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Abstract Background Water bodies are affected by chemical contamination, including micropollutants, which is not fully captured by conventional chemical monitoring methods. The inclusion of integrative, effect-based in vivo and in vitro methods in standardized assessment procedures offers the possibility of bridging discrepancies between chemical and biological assessments and has already been proposed in several studies. However, there is a need to develop a comparable ecotoxicological assessment system for surface waters as for chemical and ecological status. This study aims to contribute to this discourse by investigating the temporal and spatial variation of ecotoxicological effects by assessing water grab samples of 15 different sites in central Germany over the course of 1 year using different in vitro assays. Results The level of measured estrogenicity and anti-estrogenicity varied between the four measurement campaigns, while baseline toxicity, dioxin-like effects and mutagenicity showed relatively constant detectable effects over the study period. The impact of conventionally treated wastewater appeared to be one of the strongest influencing stressors, as direct comparisons of ecotoxicity upstream and downstream of wastewater treatment plant dischargers showed a significant increase for most of the conducted bioassays. Comparison of the measured estrogenicity with proposed threshold values showed effects within ecotoxicologically relevant ranges. Conclusions Bioassays record ecotoxicological effects on the basis of specific modes of action, allowing whole groups of substances to be identified as pollutants. Recording ecotoxicological status in this way is a useful complement to water assessment tools and can contribute to successful water management. Although most of the assays in this study were very consistent in detecting strong anthropogenic influences, possible temporal variations of individual assays should be taken into account when planning sampling strategies to improve the comparability of results.

Background: Water bodies are affected by chemical contamination, including micropollutants, which is not fully captured by conventional chemical monitoring methods. The inclusion of integrative, effect-based in vivo and in vitro methods in standardized assessment procedures offers the possibility of bridging discrepancies between chemical and biological assessments and has already been proposed in several studies. However, there is a need to develop a comparable ecotoxicological assessment system for surface waters as for chemical and ecological status. This study aims to contribute to this discourse by investigating the temporal and spatial variation of ecotoxicological effects by assessing water grab samples of 15 different sites in central Germany over the course of 1 year using different in vitro assays. Results: The level of measured estrogenicity and anti-estrogenicity varied between the four measurement campaigns, while baseline toxicity, dioxin-like effects and mutagenicity showed relatively constant detectable effects over the study period. The impact of conventionally treated wastewater appeared to be one of the strongest influencing stressors, as direct comparisons of ecotoxicity upstream and downstream of wastewater treatment plant dischargers showed a significant increase for most of the conducted bioassays. Comparison of the measured estrogenicity with proposed threshold values showed effects within ecotoxicologically relevant ranges. Conclusions: Bioassays record ecotoxicological effects on the basis of specific modes of action, allowing whole groups of substances to be identified as pollutants. Recording ecotoxicological status in this way is a useful complement to water assessment tools and can contribute to successful water management. Although most of the assays in this study were very consistent in detecting strong anthropogenic influences, possible temporal variations of individual assays should be taken into account when planning sampling strategies to improve the comparability of results. [ABSTRACT FROM AUTHOR]

Growing concerns about the environmental impact of ionic liquids (ILs) have spurred research into their (eco)toxic effects, but studies on their mode of toxic action (MOA) still remain limited. However, understanding the MOA and identifying structural features responsible for enhanced toxicity is crucial for characterising the hazard and designing safer alternatives. Therefore, 45 ILs, with systematically varied chemical structures, were tested for cytotoxicity and two specific endpoints in reporter gene assays targeting the Nrf2-ARE mediated oxidative stress response (AREc32) and aryl hydrocarbon receptor activation (AhR-CALUX). While none of the ILs activated the reporter genes, cytotoxicity was high and markedly different between cell lines. Seven and 25 ILs proved more cytotoxic than predicted by baseline toxicity model in the AREc32 and the AhR-CALUX assays, respectively. The length of the side chain and headgroup structures of ILs altered the MOA of ILs. Cellular metabolism of the ILs, investigated by LC-MS/MS, showed side-chain oxidation of the long-chain quaternary ammonium compounds in AhR-CALUX cells and, to a lower extent, in AREc32 cells, however, this transformation could not explain the high cytotoxicity. Effect data for 72 ILs for ten endpoints retrieved from the Tox21 database identified the inhibition of aromatase activity and of mitochondrial membrane potential as potential MOAs. However, in vitro fluorimetric assays for these endpoints demonstrated that effects were activated in a non-specific manner, probably through cytotoxicity. Although many of the ILs tested induced cytotoxicity at concentrations lower than baseline toxicity, the specific MOAs responsible could not be identified. Alternatively, we suggest that the descriptors currently used may fail to define the affinity of ILs for cells. Testing of the affinity of ILs for a diverse range of biomolecules is needed to accurately describe their interactions with cells.

Abstract Background Floodplains are biodiversity hotspots and provide numerous ecosystem services. In recent decades, however, 70–90% of Europe’s floodplains have been structurally degraded. Accordingly, many (inter-)national programs aim to restore and protect floodplain ecosystems. The success of such measures also depends on the chemical contamination, especially of floodplain soils and sediments, which serve as sinks and sources for a variety of pollutants. In this study, we assess the current ecotoxicological status of a floodplain restoration site along the Main River (Frankfurt am Main, Germany) and estimate its development potential with respect to the influence of a local industrial plant and potential legacy contaminations. We therefore use in vitro effect-based methods (EBMs) testing for baseline toxicity, mutagenicity, dioxin-like and estrogenic activities, coupled with chemical analysis. Results Of all water bodies analyzed, the overall toxicity was highest in two flood depressions. In the respective water phase, estrogenic activities exceeded the environmental quality standard and sediment samples were positive for all tested endpoints. Chemical analysis of these sediments revealed high concentrations of polycyclic aromatic hydrocarbons. Soil samples from frequently flooded areas showed the highest mutagenic potential for both frameshift and point mutations with and without metabolic activation. The industrial effluent showed baseline toxic, mutagenic, and dioxin-like activities, that were highly diluted in the Main River. In turn, most of the sediment samples downstream of the industrial discharge showed significantly elevated baseline toxic, estrogenic and dioxin-like activities as well as increased chemical contamination. Conclusion Based on the results of this study, we rate the overall ecotoxicological status of a recently established tributary and groundwater-fed ponds as good, and identified two flood depressions near the Main River as hot spots of contamination. We assume that the observed mutagenicity in the floodplain soils is related to legacy contaminations from former aniline and azo dye production. In terms of the development potential of the floodplain restoration site, we emphasize considering the remobilization of pollutants from these soils and suppose that, in the long term, pollution of the Main River and the local industrial plant may negatively impact sediment quality in its tributaries. With this study, we confirmed the utility of in vitro EBMs for identifying chemically and ecotoxicologically relevant sites.

Background: Floodplains are biodiversity hotspots and provide numerous ecosystem services. In recent decades, however, 70–90% of Europe's floodplains have been structurally degraded. Accordingly, many (inter-)national programs aim to restore and protect floodplain ecosystems. The success of such measures also depends on the chemical contamination, especially of floodplain soils and sediments, which serve as sinks and sources for a variety of pollutants. In this study, we assess the current ecotoxicological status of a floodplain restoration site along the Main River (Frankfurt am Main, Germany) and estimate its development potential with respect to the influence of a local industrial plant and potential legacy contaminations. We therefore use in vitro effect-based methods (EBMs) testing for baseline toxicity, mutagenicity, dioxin-like and estrogenic activities, coupled with chemical analysis. Results: Of all water bodies analyzed, the overall toxicity was highest in two flood depressions. In the respective water phase, estrogenic activities exceeded the environmental quality standard and sediment samples were positive for all tested endpoints. Chemical analysis of these sediments revealed high concentrations of polycyclic aromatic hydrocarbons. Soil samples from frequently flooded areas showed the highest mutagenic potential for both frameshift and point mutations with and without metabolic activation. The industrial effluent showed baseline toxic, mutagenic, and dioxin-like activities, that were highly diluted in the Main River. In turn, most of the sediment samples downstream of the industrial discharge showed significantly elevated baseline toxic, estrogenic and dioxin-like activities as well as increased chemical contamination. Conclusion: Based on the results of this study, we rate the overall ecotoxicological status of a recently established tributary and groundwater-fed ponds as good, and identified two flood depressions near the Main River as hot spots of contamination. We assume that the observed mutagenicity in the floodplain soils is related to legacy contaminations from former aniline and azo dye production. In terms of the development potential of the floodplain restoration site, we emphasize considering the remobilization of pollutants from these soils and suppose that, in the long term, pollution of the Main River and the local industrial plant may negatively impact sediment quality in its tributaries. With this study, we confirmed the utility of in vitro EBMs for identifying chemically and ecotoxicologically relevant sites. [ABSTRACT FROM AUTHOR]

Background: Bisphenol A (BPA) is currently one of the most widely used synthetic chemicals in the production of a wide range of plastics. Due to its diverse endocrine disrupting potential alternative bisphenols, also referred to as analogues, have been developed. Although the toxicity of BPA is well studied, the (eco)toxicological effects of the bisphenol analogues are largely unknown. The similar molecular structure of the analogues suggests comparable toxicological effects. This study aims to extend the (eco)toxicological knowledge on the bisphenol analogues by evaluating eleven bisphenol analogues compared to the reference substance BPA in in vitro bioassays. The examined endpoints are endocrine potential on three nuclear receptors in recombinant yeast cells of Saccharomyces cerevisiae, baseline toxicity (also referred to as non-specific toxicity, describing the minimal toxicity of a chemical) in the luminescent bacterium Aliivibrio fischeri, and mutagenicity in two strains of Salmonella typhimurium. Results: Bisphenol A showed estrogenic and anti-androgenic activity at EC50 concentrations of 0.516 mg/L (2.26 × 10–6 M) and 1.06 mg/L (4.63 × 10–6 M), respectively. The assays confirmed notable estrogenic and anti-androgenic activity for the vast majority of analogues in comparable, and often higher, efficacies to BPA. Some analogues showed anti-estrogenic instead of estrogenic activity in a range from 0.789 mg/L (1.45 × 10–6 M; TBBPA) to 2.69 mg/L (2.46 × 10–6 M; BADGE). The baseline toxicity of the analogues revealed a similar tendency of comparable to more prominent effects compared to BPA, ranging from 5.81 mg/L (1.73 × 10–5 M; BPAF) to 39.1 mg/L (1.56 × 10–4 M; BPS). There was no evidence of mutagenicity found. Conclusion: The examined bisphenol analogues prove to be equally, if not more, problematic in endocrine activities than the reference bisphenol A. Based on these results, the tested bisphenols cannot be regarded as safer alternatives and reinforce the notion of bisphenol analogues being considered as regrettable substitutions. [ABSTRACT FROM AUTHOR]

Sixty percent of discrete surface water bodies in Europe do not meet the requirements for good ecological and chemical status and in Germany, the situation is even worse with over 90% of surface water bodies failing to meet the threshold. In addition to hydromorphological degradation, intensive land use and invasive species, chemical pollution is primarily considered to be responsible for the inadequate ecological status of the water bodies. As a quantitatively important source of micropollutants, wastewater treatment plants (WWTPs) represent an important entry path for chemical stressors. It is therefore important to analyze the effectiveness of the WWTPs in eliminating micropollutants and other chemical stressors to mitigate the negative impacts of the treated wastewater (WW) in aquatic ecosystems. Accordingly, in this study, we evaluated the impacts of two conventional, medium-sized WWTPs on their small receiving water systems in the southwestern region of Hessen in Germany during two sampling campaigns (spring and fall) using effect-based methods (EBM). We hypothesized that due to the insufficient elimination of micropollutants, a broad spectrum of toxic effects would be detected in conventionally treated WW and also in the receiving surface waters downstream the WWTPs. As EBMs a battery of in vitro assays and active biomonitoring using two in vivo assays were applied. The results supported our hypothesis and showed that the untreatedWWhad a very high baseline toxicity and also high endocrine and mutagenic activities. ConventionalWWtreatment, consisting of mechanical and biological treatment with nitrification, denitrification and phosphate precipitation, reduced baseline toxicity by more than 90% and endocrine activities by more than 80% in both WWTPs. Despite these high elimination rates, the remaining baseline toxicity, the endocrine, dioxin-like and mutagenic activities of the conventionally treated WW were so high that negative effects on the two receiving waters were to be expected. This was confirmed in the active monitoring with the amphipod Gammarus fossarum and the mudsnail Potamopyrgus antipodarum, as mortality of both species increased downstream of the WWTPs and reproduction in P. antipodarum was also affected. These results indicate that advanced WW treatment is needed to more effectively eliminate chemical stressors to prevent negative impacts of treated WW particularly in small receiving waters. [ABSTRACT FROM AUTHOR]

Sixty percent of discrete surface water bodies in Europe do not meet the requirements for good ecological and chemical status and in Germany, the situation is even worse with over 90% of surface water bodies failing to meet the threshold. In addition to hydromorphological degradation, intensive land use and invasive species, chemical pollution is primarily considered to be responsible for the inadequate ecological status of the water bodies. As a quantitatively important source of micropollutants, wastewater treatment plants (WWTPs) represent an important entry path for chemical stressors. It is therefore important to analyze the effectiveness of the WWTPs in eliminating micropollutants and other chemical stressors to mitigate the negative impacts of the treated wastewater (WW) in aquatic ecosystems. Accordingly, in this study, we evaluated the impacts of two conventional, medium-sized WWTPs on their small receiving water systems in the southwestern region of Hessen in Germany during two sampling campaigns (spring and fall) using effect-based methods (EBM). We hypothesized that due to the insufficient elimination of micropollutants, a broad spectrum of toxic effects would be detected in conventionally treated WW and also in the receiving surface waters downstream the WWTPs. As EBMs a battery of in vitro assays and active biomonitoring using two in vivo assays were applied. The results supported our hypothesis and showed that the untreated WW had a very high baseline toxicity and also high endocrine and mutagenic activities. Conventional WW treatment, consisting of mechanical and biological treatment with nitrification, denitrification and phosphate precipitation, reduced baseline toxicity by more than 90% and endocrine activities by more than 80% in both WWTPs. Despite these high elimination rates, the remaining baseline toxicity, the endocrine, dioxin-like and mutagenic activities of the conventionally treated WW were so high that negative effects on the two receiving waters were to be expected. This was confirmed in the active monitoring with the amphipod Gammarus fossarum and the mudsnail Potamopyrgus antipodarum, as mortality of both species increased downstream of the WWTPs and reproduction in P. antipodarum was also affected. These results indicate that advanced WW treatment is needed to more effectively eliminate chemical stressors to prevent negative impacts of treated WW particularly in small receiving waters.

In vitrobioassays can directly obtain the toxicity information of numerous coexisting pollutants in water environment, and has become one of the important means for toxic effect evaluations and diagnosis. However, due to the lack of toxicity effect limit standards for determining the water quality, it is difficult to use bioassays for water quality management. Therefore, more and more research is focusing on deriving the effect-based trigger values (EBTs) of in vitrobioassays. This paper reviews the establishment background and derivation principles of EBTs, and summarizes a variety of derivation methods of EBTs. At present, the methods of derivation of EBTs are divided into two categories according to the protection objectives, one is the health protection objective and the other is the ecological protection objective. EBTs for drinking water are based on the premise of protecting human health and are based on allowable daily intake (ADI), in vivo safe concentration, daily dose of 10% increase in cancer inci- dence (TD10 ) and guideline values (GV) in environmental quality standard (EQS). While, EBTs for surface water, aiming at ecological protection, were derived based on GVs values in the EQS and hazardous concentrations at the 5th percentile (HC5 ) of the species sensitivity distribution (SSD). Derivation of EBTs from GV and HC5 are two widely used frameworks. The former is dedicated to reading EBT values from GV of EQS and trying to establish derivation methods that can be widely applied to various toxicity endpoints. The latter is to obtain HC5 values of positive compounds from the species sensitivity curve. At the same time, combined with the background parameters of the water body to be measured, the EBT value of the protection ecosystem was derived. This paper compares the EBT values and characteristics derived from different methods for in vitro bioassays and summarizes the applica- tion of EBTs in water environments in order to provide theoretical basis and technical support for high-throughput in vitrobioassays for water quality assessment. [ABSTRACT FROM AUTHOR]

In recent years, an invasive cassava mealybug Phenacoccus manihoti has been threatening cassava cultivation alongside another invasive papaya mealybug Paracoccus marginatus which invaded the country more than a decade ago. In order to evaluate their responses against the commonly used neonicotinoid insecticides: thiamethoxam 25 WG and imidacloprid 17.8 SL, acute toxicity experiments to determine the susceptibility baselines in populations of two invasive mealybugs in the cassava agro-ecosystem, namely, cassava mealybug P. manihoti and papaya mealybug P. marginatus were performed upto 15 generations. A systemic uptake method was used for the bioassay. The LC50 values of thiamethoxam for F1 generation were 3.298 ppm whereas it was 1.066 ppm for F15 in cassava mealybug. The LC50 values of F1 generation were 2.014 ppm and that of F15 generation was 1.384 ppm when tested with imidacloprid. In the case of papaya mealybug, the LC50 values ranged from 6.138 ppm (F1) to 2.503 ppm (F15) for thiamethoxam and 7.457 ppm (F1) to 3.231 ppm (F15) for imidacloprid. All the susceptibility indices calculated were less than threefold. The rate of resistance development was negative in all cases showing that none of the tested populations harboured any resistance without insecticidal selection pressure. Tentative discriminating doses were fixed for both chemicals with the help of LC95 values obtained from the bioassay experiments, namely five ppm for both thiamethoxam and imidacloprid in the case of cassava mealybug and 10 ppm and 15 ppm, respectively, for thiamethoxam and imidacloprid in the case of papaya mealybug. [ABSTRACT FROM AUTHOR]

Background: Due to their high biodiversity, small water bodies play an important role for freshwater ecosystems. Nonetheless, systematic pesticide monitoring in small creeks with a catchment <30 km² is rarely conducted. Methods: In this study, event-driven water samples were taken from May until November 2017 and March until July 2018 after 20 rain events at three sampling sites with catchment areas of <27 km² in the Wetterau, a region with intensive agriculture in Southern Hesse, Germany. Additionally, enriched extracts of the native water samples from the campaign in 2018 were used for the Microtox assay to determine baseline toxicity to invertebrates over time and sum of toxic units (STU) were calculated to compare the potential toxicity of the samples. Results: Overall, 37 pesticides and 17 transformation products were found, whereby the herbicide metamitron (79 µg/L) showed the highest concentration. Regularly, pesticide concentrations peaked at the time of the highest water level within each sampling event. Within each sampling event maximum pesticide concentration was mostly reached in water samples taken during the first two hours. The sum of the time-weighted mean concentration values of all pesticides was between 2.0 µg/L and 7.2 µg/L, whereby the measured concentrations exceeded their regulatory acceptable concentration (RAC) at 55% of all sampling events for at least one pesticide. The mean EC50 values varied between 28.6 ± 13.1 to 41.3 ± 12.1 REF (relative enrichment factor). The results indicated that several samples caused baseline toxicity, whereby the highest activity was measured at the time of highest water levels and pesticides concentrations, and then steadily decreased in parallel with the water level. Median STUs of invertebrates ranged from -2.10 to -3.91, of algae/aquatic plants from -0.79 to -1.84 and of fish from -2.47 to -4.24. For one of the three sampling sites, a significant linear correlation between baseline toxicity and STUinvertebratewas found (r² = 0.48). Conclusion: The results of the present study suggest that (1) current pesticide monitoring programs underestimate risks posed by the exposure to pesticides for aquatic organisms and (2) pre-authorization regulatory risk assessment schemes are insufficient to protect aquatic environments. [ABSTRACT FROM AUTHOR]

Background Due to their high biodiversity, small water bodies play an important role for freshwater ecosystems. Nonetheless, systematic pesticide monitoring in small creeks with a catchment

The early-life stage (ELS) toxicity syndrome for fish is well described and has been reported in hundreds of toxicity studies. It is generally characterized by a reduced heart rate, yolk sac and pericardial edemas, and various morphological abnormalities, the most common being spinal curvature. For many of those studies, it appears that the ELS toxicity syndrome is the result of nonspecific (baseline) toxicity that occurs at aqueous and whole-body concentrations that are just below lethal concentrations. Baseline toxicity is essentially a nonspecific response that results from chemicals accumulating in and disturbing the function of biological membranes that leads to lethality and sublethal effects at relatively high doses. The commonality of this acute ELS toxicity syndrome among highly diverse organic and inorganic chemicals is remarkable. It is important to identify baseline toxicity because it is considered minimal toxicity that acts in all tissues and cells, and it has the potential to impair all cellular functions. This means if an effect is observed around baseline-toxic concentrations, it is likely that other cellular functions are also affected (i.e., the effect is not specific). The fish ELS toxicity syndrome can also be the result of specific effects involving receptor interactions; therefore, we emphasize the importance of distinguishing between specific and nonspecific toxicity responses to provide the most relevant data for environmental risk assessment., (© The Author(s) 2025. Published by Oxford University Press on behalf of the Society of Environmental Toxicology and Chemistry. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Protonophoric uncoupling of phosphorylation is an important factor when assessing chemicals for their toxicity, and has recently moved into focus in pharmaceutical research with respect to the treatment of diseases such as cancer, diabetes, or obesity. Reliably identifying uncoupling activity is thus a valuable goal. To that end, we screened more than 6000 anionic compounds for in vitro uncoupling activity, using a biophysical model based on ab initio COSMO-RS input parameters with the molecular structure as the only external input. We combined these results with a model for baseline toxicity (narcosis). Our model identified more than 1250 possible uncouplers in the screening dataset, and identified possible new uncoupler classes such as thiophosphoric acids. When tested against 423 known uncouplers and 612 known inactive compounds in the dataset, the model reached a sensitivity of 83% and a specificity of 96%. In a direct comparison, it showed a similar specificity than the structural alert profiler Mitotox (97%), but much higher sensitivity than Mitotox (47%). The biophysical model thus allows for a more accurate screening for uncoupling activity than existing structural alert profilers. We propose to use our model as a complementary tool to screen large datasets for protonophoric uncoupling activity in drug development and toxicity assessment. [ABSTRACT FROM AUTHOR]

Nonpolar narcosis, also known as baseline toxicity, has been described as the minimal toxicity that an organic chemical may elicit based on its lipophilicity. Although lethal effects of narcosis‐inducing chemicals (NICs) have been thoroughly investigated, knowledge of sublethal effects is still very limited. We investigated the effects of 3 well‐known NICs (phenanthrene, 1,3,5‐trichlorobenzene, and pentachlorobenzene) on a variety of organismal endpoints (malformations, swim bladder inflation, respiration, heart rate, swimming activity, and turning angles), which can be plausibly linked to narcosis in zebrafish embryos. Baseline toxicity recorded as mortality is typically observed in similar exposure ranges in a wide variety of species including fish, corresponding to a chemical activity range between 0.01 and 0.1. In the present study, we found that sublethal effects occurred at concentrations approximately 5 times below lethal concentrations. Altered swimming activity and impaired swim bladder inflation were the most sensitive endpoints occurring at exposure levels below the generally accepted threshold for baseline toxicity for 2 out of 3 compounds. Overall, most effective exposure levels across the sublethal endpoints and compounds did fall within the range typically associated with baseline toxicity, and deviations were generally limited to a factor 10. Although there could be benefit in adding sublethal endpoints to toxicity tests, such as the fish embryo acute toxicity (FET) test, based on the present sublethal endpoints and available evidence from our and other studies, the underestimation of toxicity as a result of the sole assessment of mortality as an endpoint in an FET test may be limited for narcosis. Environ Toxicol Chem 2021;40:2802–2812. © 2021 SETAC [ABSTRACT FROM AUTHOR]

Tomato pinworm, Tuta absoluta is a serious and notorious pest on tomato. Control mainly relies on insecticides because of their high infestation levels on all plant parts and life stages of the crop. This study, investigated the efficacy of different insecticides, against Tuta absoluta for different populations in laboratory conditions. The LC50 ranged from 0.27 to 2.0 ppm for chlorantraniliprole, from 1.01 to 2.25 ppm for flubendiamide, from 0.32 to 0.90 ppm for spinosad, from 0.98 to 6.52 ppm for imidacloprid, from 0.82 to 6.38 ppm for indoxacarb, from 967.32 to 1911.98 ppm, for chlorpyriphos, The resistance ratios ranged from 1.1 to 7.7-fold difference in all six cases. The laboratory experimental results showed that chlorantraniliprole and spinosad were the most toxic insecticides as compared to other chemicals and showed homogenous response to them. [ABSTRACT FROM AUTHOR]

BACKGROUND Ozone gas is commercially used for deodorization and microbial control. Its efficacy against stored product insect pests is well documented. In the midst of the common bed bug (Cimex lectularius L.) outbreak, claims were made that ozone gas was effective for their control. This study was conducted to determine baseline ozone concentrations and exposure times required for the control of an insecticide‐susceptible C. lectularius strain under laboratory conditions. Dichlorvos (DDVP), an organophosphate class fumigant insecticide was used as a positive control. RESULTS: Nymphs and adults were more susceptible to ozone than eggs. Complete (100%) nymph and adult mortality was achieved at an ozone concentration (C) of 1500 ppm and exposure time (T) of 180 min, or concentration × time product (CT) of 270 000 ppm‐min, whereas eggs required an eightfold higher CT (2 040 000 ppm‐min). DDVP vapor was 2070‐, 2542‐ and 450‐fold more potent than ozone, against nymphs, adults and eggs, respectively. CONCLUSIONS: Baseline ozone toxicity data provide insights on the practicality of using this gas for the management of common bed bugs. High ozone CT products required for C. lectularius control, particularly eggs, suggest that its use for treating infested human dwellings is not feasible due to logistic, safety and monetary concerns. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Ionizable organic chemicals (IOCs) such as organic acids and bases are an important substance class requiring aquatic hazard evaluation. Although the aquatic toxicity of IOCs is highly dependent on the water pH, many toxicity studies in the literature cannot be interpreted because pH was not reported or not kept constant during the experiment, calling for an adaptation and improvement of testing guidelines. The modulating influence of pH on toxicity is mainly caused by pH‐dependent uptake and bioaccumulation of IOCs, which can be described by ion‐trapping and toxicokinetic models. The internal effect concentrations of IOCs were found to be independent of the external pH because of organisms' and cells' ability to maintain a stable internal pH milieu. If the external pH is close to the internal pH, existing quantitative structure–activity relationships (QSARs) for neutral organics can be adapted by substituting the octanol–water partition coefficient by the ionization‐corrected liposome–water distribution ratio as the hydrophobicity descriptor, demonstrated by modification of the target lipid model. Charged, zwitterionic and neutral species of an IOC can all contribute to observed toxicity, either through concentration‐additive mixture effects or by interaction of different species, as is the case for uncoupling of mitochondrial respiration. For specifically acting IOCs, we recommend a 2‐step screening procedure with ion‐trapping/QSAR models used to predict the baseline toxicity, followed by adjustment using the toxic ratio derived from in vitro systems. Receptor‐ or plasma‐binding models also show promise for elucidating IOC toxicity. The present review is intended to help demystify the ecotoxicity of IOCs and provide recommendations for their hazard and risk assessment. Environ Toxicol Chem 2020;39:269–286. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Abstract The freely dissolved concentration (C free) was measured for PAHs and PCBs in sediments of the German Bight and Wadden Sea. Ex-situ Solid Phase Microextraction (SPME) was applied using Polydimethlysiloxane (PDMS) coated glass fibers followed by automated thermal desorption and GC–MS analysis. This study provides the first dataset on the spatial distribution of C free for PAHs and PCBs in the German Bight and the Wadden Sea. We found elevated PCB concentrations in the Wadden Sea and especially in the Weser estuary. Sandy North Sea sediments were rather less contaminated, except for some former dumping sites. The sorption strength of PAHs was generally stronger, while PCBs in the Wadden Sea sediments were only weakly bound. This SPME method is a rapid and sensitive tool to study C free of hydrophobic organic chemicals to improve todays sediment risk assessment. Graphical abstract Unlabelled Image Highlights • First dataset on C free of PAHs and PCBs in sediments of the German Bight and Wadden Sea. • Elevated bioavailable PCB concentrations in sediments of the Wadden Sea. • Regional differences in sorption strength were identified. • Baseline toxicity was below threshold for lethality at all stations. [ABSTRACT FROM AUTHOR]

Chemical activity quantifies the energetic level of an organic compound relative to its pure liquid [0–1], and several studies have reported that baseline toxicity generally requires chemical activities of 0.01–0.1. The first aim was to challenge this chemical activity range for baseline toxicity. Algal growth inhibition data (median effective concentrations, EC 50 ) were compiled from two recent studies and included 108 compounds categorised as non-polar (mode of toxic action, MOA1) and polar (MOA2) narcotics. These data were linked to chemical activity by (1) plotting them relative to a regression for (subcooled) liquid solubility (S L ), which served as visual reference for chemical activity of unity and (2) determining EC 50 /S L ratios that essentially equal median effective chemical activity (Ea 50 ). Growth inhibition required chemical activity >0.01 for MOA1 and >0.001 for MOA2 compounds. The second aim was to identify compounds exerting excess toxicity, i.e., when growth inhibition occurred at chemical activity <0.001. From a recent review with 2323 data entries, 315 EC 50 values passed our selection criteria. 280 of these EC 50 values were within or near the baseline toxicity range (Ea 50 >0.001), and 25 compounds were found to exert excess toxicity (Ea 50 <0.001). Of these compounds, 16 are pesticides or precursors. Methodologically, this study includes two methods for translating EC 50 values into the chemical activity framework, each having advantages and limitations. Scientifically, this study confirms that baseline toxicity generally requires chemical activities of 0.01–0.1 and extends the application of the chemical activity approach beyond baseline toxicity, by demonstrating its utility to identify compounds that exert excess toxicity. [ABSTRACT FROM AUTHOR]

Abstract: Fish early life stage (ELS) tests (Organisation for Economic Co‐operation and Development test guideline 210) are widely conducted to estimate chronic fish toxicity. In these tests, fish are exposed from the embryonic to the juvenile life stages. To analyze whether certain modes of action are related to high toxic ratios (i.e., ratios between baseline toxicity and experimental effect) and/or acute‐to‐chronic ratios (ACRs) in the fish ELS test, effect concentrations (ECs) for 183 compounds were extracted from the US Environmental Protection Agency's ecotoxicity database. Analysis of ECs of narcotic compounds indicated that baseline toxicity could be observed in the fish ELS test at similar concentrations as in the acute fish toxicity test. All nonnarcotic modes of action were associated with higher toxic ratios, with median values ranging from 4 to 9.3 × 104 (uncoupling < reactivity < neuromuscular toxicity < methemoglobin formation < endocrine disruption < extracellular matrix formation inhibition). Four modes of action were also found to be associated with high ACRs: 1) lysyl oxidase inhibition leading to notochord distortion, 2) putative methemoglobin formation or hemolytic anemia, 3) endocrine disruption, and 4) compounds with neuromuscular toxicity. For the prediction of ECs in the fish ELS test with alternative test systems, endpoints targeted to the modes of action of compounds with enhanced toxic ratios or ACRs could be used to trigger fish ELS tests or even replace these tests. Environ Toxicol Chem 2018;37:955–969. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Sediment cores and bottom water samples from across the Baltic Sea region were analyzed for freely dissolved concentrations (C free ), total sediment concentrations (C T ) and the dissolved aqueous fraction in water of seven indicator PCBs. Ex-situ equilibrium sampling of sediment samples was conducted with polydimethylsiloxane (PDMS) coated glass fibers that were analyzed by automated thermal desorption GC-MS, which yielded PCB concentrations in the fiber coating (C PDMS ). Measurements of C PDMS and C T were then applied to determine (i) spatially resolved freely dissolved PCB concentrations; (ii) baseline toxicity potential based on chemical activities (a); (iii) site specific mixture compositions; (iv) diffusion gradients at the sediment water interface and within the sediment cores; and (vi) site specific distribution ratios (K D ). The contamination levels were low in the Gulf of Finland and moderate to elevated in the Baltic Proper, with the highest levels observed in the western Baltic Sea. The SPME method has been demonstrated to be an appropriate and sensitive tool for area surveys presenting new opportunities to study the in-situ distribution and thermodynamics of hydrophobic organic chemicals at trace levels in marine environments. [ABSTRACT FROM AUTHOR]

Charged organic chemicals are a prevailing challenge for toxicity modelling. In this contribution we strive to recapitulate the lessons learned from the well-known modelling of narcosis (or baseline toxicity) of neutral chemicals and apply the concept to charged chemicals. First we reevaluate the organism- and chemical independent critical membrane concentration causing 50% mortality,. c mem t o x , based on a critical revision of a previously published toxicity dataset for neutral chemicals. In accordance to values reported in the literature we find a mean value for c mem t o x of roughly 100 mmol/kg (membrane lipid) for a broad variety of 42 aquatic organisms (333 different chemicals), albeit with a considerable scatter. Then we apply this concept to permanently charged ionic liquids (ILs). Using COSMO mic , a quantum mechanically based mechanistic model that makes use of the COSMO-RS theory, we predict membrane-water partition coefficients ( K mem/w ) of the anionic and cationic IL components. Doing so, c mem t o x ( t o t a l ) for permanently charged ILs can be estimated assuming independent, concentration additive contributions of the cationic and its respective anionic species. The resulting values for some of the toxicity data for ionic liquids are consistent with the expected range for baseline toxicity for neutral chemicals while other values are consistently greater or smaller. Based on the calculation of toxic ratios we identify ILs that exert a specific mode of toxic action. Limitations of the modelling approach especially but not exclusively due to the use of nominal concentrations instead of freely-dissolved concentrations in the published literature are critically discussed. [ABSTRACT FROM AUTHOR]

Crude oil and refined petroleum products contain many polycyclic and heterocyclic aromatic hydrocarbons, in particular, alkylated PAHs. Although alkylated PAHs are found in significantly higher quantities than their corresponding unsubstituted PAHs, the most studies on the physico-chemical properties and toxicities of these compounds have been conducted on unsubstituted PAHs. In this study, we measured crucial physico-chemical properties (i.e., water solubility, partition coefficients between polydimethylsiloxane and water ( K PDMSw ), and partition coefficient between liposomes and water ( K lipw )) of selected alkylated PAHs, and evaluated their toxicity using the luminescence inhibition of Aliivibrio fischeri and growth inhibition of Raphidocelis subcapitata . In general, the logarithms of these properties for alkylated PAHs showed good linear correlations with log K ow , as did those for unsubstituted PAHs. Changes in molecular symmetry on the introduction of alkyl groups on aromatic ring structure significantly altered water solubility. The inhibition of bacterial luminescence and algal growth by alkylated PAHs can be explained well by the baseline toxicity hypothesis, and good linear relationships between log K ow or log K lipw and log (1/EC 50 ) were found. [ABSTRACT FROM AUTHOR]

Three water contaminants were selected to be tested in the zebrafish embryo toxicity test (DarT) in order to investigate the sensitivity of the zebrafish embryo toxicity test with respect to mixture effect detection. The concentration-response curves for the observed effects lethality and hypo-pigmentation were calculated after an exposure of the embryos for 96 h with a fungicide (carbendazim), a plasticizer or propellent precursor (2,4-DNT: 2,4- dinitrotoluene) and an aromatic compound (AαC: 2-amino-9H-pyrido[2,3- b ]indol), respectively. Follow-up mixture tests were based on the calculated LC 50 or EC 50 of the single compounds and combined effects were predicted according to the mixture concepts of concentration addition (CA) and independent action (IA). The order of toxicity for the single substances was carbendazim (LC 50 = 1.25 μM) < AαC (LC 50 = 8.16 μM) < 2,4-DNT (LC 50 = 177.05 μM). For AαC and 2,4 DNT hypo-pigmentation was observed in addition (AαC EC 50 = 1.81 μM; 2,4-DNT EC 50 = 8.81 μM). Two binary and one ternary mixture were studied on lethality and one on hypo-pigmentation: 2,4-DNT/AαC (LC 50 = 119.21 μM, EC 50 = 5.37 μM), carbendazim/AαC (LC 50 = 4.49 μM) and AαC/Carbendazim/2,4 DNT (LC 50 = 108.62 μM). Results showed that the effects were in agreement with the CA model when substances were tested in mixtures. Therefore, in a reasonable worst case scenario substance combination effects in fish embryos were at maximum only prone to overestimation when using CA as the mixture concept. [ABSTRACT FROM AUTHOR]

In the present study, quantitative structure–activity relationship (QSAR) techniques based on toxicity mechanism and density functional theory (DFT) descriptors were adopted to develop predictive models for the toxicity of alkylated and parent aromatic hydrocarbons to Vibrio fischeri . The acute toxicity data of 17 aromatic hydrocarbons from both literature and our experimental results were used to construct QSAR models by partial least squares (PLS) analysis. With consideration of the toxicity process, the partition of aromatic hydrocarbons between water phase and lipid phase and their interaction with the target biomolecule, the optimal QSAR model was obtained by introducing aqueous freely dissolved concentration. The high statistical values of R 2 (0.956) and Q CUM 2 (0.942) indicated that the model has good goodness-of-fit, robustness and internal predictive power. The average molecular polarizability ( α ) and several selected thermodynamic parameters reflecting the intermolecular interactions played important roles in the partition of aromatic hydrocarbons between the water phase and biomembrane. Energy of the highest occupied molecular orbital ( E HOMO ) was the most influential descriptor which dominated the toxicity of aromatic hydrocarbons through the electron-transfer reaction with biomolecules. The results demonstrated that the adoption of freely dissolved concentration instead of nominal concentration was a beneficial attempt for toxicity QSAR modeling of hydrophobic organic chemicals. [ABSTRACT FROM AUTHOR]

The pollution state in the German Bight was investigated by determination of pollutant concentrations of sediment samples using equilibrium passive sampling. Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAH) were determined in the pore water of North Sea sediment. The freely dissolved pore water concentration (C free) was measured applying Solid Phase Microextraction (SPME) by using PDMS-coated glass fibers. The obtained results show that the North Sea contamination level with the investigated pollutants is relatively low. However, the stations close to the sediment-dumping site were higher contaminated. A macrofauna analysis showed that bioturbation activities were mostly present in the upper sediment layers, but a direct bioturbation influence on the sediment concentration distribution could not be shown. Overall, the contamination load was below baseline toxicity, but considering that several other priority pollutants will also make a contribution to the baseline toxicity, it can be counted as relatively high. [Display omitted] • Baseline toxicity was below the threshold for lethality at all stations. • The stations close to the dumping site were more contaminated. • Bioturbation was highest in the upper sediment layers. • No direct influence of bioturbation on the sediment concentration could be seen. • Higher chemical load might negatively affect the species bioturbation potential. [ABSTRACT FROM AUTHOR]

Recently, high-quality data were published on the algal growth inhibition caused by 50 non-polar narcotic compounds, of which 39 were liquid compounds with defined water solubility. In the present study, the toxicity data for these liquids were applied to challenge the chemical activity range for baseline toxicity. First, the reported effective concentrations (EC 50 ) were divided by the respective water solubilities (S water ), since the obtained EC 50 /S water ratio essentially equals the effective chemical activity (Ea 50 ). The majority of EC 50 /S water ratios were within the expected chemical activity range of 0.01–0.1 for baseline toxicity, and none of the ratios were significantly below 0.01. On a practical level, these findings suggest EC 50 values for baseline toxicity to be at or above 1% of liquid solubility, which would have been accurate or conservative for all 39 liquids with defined water solubility in the applied dataset. On an environmental risk assessment level, predicted no-effect concentrations (PNECs) for baseline toxicity could even be set as a percentage of saturation, which can easily be extended to mixtures. However, EC 50 values well below 1% of liquid saturation can still occur and would be a direct indication of excess toxicity. [ABSTRACT FROM AUTHOR]

Polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCDD) are major brominated flame retardants (BFRs) that are now banned or under restrictions in many countries because of their persistence, bioaccumulation potential and toxicity (PBT properties). However, there is a wide range of alternative BFRs, such as decabromodiphenyl ethane and tribromophenol, that are increasingly used as replacements, but which may possess similar hazardous properties. This necessitates hazard and risk assessments of these compounds. For a set of 36 alternative BFRs, we searched 25 databases for chemical property data that are needed as input for a PBT assessment. These properties are degradation half-life, bioconcentration factor (BCF), octanol–water partition coefficient ( K ow ), and toxic effect concentrations in aquatic organisms. For 17 of the 36 substances, no data at all were found for these properties. Too few persistence data were available to even assess the quality of these data in a systematic way. The available data for K ow and toxicity show surprisingly high variability, which makes it difficult to identify the most reliable values. We propose methods for systematic evaluations of PBT-related chemical property data that should be performed before data are included in publicly available databases. Using these methods, we evaluated the data for K ow and toxicity in more detail and identified several inaccurate values. For most of the 36 alternative BFRs, the amount and the quality of the PBT-related property data need to be improved before reliable hazard and risk assessments of these substances can be performed. [ABSTRACT FROM AUTHOR]

The populations of cotton leafhopper,Amrasca biguttula biguttulawere collected from two different locations, viz. Coimbatore and Salem, and the identified susceptible Salem population was cultured continuously for four generations without exposure to insecticides and the baseline toxicity data were established by leaf dip bioassay method (IRAC method No. 8). The tentative discriminating doses fixed, based on the susceptibleA. biguttula biguttulapopulation, were 1.10, 0.10, 0.02 and 1.0 ppm for imidacloprid, thiamethoxam, acetamiprid and thiacloprid, respectively. Insecticide resistance was then monitored using the above doses against leafhoppers collected from Coimbatore, Bhavanisagar, Salem and Srivilliputhur. The level of resistance inA. biguttula biguttula,as revealed by per cent survival, varied from 6.67 (Salem) to 15.38 (Srivilliiputhur) for imidacloprid; 3.33 (Salem) to 15.09 (Srivilliputhur) for thiamethoxam; 5.00 (Bhavanisagar) to 20.00 (Srivilliputhur) for acetamiprid; and 5.00 (Bhavanisagar) to 9.09 (Srivilliputhur) for thiacloprid. [ABSTRACT FROM AUTHOR]

Highlights: [•] REACH-relevant algal toxicity data were obtained for 50 nonpolar narcotic chemicals. [•] Most of the tested compounds so far lacked published algal growth inhibition values. [•] Toxicity of non-polar narcotic compounds correlated with hydrophobicity: R 2 =0.95. [•] MLR QSAR model was derived for non-polar and polar narcotic compounds: R 2 =0.92. [•] The Verhaar classification of non-polar narcotics appears to apply for algae. [Copyright &y& Elsevier]

Abstract: Effects of individual petroleum hydrocarbons on the luminescence inhibition of Vibrio fischeri were evaluated according to a standard protocol to develop a quantitative structure−activity relationship and identify the apparent toxicity cutoff. Eighteen aromatic hydrocarbons, including benzene and its derivatives and polycyclic aromatic hydrocarbons (PAHs), were chosen as model compounds with their log K ow values between 2.7 and 6.4. The obtained values of 50 percent luminescence inhibition (EC50) showed a good linear correlation with log K ow up to ~5. However, toxic effects were not observed for more hydrophobic chemicals with log K ow value >5. The calculated chemical activities that caused EC50 were mostly between 0.01 and 0.1. This agrees with an earlier hypothesis concerning a chemical activity resulting the critical membrane concentration of aromatic hydrocarbons. The highest chemical activities for aromatic hydrocarbons with log K ow value >5 or melting point >100°C are <0.01 when they are spiked at their water solubility level according to the standard test protocol; this occurs for two primary reasons: (1) partitioning between organism and the test solution and (2) decreasing fugacity ratio with increasing melting point. Accordingly, luminescence inhibition by petroleum hydrocarbons is well explained by the baseline toxicity model. However, the apparent toxicity cutoff observed for single chemicals is not necessarily valid in a complex mixture, because baseline toxicity is regarded concentration additive. [Copyright &y& Elsevier]

Background Tuta absoluta (Meyrick), in only a few years, has become a serious threat to global tomato production. Depending on the cropping system and infestation pressure, T. absoluta control may rely heavily on insecticide applications. By means of a validated IRAC bioassay method, the toxicity of all insecticides registered for T. absoluta control in Greece has been estimated. A non-registered pyrethroid insecticide was also included in this study. Results Low heterogeneity was detected in the populations tested with most insecticides. The LC50 ranged from 0.31 to 1.31 mg L−1 for flubendiamide, from 0.12 to 0.53 mg L−1 for chlorantraniliprole, from 0.03 to 0.12 mg L−1 for emamectin benzoate, from 0.08 to 0.26 mg L−1 for spinosad, from 31.8 to 159.5 mg L−1 for metaflumizone, from 1.73 to 17.5 mg L−1 for indoxacarb, from 530 to 2038 mg L−1 for chlorpyriphos and finally from 475 to 794 mg L−1 for cypermethrin. The variability of the LC50 values among the tested populations was low ( RR under 5×), except for indoxacarb ( RR = 10×). In the absence of a reference strain, comparisons with the recommended label rates were performed. Evidence of potential control failures was detected using probit analysis estimates for cypermethrin, chlorpyriphos and metaflumizone. Conclusions For most registered insecticides, a solid set of baseline data has been presented that can be used in future resistance monitoring studies. The interaction of metaflumizone with T. absoluta has been discussed, and for chlorpyriphos it is suspected that the resistance level is underestimated with the present dataset. Finally, it has been demonstrated that the pyrethroid cypermethrin would provide insufficient control of the pest.© 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Diamondback moth, Plutella xylostella (L.) is a serious insect pest of vegetables world-wide, and has evolved resistance to various kinds of insecticides. Studies were conducted to determine the baseline toxicity of metaflumizone and the possibility of cross-resistance between metaflumizone and indoxacarb, two sodium channel blocking insecticides (SCBIs), in field populations of P. xylostella from China. The variation in susceptibility to metaflumizone among 29 field populations of P. xylostella collected from 14 geographical locations in China was less than five-fold, with 50% lethal concentrations (LCsos) varying from 1.34 to 6.55 mg/liter. Limited variations in LC50s (less than five-fold, ranging from 1.76 to 8.16 rag/liter) were also observed in the four laboratory-selected strains with high levels of resistance to abamectin, spinosad, fipronil, or Bt toxin CrylAc. The toxicity ofmetaflumizone and indoxacarb was compared among 23 out of the 29 field populations. When compared with the susceptible Roth strain, the JN-09B population showed the highest level of resistance to indoxacarb (ll0-fold), but two-fold tolerance to metaflumizone. The other 22 populations (with 5- to 58-fold of resistance to indoxacarb) had 1- to three-fold tolerance to metaflumizone. Metaflumizone could provide an effective alternative insecticide for diamondback moth management. Although the field populations of P. xylostella tested with various levels of resistance to indoxacarb did not have cross-resistance to metaflumizone, metaflumizone should be rotated with other chemicals of different modes of action instead of indoxacarb. [ABSTRACT FROM AUTHOR]