Lowest Observed Effect Concentration Research Articles

Toxicodynamics of cadmium in the green mussel Perna viridis (Linnaeus, 1758) using bioenergetic and physiological biomarkers.

This study evaluated the toxicity of cadmium (Cd) on the green mussel Perna viridis, aiming to identify toxicological endpoints and investigate its responses across physiological, bioenergetic, and biochemical parameters. The 96-hour LC50 value for Cd in P. viridis was 3.03 ± 0.12 mg L-1, with a 95% confidence interval of 2.35-3.91 mg L-1. Chronic toxicity tests revealed a No Observable Effect Concentration (NOEC), Lowest Observable Effect Concentration (LOEC), and chronic toxicity values of 0.20, 0.37, and 0.29 mg L-1, respectively. Cadmium accumulation in treated mussels increased 46- to 215-fold compared to the control group. Superoxide dismutase, catalase, glutathione S-transferase, and glutathione peroxidase levels in exposed mussels exhibited a significant increase compared to the control group. The redox index ratio, acetylcholinesterase activity, and lysosomal membrane stability decreased with increasing exposure concentrations. Levels of reduced and oxidized glutathione, glutathione reductase, lipid peroxidation, and metallothionein-like proteins increased in exposed mussels. Clearance rate, respiration rate, and excretion rate decreased in a dose-dependent manner. Protein, carbohydrate, and lipid levels decreased with increasing exposure concentration (p < 0.001). Mitochondrial electron transport system activity increased, while cellular energy allocation (p < 0.001) and scope for growth decreased in a dose-dependent manner (p < 0.01). The significant increase in antioxidants suggests heightened oxidative stress in mussels under Cd exposure. The physiological activities of the mussels were severely affected, ultimately leading to a reduced scope for growth. The toxicological data generated in this study contribute to the development of seawater quality criteria for the metal Cd.

Paralysis caused by dinotefuran at environmental concentration via interfering the Ca2+-ROS-mitochondria pathway in Chironomus kiiensis.

Dinotefuran as the third-generation of neonicotinoid insecticides is extensively used in agriculture worldwide, posing a potential toxic threat to non-target animals and humans. However, the chronic toxicity mechanism related to mitochondria damage of dinotefuran to non-target animals at environmental concentration is unclear. In this study, the mitochondria damage and oxidative stress of dinotefuran on Chironomus kiiensis were investigated at environmental concentrations by long-term exposure. At the same time, relevant gene expressions of these toxicity indexes were measured as sensitive ecotoxicity biomarkers to reflect the toxic effects of dinotefuran on Chironomidae. Our present study showed that chronic exposure to environmental concentrations of dinotefuran resulted in behavioral inhibition in the larvae of Chironomidae. For burrowing inhibition of 10 days, the lowest observed-effect concentration (LOEC) and 50% inhibitory concentration (IC50) were 0.01 (0.01-0.04) and 0.60 (0.44-0.82) μg/L, respectively. Dinotefuran promoted the release of intracellular calcium ions (Ca2+) in Chironomidae via dysregulating the gene expressions of atp2b, camk ii, and calm. Subsequently, the disruption of the Ca2+ signaling pathway induced oxidative stress by raising reactive oxygen species (ROS), hydrogen peroxide (H2O2), and malonaldehyde (MDA) levels. Thus, the over-release of Ca2+ and ROS disordered the normal functioning of mitochondrial-related pathways by dysregulating the expressions of mitochondria-related genes of atpef0a, sdha, and cyt b. Our findings showed that low environmental concentrations of dinotefuran caused paralysis of the midge via interfering the Ca2+-ROS-mitochondria pathway. These results provided data support for assessing the potential environmental risk of dinotefuran.

Effects of anthranilic diamide insecticides on metamorphosis in the common toad Rhinella arenarum (Hensel, 1867) at concentrations found in aquatic environments

ABSTRACT Anthranilic diamides (AD) are a modern class of insecticides used as alternatives to pyrethroids and neonicotinoids, particularly against lepidopteran pests. Despite their widespread use and presence in surface waters, little is known regarding their effects on amphibians. The aim of this study was to examine the effects of environmentally-relevant concentrations of AD insecticides chlorantraniliprole (CHLO) and cyantraniliprole (CYAN) on metamorphosis of the toad Rhinella arenarum. Tadpoles were exposed to CHLO or CYAN at concentrations ranging from 5 and 5000 µg/L from stage 27 until metamorphosis completion. Both insecticides produced a non-monotonic acceleration of the time required for individuals to progress through development and a decrease in the proportion of individuals completing metamorphosis, although a delay in metamorphosis was also observed at 5 µg/L of CHLO. Snout-vent length and body weight of metamorphosed toads were not markedly affected by either insecticide. CHLO was more toxic than CYAN, with a lowest observed effect concentration (LOEC) for CHLO on time to metamorphosis defined as 5 µg/L compared to 5000 µg/L for CYAN. The LOEC for reduced metamorphic success defined as 50 µg/L for CHLO compared to 500 µg/L for CYAN. As most effects occurred after stage 39, when metamorphosis depends upon thyroid hormones, it is conceivable that that AD insecticides act as endocrine disruptors. These findings suggest that contamination of surface waters with CHLO and CYAN may disrupt amphibian development in the wild and warrant further research to investigate the possibility of endocrine-disruption by ADs.

Acute and Chronic Ecotoxicity of Daphnia magna Exposed to Ash Leachate from the Cotopaxi Volcano, Ecuador.

Ecuador's wetlands and aquatic ecosystems are chronically exposed to ash contamination due to the frequent volcanoes' eruptions in the country. Still, the short and long-term effects of ash contamination on the aquatic biota are not well understood. We used ashes released by the Cotopaxi volcano in 2016 to investigate their acute and chronic effects in Daphna magna. We calculated the half maximal effective concentration (EC50) after 2 and 21 days of exposure, the non-observed effect concentration (NOEC), and the lowest observed effect concentration (LOEC) on offspring production. We also analyzed the metal concentration present in the ashes. The EC50 values at 2 and 21 days were found at 80% and 5% ash leachate concentrations, respectively. After 21 days of exposure, high mortality and low neonatal production were observed in all leachate concentrations (NOEC was at 15%, and LOEC was at 20% leachate concentration). Our results suggest that the ashes from the Cotopaxi volcano can cause acute and chronic toxicity to aquatic life and should be classified as hazardous waste, depending on the dose. There is an urgent need for further studies that assess toxicity caused by the intense volcanic activity in Ecuador.

Ecotoxicity of the chlorantraniliprole insecticide on Ceriodaphnia dubia

Studies on the toxic effects of pesticides to aquatic organisms are necessary to establish safe concentrations of exposure, promoting the protection of aquatic life. The insecticide chlorantraniliprole has been used since 2007 in several crops of vegetables and fruits, but despite its wide and continuous use, little ecotoxicological information is reported in the literature. Then, the objective of this work is to evaluate the ecotoxicological aspects of this insecticide in the test organism Ceriodaphnia dubia through toxicity tests, aiming at determining the values of NOEC (no observed effect concentration), LOEC values (lowest observed effect concentration), CV (chronic value) and EC(I)50, 48 h (acute effect concentration). The results indicated that C. dubia showed greater sensitivity when compared to other organismal groups exposed to the same insecticide, with EC(I)50, 48 h values of 2.9 ± 1.11 µg.L-1, NOEC of 0.61 ± 0.33 µg.L-1 and LOEC of 0.91 ± 0.49 µg.L-1. Based on toxicity tests with C. dubia and considering the protection of aquatic life, a safe environmental concentration of 0.74 µg. L-1 of the insecticide chlorantraniliprole is recommended.

Mercury concentrations in Seaside Sparrows and Marsh Rice Rats differ across the Mississippi River Estuary

Mercury (Hg) concentrations and their associated toxicological effects in terrestrial ecosystems of the Gulf of Mexico are largely unknown. Compounding this uncertainty, a large input of organic matter from the 2010 Deepwater Horizon oil spill may have altered Hg cycling and bioaccumulation dynamics. To test this idea, we quantified blood concentrations of total mercury (THg) in Seaside Sparrows (Ammospiza maritima) and Marsh Rice Rats (Oryzomys palustris) in marshes west and east of the Mississippi River in 2015 and 2016. We also tested for a difference in THg concentrations between oiled and non-oiled sites. To address the potential confounding effect of diet variation on Hg transfer, we used stable nitrogen (δ15N) and carbon (δ13C) isotope values as proxies of trophic position and the source of primary production, respectively. Our results revealed that five to six years after the spill, THg concentrations were not higher in sites oiled by the spill compared to non-oiled sites. In both species, THg was higher at sites east of the Mississippi River compared to control and oiled sites, located west. In Seaside Sparrows but not in Marsh Rice Rats, THg increased with δ15N values, suggesting Hg trophic biomagnification. Overall, even in sites with the most elevated THg, concentrations were generally low. In Seaside Sparrows, THg concentrations were also lower than previously reported in this and other closely related passerines, with only 7% of tested birds exceeding the lowest observed effect concentration associated with toxic effects across bird species (0.2 µg/g ww). The factors associated with geographic heterogeneity in Hg exposure remain uncertain. Clarification could inform risk assessment and future restoration and management actions in a region facing vast anthropogenic changes.

Not all that glitters is gold: Glitter causes acute toxicity to nauplii of Artemia sp.

Glitter has been reported as a relevant pollutant, as it is widely used in cosmetic and textile products and craftwork, and often associated with domestic sewage. The particular glitter is composed of thin layers of plastic and metal. This study assessed the acute toxicity of glitter dispersions in the brine shrimp Artemia sp. Nauplii of Artemia sp. that were exposed to glitter dispersions (0.01, 0.1, 1, 10, and 100 mg/L), obtained by diluting a stock solution in seawater; the control consisted of filtered seawater only. Three replicates were used per treatment and consisted of glass tubes filled with 10 mL of the test solution, and ten nauplii aging over 48 h. After 48 h, the survivors were counted and examined under a microscope. The mean size of glitter particles was 3.94 (±0.98) µm; approximately 44 % of particles were in the range of very fine sand, and 27 % coarse silt. Significant lethal effects (p &lt; 0.05) occurred from 0.1 mg/L (Lowest Observed Effect Concentration - LOEC); the lethal concentration to 50 % organisms (LC50-48h) was 0.350 (0.348 - 0.351) mg/L. The exposed organisms also exhibited patches in their digestive tracts, and particles were stranded in their appendices. The results indicate the toxic potential of glitter to brine shrimp. This investigation indicates the need for further studies on the toxicity of glitter to marine invertebrates. Highlights Glitter includes particles of sizes similar to those of marine microalgae Exposure to glitter suspensions caused toxicity in brine shrimps from 0.1 mg/L The nauplii of Artemia were more sensitive to glitter than echinoderm embryos Metallic parts of the glitter were observed in the digestive tract of the brine shrimp nauplii

Multilevel assessment of carbamazepine effects: An integrative approach using zebrafish early-life stages

Carbamazepine (CBZ) is the most commonly used drug in epilepsy treatment, and its metabolites are commonly detected among persistent pharmaceuticals in the aquatic environment. This study aimed to investigate CBZ effects on early-life-stage zebrafish (Danio rerio) (from 2 to 168 hpf) by employing of an integrative approach linking endpoints from molecular to individual level: (i) development; (ii) locomotor activity; (iii) biochemical markers (lactate dehydrogenase, glutathione-S-transferase, acetylcholinesterase and catalase) and (iv) transcriptome analysis using microarray. A 168 h - LC50 of 73.4 mg L−1 and a 72 h - EC50 of 66.8 mg L−1 for hatching were calculated while developmental effects (oedemas and tail deformities) were observed at CBZ concentrations above 37.3 mg L−1. At the biochemical level, AChE activity proved to be the most sensitive parameter, as evidenced by its decrease across all concentrations tested (∼25% maximum reduction, LOEC (lowest observed effect concentration) < 0.6 μg L−1). Locomotor behaviour seemed to be depressed by CBZ although this effect was only evident at the highest concentration tested (50 mg L−1). Molecular analysis revealed a dose-dependent effect of CBZ on gene expression. Although only 25 genes were deregulated in organisms exposed to CBZ when compared to controls, both 0.6 and 2812 μg L−1 treatments impaired gene expression related to development (e.g. crygmxl1, org, klf2a, otos, stx16 and tob2) and the nervous system (e.g. Rtn3, Gdf10, Rtn3), while activated genes were associated with behavioural response (e.g. prlbr and taar). Altogether, our results indicate that environmentally relevant CBZ concentrations might affect biochemical and genetic traits of fish. Thus, the environmental risk of CBZ cannot be neglected, especially in a realistic scenario of constant input of domestic effluents into aquatic systems.

Effects of two pharmaceuticals: Doxycycline and norfloxacin on plant and animal organisms living in the freshwater

The main reason for the appearance of pharmaceutical compounds in the aquatic environment is their regular excretion by humans and animals in an unchanged form or slightly metabolized. Pharmaceuticals limit the habitable living environment for aquatic organisms, because they can be toxic not only to bacteria but also to non-target organisms. Plants of the Lemnoideae subfamily and crustaceans Daphniindae family are widely used as bioindicators in freshwater environmental risk assessments. This study aimed to use biotests (Lemna test and Daphtoxkit) to determine the effect of two pharmaceuticals: antibiotic – Doxycycline (DOX) and semi-synthetic chemotherapeutic drug – Norfloxacin (NOR) on plants Lemna minor and crustaceans Daphnia magna. Standard Lemna test was extended to include pharmaceutical effects on plant chlorophyll content (LCC) and fluorescence (Fo, Fm, and Fv/Fm), and the confirmation of drug toxicity was the biotest Daphtoxkit assessing the immobilization (IM) of organisms. Studies have shown that DOX was more toxic than NOR on tested aquatic organisms: plants and crustaceans. The lowest observed effect concentration (EC20) of DOX and NOR reduced by 20 % LCC and Iy of L. minor was 2.14 and 8.11 mg × L−1, respectively. The LCC was an early and sensitive indicator of the phytotoxic effects of DOX in L. minor before morphological changes were observed. Confirmation of drug toxicity was the Daphtoxkit. The EC20 (180. min) of DOX and NOR, IM of daphnia by 20 % was 117.18 and 215.42 mg × L−1, respectively. In conclusion, DOX and NOR in aquatic environments may have significant implications for tested organisms and their ecosystems.

Efficacy of binary mixtures and antagonistic effect of Azadirachta indica on Afranamum melegueta against helminth parasites of fish in Epe lagoon

This research aims to investigate the efficacy of binary mixtures and interaction of extracts of Azadirachta indica and Afranamum melegueta in reference with praziquantel at Fish Low Observed Effect Concentration (LOEC) on classes of fish parasite species. An in-vitro study was conducted using binary extract mixtures of A.melegueta and A.indica (ratios 1:3, 1:1 and 3:1) respectively on each of the classes of fish helminth parasites and saline solution was used as the control. Average Survival Time (AST) and percentage Reduction in Survival Time (%RST) as measure of sensitivity were estimated for the parasites at varying toxicities (fish 96 h LC5, LC10, LC50) with reference to praziquantel. Saponin and Terpenoid had the highest presence in ethanol mix (water) in A.indica and A.melegueta. The sensitivities of the parasites to the extracts and praziquantel in decreasing order is; A.melegueta (singly) > Praziquantel > 3:1 mix > 1:1 mix > 1:3 mix > A.indica (singly). Increase in the proportion of A. indica decreases the combined effect of the mixtures on the parasites, thereby, decreasing the effect of A. melegueta when acting singly. Tenuisentis sp, an acanthocephalan showed sensitivity of RST >80 % against A. melegueta (singly) similar to praziquantel, the sensitivity was reduced to RST <80 % with 3:1 mix, and significantly reduced to RST close to 60 % with 1:3 mix. Other parasite species had similar trend. There was significant correlation (r > 0.70) between parasite sensitivities to praziquantel and A.melegueta (singly) as well as its binary mixtures at the fish Low Observed Effect Concentration (LOEC). This indicates that the binary extract mixtures could serve as potential alternatives to the use of chemotherapy considering their potency and wide margin of fish host safety.

Tire particles and their leachates reduce the filtration rate of the mussel Mytilus edulis

Microplastics (MPs) are found in aquatic environments all over the world. Among MPs, tire wear particles (TWPs) are a major contributor to microplastic pollution, and their effects on marine ecosystems are of emerging concern. The blue mussel (Mytilus edulis) is a keystone species in coastal ecosystems with a high risk of exposure to microplastic pollution as the microplastics often overlap in size with the plankton consumed by mussels. In the present study, we investigated the effect of tire particles and their leachates on the filtration rates of M. edulis after short (72 h) and long-term (3 weeks) exposure. Acute exposure to leachates alone causes a significant decrease in the filtration rates of M. edulis with a low observed effect concentration (LOEC) of 1.25 g L−1 and a median effect concentration (EC50) = 3 g L−1. At a concentration of 1.25 g L−1, the filtration rate was reduced compared to the control on average by 38% when mussels were exposed to either TWP or leachates for 72 h. Similarly, mussels exposed to tire particles or their leachates for 3 weeks showed a 46% reduction in filtration rates, compared to the control group. A non-significant difference in filtration rate decrease was found between leachates alone or TWP, which indicates that leachates are the main responsible for the observed toxicity. Our findings indicate that elevated levels of TWP pollution can cause an adverse impact on M. edulis. This could disrupt the natural grazing pressure exerted by M. edulis on phytoplankton, potentially leading to an increased likelihood of algal blooms and hypoxia occurrence in coastal ecosystems.

Ecotoxic response of Rhizobium sp. to the commonly used pesticides (paraquat and dichlorvos)

This study investigated the 96-hour ecotoxicity response of Rhizobium sp. to paraquat and dichlorvos at application concentrations ranging from 0.01 mg/L to 100 mg/L. The test organism was isolated and enumerated using yeast extract mannitol agar. Paraquat proved to be more toxic than dichlorvos based on the toxicity parameters established using probit regression analysis. Rhizobium sp. showed no growth (100% mortality) at the higher concentrations of 10 mg/L and 100 mg/L for paraquat; for dichlorvos, this absence of growth was only seen at the highest application concentration of 100 mg/L. Overall, Rhizobium sp. tolerated the insecticide, dichlorvos, better than the herbicide, paraquat. At the lowest concentration of 0.01 mg/L, it displayed moderate tolerance indices of between 0.534 and 0.589 for both pesticides. At 0.1 mg/L and 1.0 mg/L pesticide concentrations, the 96-hour tolerance indices obtained were less than 0.39, indicative of very low tolerance. Neither pesticide was tolerated at 10 mg/L and 100 mg/L. Statistical comparisons of the tolerance indices between the two pesticides and from one pesticide concentration to the other showed significant differences both within and the between groups (p≤0.05). The median lethal concentrations (LC50) were 0.0158 mg/L and 0.0350 mg/L for paraquat and dichlorvos, respectively. The lowest observed effect concentration (LOEC) and no observed effect concentration (NOEC) were 0.0011 and 0.0027, respectively for paraquat and 0.0017 and 0.0047, respectively for dichlorvos. The results indicated that pesticides have adverse acute effects on key microbial ecosystem service providers like Rhizobium sp. and should, thus, be used with restraint.

A Novel Transgenic Model to Study Thyroid Axis Activity in Early Life Stage Medaka.

Identifying endocrine disrupting chemicals in order to limit their usage is a priority and required according to the European Regulation. There are no Organization for Economic Co-operation and Development (OECD) test guidelines based on fish available for the detection of Thyroid axis Active Chemicals (TACs). This study aimed to fill this gap by developing an assay at eleuthero-embryonic life stages in a novel medaka (Oryzias latipes) transgenic line. This transgenic line expresses green fluorescent protein (GFP) in thyrocytes, under the control of the medaka thyroglobulin gene promoter. The fluorescence expressed in the thyrocytes is inversely proportional to the thyroid axis activity. When exposed for 72 h to activators (triiodothyronine (T3) and thyroxine (T4)) or inhibitors (6-N-propylthiouracil (PTU), Tetrabromobisphenol A (TBBPA)) of the thyroid axis, the thyrocytes can change their size and express lower or higher levels of fluorescence, respectively. This reflects the regulation of thyroglobulin by the negative feedback loop of the Hypothalamic-Pituitary-Thyroid axis. T3, T4, PTU, and TBBPA induced fluorescence changes with the lowest observable effect concentrations (LOECs) of 5 μg/L, 1 μg/L, 8 mg/L, and 5 mg/L, respectively. This promising tool could be used as a rapid screening assay and also to help decipher the mechanisms by which TACs can disrupt the thyroid axis in medaka.

The Developmental Toxicity and Endocrine-Disrupting Effects of Fenpropathrin on Gobiocypris rarus during the Early Life Stage.

In the present study, the developmental toxicity and endocrine-disrupting effects of fenpropathrin on Gobiocypris rarus during the early life stage were studied using a semi-static water exposure method. The results showed that the LOEC (lowest observed effect concentration) of fenpropathrin on the incubation of rare minnow embryos was above 2.5 μg·L-1. The LOEC and NOEC (no observed effect concentration) of fenpropathrin on the developmental malformations and death indicators were 2.0 and 1.5 μg·L-1, respectively. After exposure to 1.5 μg·L-1 of fenpropathrin for 31 days, the expressions of androgen receptor genes (AR) and sex hormone-synthesis-related genes (CYP17 and CYP19a) were significantly decreased and the expressions of thyroid hormone receptor genes (TRβ) and aryl hydrocarbon receptor genes (AhR1a and AhR2) were significantly increased in juvenile Gobiocypris rarus. The expression levels of the androgen receptor gene (AR), estrogen receptor gene (ER1), and the sex hormone-synthesis-related genes (HMGR, CYP17, and CYP19a) were significantly decreased, while the estrogen receptor gene (ER2a), thyroid hormone receptor gene (TRβ), and aromatic hydrocarbon receptor genes (AhR1a and AhR2) were upregulated in juvenile Gobiocypris rarus under exposure to 2.0 μg·L-1 of fenpropathrin. Relatively low concentrations of fenpropathrin can affect the expression of sex hormone receptor genes, genes related to sex hormone synthesis, thyroid hormone receptor genes, and aromatic hydrocarbon receptor genes, thus interfering with the reproductive system, thyroid system, and metabolic level in Gobiocypris rarus. Therefore, more attention should be paid to the endocrine-disrupting effect caused by the pyrethroid insecticides in the water environment. Furthermore, studies on the internal mechanism of the endocrine-disrupting effect of pyrethroid insecticides on fish is needed in the future.

Influence of exposure scenario on the sensitivity to caffeine

The chorion acts as a protective barrier, restricting some chemical absorption into the embryo and the surrounding fluids. In this sense, larvae may only have direct contact with some chemicals after dechorionation. This study aimed to evaluate the effects of caffeine (CAF) (0, 13, 20, 44, 67, and 100 mg.L−1) under different exposure scenarios (embryos with chorion or embryos/larvae already hatched) and rank the stage sensitivity. Thus, three scenarios were investigated: from 2 to 120 hours post fertilization (hpf) (5 days of exposure- 5dE), from 72 to 120 hpf (2dE), and from 96 to 120 hpf (1dE). Heart rate (48 hpf) and energy reserves (120 hpf) were measured in the 5dE scenario, and behavior and acetylcholinesterase (AChE) activity were evaluated at 120 hpf in all scenarios (5dE, 2dE, and 1dE). At 120 hpf, some of the fish was transferred to clean medium for a 10 days depuration period (10dPE). Behavior and AChE activity were assessed after this period. In the 5dE scenario, CAF increased heartbeat (13, 20, and 30 mg.L−1) and reduced carbohydrates (67, and 100 mg.L−1), while inhibiting AChE activity (100 mg.L−1) in the 5dE, 2dE, and 1dE scenarios. CAF reduced the total distance moved in the 5dE (67, and 100 mg.L−1), 2dE (20, 30, 44, 67, and 100 mg.L−1), and 1dE fish (67, and 100 mg.L−1) and increased erratic movements. Based on the lowest observed effect concentration (LOEC) for total distance moved (20 mg.L−1) and higher inhibition of AChE activity (100 mg.L−1) (65%), 2dE fish appear to be more sensitive to CAF. After 10dPE, a recovery in behavior was detected in all scenarios (5dE, 2dE, and 1dE). AChE activity remained inhibited in the 2dE scenario while increasing in the 1dE scenario. This study demonstrated that the presence of the chorion is an important factor for the analysis of CAF toxicity. After the loss of the chorion, organisms show greater sensitivity to CAF and can be used to evaluate the toxicity of various substances, including nanomaterials or chemicals with low capacity to cross the chorion. Therefore, the use of hatched embryos in toxicity tests is suggested, as they allow a shorter and less expensive exposure scenario that provides similar outcome as the conventional scenario.

Ecotoxicity effect factors for plastic additives on the aquatic environment: New approach for life cycle impact assessment

All plastic contains additives. Once in the environment, these will start to leach out and will expose and harm aquatic biota, causing potentially lethal and sub-lethal toxic effects. Even though life cycle assessment covers the toxic impacts of several thousands of chemicals, models to assess the toxic impacts of plastic additives are only emerging. We gathered 461 data points from the literature (266 for freshwater and 195 for marine ecosystems) for 75 species belonging to 9 different phyla. The endpoints effective concentration and lethal concentration, no observed effects concentrations and lowest observed effect concentration tested in acute and chronic exposure, were harmonized into chronic values by applying extrapolation factors. The collected data points covered 75 main plastic additives. This allowed us to calculate 25 Effect factors, 19 for single chemicals and four for overarching categories (alkylphenols, benzophenones, brominated flame retardants and phosphates. In addition, we calculated an aggregated effect factor for chemicals that did not fit in any of the previous groups, as well as a Generic effect factor including 404 gathered data points. The estimated potentially affected fraction (PAF) for the single additives varied between 20.69 PAF·m3·kg−1 for diethyl phthalate and 11081.85 PAF·m3·kg−1 for 4-Nonylphenol. The factors can in future be combined with fate and exposure factors to derive a characterization factor for toxicity caused by additives in aquatic species. This is an important advancement for the assessment of the impacts of plastic debris on aquatic species, thus providing information for decision-makers, as well as guiding policies for the use of additives, ultimately aiming to make the plastic value chain more sustainable.

Ecotoxicity of Lead to a Phytoplankton Community: Effects of pH and Phosphorus Addition and Implications for Risk Assessment.

Ecological risk assessment and water quality criteria for lead (Pb) are increasingly making use of bioavailability-based approaches to account for the impact of toxicity-modifying factors, such as pH and dissolved organic carbon. For phytoplankton, which are among the most Pb-sensitive freshwater species, a Pb bioavailability model has previously been developed based on standard single-species exposures at a high phosphorus (P) concentration and pH range of 6.0 to 8.0. It is well known that P can affect metal toxicity to phytoplankton and that the pH of many surface waters can be above 8.0. We aimed to test whether the single-species bioavailability model for Pb could predict the influence of pH on Pb toxicity to a phytoplankton community at both low and high P supply. A 10-species phytoplankton community was exposed to Pb for 28 days at two different pH levels (7.2 and 8.4) and two different P supply levels (low and high, i.e., total P input 10 and 100 µg/L, respectively) in a full factorial 2 × 2 test design. We found that the effects of total Pb on three community-level endpoints (biodiversity, community functioning, and community structure) were highly dependent on both pH and P supply. Consistent lowest-observed-effect concentrations (LOECs) ranged between 21 and >196 µg total Pb/L and between 10 and >69 µg filtered Pb/L. Long-term LOECs were generally higher, that is, 69 µg total Pb/L (42 µg filtered Pb/L) or greater, across all endpoints and conditions, indicating recovery near the end of the exposure period, and suggesting the occurrence of acclimation to Pb and/or functional redundancy. The highest toxicity of Pb for all endpoints was observed in the pH 7.2 × low P treatment, whereas the pH 8.4 × low P and pH 8.4 × high P treatment were the least sensitive treatments. At the pH 7.2 × high P treatment, the algal community showed an intermediate Pb sensitivity. The effect of pH on the toxicity of filtered Pb could not be precisely quantified because for many endpoints no effect was observed at the highest Pb concentration tested. However, the long-term LOECs (filtered Pb) at low P supply suggest a decrease in Pb toxicity of at least 1.6-fold from pH 7.2 to 8.4, whereas the single-species algal bioavailability model predicted a 2.5-fold increase. This finding suggests that bioavailability effects of pH on Pb toxicity cannot be extrapolated as such from the single species to the community level. Overall, our data indicate that, although the single-species algal Pb bioavailability model may not capture pH effects on Pb ecotoxicity in multispecies systems, the bioavailability-based hazardous concentration for 5% of the species was protective of long-term Pb effects on the structure, function, and diversity of a phytoplankton community in a relevant range of pH and P conditions. Environ Toxicol Chem 2023;42:2684-2700. © 2023 SETAC.

Acute toxicity and genotoxicity of the S-metolachlor-based herbicide Dual Gold® on Leptodactylus luctator (Hudson, 1892) tadpoles (Anura: Leptodactylidae).

Herbicides used in agriculture and their metabolites are frequently detected in surface water bodies, where they can persist and cause adverse effects on aquatic organisms. The aim of this study was to evaluate the acute toxicity and genotoxic effects of the S-metolachlor (SM)-based herbicide Dual Gold® (DG®), on Leptodactylus luctator tadpoles (Anura: Leptodactylidae). To assess the toxicity of the herbicide, including the median lethal concentration (LC50) at 24h, the no-observed-effect concentration (NOEC), and the lowest-observed-effect concentration (LOEC), tadpoles were exposed to five nominal concentrations of DG® (5.0, 6.2, 7.8, 9.8, and 12.2 mg/L), and to dechlorinated water as a negative control (NC). The LC5024h of DG® was 7.0 mg/L, the NOEC was 5.0 mg/L and the LOEC=6.2 mg/L. L. luctator tadpoles were sensitive to the herbicide, reaching 100% mortality after 24 h of exposure to the highest concentration tested (12.2 mg/L). To evaluate the potential genotoxicity of the herbicide, the frequencies of micronuclei (MN) and other erythrocyte nuclear abnormalities (ENA) were determined in larvae exposed to three nominal concentrations of DG® (1.0, 5.0, and 6.2 mg/L) for 48 and 96 h. The frequencies of MN and ENA were compared with a positive control (40 mg/L of Cyclophosphamide) and a negative control. The frequencies of MN and ENA in the erythrocytes of tadpoles exposed to the test concentrations of DG® and Cyclophosphamide were significantly higher than in the negative control group at both 48 and 96 h (with the only exception of MN at 1.0 mg/L at 48 h). Our results confirm the genotoxic and cytotoxic effects of this widely used herbicide in agriculture, a fact that represents a potential risk to amphibians that develop in ponds associated with or immersed in agroecosystems.

A Critical Review of Amphibian Per- and Polyfluoroalkyl Substance Ecotoxicity Research Studies: Identification of Screening Levels in Water and Other Useful Resources for Site-Specific Ecological Risk Assessments.

With the goal of aiding risk assessors conducting site-specific risk assessments at per- and polyfluoroalkyl substance (PFAS)-contaminated sites, this critical review synthesizes information on the ecotoxicity of PFAS to amphibians in 10 amphibian species and 16 peer-reviewed publications. The studies in this review consisted of spiked-PFAS chronic toxicity experiments with perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), and 6:2 fluorotelomer sulfonate (6:2 FTS) that evaluated apical endpoints typical of ecological risk-based decision making (survival, growth, and development). Body mass was the most sensitive endpoint, showing clear and biologically meaningful population level adverse effect sizes (≥20% adverse effects). From these results, we recommend chronic no observed effect concentration (NOEC) screening levels of 590 µg/L for PFOS and 130 µg/L for PFOA. At or above recommended chronic lowest observed effect concentration screening levels of 1100 µg/L PFOS and 1400 µg/L PFOA, there is an increased chance of adverse biologically relevant chronic effects. Biologically relevant adverse effects were not observed for PFHxS and 6:2 FTS, so unbounded NOECs of 1300 µg/L PFHxS and 1800 µg/L 6:2 FTS are recommended. Screening levels are also provided for the concentration of PFAS in an amphibian diet, amphibian tissue, and moss substrate. In addition, we recommend bioconcentration factors that can be useful to predict concentrations of PFAS in amphibians using concentrations in water; these values are useful for food web modeling to understand risks to vertebrate wildlife that prey on amphibians. Overall, the present study provides a guide to the wealth of ecotoxicological research on PFAS conducted by our research group and highlights the need for additional work that would improve the understanding of chemical risks to amphibians. Environ Toxicol Chem 2023;00:1-13. © 2023 SETAC.

Toxic effects of ship exhaust gas closed-loop scrubber wash water.

To meet the strict requirements of reducing sulfur emissions, an increasing number of commercial ships have installed exhaust gas cleaning systems (EGCSs). However, wash water produced during the cleaning process is discharged back to the marine environment. We investigated the effects of closed-loop scrubber (natrium-alkali method) wash water on three trophic species. Severe toxic effects were found when Dunaliella salina, Mysidopsis bahia, and Mugilogobius chulae were exposed to 0.63-6.25, 0.63-10, and 1.25-20% concentrations of wash water, respectively. The 50% effective concentration in 96h (EC50-96h) for D. salina was 2.48%, and the corresponding total polycyclic aromatic hydrocarbons (PAHs) and heavy metals were 22.81 and 23.67μg L-1. The 50% lethal concentration in 7d (LC50-7d) values for M. bahia and M. chulae were 3.57% and 20.50%, respectively. The lowest observed effect concentration (LOEC) values for M. bahia and M. chulae were 1.25% and 2.5%, respectively, and the corresponding total PAHs and heavy metals were 11.50 and 11.93 and 22.99 and 23.86μg L-1. M. bahia's body weight was negatively correlated with the amount of wash water. Low concentrations of wash water (0-5%) had no significant effect on the reproduction of M. bahia. Although concentrations of 16 PAHs and 8 heavy metals are known, different compounds might react with each other and form more unknown toxic substances, and the measured toxicity comes from synergistic effects between various pollutants. Therefore, future work is needed to clarify other more toxic contaminants in wash water. We highly recommend that wash water be treated before being discharged to the marine environment.