Biological effects of tris (1-chloro-2-propyl) phosphate (TCPP) on immunity in mussel Mytilus galloprovincialis

Exploring the immune resilience of Mediterranean mussels: recent advances and future directions

The Mediterranean mussel (Mytilus galloprovincialis) is a key species in European aquaculture, known for its economic and societal importance, particularly as a primary source of income for local fisheries in European coastal areas. While historically resilient to the mass mortality events that have affected other bivalve species, M. galloprovincialis may face increasing threats from emerging pathogens, including bacteria, viruses, and eukaryotic parasites. These microorganisms, often opportunistic, pose heightened risks in the current climate change scenario, where heatwaves are becoming increasingly frequent and the persistent presence of pollutants is suspected to impair the functional response of hemocytes. Over the past decade, significant advancements in immunological research have provided deeper insights into the cellular and molecular mechanisms underlying the robust defense system of M. galloprovincialis, which allows this species to efficiently cope with a broad range of infections. By analyzing the scientific literature published on mussel immunology over the past ten years, this review consolidates current knowledge on the immune system of the Mediterranean mussel. We place a particular focus on the cellular and molecular components involved in the recognition and elimination of microbial pathogens and discuss how the most recent discoveries may inform improved management and disease mitigation strategies for Mediterranean mussel farming in the in the years to come.

Toxicity of organophosphate flame retardant in marine rotifers: Evidence from the population, individual, biochemical and molecular levels

Tris (1-chloro-2-propyl) phosphoric acid (TCPP), a widely used organophosphate flame retardant, has been detected in various aquatic environments due to its extensive industrial application. TCPP is well-known to negatively impact large aquatic organisms. However, the effects of TCPP on zooplankton remain poorly understood. This study explored the ecological risk of TCPP in low-trophic marine organisms by evaluating the marine rotifer Brachionus plicatilis at the molecular, biochemical, individual, and population levels after exposure to TCPP concentrations of 14.79, 44.37, and 73.94 μM. Results showed that exposure to TCPP inhibited body size, feeding behavior, life expectancy, generation time, net reproductive rate, reproduction rate, and population growth rate of rotifers, thus impairing their growth, survival, reproduction, and population expansion. Environmental concentrations surpassing 0.031 μM and 0.23 μM adversely impact rotifer reproduction and survival, respectively. Biochemically, TCPP induced oxidative stress, increased amylase activity, decreased lipase activity, and total protein content. Transcriptome analysis revealed that TCPP could induce abnormal mitochondrial function, impaired energy metabolism, programmed cell death by generating excessive reactive oxygen species, and affect cellular DNA replication. Results indicate that TCPP disrupts homeostasis in rotifers by inducing oxidative stress, significantly suppressing individual and population parameters. These findings provide critical insights for assessing the ecological risk posed by TCPP to zooplankton and the stability of aquatic ecosystems.

Tris(1-chloro-2-propyl) phosphate enhances the adverse effects of biodegradable polylactic acid microplastics on the mussel Mytilus coruscus

Microplastics (MPs) and organophosphate flame retardants (OPFRs) have recently become ubiquitous and cumulative pollutants in the oceans. Since OPFRs are added to or adsorbed onto MPs as additives, it is necessary to study the composite contamination of OPFRs and MPs, with less focus on bio-based PLA. Therefore, this study focused on the ecotoxicity of the biodegradable MP polylactic acid (PLA) (5 μm, irregular fragments, 102 and 106 particles/L), and a representative OPFRs tris(1-chloro-2-propyl) phosphate (TCPP, 0.5 and 50 μg/L) at environmental and high concentrations. The mussel Mytilus coruscus was used as a standardised bioindicator for exposure experiments. The focus was on examining oxidative stress (catalase, CAT, superoxide dismutase, SOD, malondialdehyde, MDA), immune responses acid (phosphatase, ACP, alkaline phosphatase, AKP, lysozyme, LZM), neurotoxicity (acetylcholinesterase, AChE), energy metabolism (lactate dehydrogenase, LDH, succinate dehydrogenase, SDH, hexokinase, HK), and physiological indices (absorption efficiency, AE, excretion rate, ER, respiration rate, RR, condition index, CI) after 14 days exposure. The results of significantly increased oxidative stress and immune responses, and significantly disturbed energy metabolism and physiological activities, together with an integrated biomarker response (IBR) analysis, indicate that bio-based PLA MPs and TCPP could cause adverse effects on mussels. Meanwhile, TCPP interacted significantly with PLA, especially at environmental concentrations, resulting in more severe negative impacts on oxidative and immune stress, and neurotoxicity. The more severe adverse effects at environmental concentrations indicate higher ecological risks of PLA, TCPP and their combination in the real marine environment. Our study presents reliable data on the complex effects of bio-based MP PLA, TCPP and their combination on marine organisms and the environment.

Nano titanium dioxide alleviates the toxic effects of tris (2-chloropropyl) phosphate on the digestive gland and hemolymph of thick-shell mussel Mytilus coruscus

In the marine environment, nanoparticles play a role in adsorbing and catalytically degrading organic pollutants, thereby mitigating their toxic effects on aquatic organisms. This study aimed to investigate the impact of nano titanium dioxide (nTiO2) and tris (2-chloropropyl) phosphate (TCPP) on the hemolymph and digestive function of the thick-shell mussel Mytilus coruscus. Mussels were divided into a control group, a group exposed to TCPP alone, a group exposed to a combination of TCPP and 0.5 mg/L nTiO2, and a group exposed to a combination of TCPP and 1 mg/L nTiO2. After 14 days of exposure, oxidative stress responses, including superoxide dismutase (SOD) activity and malondialdehyde (MDA) content, immune defense responses, including acid phosphatase (ACP) and alkaline phosphatase (AKP) activities, and gene expression, including HSP70 expression, were measured in the hemolymph and digestive glands of the mussels. Compared to the control group, mussels solely exposed to 100 μg/L TCPP exhibited a significant reduction in SOD activity in the hemolymph. When TCPP was co-exposed with 0.5 mg/L nTiO2, there were significant increases in MDA content and AKP activity in both the digestive gland and hemolymph compared to the control group. Upon co-exposure of TCPP with 1 mg/L nTiO2, MDA content and AKP activity in the digestive gland significantly decreased, while SOD, ACP, and AKP activity in the hemolymph significantly increased and MDA content significantly decreased, returning to the control group levels. Furthermore, in the combined exposure, HSP70 gene expression significantly decreased as the nTiO2 concentration increased from 0.5 mg/L to 1 mg/L. In summary, TCPP impacted the hemolymph and digestive function of mussels, whereas a concentration of 1 mg/L nTiO2 effectively alleviated the toxic effects of TCPP. This study is crucial for assessing the ecological risks of nanoparticles and emerging organic pollutants in marine environments, and provides new insights into the interaction between nTiO2 and TCPP, as well as the influence of nTiO2 concentration on mitigating TCPP toxicity.

Toxicity assessment of microplastics within the Loire River in the clam Corbicula fluminea exposed to environmentally relevant exposure conditions

The dispersed pollution caused by microplastics (MPs) represents a current and global concern. While the fragmentation of plastic debris into smaller particles occurs in rivers, little MP research is done on freshwater species and is published compared to the marine environment. The Loire River is the longest river in France and is subject to moderate to high anthropic pressure while it represents major societal and economic issues. However, there are not many studies that have been put forward with regards to the effect of environmental MPs (EMPs) on aquatic organisms and no policies have been enacted to monitor the plastic pollution. In this study, freshwater bivalves, Corbicula fluminea, were exposed for 21 days to environmentally relevant concentrations of a mixture of <200 µm MPs generated from plastic litter collected directly along the banks of the Loire River. This mixture was composed of 40% polyethylene (PE), 40% polypropylene (PP), 10% polyethylene terephthalate (PET) and 10% polyvinylchloride (PVC) (mass percentage). Ecotoxicological effects were assessed from the individual to the molecular levels on several endpoints: condition index, filtration efficiency, enzyme activities, lipid peroxidation, energy reserves and gene expression. The ingestion of EMPs caused damages at the biochemical level. Indeed, we reported an increase in catalase activity in gills and digestive mass, a decrease in TBARs in gills, a decrease in acetylcholinesterase activity in the digestive mass, a decrease of glycogen and lipid contents in the whole organisms and a significant induction of the expression of gst, cat, mp, acp genes. The current results suggest therefore that long-term exposure to realistic doses of EMPs causes toxicity towards freshwater benthic biota. The analysis of biomarker activities and the analysis of gene expression are complementary to prevent the effects of a plastic contamination at higher biological levels in aquatic organisms.

Remediation of soil contaminated with tris-(1-chloro-2-propyl) phosphate using plant and microorganism combined technology: A greenhouse experiment

The remediation of tris-(1-chloro-2-propyl) phosphate (TCIPP) -contaminated soil by the plant (ryegrass, Lolium perenne L.) and microorganism (TCIPP degrading bacteria, Ochrobactrum sp. DT-6) alone or in combination was investigated in this study. TCIPP can inhibit the growth and development of ryegrass and there is a clear dose-effect relationship. Inoculation with strain DT-6 was able to mitigate the toxic influence of TCIPP on ryegrass, but this mitigation effect was not significant. TCIPP in the soil was relatively easy to be uptaken by the ryegrass roots and migrated to the shoots. Furthermore, as the soil TCIPP concentration rose, the concentration of TCIPP in ryegrass also exhibited a corresponding increase. The biological concentration factor (BCF) ranged from 0.33 to 1.88 and the biological accumulation coefficient (BAC) ranged from 0.54 to 3.98. They all significantly decreased with higher soil TCIPP concentrations. The translocation factor (TF) values ranged from 1.55 to 2.34. Inoculation of strain DT-6 significantly reduced TCIPP concentrations in ryegrass roots, stems, and leaves as well as the values of BAC and BCF under low and medium TCIPP concentration treatment conditions, but the effect on TF values was not remarkable. The planting of ryegrass significantly raised the elimination of TCIPP from the soil to 64.6-93.3%, but the influence of inoculation with strain DT-6 on the remediation effect by ryegrass was not significant. The percentage contribution of phytoextraction to the elimination of TCIPP from soils ranged from only 0.64-5.23%.

Organophosphate ester exposure among Chinese waste incinerator workers: Urinary levels, risk assessment and associations with oxidative stress

Organophosphate esters (OPEs), which are frequently used as flame retardants and plasticizers in versatile products, are readily released to the external environment. Although workers at municipal waste incineration plants may be extensively exposed to OPEs, only scarce health monitoring and risk assessments have been conducted in this population. In this study, we investigated the levels of eight metabolites of organophosphate esters (mOPEs) and the oxidative stress marker 8-hydroxy-2-deoxyguanosine (8-OHdG) in urine samples from 73 waste incinerator workers and 97 general residents from Shenzhen, China between September 2016 and June 2017. The overall detection rate of mOPEs was 82.2 %-100 %, and higher concentrations of di-p-cresyl phosphate and chlorinated mOPEs [bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2propyl) phosphate (BCIPP), bis(1,3-dichloro-2-propyl) phosphate) (BDCIPP)] were found among incinerator workers than among general residents. The incinerator workers also showed significantly higher levels of 8-OHdG than general residents, but the measured levels of most mOPEs were not significantly correlated with the level of 8-OHdG; this may be because co-exposure to multiple toxic compounds can lead to oxidative stress. Risk assessment using Monte Carlo simulations revealed that 95 % of the incinerator workers were free from non-carcinogenic effects due to OPEs exposure (hazard index = 0.27, 95 % CI: 0.09, 0.77). However, the carcinogenic risk of tris(2-chloroethyl) phosphate (TCEP) for incinerator workers was between 10-6 and 10-4. These results indicate that incinerator workers are extensively exposed to OPEs, and better protective measures need to be implemented.

Parental whole life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) disrupts embryonic development and thyroid system in zebrafish offspring

Tris (2-chloroethyl) phosphate (TCEP), an emerging environmental pollutant, has been frequently detected in natural waters. The objective of this study was to investigate possible parental transfer of TCEP and transgenerational effects on the early development and thyroid hormone homeostasis in F1 larvae following parental whole life-cycle exposure to TCEP. To this end, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations (0.8, 4, 20 and 100 μg/L) of TCEP for 120 days until sexual maturation. Parental exposure to TCEP resulted in significant levels of TCEP, developmental toxicity including decreased survival and final hatching rates, accelerated heart rate and elevated malformation rate, as well as induction of oxidative stress and cell apoptosis in F1 offspring. In F1 eggs, declined thyroxin (T4) levels were observed, consistent with those in plasma of F0 adult females, indicating the maternal transfer of thyroid endocrine disruption to the offspring. In addition, mRNA levels of several genes along the hypothalamic-pituitary-thyroid (HPT) axis were significantly modified in F1 larvae, which could be linked to transgenerational developmental toxicity and thyroid hormone disruption. For the first time, we revealed that the parental exposure to environmentally relevant levels of TCEP could cause developmental toxicity and thyroid endocrine disruption in subsequent unexposed generation.

nTiO2 alleviates the toxic effects of TCPP on mussels by adjusting respiratory metabolism and gut microbiota

As a good carrier of contaminants, nanotitanium dioxide (nTiO₂) can absorb organic pollutants, producing toxicological effects on organisms. However, the complex effects of nTiO₂ with contaminants on marine mussels are still unclear. In this study, we exposed mussels to tris (2-chloropropyl) phosphate (TCPP) 100 μg/L (T1), 0.5 mg/L nTiO₂ + 100 μg/L TCPP (T2), 1.0 mg/L nTiO₂ + 100 μg/L TCPP (T3) and control (0 nTiO₂ + 0 μg/L TCPP) treatments, and assessed the combined effects of TCPP with nTiO₂ on the thick-shelled mussel Mytilus coruscus by detecting the activities of gill pyruvate kinase (PK), hexokinase (HK), lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH), also gill acetylcholine (Ach) and muscle lactic acid (LD) contents and gut microbiota after 14-d exposure. Compared with the control group, PK activity was increased significantly, but SDH, LDH activities and LD content were decreased significantly in T1, with the addition of nTiO₂, there were not significantly different in T3. However, Ach content in T3 was significantly higher than the control and T1. Moreover, KEGG of the gut microbiota via 16 s rRNA sequencing showed that most pathways returned to the control level in T3. The results showed that TCPP affected the respiratory metabolism of mussels, changed the community structure of intestinal microflora in mussels, and nTiO₂ alleviated the toxicity of TCPP. Our study provides new insights for ecological risk assessment of TCPP in bivalves in the complex aquatic environment and the novel role of nTiO₂ in regulating the toxicity of TCPP.

Genotoxic and Toxic Effects of The Flame Retardant Tris(Chloropropyl) Phosphate (TCPP) in Human Lymphocytes, Microalgae and Bacteria

Tris(chloropropyl) phosphate (TCPP) is a characteristic and widely used organophosphorus flame retardant. TCPP is comprised of four isomers and the most abundant is tris(1-chloro-2-propyl) phosphate. TCPP can be released into the environment, with potential impacts on living organisms and humans due to its extensive industrial use. Aiming to assess the potential risks of TCPP on human health and the environment, its toxic and genotoxic effects-using organisms from different trophic levels, i.e., bacteria, green microalgae, and human cells-were investigated. TCPP exposure at nominal concentrations of 10, 20, 30 and 40 μg mL^-1 was studied to identify the potential risk of inducing genotoxic effects in cultured human lymphocytes. Treatment with 30 and 40 μg mL^-1 of TCPP induced marginally significant micronuclei (MN) frequencies as well as cytotoxic effects. Freshwater microalgae species treated with TCPP (0.5, 1, 10, 20 and 50 μg L^-1) showed different growth rates over time. All the tested microalgae species were adversely affected after exposure to TCPP during the first 24 h. However, differences among the microalgae species' sensitivities were observed. In the case of the freshwater species, the most sensitive was found to be Chlorococcum sp. The marine algal species Dunaliella tertiolecta and Tisochrysis lutea were significantly affected after exposure to TCPP. The effects of TCPP on Aliivibrio fischeri that were observed can classify this flame retardant as a "harmful" compound. Our results suggest a potential risk to aquatic organisms and humans from the wide utilization of TCPP and its consequent release into the environment. These results highlight that further research should be conducted to investigate the effects of TCPP individually and in combination with other organophosphorus flame retardants in various organisms. In addition, the concern induced by TCPP points out that measures to control the introduction of TCPP into the environment should be taken.

Sub-chronic ecotoxicity of triphenyl phosphate to earthworms (Eisenia fetida) in artificial soil: Oxidative stress and DNA damage

As a flame retardant, triphenyl phosphate (TPHP) is commonly added to various daily products. Due to its easy diffusion, TPHP pollution has become a global concern. Despite the wide focus on environmental risk, the sub-chronic ecotoxicity of TPHP in soil organisms remains unclear. In this study, the artificial soil exposure method was used to analyze the oxidative stress and DNA damage in earthworms with 0, 20, 40, 60 and 80 mg/kg TPHP treatments through the response of reactive oxygen species (ROS), antioxidant and detoxifying enzymes, malondialdehyde (MDA) and olive tail moment (OTM) at 7, 14, 21 and 28 days. Throughout the experimental period, the results showed that the ROS content in earthworms treated with 20, 40, 60 and 80 mg/kg TPHP treatments increased by 9.43-18.37 %, 6.07-25.73 %, 7.71-42.61 % and 8.22-46.70 %, respectively, compared to the control treatment. Meanwhile, the activities of antioxidant and detoxification enzymes in earthworms with all TPHP treatments were significantly activated after exposure for 7 and 14 days, and then inhibited at 21 and 28 days. Despite the protection of antioxidant enzymes and detoxification enzymes, MDA content in earthworms with the 20 mg/kg treatment still significantly increased at 7 and 14 days of exposure, as well as in the other three treatments. Compared to the control treatment, the obviously higher OTM values in earthworms with TPHP treatments possibly indicated a genotoxicity of TPHP in earthworms. Furthermore, the integrated biomarker response index (IBRv2) revealed that earthworms showed an obvious biochemical response TPHP-contaminated soil, which was strongly correlated with TPHP concentrations and exposure time. This study provides insights into the TPHP hazard in the soil environment and offers a reference to assess its environmental risk to soil ecosystems.

Hormesis and insects: Effects and interactions in agroecosystems

Insects in agroecosystems contend with many stressors - e.g., chemicals, heat, nutrient deprivation - that are often encountered at low levels. Exposure to mild stress is now well known to induce hormetic (stimulatory) effects in insects, with implications for insect management, and ecological structure and function in agroecosystems. In this review, we examine the major ecological niches insects occupy or guilds to which they belong in agroecosystems and how hormesis can manifest within and across these groups. The mechanistic underpinnings of hormesis in insects are starting to become established, explaining the many phenotypic hormetic responses observed in insect reproduction, development, and behavior. Whereas potential effects on insect populations are well supported in laboratory experiments, field-based hypothesis-driven research on hormesis is greatly lacking. Furthermore, because most ecological paradigms are founded within the context of communities, entomological agroecologists interested in hormesis need to 'level up' and test hypotheses that explore effects on species interactions, and community structure and functioning. Embedded in this charge is to continue experimentation on herbivorous pest species while shifting more focus towards insect natural enemies, pollinators, and detritivores - guilds that play crucial roles in highly functioning agroecosystems that have been understudied in hormesis research. Important areas for future insect agroecology research on hormesis are discussed.

Hormetic dose responses induced by organic flame retardants in aquatic animals: Occurrence and quantification

The organic flame retardants (OFRs) have attracted global concerns due to their potential toxicity and ubiquitous presence in the aquatic environment. Hormesis refers to a biphasic dose response, characterized by low-dose stimulation and high-dose inhibition. The present study provided substantial evidence for the widespread occurrence of OFRs-induced hormesis in aquatic animals, including 202 hormetic dose response relationships. The maximum stimulatory response (MAX) was commonly lower than 160% of the control response, with a combined value of 134%. Furthermore, the magnitude of MAX varied significantly among multiple factors and their interactions, such as chemical types and taxonomic groups. Moreover, the distance from the dose of MAX to the no-observed-adverse-effect-level (NOAEL) (NOAEL: MAX) was typically below 10-fold (median = 6-fold), while the width of the hormetic zone (from the lowest dose inducing hormesis to the NOAEL) was approximately 20-fold. Collectively, the quantitative features of OFRs-induced hormesis in aquatic animals were in accordance with the broader hormetic literature. In addition, the implications of hormetic dose response model for the risk assessment of OFRs were discussed. This study offered a novel insight for understanding the biological effects of low-to-high doses of OFRs on aquatic animals and assessing the potential risks of OFRs in the aquatic environment.

Amino-functionalized MIL-88B as heterogeneous photo-Fenton catalysts for enhancing tris-(2-chloroisopropyl) phosphate (TCPP) degradation: Dual excitation pathways accelerate the conversion of FeIII to FeII under visible light irradiation

In this work, the amino-functionalized metal-organic frameworks (MIL-88B-NH₂) was synthesized, characterized and used as heterogeneous photo-Fenton catalyst for tris-(2-chloroisopropyl) phosphate (TCPP) degradation. The photo-Fenton activity of MIL-88B-NH₂ was investigated on the basis of influence factors, such as initial pH and TCPP concentration, and coexisting impurities. The results revealed that MIL-88B-NH₂+H₂O₂+Vis system exhibited a satisfactory degradation efficiency of TCPP (almost 100%) within 60 min accompanied by a good reusability. Noticeably, the degradation kinetics constant of TCPP by MIL-88B-NH₂+H₂O₂+Vis system was 0.086 min^-1, which was visibly higher than that of MIL-88B+H₂O₂+Vis system (0.021 min^-1) since the addition of amino-functionalized organic linker inhibiting the recombination rate of the photo-generated electron-hole pairs and improving the visible light response. Combined with the characterization, the conversion of Fe^III to Fe^II could be accelerated by the photo-generated electron from the excitation of Fe-O clusters and NH₂ functionalities, which strengthened the decomposition of H₂O₂ and formed plenty •OH. Simultaneously, six steady products were validated and potential degradation pathways of TCPP were proposed. It was anticipated that MIL-88B-NH₂ could be considered as a desirable and alternative candidate in the application of heterogeneous photo-Fenton reaction to control the environmental risks caused by organophosphate flame retardants (OPFRs).

Effects of tris (2-chloroethyl) phosphate (TCEP) on survival, growth, histological changes and gene expressions in juvenile yellow catfish Pelteobagrus fulvidraco

Tris (2-chloroethyl) phosphate (TCEP) is an emerging aquatic environmental pollutant. In the present study, juvenile yellow catfish (Pelteobagrus fulvidraco) were exposed to environmentally relevant concentrations of TCEP for 30 days. The results showed that TCEP exposure decreased the survival rate (100 μg/L), body weight (10 and 100 μg/L) and specific growth rate (10 and 100 μg/L) of juvenile yellow catfish. Exposure to TCEP resulted in pronounced damages of gill structures. Gene transcription analysis showed that the antioxidant capacity of the liver and gills was affected; CYP1A1 might contribute to phase I metabolism of TCEP in the liver rather than CYP1B1; TCEP stress might increase the demand of ion transport in fish gill; TCEP could stimulate the immune response and might induce apoptosis via a p53-Bax pathway and caspase-dependent pathway in gills. Collectively, these findings provide new insights into the toxic effects of TCEP on fish.

Phytotoxicity of tris-(1-chloro-2-propyl) phosphate in soil and its uptake and accumulation by pakchoi (Brassica chinensis L. cv. SuZhou)

This study investigated physiological and biochemical changes in pakchoi at different growth stages (25 and 50 d) under different tris-(1-chloro-2-propyl) phosphate (TCIPP) treatments (10, 100, 500, and 1000 μg kg^-1). The uptake and accumulation of TCIPP by pakchoi and variation of TCIPP speciation in soil were also determined. TCIPP decreased the length and fresh weight of pakchoi root compared with those in blank controls, and this effect was significant when the concentration of TCIPP was higher than 100 μg kg^-1. The fresh weight of pakchoi stems and leaves, the chlorophyll content, and the activities of superoxide dismutase, peroxidase, and catalase in the leaves first increased and then decreased with increasing TCIPP concentration. The inflection point of the variation in these indices was 100 μg kg^-1 TCIPP in soil. The contents of proline and malondialdehyde increased continuously with increasing TCIPP concentration. The uptake of TCIPP by pakchoi increased linearly with increasing TCIPP concentration, and the highest TCIPP concentrations in the roots, stems, and leaves were 275.9, 80.0, and 2126.3 μg kg^-1, respectively. TCIPP was easily transferred from the roots to leaves of pakchoi, with translocation factor of up to 12.6. The content of bioavailable TCIPP in soil was high, accounting for 46.5%. Planting pakchoi could significantly reduce the content of bioavailable TCIPP, with removal rate of 39.9%-54.1%. After 50 d of planting pakchoi, the removal rate of TCIPP in soil (10.4%-18.6%) was significantly higher than that in the control without plant, but the contribution of phytoextraction was small, accounting for 2.62%-26.6%.

Evaluation of a four-zone indoor exposure model for predicting TCPP concentrations in a low-energy test house

Numerous chemicals have been detected in indoor environments that have potential impacts on occupant health and comfort. However, due to limited resources, it's infeasible to assess indoor exposure of each chemical for all indoor conditions through measurements alone. Hence, indoor exposure models have been developed to predict time-varied exposure for a wide range of sources and chemicals under different conditions. The Indoor Environmental Concentrations in Buildings with Conditioned and Unconditioned Zones (IECCU) model was developed by the United States Environmental Protection Agency. This study evaluated the predictive ability of the IECCU by comparing airborne tris(1-chloro-2-propyl) phosphate (TCPP) concentrations measured from 2013 to 2018 in a test house to modeled predictions. Inputs to IECCU included building and environment (i.e., air zone configuration and geometry, interzonal airflow rates and air temperature in each zone), parameters for both source (spray polyurethane foam (SPF)) and sinks (gypsum and wallboard), and simulation conditions. Simulations were conducted using three sets of inputs. Simulation 1 and 2 differed in using quantified versus design inputs for temperatures and airflow rates. Simulation 1 and 3 differed in the configured air zones in the IECCU model. Given the best available inputs (Simulation 1), IECCU predicted basement concentrations that were generally higher but within a factor of three of the measurements. The basement prediction/measurement ratios for all three simulations ranged from 0.5 to 8.3 and the average was 2.9, while the predicted concentrations in the living zone were generally lower but still within an order of magnitude of the measurements. The prediction accuracy decreased with time. For Simulation 1, predicted basement concentrations were on average 1.4 times higher than measurements in 2013 and 2014. However, the ratio increased to 4.7 in 2018. The design inputs of Simulation 2 resulted in greater discrepancy between measurements and predictions than the measured inputs of Simulation 1. In addition, Simulation 2 did not capture diurnal variation as well as Simulation 1. Comparisons of Simulation 1 and 2 demonstrate the importance of using accurate temperature and airflow model inputs for more accurately predicting concentrations. Furthermore, a sensitivity analysis indicated that to improve the accuracy of IECCU predictions for TCPP emission from SPF, efforts are needed to accurately measure the mass transfer parameters for SPF, especially the SPF/air partition coefficient and the initial TCPP concentration in SPF.

Tris (1-chloro-2-propyl) phosphate exposure to zebrafish causes neurodevelopmental toxicity and abnormal locomotor behavior

The organophosphate flame retardant, tris (1-chloro-2-propyl) phosphate (TCPP), is ubiquitous in environmental matrices; however, there is a paucity of information concerning its systemic toxicity. Herein, we investigated the effects of TCPP exposure on zebrafish neurodevelopment and swimming behavior to elucidate the underlying molecular mechanisms of neurotoxicity. Under TCPP gradient concentration exposure, the hatching rates were declined by up to 33.3% in 72 hpf, and the malformation rates increased from 15% to 50%. Meanwhile, TCPP led to abnormal behaviors including decreased locomotive activity in the dark and slow/insensitive responses to sound and light stimulation of larvae. TCPP caused excessive apoptosis and ROS accumulation in early embryonic development, with hair cell defects and structural deformity of neuromast. Abnormal expression of neurodevelopment (pax6a, nova1, sox11b, syn2a, foxo3a and robo2) and apoptosis-related genes (baxa, bcl2a and casp8) revealed molecular mechanisms regarding abnormal behavioral and phenotypic symptoms. Chronic TCPP exposure led to anxiety-like behavior and excessive panic, lower capacity for discrimination and risk avoidance, and conditioned place preference in adults. Social interaction tests demonstrated that long-term TCPP stress resulted in unsociable, eccentric, lonely and silent behaviors in adults. Zebrafish memory and cognitive function were severely reduced as concluded from T-maze tests. Potential mechanisms triggering behavioral abnormality were attributed to histopathological injury of diencephalon, abnormal changes in nerve-related genes at transcription and expression levels, and inhibited activity of AChE by TCPP stress. These findings provide an important reference for risk assessment and early warning to TCPP exposure, and offer insights for prevention/mitigation of pollutant-induced nervous system diseases.

Embryotoxicity characterization of the flame retardant tris(1-chloro-2-propyl)phosphate (TCPP) in the invertebrate chordate Ciona intestinalis

Tris(1-chloro-2-propyl)phosphate (TCPP) is the most common chlorinated organophosphorus flame retardant in seawater. Due to its chemical features and abundance, TCPP has been classified as a high hazard, and restrictions of use have been set in multiple countries. Despite TCPP being highly present in the marine environment, only a few studies have explored the TCPP impact on the development of marine invertebrates. Ascidians are important invertebrate members of benthic marine communities and reliable model systems for ecotoxicological research. The aim of this study was to assess the adverse effects of TCPP exposure on the embryogenesis of the ascidian Ciona intestinalis. Our results showed that this pollutant affected both muscles and nervous system development. Malformations appeared similar to those reported in other animal models for other flame retardants, suggesting that these molecules could share a common mechanism of action and induce a mixture effect when simultaneously present in the aquatic environment even at sub-teratogenic concentrations.

Microplastics aggravate the adverse effects of BDE-47 on physiological and defense performance in mussels

The highly hydrophobic surfaces make microplastics a potential carrier of organic pollutants in the marine environment. In order to explore the toxic effects of polybrominated diphenyl ethers (BDE-47) combined with microplastics on marine organisms, we exposed the marine mussel Mytilus coruscus to micro-PS combined with BDE-47 for 21 days to determine the immune defense, oxidative stress and energy metabolism of the mussels. The results showed that the clearance rate (CR) of mussels exposed to single micro-PS, single BDE-47 or both was lower than control group. In general, compared to single BDE-47 exposure, the combination of micro-PS and BDE-47 significantly increased respiration rate (RR), activities of acid phosphatase (ACP) and alkaline phosphatase (ALP), reactive oxygen species (ROS) production and malondialdehyde (MDA) concentrations, but significantly decreased lactate dehydrogenase (LDH) activity and the relative expression of heat shock protein (Hsp70 and 90). Overall, combined stress has more adverse effects on defense performance and energy metabolism in mussels and micro-PS seem to exacerbate the toxicological effects of BDE-47. As microplastics pollution may deteriorate in the future, the health of mussels may be threatened in organically polluted environment, which eventually change the stability of the structure and function of intertidal ecosystem.

Biomarkers of oxidative stress and cell damage in freshwater bivalves Diplodon parodizi exposed to landfill leachate

Landfill is a public and environmental health problem; establishing and understanding methodologies to decrease its toxicity are thus necessary. Leachate samples were collected, at a sanitary landfill, immediately after the exit from the landfill, i.e. raw leachate (collection point A), after conventional treatment (point B) and after treatment by wetlands (point C). D. parodizi specimens were exposed to 3%, 10% and control (0%) dilutions of leachate from these collection points for 7 days. Markers of antioxidant defences and cell damage were analysed. At point B, the gills of D. parodizi showed higher glutathione-S-transferase (GST) and glutathione reductase (GR) activity; the latter is a supplier of glutathione reductase (GSH). The low GST activity at point A was associated with the hormesis effect. Higher levels of superoxide dismutase (SOD), ethoxyresorufin-O-deethylase (EROD) and glutathione peroxidase (GPx) occurred at point A. Glucose-6-phosphate dehydrogenase (G6PDH) was inhibited at the points with the highest pollutant load and at the highest leachate dilutions. Higher levels of markers at point A may be related to the high pollutant charge and specific compounds present in the untreated leachate. The multi-xenobiotic resistance mechanism (MXR), metallothionein-like proteins (MT) and lipid peroxidation (LPO) did not vary among treatments. The biomarker responses showed negative effects of the leachate on the freshwater bivalve and simultaneously showed that the wetland treatment employed at the Caximba sanitary landfill is effective.

Biodegradation of tricresyl phosphate isomers by Brevibacillus brevis: Degradation pathway and metabolic mechanism

Tricresyl phosphates (TCPs), a typical sort of organophosphate flame retardants, has received extensive concerns due to its potential adverse effects. However, limited information is available on the efficient and safe removal methods of TCPs. In this regard, TCPs were tentatively biodegraded with Brevibacillus brevis. A probable degradation pathway was further proposed with the cellular reactions discussed in detail. Experiments showed that B. brevis at 2 g L^-1 could degrade 1 mg L^-1 tri-m-cresyl phosphate, tri-p-cresyl phosphate, and tri-o-cresyl phosphate by 82.91%, 93.91%, and 53.92%, respectively, within five days. In the process of biodegradation, B. brevis metabolism caused the release of Na⁺ and Cl^- as well as the absorption of some nutrient ions including K⁺, PO₄^3-, Mg²⁺, and SO₄^2-; the presence of oxalic acid, citric acid, acetic acid, and malonic acid was also detected. Similar metabolic pathways were found among different TCPs isomers, but tri-o-cresyl phosphate induced more reactive oxygen species than the other two did. This work develops novel insights into the potential mechanisms of TCPs biodegradation by microorganisms.

The Amazon River: A Major Source of Organic Plastic Additives to the Tropical North Atlantic?

The release of emerging organic contaminants is identified among the most critical hazards to the marine environment, and plastic additives have received growing attention due to their worldwide distribution and potential deleterious effects. Here, we report dissolved surface water concentrations of two important families of plastic additives (organophosphate esters (OPEs) and bisphenols) and other related organic compounds (perfluorinated chemicals) measured in the North Atlantic from Cape Verde to the West Indies. We found that OPEs were the most abundant contaminants, reaching remarkably high concentrations in open ocean waters (1200 km offshore of the American Coast, at the location of the Amazon river plume during the sampling period), with up to 1.3 μg L^-1 (Σ₉OPEs). A Lagrangian analysis confirmed that these high concentrations of contaminants originated from the Amazon River plume and were transported more than 3000 km by the North Brazil Current and its retroflection. We thus consider the Amazon River as a major source of organic contaminants of emerging concern to the tropical North Atlantic Ocean and suggest that medium-/long-range contaminant transport occurs, most certainly facilitated by the highly stratified conditions offered by the river plume.