Use of species sensitivity distributions to characterize hazard for insecticidal traits

Characterization of the Spectrum of Activity of IPD079Ea: A Protein Derived From Ophioglossum pendulum (Ophioglossales: Ophioglossaceae) With Activity Against Western Corn Rootworm [Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)]

Western corn rootworm (Diabrotica virgifera virgifera LeConte) is a major pest of corn in both North America and Europe and as such presents significant challenges for farmers. IPD079Ea protein is encoded by the ipd079Ea gene from Ophioglossum pendulum (a species of fern) and was found to have activity against western corn rootworm in multiple corn events transformed to express the IPD079Ea protein. In chronic laboratory hazard studies, IPD079Ea protein was fed to eleven species in the order Coleoptera and four species in the order Lepidoptera to assess the spectrum of activity. Activity was observed on certain species of the Chrysomelidae and Coccinellidae families, with western corn rootworm as the most sensitive insect tested. No adverse effects on mortality or other sublethal endpoints were observed on any species within Lepidoptera. Overall, IPD079Ea protein appears not to have broad insecticidal properties and has potential value as an effective trait to control western corn rootworm in agricultural systems.

Ecotoxicity of cationic cellulose polymers to aquatic biota: The influence of charge density

Better performances of cellulose-based polymers can be achieved by adjust their architecture including the density of cationic modifications. In this study, the influence of cationic substitution on the ecotoxicity of four quaternized hydroxyethyl cellulose polymers (SK-H, SK-L, SK-M, SK-MH) was studied, using an aquatic biota acute ecotoxicity classification, and rheological and physicochemical characterization. The ecotoxicity characterization was achieved by performing standard ecotoxicity assays with seven key trophic level species: Vibrio fischeri, Raphidocelis subcapitata, Chlorella vulgaris, Daphnia magna, Brachionus calyciflorus, Heterocypris incongruens, and Danio rerio. Median effective concentrations were used to compute hazard concentrations, through the species sensitive distribution curves method. The microalga C. vulgaris and rotifer B. calyciflorus were the most sensitive species to the studied polymers. The SK-H variant was highly toxic to the rotifer. Overall, variants with intermediate levels of cationic charge (SK-M, SK-MH) presented the lowest toxicity. The SK-M variant showed the lowest value of maximum acceptable concentration (0.00354 mg/L), thus being indicated as the least toxic variant. Therefore, the obtained results suggest that industry could direct the development of this type of polymers by tailoring its cationic substitution to moderate levels, in such a way that both functionality and environmental toxicity could be maximized.

In Silico Methods for Environmental Risk Assessment: Principles, Tiered Approaches, Applications, and Future Perspectives

This chapter aims to introduce the reader to the basic principles of environmental risk assessment of chemicals and highlights the usefulness of tiered approaches within weight of evidence approaches in relation to problem formulation i.e., data availability, time and resource availability. In silico models are then introduced and include quantitative structure-activity relationship (QSAR) models, which support filling data gaps when no chemical property or ecotoxicological data are available. In addition, biologically-based models can be applied in more data rich situations and these include generic or species-specific models such as toxicokinetic-toxicodynamic models, dynamic energy budget models, physiologically based models, and models for ecosystem hazard assessment i.e. species sensitivity distributions and ultimately for landscape assessment i.e. landscape-based modeling approaches. Throughout this chapter, particular attention is given to provide practical examples supporting the application of such in silico models in real-world settings. Future perspectives are discussed to address environmental risk assessment in a more holistic manner particularly for relevant complex questions, such as the risk assessment of multiple stressors and the development of harmonized approaches to ultimately quantify the relative contribution and impact of single chemicals, multiple chemicals and multiple stressors on living organisms.

Environmental risk assessment of the DvSSJ1 dsRNA and the IPD072Aa protein to non-target organisms

Event DP-Ø23211-2 (hereafter referred to as DP23211) maize expresses the DvSSJ1 double-stranded RNA (DvSSJ1 dsRNA) and the IPD072Aa protein, encoded by the ipd072Aa gene. DvSSJ1 dsRNA and the IPD072Aa protein each provide control of corn rootworms (Diabrotica spp.) when expressed in plants. As part of the environmental risk assessment (ERA), the potential hazard to non-target organisms (NTOs) exposed to the DvSSJ1 dsRNA and the IPD072Aa protein expressed in DP23211 maize was assessed. Worst-case estimated environmental concentrations (EECs) for different NTO functional groups (pollinators and pollen feeders, soil dwelling detritivores, predators and parasitoids, aquatic detritivores, insectivorous birds, and wild mammals) were calculated using worst-case assumptions. Several factors that reduce exposure to NTOs under more realistic environmental conditions were applied, when needed to provide more environmentally relevant EECs. Laboratory bioassays were conducted to assess the activity of DvSSJ1 dsRNA or the IPD072Aa protein against selected surrogate species, and margins of exposure (MOEs) were calculated by comparing the Tier I hazard study results to worst-case or refined EECs. Based on specificity and MOE values, DvSSJ1 dsRNA and the IPD072Aa protein expressed in DP23211 maize are not expected to be harmful to NTO populations at environmentally relevant concentrations.

A quantitative structure-activity relationships approach to predict the toxicity of narcotic compounds to aquatic communities

Species may vary markedly in terms of their sensitivity to toxicants, and such variation can be described through the species sensitivity distribution (SSD) approach. Using SSD cumulative functions, it is possible to calculate the hazardous concentration for 5% of the species (HC₅), namely the contaminant concentration at which 5% of species will be affected. HC₅ is often utilised to derive the predicted no-effect concentration, or the concentration at which a chemical will likely have no toxic effects on the different species present in an ecosystem. However, the lack of sufficient ecotoxicological data frequently obstructs the derivation of SSD curves and consequently the HC₅. In the last 30 years, quantitative structure-activity relationship (QSAR) models have been widely used to predict the toxicity of chemicals to single species. The aim of this study was to evaluate the possibility of extending the applicability domain of these models from single species to the community level by predicting the HC₅ values for aquatic communities and bypassing the need to derive SSD curves. This approach's practical advantage is that it would allow information on the toxicity of contaminants to be obtained on a hierarchical scale (aquatic community), which is ecologically more relevant than on the scale of single species, without the need for a robust toxicity data set. In the first part of the study, two simple QSAR models were developed for narcotic and polar narcotic compounds. Then, the QSAR model developed for narcotic compounds was utilised to define the baseline toxicity for aquatic communities and to calculate the toxicity ratios for various specifically acting compounds (insecticides and herbicides).

Probabilistic ecological risk assessment of heavy metals using the sensitivity of resident organisms in four Korean rivers

The environment has been continuously exposed to heavy metals by various routes, from both natural and artificial sources. In particular, heavy metals in water can affect aquatic organisms adversely, even at very low concentrations, and can lead to the disturbance of the ecosystem balance and biodiversity. Ecological risk assessments are conducted to protect the environment from such situations, primarily by deriving the predicted no-effect concentration (PNEC) from the species sensitivity distribution (SSD). This study developed the SSDs based on the species living in Korean freshwater for four heavy metals including cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The species compositions of the SSDs were examined, and three types of PNECs were derived by applying different assessment factors (AF). In addition, the occurrence and concentrations of heavy metals in Korean rivers were investigated, and the ecological risk assessment was carried out to compare the SSDs with the environmental concentrations. The SSDs were developed using a sufficient number of species, but the missing data of plants and insects provided an incomplete species composition. The results show that Cd and Pb in the environmental concentrations of rivers would not cause any risk to aquatic organisms from the derived PNEC. However, some organisms might be adversely affected by the concentrations of Zn, and a small amount of risk was expected under the conservative PNEC. The distribution of Cu in the rivers was not considered to be safe for aquatic organisms because the average environmental concentrations potentially affected the proportion of the SSD, and the environmental concentrations exceeded the PNECs. The concentrations of Cu and Zn in industrial waters indicated a considerable risk to aquatic organisms, and the probability of exceeding the PNECs appeared to be quite high. Therefore, this study indicates that additional actions and parallel field studies are required based on the risk posed to aquatic organisms by Cu and Zn in four Korean rivers.

Characterization of the Spectrum of Insecticidal Activity for IPD072Aa: A Protein Derived from Pseudomonas chlororaphis with Activity Against Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)

Western corn rootworm (Diabrotica virgifera virgifera LeConte) presents significant pest management challenges for farmers in both North America and Europe. IPD072Aa, a protein derived from Pseudomonas chlororaphis, has previously been shown to have activity against western corn rootworm. In the current study, the spectrum of activity of IPD072Aa was evaluated in controlled laboratory diet bioassays. IPD072Aa was fed at high concentrations in subchronic or chronic bioassays to 11 different insect species, representing 4 families within Coleoptera, and an additional 4 species representing four families of Lepidoptera. No adverse effects were noted in the Lepidoptera species. Within the order Coleoptera, western corn rootworm was the most sensitive species tested. A range of responses was observed within each of the four families of Coleoptera evaluated that included either no-observed effects or reduced growth, developmental delays, and/or reduced survival. These data will help inform the environmental risk assessment of genetically modified plants that express the IPD072Aa protein for western corn rootworm control.

Occurrence, toxicity and transformation of six typical benzotriazoles in the environment: A review

Benzotriazoles (BTs) are a group of heterocyclic compounds which have been widely applied in industrial activities and domestic life mainly as corrosive inhibitors. BTs have been ubiquitously detected in receiving environments and cause potential toxicity to non-target organisms. This paper reviews the occurrence and fate of six selected benzotriazole compounds in different environmental and biological matrices, as well as the transformation and toxicity. Due to their high hydrophilicity and insufficient removal in wastewater treatment plants (WWTPs), these compounds were widely detected in aquatic environments with concentrations mainly from tens ng/L to tens μg/L. Considerable residual levels of BTs in plant, fish, air, tap water and human urine have implied the potential risks to various organsims. The reported acute toxicity of BTs are generally low (EC₅₀ in mg/L level). Some observed sublethal effects including endocrine disrupting effects, hepatotoxicity and neurotoxicity, as well as the ability to promote the development of endometrial carcinoma still raise a concern. BTs are found often more recalcitrant to biodegradation compared to photolysis and ozonation. Environmental factors including pH, temperature, irradiation wavelength, redox condition as well as components of matrix are proved crucial to the removal of BTs. Further studies are needed to explore the precise environment fate and toxicity mechanism of BTs, and develop advanced treatment technologies to reduce the potential ecological risks of BTs.