Realistic Exposure Scenarios Research Articles

Insights into mode of action mediated responses following pharmaceutical uptake and accumulation in plants

The reuse of wastewater to meet irrigation requirements and slurries, sludges and manures as fertilisers to meet crop nutrient demands inadvertently introduces human and veterinary-use pharmaceuticals into the agro-ecosystem. This review synthesises recent research, which has observed sub-lethal effects, following pharmaceutical uptake by plants. Potential links between pharmaceutical mode of action and observed sub-lethal effects in the plant were then examined. Common receptors and biological pathways across species suggests a clear need to integrate plant cellular biology into our understanding of the impacts of pharmaceuticals on important plant functions and processes. To help prioritise future research efforts an analysis of shared mammalian and plant biochemical pathways was undertaken to identify classes of pharmaceuticals which may present a greater risk to key plant functions. These included sulfonylurea antihyperglycemics, steroids, opiods, antipsychotic phenothiazines and pharmaceuticals targeting several neurotransmitters shared between mammals and plants (including beta-blockers, antihistamines and benzodiazepines). Whilst a number of pharmaceutical induced sub-lethal effects have been observed, this review highlights the clear need to study a wider range of pharmaceuticals on a broader range of plant species, including cover crops and wild plants, under realistic exposure scenarios, to fully understand the wider implications of pharmaceutical exposure in agro-ecosystems. State-of-the art omics-techniques offer great potential to understand the mode of action of pharmaceuticals in plants and elucidate links between the pharmaceutical intended mode of action and observed plant effects. In addition, studies under co-stress from pharmaceutical exposure and other stressors such as increased temperatures, drought or pests are lacking and present an urgent research need in the face of feeding a growing population under the threats of climate change.

When and How to Conduct Ecotoxicological Tests Using Natural Field-Collected Sediment.

In recent years, the sediment compartment has gained more attention when performing toxicity tests, with a growing emphasis on gaining more ecological relevance in testing. Though many standard guidelines recommend using artificially formulated sediment, most sediment studies are using natural sediment collected in the field. Although the use of natural field-collected sediment contributes to more environmentally realistic exposure scenarios and higher well-being for sediment-dwelling organisms, it lowers comparability and reproducibility among studies as a result of, for example, differences in the base sediment depending on sampling site, background contamination, particle size distribution, or organic matter content. The aim of this methodology contribution is to present and discuss best practices related to collecting, handling, describing, and applying natural field-collected sediment in ecotoxicological testing. We propose six recommendations: (1) natural sediment should be collected at a well-studied site, historically and by laboratory analysis; (2) larger quantities of sediment should be collected and stored prior to initiation of an experiment to ensure a uniform sediment base; (3) any sediment used in ecotoxicological testing should be characterized, at the very least, for its water content, organic matter content, pH, and particle size distribution; (4) select spiking method, equilibration time, and experimental setup based on the properties of the contaminant and the research question; (5) include control-, treated similarly to the spiked sediment, and solvent control sediment when appropriate; and (6) quantify experimental exposure concentrations in the overlying water, porewater (if applicable), and bulk sediment at least at the beginning and the end of each experiment. Environ Toxicol Chem 2024;43:1757-1766. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Potential mechanisms of lung injury and repair after hexavalent chromium [Cr(VI)] aerosol whole-body dynamic exposure

Hexavalent chromium [Cr(VI)], known as "Top Hazardous Substances", poses a significant threat to the respiratory system. Nevertheless, the potential mechanisms of toxicity and the lung's repair ability after injury remain incompletely understood. In this study, Cr(VI) aerosol whole-body dynamic exposure system simulating real exposure scenarios of chromate workers was constructed to evaluate the lung injury and repair effects. Subsequently, miRNA sequencing, mRNA sequencing and metabolomics analyses on lung tissue were performed to explore the underlying mechanisms. Our results revealed that Cr(VI) exposure led to an increase in lactic dehydrogenase activity and a time-dependent decline in lung function. Notably, after 13 w of Cr(VI) exposure, alveolar hemorrhage, thickening of alveolar walls, emphysema-like changes, mitochondrial damage of alveolar epithelial cells and macrophage polarization changes were observed. Remarkably, a two-week repair intervention effectively ameliorated lung function decline and pulmonary injury. Furthermore, significant disruptions in the expressions of miRNAs and mRNAs involved in oxidative phosphorylation, glycerophospholipid metabolism and inflammatory signaling pathways were found. The two-week repair period resulted in the reversal of expression of oxidative phosphorylation related genes, and inhibited the inflammatory signaling pathways. This study concluded that the inhibition of the mitochondrial oxidative phosphorylation pathway and the subsequent enhancement of inflammatory response might be key mechanisms underlying Cr(VI) pulmonary toxicity, and timely cessation of exposure could effectively alleviate the pulmonary injury. These findings shed light on the potential mechanisms of Cr(VI) toxicity and provide crucial insights into the health protection for occupational populations exposed to Cr(VI).

Characterization and distribution of microplastics in the commercial fishes along the coast of Chennai

The emerging major pollutants, microplastics (<5 mm) are being observed ubiquitously in almost all environments. Owing to food safety, the contamination of microplastics in economically important species is gaining attention. This study focuses on the presence of microplastics with an average concentration in Sphyraena jello (11 MPs/individual), Nemipterus japonicus (1.7 MPs/individual), Leiognathus sp., (5.3 MPs/individual), and Sardinella longiceps (3.2 MPs/individual) collected from the coasts of Chennai, India, with different feeding habits and habitats.. The gastrointestinal tract (GIT) of four different species of fishes (n = 160; 40 numbers in each species) from coastal regions is analysed. A total of 607 microplastic particles were found in the GIT, with a mean range of 1.7–11 particles per individual. Among the various forms and colours of microplastic fibres (62.26 %), blue (42.92 %) was dominant. The size fraction of microplastics observed ranged from less than 0.1 mm to 5 mm and about 67.22 % of polymers observed were of polyethylene and polypropylene. The study enables the estimation of the abundance of microplastics of a particular size with high incidence percentage. The ability to forecast environmentally major quantities of microplastics, especially for smaller microplastics, empowers researchers to establish realistic exposure scenarios in forthcoming toxicity investigations. The preliminary research focuses on need to study the abundance of microplastics for the implementation of legislation to stop plastic pollution and the awareness about the impact on the environment and on human health.

The genus Artemia, the nanoplastics, the microplastics, and their toxic effects: a review.

Plastic pollution is a threat to the marine environment, the destination of mismanaged plastic. Due to reduced size, microplastics and nanoplastics (MNPs) can interact with a wide range of organisms. Non-selective filter feeder zooplanktonic microcrustaceans are potential targets for MNP accumulation. Zooplankton is a key group for the food web, linking primary producers to secondary consumers. The genus Artemia has been widely used to investigate the effects of plastic particles on the biota. The present work critically reviewed the ecotoxicological studies about plastic particles and Artemia, pointing out methodological aspects and effects caused by MNPs, highlighting their importance and limitations, and suggesting directions for future research. We analyzed twenty-one parameters into four categories: characteristics of plastic particles, general particularities of brine shrimp, methodologies of the cultures, and toxicological parameters. The principal gaps in the area are the lack of methodological standardization regarding the physicochemical parameters of the particles, the biology of the animals, and culture conditions. Even though few studies performed realistic exposure scenarios, results indicate MNPs as potential harmful contaminants to microcrustaceans. The main effects reported were particle ingestion and accumulation followed by reduced brine shrimp survival/mobility. The present review poses Artemia as suitable animals for investigations concerning the risks of MNP exposure at the individual level and to the ecosystems, although protocol standardization is still needed.

Fetal atomic bomb survivor dosimetry using the J45 series of pregnant female phantoms with realistic survivor exposure scenarios: comparisons to dose estimates in the DS02 system.

A significant source of information on radiation-induced biological effects following in-utero irradiation stems from studies of atomic bomb survivors who were pregnant at the time of exposure in Hiroshima, and to a lesser extent, from survivors in Nagasaki. Dose estimates to the developing fetus for these survivors have been assigned in prior dosimetry systems of the Radiation Effects Research Foundation as the dose to the uterine wall within the non-pregnant adult stylized phantom, originally designed for the dosimetry system DS86 and then carried forward in DS02. In a prior study, a new J45 (Japanese 1945) series of high-resolution phantoms of the adult pregnant female at 8weeks, 15weeks, 25weeks, and 38-weeks post-conception was presented. Fetal and maternal organ doses were estimated by computationally exposing the pregnant female phantom series to DS02 free-in-air cumulative photon and neutron fluences at three distances from the hypocenter at both Hiroshima and Nagasaki under idealized frontal (AP) and isotropic (ISO) particle incidence. In this present study, this work was extended using realistic angular fluences (480 directions) from the DS02 system for seven radiation source terms, nine different radiation dose components, and five shielding conditions. In addition, to explore the effects of fetal position within the womb, four new phantoms were created and the same irradiation scenarios were performed. General findings are that the current DS02 fetal dose surrogate overestimates values of fetal organ dose seen in the J45 phantoms towards the cranial end of the fetus, especially in the later stages of pregnancy. For example, for in-open exposures at 1000m in Hiroshima, the ratio of J45 fetal brain dose to DS02 uterine wall dose is 0.90, 0.82, and 0.70 at 15weeks, 25weeks, and 38-weeks, respectively, for total gamma exposures, and are 0.64, 0.44, and 0.37 at these same gestational ages for total neutron exposures. For organs in the abdominal and pelvic regions of the fetus, dose gradients across gestational age flatten and later reverse, so that DS02 fetal dosimetry begins to underestimate values of fetal organ dose as seen in the J45 phantoms. For example, for the same exposure scenario, the ratios of J45 fetal kidney dose to DS02 uterine wall dose are about 1.09 from 15 to 38weeks for total gamma dose, and are 1.30, 1.56, and 1.75 at 15weeks, 25weeks, and 38weeks, respectively, for the total neutron dose. Results using the new fetal positioning phantoms show this trend reversing for a head-up, breach fetal position. This work supports previous findings that the J45 pregnant female phantom series offers significant opportunities for gestational age-dependent assessment of fetal organ dose without the need to invoke the uterine wall as a fetal organ surrogate.

Cadmium, lead, and mercury in two commercial squid species from the north Adriatic Sea (central Mediterranean): contamination levels and health risk assessment

In this study, lead (Pb), cadmium (Cd), and total mercury (Hg) concentrations in European squids (Loligo vulgaris) and flying squids (Todarodes sagittatus) from the northern Adriatic Sea (Italy) were analyzed. The risk of the Italian population being exposed to potentially hazardous metal concentrations through the consumption of these products was also assessed. Compared to European squids, flying squids showed three times higher total Hg concentrations and one hundred times higher Cd concentrations to the point that more than 6 and 25% of the samples exceeded the maximum Hg and Cd limits established by the current legislation. From the evaluation of dietary exposure levels, it emerged that the consumption of flying squids was associated with the highest Pb intake by children and, consequently, with the lower margin of exposure values in relation to the risk of neurotoxicity (margin of exposure=33). Consumption of flying squids, especially by children, was also associated with higher intakes of Cd, inorganic, and methyl-Hg, which, respectively, accounted for 156, 113, and 23% of the tolerable weekly intakes established for these contaminants at European level. The obtained results raise concern and it may be necessary to provide specific dietary advice on the moderate dietary consumption of some cephalopod species, especially to the youngest and most vulnerable segment of the population. However, besides the highly conservative deterministic method adopted in this study, a refined consumer exposure assessment should be performed through the probabilistic methodology, which is more suitable to represent the real exposure scenario.

Microplastics altered cellular responses, physiology, behaviour, and regeneration of planarians feeding on contaminated prey

Freshwater benthic environments are among the major sinks of microplastics (MPs, < 5 mm) sourced on inland anthropogenic activities. The ecotoxicological effects of MPs on benthic macroinvertebrates have been assessed preferably in collectors, shredders, and filter-feeders, but resulting in insufficient knowledge on the potential trophic transfer and its effects on macroinvertebrates with predator behaviour such as planarians. This work evaluated the behavioural (feeding, locomotion), physiological (regeneration) and biochemical responses (aerobic metabolism, energy reserves, oxidative damage) of the planarian Girardia tigrina after consuming contaminated live prey Chironomus riparius larvae previously exposed to microplastics of polyurethane (PU-MPs; 7–9 μm in size; 375 mg PU-MPs/kg). After the feeding period (3 h), planarians consumed 20 % more contaminated prey than uncontaminated prey, probably related to increased curling/uncurling movements of larvae (that might be more appellative to planarians). Histological analysis revealed planarians' limited intake of PU-MPs, mainly detected near the pharynx. The consumption of contaminated prey (and intake of PU-MPs) did not result in oxidative damage but slightly increased the aerobic metabolism and energy reserves which show that the consumption of more prey was sufficient to cope with the potential adverse effects of internalized MPs. Moreover, no effects were observed in the locomotion of planarians in good agreement with the hypothesis of sufficient energy acquired by the exposed planarians. Despite the previous, it seems that the energy acquired was not allocated for planarians' regeneration since a significant delay in the regeneration of the auricles was observed for planarians feeding on contaminated prey. Therefore, further studies should be performed considering the potential long-term effects (i.e., reproduction/fitness) and the effects of MPs that might result from continuous feeding on contaminated prey, representing a more realistic exposure scenario.

Physiologically-Based Kinetic Modeling Predicts Similar In Vivo Relative Potency of Senecionine N-Oxide for Rat and Human at Realistic Low Exposure Levels.

This study aims to determine if previously developed physiologically-based kinetic (PBK) model in rat can be modified for senecionine (SEN) and its N-oxide (SENO), and be used to investigate potential species differences between rat and human in relative potency (REP) of the N-oxide relative to the parent pyrrolizidine alkaloid (PA). In vitro derived kinetic parameters including the apparent maximum velocities (Vmax ) and Michaelis-Menten constants (Km ) for SENO reduction and SEN clearance are used to define the PBK models. The rat model is validated with published animal data, and the toxicokinetic profiles of SEN from either orally-administered SENO or SEN are simulated. REP values of SENO relative to SEN amount to 0.84 and 0.89 in rat and human, respectively. The REP value can be dose- and species-dependent, with the values for rat and human being comparable at low realistic exposure scenarios. In summary, PBK modeling serves as a valuable New Approach Methodology (NAM) tool for predicting REP values of PA-N-oxides and may actually result in more accurate REP values for human risk assessment than what would be defined using in vivo animal experiments.

СОДЕРЖАНИЕ ХЛОРОФОРМА В КРОВИ НАСЕЛЕНИЯ КАК БИОМАРКЕР ЭКСПОЗИЦИИ ПОБОЧНЫМИ ПРОДУКТАМИ ДЕЗ-ИНФЕКЦИИ ПИТЬЕВОЙ ВОДЫ

The modern methodological approaches, such as biomonitoring, could be used to improve the evidence base reliability and reduce uncertainty under chemicals health risk assessments and hygienic rationing. The aim of the study was to substantiate using the results of chloroform determination in human blood as a biomarker of exposure to drinking water disinfection byproducts under republican conditions. A gas chromatography-mass spectrometry meth-od for determination of chloroform in whole blood based on the use of acetoni-trile as solvent and additional extraction of chloroform from acetonitrile su-pernatant by small amounts of hexane was developed. Chloroform concentra-tions in the blood of population at the territories supplied with chlorinated drinking water are significantly higher than that of population at the territories supplied with water without chlorination (0.03–0.54 ng/ml, P95 0.27 ng/ml versus 0.00–0.37 ng/ml, P95 0.13 ng/ml respectively). A proposed linear de-pendence model enables to predict the chloroform blood level in the exposed population based on water concentrations and vice versa. We recommend the determination of chloroform in the whole blood of the population as an in-formative biomarker of cumulative exposure, reflecting real exposure scenarios for the preceding period of time, based on identified trends.

Analysis of the literature shows a remarkably consistent relationship between size and abundance of microplastics across different environmental matrices

Microplastics come in a variety of shapes, polymer types and sizes. Due to the lack of a harmonised approach to analyse and quantify microplastics, there are huge disparities in size detection limits and size classifications used in the literature. This has caused large variations in reported microplastic data and has made comparing microplastic abundance between studies extremely challenging. Herein, we applied a simple mathematical approach that allows for a meaningful comparison between size and abundance (number of particles) of microplastics irrespective of the size classifications used. This method was validated using two separate datasets (microplastics in air and sediment) and applied to re-analyse 127 publications reporting microplastics in various environmental matrices. We demonstrate a strong negative linear relationship between microplastic concentrations and their sizes with comparable slopes across all matrices. Using this method, it is possible to compare the concentration of microplastics of various sizes between studies. It also allows estimation of the abundance of microplastics of a specific size where data are not available. This enables researchers to predict environmentally relevant concentrations of microplastics (particularly for smaller microplastics) and provide realistic exposure scenarios in future toxicity studies, which will greatly improve our understanding of the risks that microplastics pose to living organisms.

Simplified modeling of implanted medical devices with metallic filamentary closed loops exposed to low or medium frequency magnetic fields

Background and objectivesElectric currents are induced in implanted medical devices with metallic filamentary closed loops (e.g., fixation grids, stents) when exposed to time varying magnetic fields, as those generated during certain diagnostic and therapeutic biomedical treatments. A simplified methodology to efficiently compute these currents, to estimate the altered electromagnetic field distribution in the biological tissues and to assess the consequent biological effects is proposed for low or medium frequency fields. MethodsThe proposed methodology is based on decoupling the handling of the filamentary wire and the anatomical body. To do this, a circuital solution is adopted to study the metallic filamentary implant and this solution is inserted in the electromagnetic field solution involving the biological tissues. The Joule losses computed in the implant are then used as a forcing term for the thermal problem defined by the bioheat Pennes’ equation. The methodology is validated against a model problem, where a reference solution is available. ResultsThe proposed simplified methodology is proved to be in good agreement with solutions provided by alternative approaches. In particular, errors in the amplitude of the currents induced in the wires result to be always lower than 3%. After the validation, the methodology is applied to check the interactions between the magnetic field generated by different biomedical devices and a skull grid, which represents a complex filamentary wire implant. ConclusionsThe proposed simplified methodology, suitable to be applied to closed loop wires in the low to intermediate frequency range, is found to be sufficiently accurate and easy to apply in realistic exposure scenarios. This modeling tool allows analyzing different types of small implants, from coronary and biliary duct stents to orthopedic grids, under a variety of exposure scenarios.

Adapting classic paradigms to analyze alterations of shoal-wide behavior in early-life stages of zebrafish (Danio rerio) – A case study with fluoxetine

Given the strong increase in prescription of neuroactive pharmaceuticals, neurotoxicity has received growing concern in science and the public. Regulatory requirements stimulated the development of new methods to evaluate the risk of neurotoxic substances for humans and the environment, and, with respect to potential damage to aquatic ecosystems, a variety of behavior-based assays have been proposed for neurotoxicity testing, most of which, however, are restricted to changes in the behavior of individual fish. Since many fish species form shoals under natural conditions, this may cause important aspects of behavior to be overlooked and there is a need for behavior assays integrating individual behavior with behavior of the entire swarm. In order to combine more environmentally realistic sub-chronic exposure scenarios with undistorted social behavior and animal welfare considerations, two behavioral assays are proposed that might be integrated into early-life stage toxicity studies according to OECD TG 210, which are commonly run for a multitude of regulations: To this end, protocols for a novel tank test and a predator response assay were adapted to also record the behavior of free-swimming zebrafish (Danio rerio) juveniles within shoals. Comparisons of the diving response (novel tank) or the shoal's coherence and position relative to the stimulus (predator) with control groups allow conclusions about the anxiety state of the fish, which might well have an impact on survival chances in the wild. As a model substance, the antidepressant fluoxetine ((RS)-N-Methyl-3-phenyl-3-(4-trifluoromethylphenoxy)propylamine) produced adverse effects down to concentrations three orders of magnitude below the EC10 from acute fish embryo toxicity tests according to OECD TG 236. With the integration of such behavior tests into OECD TG 210, important population-relevant information on potential neurotoxicity can be collected without increasing the number of experimental animals.

Accumulation of microplastics and Tcep pollutants in agricultural soil: Exploring the links between metabolites and gut microbiota in earthworm homeostasis

Agricultural soil contamination with plastic film has become a critical global environmental problem, requiring greater research on the possible occurrence and biological risk of microplastics (MPs) and their additives in soil ecosystems. The presence of MPs and tris (2-chloroethyl) phosphate (Tcep) in agricultural soil was investigated at nine sites in the present study. Polyethylene MPs (PE-MPs) and Tcep were found at all nine sites. To study co-exposure effects on soil microbiota and earthworms, and to mimic a realistic exposure scenario, 0.05 % (w/w) PE-MPs with three particle size ranges were combined with Tcep (1.0 mg/kg). After 28 days of exposure, there was no indication that added PE-MPs and/or Tcep significantly affected the soil microbial community structure. In earthworms, size-selective intake, digestion and egestion of PE-MPs may occur, with Tcep co-exposure affecting the residual Tcep concentration in earthworm intestines (3.52–9.31 μg/g dw). Long-term earthworm PE-MPs intake caused intestinal damage, and Tcep co-exposure increased oxidative stress, thereby influencing their feeding behavior and growth, resulting in weight loss (3.42 %–14.96 %), especially for the most common PE-MPs sizes (0–300 μm). High performance liquid chromatography-mass spectrometry (LC-MS) was used for metabolomic analysis, revealing the significant up-regulation of citrate (p < 0.001) and down-regulation of l-glutamate (p < 0.05) in co-exposure groups. Co-exposure resulted in the alteration of most metabolic pathways, thereby impairing nervous, digestive and excretory systems in the earthworm, with an associated decrease in amino acid metabolism and changes in tricarboxylic acid (TCA) cycle intermediates. Gut microbiota, such as Proteobacteria (Verminephrobacter and Bradyrhizobium) and Firmicutes (Bacillus), are critically important in maintaining earthworm metabolic homeostasis, particularly for the TCA cycle and amino acid metabolism. Overall, MPs and Tcep co-exposure in agricultural soil enhanced their toxicity to earthworms and may potentially endanger the development of agricultural sustainability.

Pathogenicity of La Jolla Virus in Drosophila suzukii following Oral Administration.

Drosophila suzukii (Ds) is an invasive pest insect that causes severe and widespread damage to soft fruit crops. Chemical control based on topical insecticides is inefficient and harmful to consumers and the environment, prompting interest in the development of biological control measures such as insect viruses with narrow host specificity. We previously described a strain of La Jolla virus (LJV) found in moribund Ds specimens in Germany. We demonstrated a pathogenic effect following the intrathoracic injection of LJV into adult Ds flies. However, the development of an effective biocontrol product based on LJV would require the characterization of (1) virulence following oral delivery, particularly in larvae, and (2) stability under different pH and temperature conditions reflecting realistic exposure scenarios. Here we describe the pathogenicity of LJV following oral delivery to Ds adults and larvae. The oral infection of Ds adults with LJV reduced survival in a concentration-dependent manner, whereas the oral infection of Ds larvae caused the arrest of development during pupation. LJV remained stable and infectious following exposure to a broad pH range and different temperatures. We, therefore, demonstrated that LJV is promising as a candidate biological control agent against Ds.

Global meta‐analysis reveals diverse effects of microplastics on freshwater and marine fishes

AbstractMicroplastic debris is a globally ubiquitous pollutant with diverse consequences for fishes, ranging from severe negative impacts to neutral, or even, positive effects. In the present study, we conducted a systematic review and meta‐analysis of experimental and observational studies to test for the impacts of microplastic exposure on freshwater, estuarine and marine fishes across diverse taxonomies, geographies, and ecosystem contexts. We report evidence for the detrimental, albeit variable, impacts of microplastics, including reduced consumption, altered feeding behavior, obstructed digestion and assimilation, decreased growth, and compromised immunity. By contrast, microplastics appeared to invoke neutral responses in several other ecological and physiological processes, such as body condition, fecundity, hatching success and survival. The results from this study also point to the mismatch between the types, shapes, and sizes of microplastics investigated in experimental settings versus those found in fish in the wild, as well as a striking difference between the 728 fish species investigated for microplastic contamination in the wild versus the only 22 fish species evaluated for the effects of microplastics in the laboratory. The present study reiterates the necessity for more consistent methodological approaches to analyzing and reporting the effects of microplastic exposure, including greater taxonomic breadth and the use of environmentally relevant polymers in future studies. Furthermore, model simulations that explore individual‐ and population‐level implications of realistic exposure scenarios are needed. Overall, the current weight of evidence supports continued management and policy actions to reduce the microplastic production, use, and release into the world's waters.

Radiological risk assessment to marine biota from exposure to NORM from a decommissioned offshore oil and gas pipeline

Scale residues can accumulate on the interior surfaces of subsea petroleum pipes and may incorporate naturally occurring radioactive materials (NORM). The persistent nature of ‘NORM scale’ may result in a radiological dose to the organisms living on or near intact pipelines. Following a scenario of in-situ decommissioning of a subsea pipeline, marine organisms occupying the exteriors or interiors of petroleum structures may have close contact with the scale or other NORM-associated contaminated substances and suffer subsequent radiological effects. This case study used radiological dose modelling software, including the ERICA Tool (v2.0), MicroShield® Pro and mathematical equations, to estimate the likely radiological doses and risks of effects from NORM-contaminated scale to marine biota from a decommissioned offshore oil and gas pipeline. Using activity concentrations of NORM (226Ra, 210Po, 210Pb, 228Ra, 228Th) from a subsea pipeline from Australia, environmental realistic exposure scenarios including radiological exposures from both an intact pipe (external only; accounting for radiation shielding by a cylindrical carbon steel pipe) and a decommissioned pipeline with corrosive breakthrough (resulting in both internal and external radiological exposure) were simulated to estimate doses to model marine organisms. Predicted dose rates for both the external only exposure (ranging from 26 μGy/h to 33 μGy/h) and a corroded pipeline (ranging from 300 μGy/h to 16,000 μGy/h) exceeded screening levels for radiological doses to environmental receptors. The study highlighted the importance of using scale-specific solubility data (i.e., Kd) values for individual NORM radionuclides for ERICA assessments. This study provides an approach for conducting marine organism dose assessments for NORM-contaminated subsea pipelines and highlights scientific gaps required to undertake risk assessments necessary to inform infrastructure decommissioning planning.

Predicting Combined Effects of Chemical Stressors: Population-Level Effects of Organic Chemical Mixtures with a Dynamic Energy Budget Individual-Based Model.

Most regulatory ecological risk-assessment frameworks largely disregard discrepancies between the laboratory, where effects of single substances are assessed on individual organisms, and the real environment, where organisms live together in populations and are often exposed to multiple simultaneously occurring substances. We assessed the capability of individual-based models (IBMs) with a foundation in the dynamic energy budget (DEB) theory to predict combined effects of chemical mixtures on populations when they are calibrated on toxicity data of single substances at the individual level only. We calibrated a DEB-IBM for Daphnia magna for four compounds (pyrene, dicofol, α-hexachlorocyclohexane, and endosulfan), covering different physiological modes of action. We then performed a 17-week population experiment with D. magna (designed using the DEB-IBM), in which we tested mixture combinations of these chemicals at relevant concentrations, in a constant exposure phase (7-week exposure and recovery), followed by a pulsed exposure phase (3-day pulse exposure and recovery). The DEB-IBM was validated by comparing blind predictions of mixture toxicity effects with the population data. The DEB-IBM accurately predicted mixture toxicity effects on population abundance in both phases when assuming independent action at the effect mechanism level. The population recovery after the constant exposure was well predicted, but recovery after the pulse was not. The latter could be related to insufficient consideration of stochasticity in experimental design, model implementation, or both. Importantly, the mechanistic DEB-IBM performed better than conventional statistical mixture assessment methods. We conclude that the DEB-IBM, calibrated using only single-substance individual-level toxicity data, produces accurate predictions of population-level mixture effects and can therefore provide meaningful contributions to ecological risk assessment of environmentally realistic mixture exposure scenarios. Environ Toxicol Chem 2022;41:2240-2258. © 2022 SETAC.

Chronic level of exposures to low-dosed MoS2 nanomaterials exhibits more toxic effects in HaCaT keratinocytes

Molybdenum disulfide nanomaterials (MoS2 NMs) have shown significant role as photocatalysts, lubricating agents and sterilant due to their remarkable physicochemical properties. Because of the increasing demand for MoS2 NMs in numerous industrial domains, greater occupational exposure and subsequent NMs release into environment would be unavoidable. However, much efforts have been made to uncover the biological effects of NMs at unrealistic high concentration or acute duration, placing constraints on setting the realistic occupational exposure thresholds with confidence. In order to fill the current knowledge gap, this study aimed to evaluate the nanotoxicity of MoS2 NMs with or without surface defects under the more realistic exposure mode. Noteworthily, the artificial sweat transformed-occupational exposure-cytotoxicity investigation of MoS2 NMs was established as the main studied line. And the high cellular internalization and augmented oxidative stress triggered by surface defect could be recognized as the main factors for triggering serious cellular damage. Moreover, the HaCaTs exhibited loss of cell membrane integrity, dysfunction of mitochondria, disorder of endoplasmic reticulum and damages of nuclei after chronic exposure, compared with acute exposure. The study provided closely realistic exposure scenarios for NMs which exhibited significant difference from acute toxic investigation, enriching understanding towards real environmental safety of NMs.

Analysis of Numerical Artifacts Using Tetrahedral Meshes in Low Frequency Numerical Dosimetry

Anatomical realistic voxel models of human beings are commonly used in numerical dosimetry to evaluate the human exposure to low-frequency electromagnetic fields. The downside of these models is that they do not correctly reproduce the boundaries of curved surfaces. The stair-casing approximation errors introduce computational artifacts in the evaluation of the induced electric field and the use of post-processing filtering methods is essential to mitigate these errors. With a suitable exposure scenario, this paper shows that tetrahedral meshes make it possible to remove stair-casing errors. However, using tetrahedral meshes is not a sufficient condition to completely remove artifacts, because the quality of the tetrahedral mesh plays an important role. The analyses carried out show that in real exposure scenarios, other sources of artifacts cause peak values of the induced electric field even with regular meshes. In these cases, the adoption of filtering techniques cannot be avoided.