The experimental design presented might constitute a suitable alternative to conventional laboratory single-species testing.

The strobilurin fungicides.

Strobilurins are one of the most important classes of agricultural fungicide. Their invention was inspired by a group of fungicidally active natural products. The outstanding benefits they deliver are currently being utilised in a wide range of crops throughout the world. First launched in 1996, the strobilurins now include the world's biggest selling fungicide, azoxystrobin. By 2002 there will be six strobilurin active ingredients commercially available for agricultural use. This review describes in detail the properties of these active ingredients--their synthesis, biochemical mode of action, biokinetics, fungicidal activity, yield and quality benefits, resistance risk and human and environmental safety. It also describes the clear technical differences that exist between these active ingredients, particularly in the areas of fungicidal activity and biokinetics.

Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sediments.

The partitioning, bioavailability, and toxicity of cypermethrin in water-sediment systems was investigated. Cypermethrin adsorbed extensively and rapidly, with an overall mean organic carbon (OC) adsorption partition coefficient (Koc) of 350,000, and approximately 99% adsorption occurred within 24 h. Bioavailability was measured via body burdens of Daphnia magna and Chironomus tentans. Mean biota-sediment accumulation factors (BSAFs), that is, the concentration in the organism as a proportion of the concentration in the sediment, decreased with increasing OC content. The BSAF values were 0.31, 0.14, and 0.08 for D. magna and 0.63, 0.19, and 0.08 for C. tentans, in 1, 3, and 13% OC sediments, respectively. The 10-d median lethal sediment concentrations (LC50s) of cypermethrin were 3.6, 18, and 32 mg/kg for Hyalella azteca and 13, 67, and 62 mg/kg for C. tentans in 1, 3, and 13% OC sediments, respectively. Predictions of aqueous concentrations at the LC50 in sediments (based on Koc) compared well to each other and to effect concentrations from studies in water alone, suggesting that equilibrium partitioning theory could be used reasonably to predict and normalize the toxicity of cypermethrin across sediments of differing OC content.