Acute toxicity of tire wear particles, leachates and toxicity identification evaluation of leachates to the marine copepod, Tigriopus japonicus

Toxicity and intergenerational accumulation effect of tire wear particles and their leachate on Brachionus plicatilis

Tire wear particles (TWP) are one of the main sources of microplastic (MP) pollution in the marine environment, causing adverse effects on marine life and attracting increasing attention. This study aimed to investigate the chemical composition of TWP (particles and leachate) and their toxic effects on Brachionus plicatilis. The results showed that Zn and acenaphthene were the most frequently detected compounds in the three TWP treatments. In the single-generation exposure experiment, TWP leachate showed the highest toxicity potential, followed by nano-TWP (<1 μm) and micro-TWP (1-20 μm). Both nano-TWP and leachate had negative effects on the lifespan and population of rotifers. High-concentration TWP leachate significantly shortened the reproductive period of rotifers, slowed down their swimming speed, and reduced the number of offspring. These negative effects were mainly attributed to the toxic mixture of nano-TWP with additives in the leachate. Furthermore, in multi-generation exposure experiments, the toxicity pattern showed a new trend: the toxicity of nano-TWP exceeded that of the leachate, while micro-TWP continued to maintain the lowest toxicity level. Continuous exposure to TWP exerted a significant negative impact on rotifer lifespan, and this effect increases cumulatively between generations. Notably, TWP was trans-generationally toxic to the lifespan of rotifers, and repeated exposure was more toxic than maternal exposure and continuous exposure. In addition, rotifers can ingest and accumulate TWP, and maternal transfer was another uptake pathway of TWP in rotifer offspring. This finding provided a new perspective for understanding the transmission mechanism of TWP in the marine food chain.

Multigenerational toxic effects in Daphnia pulex are induced by environmental concentrations of tire wear particle leachate

Microplastic pollution has emerged as the second most significant scientific issue in environmental science and ecology. Similarly, the biological effects of tire wear particles (TWPs) have garnered considerable research attention; however, studies on chronic TWP leachate toxicity at environmentally relevant concentrations remain sparse. Here, we investigated the effects of TWP leachate at environmentally relevant concentrations (0.3 mg/L and 3 mg/L) on multigenerational and transgenerational Daphnia pulex for 21 days/generation, spanning three generations (F0-F2). Growth and reproductive indices (body length, growth rate, time to first clutch, number of clutches, and total offspring/female) across generations were analyzed. Multigenerational exposure to TWP leachate did not cause D. pulex death, but impaired growth and development, prolonged sexual maturity time, and reduced reproductive capacity. The transgenerational exposure group (3 mg/L) also exhibited some sub-lethal effects, such as delayed reproduction, suggesting a transgenerational impact. Gene transcription analyses and weighted gene co-expression network analysis showed that the most impacted pathways were associated with lysosome function, apoptosis, and glutathione metabolism, indicating that TWP leachate exposure compromised immune defense mechanisms and disrupted APs, CTSB, GST, DUSP1, and ERN1 gene expression. These findings underscore multigenerational toxicity effects and TWP leachate transmission patterns on aquatic organisms at realistic environmental concentrations.

Priorities to inform research on tire particles and their chemical leachates: A collective perspective

Concerns over the ecological impacts of urban road runoff have increased, partly due to recent research into the harmful impacts of tire particles and their chemical leachates. This study aimed to help the community of researchers, regulators and policy advisers in scoping out the priority areas for further study. To improve our understanding of these issues an interdisciplinary, international network consisting of experts (United Kingdom, Norway, United States, Australia, South Korea, Finland, Austria, China and Canada) was formed. We synthesised the current state of the knowledge and highlighted priority research areas for tire particles (in their different forms) and their leachates. Ten priority research questions with high importance were identified under four themes (environmental presence and detection; chemicals of concern; biotic impacts; mitigation and regulation). The priority research questions include the importance of increasing the understanding of the fate and transport of these contaminants; better alignment of toxicity studies; obtaining the holistic understanding of the impacts; and risks they pose across different ecosystem services. These issues have to be addressed globally for a sustainable solution. We highlight how the establishment of the intergovernmental science-policy panel on chemicals, waste, and pollution prevention could further address these issues on a global level through coordinated knowledge transfer of car tire research and regulation. We hope that the outputs from this research paper will reduce scientific uncertainty in assessing and managing environmental risks from TP and their leachates and aid any potential future policy and regulatory development.

A study of the direct emission of tire wear particles on different types of roads

In the range of 5-6 Mt/y tire wear particles (TWP) are emitted from vehicles in both developed and emerging countries. In an attempt to reduce these emissions, new regulations will come into force in the EU and USA, although currently no oversight methods are actually in place. This study proposes a method for assessing direct TWP emissions (TWPD) from vehicles. The method entails labeling the tire with mercury, then collecting and fractionating the particles emitted at the rear of the wheel (RoWP), and lastly analyzing their Hg content in the laboratory using atomic absorption spectroscopy. It provides access to the magnitude, size distribution and factors affecting TWPD emissions under actual driving conditions. Furthermore, the implementation of desorption and dispersion models allows evaluation of the proportion of TWPD embedded in tire and road wear particles (TRWP) and estimating the TWPD contribution to the lower atmosphere PM1, PM2.5 and PM10 pollution within the EU-27. A key finding of this research is that ultrafine TWPD (accounting for 33-260 mg/g of abraded front tire material) account for 30-70 % of total TWPD emissions (with >93 % being in the form of inclusions), although they make up 0.5-5.7 % of RoWP mass emissions. Our data also draw attention to the magnitude and lower TRWP-embedment of TWPD emissions in urban areas.

Tire and road wear particles in infiltration pond sediments: Occurrence, spatial distribution, size fractionation and correlation with metals

Stormwater systems, such as infiltration ponds or basins, play a critical role in managing runoff water and reducing particulate pollution loads in downstream environments through decantation. Road runoff carries several pollutants, including trace metals and tire and road wear particles (TRWP). To improve our understanding of infiltration ponds as regards TRWP and their capacity to reduce TRWP loads, we have studied the occurrence, spatial distribution and size distribution of TRWP, as well as their relationship with metals, in considering the input of metals as tire additives, in the sediments of an infiltration pond located along the Nantes urban ring road (Western France), which happens to be a high-traffic roadway site. The sediment was analyzed using pyrolysis coupled with gas chromatography-mass spectrometry to determine the polymeric content of tires, specifically in quantifying the styrene-butadiene rubber (SBR) and butadiene rubber (BR) pyrolytic markers. By applying an SBR + BR-to-TRWP conversion factor, the results showed significant TRWP contamination, up to 65 mg/g, with a spatial enrichment from the entrance to the overflow section of the pond. Size fractionation revealed a bimodal distribution, indicating two distinct types of TRWP. The first type is characterized by small diameters (63-160 μm), suggesting the presence of TRWP less integrated with mineral and organic particles. The second type, characterized by larger diameters (200-500 μm), suggests a more pronounced integration with these same mineral and organic particles. A significant positive correlation between TRWP and metals (As, Cd, Cr, Cu, Li, Mo, Ni, Sb, V, Zn) was found (r > 0.739, p < 0.05). This correlation implies that TRWP and/or their associated phases may act as an indicator of metal contamination in the pond sediments. Lastly, a mass balance between TRWP inputs and the amount retained in the sediments underscores the role of infiltration ponds as "sinks" for TRWP.

Unveiling the environmental impact of tire wear particles and the associated contaminants: A comprehensive review of environmental and health risk

This review offers a novel perspective on the environmental fate and ecotoxicological effects of tire wear particles (TWPs), ubiquitous environmental contaminants ranging in size from micrometers to millimeters (averaging 10-100 micrometers). These particles pose a growing threat due to their complex chemical composition and potential toxicity. Human exposure primarily occurs through inhalation, ingesting contaminated food and water, and dermal contact. Our review delves into the dynamic interplay between TWP composition, transformation products (TPs), and ecological impacts, highlighting the importance of considering both individual chemical effects and potential synergistic interactions. Notably, our investigation reveals that degradation products of certain chemicals, such as diphenylguanidine (DPG) and diphenylamine (DPA), can be more toxic than the parent compounds, underscoring the need to fully understand these contaminants' environmental profile. Furthermore, we explore the potential human health implications of TWPs, emphasizing the need for further research on potential respiratory, cardiovascular, and endocrine disturbances. Addressing the challenges in characterizing TWPs, assessing their environmental fate, and understanding their potential health risks requires a multidisciplinary approach. Future research should prioritize standardized TWP characterization and leachate analysis methods, conduct field studies to enhance ecological realism, and utilize advanced analytical techniques to decipher complex mixture interactions and identify key toxicants. By addressing these challenges, we can better mitigate the environmental and health risks associated with TWPs and ensure a more sustainable future.

Towards realism in hazard assessment of plastic and rubber leachates - Methodological considerations

While plastic chemicals are key drivers of observed effects to aquatic species, there remains a lack of standardized and fit-for-purpose approaches for experimentally deconvoluting the effects of plastic chemicals from particle effects. This study investigated differences in chemical composition determined using two different organic solvents for extractions (dichloromethane-ethyl acetate, methanol) and by thermal desorption applied to 51 thermoplastic and elastomer products. The composition of natural water leachates of four select elastomers was also investigated. The number of chemical features in each material varied according to the extraction method, with solvent extracts exhibiting the most chemicals, and only 19 compounds commonly identified by all three methods. The number of chemical features in leachates was generally similar to the corresponding chemical extracts, but strong differences in relative composition were detected. While turbulence had minimal impact on leachate composition, particle loading strongly influenced leachate composition, temperature and salinity influenced the leachate concentration for some chemicals, and leaching time depended upon chemical mobility. Leachate composition cannot be readily predicted from particle characterization and multiple parameters are drivers of compositional variance in aquatic leachates. Recommendations for performing leaching studies that are relevant for hazard characterization in a realistic aquatic environment risk assessment scenario are suggested, with a particular focus on particle loading.

Tracking the biogeochemical behavior of tire wear particles in the environment - A review

The environmental fate and risks associated with tire wear particles (TWPs) are closely linked to their biogeochemical behaviors. However, reviews that focus on TWPs from this perspective remain scarce, hindering our understanding of their environmental fate and cascading effects on ecosystems. In this review, we summarize the existing knowledge on TWPs by addressing five key areas: (i) the generation and size-dependent distribution of TWPs; (ii) the release and transformation of TWP-leachates; (iii) methodologies for the quantification of TWPs; (iv) the toxicity of TWPs; and (v) interactions of TWPs with other environmental processes. It has been established that the size distribution of TWPs significantly influences their transport and occurrence in different matrices, leading to the release and transformation of specific TWP-chemicals that can be toxic to organisms. By highlighting the challenges and knowledge gaps in this field, we propose critical issues that need to be addressed to enhance the risk assessment of TWPs. This review aims to provide a comprehensive framework for evaluating the environmental behavior of TWPs.

Chronic toxicity and intergenerational effects of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) exposure alone and in combination with Zn2+ on Daphnia magna (Cladocera)

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and Zn2+, extensively used in the tire manufacturing process, are frequently detected in freshwater environments. However, the intergenerational effects of isolated 6PPD exposure and joint 6PPD and Zn2+ exposure at concentrations approximating environmental levels remain unknown. This study assessed the chronic toxicity and intergenerational effects of 6PPD (0.02-20 μg/L) and a mixture of 6PPD and Zn2+ (5 μg/L) over three generations in Daphnia magna bioassays. In the F0 generation, a dose-dependent decline in total offspring number was observed with 6PPD exposure alone, while co-exposure with Zn2+ exacerbated the reproductive toxicity of 6PPD. Across three generations, low-dose (0.02 µg/L) 6PPD alone and combined with Zn2+ induced a cumulative degenerative maternal effect. Conversely, high-dose (20 µg/L) 6PPD, both independently and in combination with Zn2+, exhibited an adaptive maternal effect. Notably, the grandmaternal effect emerged exclusively in the co-exposure group treated with 20 μg/L 6PPD and 5 μg/L Zn2+, with no such effect in the group exposed to 20 μg/L 6PPD alone, suggesting that Zn2+ may enhance the potential toxicity of 6PPD. Overall, this study provides novel insight into the intergenerational impacts of environmentally relevant levels of 6PPD alone and in combination with a heavy metal, elucidating the environmental risks posed by tire-derived chemicals through their synergistic effects on transgenerational toxicity.

Accumulation and depuration of tire wear particles in zebrafish (Danio rerio) and toxic effects on gill, liver, and gut

The toxic effects of tire wear particles (TWPs) in the environment are a growing concern for a variety of aquatic organisms. However, studies about TWPs toxicity on aquatic organisms are limited. This study investigated the accumulation and depuration of TWPs in zebrafish at three different concentrations (5 mg/L, 10 mg/L, and 20 mg/L), as well as the toxic effects on the gill, liver, and gut. We found that TWPs could accumulate in the gill and gut for a long time, and the number of TWPs at the high-concentration (20 mg/L) was higher than at the low-concentration (5 mg/L). TWPs induced oxidative stress in the gill and liver. The liver transcriptome profiles indicated that the high concentration of TWPs tended to up-regulate metabolic processes, whereas the low concentration of TWPs was inclined to down-regulate cellular processes. The high-concentration treatment significantly increased xenobiotic biodegradation and metabolism, and lipid metabolism-related pathways, whereas the low-concentration treatment distinctly altered amino acid metabolism-related pathways. The expression of gstt1b, ugt1a1, mgst3b, miox, hsd17b3, and cyp8b1 gene was up-regulated in all TWPs treatments. In addition, Gemmobacter and Shinella enriched in the high-concentration treatment were closely correlated with the degradation of TWPs. These findings provided objective evidence for the toxicity evaluation of TWPs on zebrafish.

Effects of tire wear particle on growth, extracellular polymeric substance production and oxidation stress of algae Chlorella vulgaris: Performance and mechanism

Tire wear particles (TWP) represent a distinctive form of microplastics (MPs) that are widely distributed in aquatic ecosystems. However, the toxicity of various types of TWP on phytoplankton remain to be further explored. Thus, three different TWPs originating from replaced bicycle, car, and electro-mobile tire (marked as BTWP, CTWP, and ETWP) were selected and their long-term biological influences on Chlorella vulgaris were investigated. Results demonstrated TWPs showed a concentration-dependent growth promotion of Chlorella vulgaris, with a maximum promotion rate reached to 40.51 % (10 mg/L, 10 d), 23.5 % (80 mg/L, 12 d), and 28.7 % (20 mg/L, 12 d) in the presence of BTWP, CTWP and ETWP, respectively. Meanwhile, TWPs could stimulate the secretion of EPS and induce oxidative stress. EPS analysis revealed the increase of polysaccharides could protect the cell from the direct contact with TWP particles. Moreover, the increased concentration of EPS also helps to induce the settlement of TWP and reduce the leachate release. The release of TWP into the environment could act as an accelerator for the growth of Chlorella vulgaris, which might further change the normal physicochemical behaviors of algae colony in aquatic system. Our findings provide new insights into the toxicity mechanism of TWPs on freshwater algae and valuable data on environmental risk assessment of TWPs.

Typical Tire Additives in River Water: Leaching, Transformation, and Environmental Risk Assessment

Tire wear particles (TWPs) released during vehicle driving can enter water bodies, leading to leaching of tire additives (TAs) in aquatic environments. However, the transformation behavior and related ecological impacts of TAs and their transformation products (TPs) remain unclear. In this study, laboratory-based simulation experiments and field investigations were conducted to explore the transformation mechanisms and ecological risks of TAs. After being placed in river water for 24 h, about 7-95% of 12 investigated TAs in TWPs were leached. Forty-eight TPs from eight TAs were tentatively identified along with different transformation pathways via suspect screening by high-resolution mass spectrometry. Semiquantitative results indicated that TPs derived from N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylene-diamine (6PPD) were predominant in leachates, while aryl hydrolysis and quinone pathways were the main transformation pathways. Field investigations on urban surface water samples from 16 sites in Hong Kong revealed the occurrence of 17 TAs and 1 TP, with concentrations ranging from 13.9 to 2230 ng/L (median ± standard deviation: 226 ± 534 ng/L). Sixteen TPs from six TAs were additionally identified via suspect screening. It is estimated that 6PPD-quinone and seven TAs could pose medium to high ecological risk, while N-(1,3-dimethylbutyl)-N'-phenyl-p-quinonediimine, a frequently detected TP, was identified as a persistent-bioaccumulative-toxic substance.

Emerging threat of marine microplastics: Cigarette butt contamination on Yellow Sea beaches and the potential toxicity risks to rotifer growth and reproduction

Cigarette butts have become one of the most common and persistent forms of debris in marine coastal areas, where they pose significant toxicity risks. This study investigated cigarette butt pollution along beaches of the Yellow Sea and used laboratory experiments to assess the toxicity of their leachate and fibers on the euryhaline rotifer Brachionus plicatilis. A pollution index confirmed pollution by this debris across all eight beaches surveyed, where the density of cigarette butts averaged 0.23 butts/m2. In controlled laboratory experiments, both the fibers and leachates from cigarette butts exhibited negative impacts on the development, reproduction, and population growth of rotifers. Unique abnormalities observed under different exposure treatments indicated toxicity specific to certain chemicals and particles. Continuous exposure to cigarette butts initially reduced rotifer fecundity, but this effect diminished over successive generations. However, the exposure induced transgenerational reproductive toxicity in the rotifers. Adaptive responses in rotifers after repeated exposure led to relative reduction in reproductive inhibition in the F3 and F4 generations. Furthermore, rotifers were capable of ingesting and accumulating cigarette butts, and maternal transfer emerged as an alternative pathway for uptake of this material in the offspring. These results increase our understanding of the ecological risks posed by cigarette butts in aquatic environments.

Combined toxicity of pristine or artificially aged tire wear particles and bisphenols to Tigriopus japonicus

Tire wear particles (TWPs) are considered an important component of microplastic pollution in the marine environment and occur together with a variety of aquatic pollutants, including frequently detected bisphenols. The adverse effects of TWPs or bisphenols on aquatic organisms have been widely reported. However, the combined toxicity of TWPs and bisphenols is still unknown. In this study, the combined toxicity of both pristine (p-) and aged TWPs (a-TWPs) and four bisphenols ((bisphenol A (BPA), bisphenol F (BPF), bisphenol S (BPS), and bisphenol AF (BPAF)) to Tigriopus japonicus was evaluated. TWPs increased the toxicity of BPA and BPF but decreased the toxicity of BPAF. For BPS, there was synergistic toxic effect in the presence of p-TWPs, but slightly antagonistic effect was observed in the presence of a-TWPs. This adsorption of BPAF by TWPs resulted in a reduction of its toxicity to the copepod. A-TWPs could release more Zn than p-TWPs, and the released Zn contributed to the synergistic effect of TWPs and BPA or BPF. The aggregation formed by TWPs in certain sizes (e.g., 90-110 μm) could cause intestinal damage and lipid peroxidation in T. japonicus. The synergistic effect of p-TWPs and BPS might be due to the aggregation size of the binary mixture. The results of the current study will be important to understand the combined toxic effect of TWPs and bisphenols and the potential toxic mechanisms of the binary mixture.

Tire and road wear particles in the aquatic organisms - A review of source, properties, exposure routes, and biological effects

With the continuous development of the modern social economy, rubber has been widely used in our daily life. Tire and road wear particles (TRWPs) are generated by friction between tires and the road surface during the processes of driving, acceleration, and braking. TRWPs can be divided into three main components according to their source: tire tread, brake wear, and road wear. Due to urban runoff, TRWPs flow with rainwater into the aquatic environment and influence the surrounding aquatic organisms. As an emerging contaminant, TRWPs with the characteristics of small particles and strong toxicity have been given more attention recently. Here, we summarized the existing knowledge of the physical and chemical properties of TRWPs, the pathways of TRWPs into the water body, and the exposure routes of TRWPs. Furthermore, we introduced the biological effects of TRWPs involved in size, concentration, and shape, as well as key toxic compounds involved in heavy metals, polycyclic aromatic hydrocarbons (PAHs), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and benzothiazole on aquatic organisms, and attempted to find the relevant factors influencing the toxic effects of TRWPs. In the context of existing policies that ignore pollution from TRWPs emissions in the aquatic environment, we also proposed measures to mitigate the impact of TRWPs in the future, as well as an outlook for TRWPs research.

Behind conventional (micro)plastics: An ecotoxicological characterization of aqueous suspensions from End-of-Life Tire particles

Million tons of tires become waste every year, and the so-called End-of-Life Tires (ELTs) are ground into powder (ELT-dp; size < 0.8 mm) and granules (ELT-dg; 0.8 < size < 2.5 mm) for recycling. The aim of this study was to evaluate the sub-lethal effects of three different concentrations (0.1, 1, and 10 mg/L) of aqueous suspensions from ELT-dp and ELT-dg on Danio rerio (zebrafish) larvae exposed from 0 to 120 h post-fertilization (hpf). Chronic effects were assessed through biomarkers, real-time PCR, and proteomics. We observed a significant increase in swimming behavior and heart rate only in specimens exposed to ELT-dp suspensions at 1 and 10 mg/L, respectively. Conversely, the activities of detoxifying enzymes ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) showed significant modulation only in specimens exposed to ELT-dg groups. Although no effects were observed through real-time PCR, proteomics highlighted alterations induced by the three ELT-dp concentrations in over 100 proteins involved in metabolic pathways of aromatic and nitrogen compounds. The results obtained suggest that the toxic mechanism of action (MoA) of ELT suspensions is mainly associated with the induction of effects by released chemicals in water, with a higher toxicity of ELT-dp compared to ELT-dg.

Short-term microplastic effects on marine meiofauna abundance, diversity and community composition

Background

Due to the copious disposal of plastics, marine ecosystems receive a large part of this waste. Microplastics (MPs) are solid particles smaller than 5 millimeters in size. Among the plastic polymers, polystyrene (PS) is one of the most commonly used and discarded. Due to its density being greater than that of water, it accumulates in marine sediments, potentially affecting benthic communities. This study investigated the ingestion of MP and their effect on the meiofauna community of a sandy beach. Meiofauna are an important trophic link between the basal and higher trophic levels of sedimentary food webs and may therefore be substantially involved in trophic transfer of MP and their associated compounds.

Methods

We incubated microcosms without addition of MP (controls) and treatments contaminated with PS MP (1-µm) in marine sediments at three nominal concentrations (103, 105, 107particles/mL), for nine days, and sampled for meiofauna with collections every three days. At each sampling time, meiofauna were collected, quantified and identified to higher-taxon level, and ingestion of MP was quantified under an epifluorescence microscope.

Results

Except for Tardigrada, all meiofauna taxa (Nematoda, turbellarians, Copepoda, Nauplii, Acari and Gastrotricha) ingested MP. Absorption was strongly dose dependent, being highest at 107 particles/mL, very low at 105 particles/mL and non-demonstrable at 103 particles/mL. Nematodes accumulated MP mainly in the intestine; MP abundance in the intestine increased with increasing incubation time. The total meiofauna density and species richness were significantly lower at the lowest MP concentration, while at the highest concentration these parameters were very similar to the control. In contrast, Shannon-Wiener diversity and evenness were greater in treatments with low MP concentration. However, these results should be interpreted with caution because of the low meiofauna abundances at the lower two MP concentrations.

Conclusion

At the highest MP concentration, abundance, taxonomic diversity and community structure of a beach meiofauna community were not significantly affected, suggesting that MP effects on meiofauna are at most subtle. However, lower MP concentrations did cause substantial declines in abundance and diversity, in line with previous studies at the population and community level. While we can only speculate on the underlying mechanism(s) of this counterintuitive response, results suggest that further research is needed to better understand MP effects on marine benthic communities.

Looking beyond the obvious: The ecotoxicological impact of the leachate from fishing nets and cables in the marine mussel Mytilus galloprovincialis

Once in the marine environment, fishing nets and cables undergo weathering, breaking down into micro and nano-size particles and leaching plastic additives, which negatively affect marine biota. This study aims to unravel the ecotoxicological impact of different concentrations of leachate obtained from abandoned or lost fishing nets and cables in the mussel Mytilus galloprovincialis under long-term exposure (28 days). Biochemical biomarkers linked to antioxidant defense system, xenobiotic biotransformation, oxidative damage, genotoxicity, and neurotoxicity were evaluated in different mussel tissues. The chemical nature of the fishing nets and cables and the chemical composition of the leachate were assessed and metals, plasticizers, UV stabilizers, flame retardants, antioxidants, dyes, flavoring agents, preservatives, intermediates and photo initiators were detected. The leachate severely affected the antioxidant and biotransformation systems in mussels' tissues. Following exposure to 1 mg·L-1 of leachate, mussels' defense system was enhanced to prevent oxidative damage. In contrast, in mussels exposed to 10 and 100 mg·L-1 of leachate, defenses failed to overcome pro-oxidant molecules, resulting in genotoxicity and oxidative damage. Principal component analysis (PCA) and Weight of Evidence (WOE) evaluation confirmed that mussels were significantly affected by the leachate being the hazard of the leachate concentrations of 10 mg·L-1 ranked as major, while 1 and 100 mg·L-1 was moderate. These results highlighted that the leachate from fishing nets and cables can be a threat to the heath of the mussel M. galloprovincialis.

Cocktail effects of tire wear particles leachates on diverse biological models: A multilevel analysis

Tire wear particles (TWP) stand out as a major contributor to microplastic pollution, yet their environmental impact remains inadequately understood. This study delves into the cocktail effects of TWP leachates, employing molecular, cellular, and organismal assessments on diverse biological models. Extracted in artificial seawater and analyzed for metals and organic compounds, TWP leachates revealed the presence of polyaromatic hydrocarbons and 4-tert-octylphenol. Exposure to TWP leachates (1.5 to 1000 mg peq L-1) inhibited algae growth and induced zebrafish embryotoxicity, pigment alterations, and behavioral changes. Cell painting uncovered pro-apoptotic changes, while mechanism-specific gene-reporter assays highlighted endocrine-disrupting potential, particularly antiandrogenic effects. Although heavy metals like zinc have been suggested as major players in TWP leachate toxicity, this study emphasizes water-leachable organic compounds as the primary causative agents of observed acute toxicity. The findings underscore the need to reduce TWP pollution in aquatic systems and enhance regulations governing highly toxic tire additives.

Comparing the Developmental Toxicity Delay and Neurotoxicity of Benzothiazole and Its Derivatives (BTHs) in Juvenile Zebrafish

In this study, a semi-static water exposure method was employed to investigate the early developmental and neurotoxic effects of four benzothiazole substances (BTHs), namely benzothiazole (BTH), 2-mercaptobenzothiazole (MBT), 2-hydroxybenzothiazole (BTON), and 2-aminobenzothiazole (2-ABTH), on zebrafish at an equimolar concentration of 10 μM. The findings revealed that all four BTHs exerted certain impacts on early development in zebrafish. MBT stimulated spontaneous movement in juvenile zebrafish, whereas BTON inhibited such movements. Moreover, all four BTHs hindered the hatching process of zebrafish larvae, with MBT exhibiting the strongest inhibition at 24 h post-fertilization (hpf). Notably, MBT acted as a melanin inhibitor by suppressing melanin production in juvenile zebrafish eyes and weakening phototaxis. Additionally, both BTH and BTON exhibited significantly lower speeds than the control group and other test groups under conditions without bright field stimulation; however, their speeds increased to average levels after percussion stimulation, indicating no significant alteration in motor ability among experimental zebrafish groups. Short-term exposure to these four types of BTHs induced oxidative damage in zebrafish larvae; specifically, BTH-, MBT-, and BTON-exposed groups displayed abnormal expression patterns of genes related to oxidative damage. Exposure to both BTH and MBT led to reduced fluorescence intensity in transgenic zebrafish labeled with central nervous system markers, suggesting inhibition of central nervous system development. Furthermore, real-time quantitative PCR results demonstrated abnormal gene expression associated with neural development. However, no significant changes were observed in 2-ABTH gene expression at this concentration. Overall findings indicate that short-term exposure to BTHs stimulates neurodevelopmental gene expression accompanied by oxidative damage.

Deep dive into the chronic toxicity of tyre particle mixtures and their leachates

Particles from the tread of vehicle tyres are a global pollutant, which are emitted into the environment at an approximate rate of 1.4 kg.year-1 for an average passenger-car. In this study, popular tyre brands were used to generate a tyre tread microparticle mixture. The chronic toxicity of both particles and chemical leachates were compared on a planktonic test species (Daphnia magna). Over 21 days of exposure, pristine tyre tread microparticles were more toxic (LC50 60 mg.L-1) than chemical lechates alone (LC50 542 mg.L-1). Microparticles and leachates showed distinct effects on reproduction and morphological development at environmentally relevant concentrations, with dose-dependent uptake of particles visible in the digestive tract. Chemical characterization of leachates revealed a metal predominance of zinc, titanium, and strontium. Of the numerous organic chemicals present, at least 54 were shared across all 5 tyre brands, with many classified to be very toxic. Our results provide a critically needed information on the toxicity of tyre tread particles and the associated chemicals that leach from them to inform future mitigation measures. We conclude that tyre particles are hazardous pollutants of particular concern that are close to or possibly above chronic environmental safety limits in some locations.

Realistic assessment of tire and road wear particle emissions and their influencing factors on different types of roads

This study aims to examine tire and road wear particle (TRWP) emissions under realistic conditions in order to provide some valuable insights into understanding their sources and fate in the environment. TRWP emissions were evaluated with a fully instrumented vehicle driving on five representative road types: urban, ring road, suburban, highway, and rural. Multiple vehicle dynamic variables were recorded to assess the factors influencing these emissions. For the first time, emitted particles were collected on filters and analyzed by means of pyrolysis coupled with gas chromatography-mass spectrometry to determine the polymeric content of tires, in specifically quantifying styrene-butadiene rubber (SBR) and butadiene rubber (BR) pyrolytic markers. The measurements obtained from the five road types revealed similar size distributions for SBR + BR emissions, with maxima found in the (ultra)fine fraction (< 0.39 µm). Upon applying an SBR + BR-to-TRWP conversion factor, (ultra)fine fraction TRWP emissions proved to be the highest for suburban (64 ± 5 µg/km), followed by highway, urban, ring road and rural routes. The output represents up to 480 tons of TRWP per year emitted in the EU27, thus suggesting a widely impregnated atmospheric compartment capable of threatening human health. Furthermore, an analysis of variables revealed that acceleration, tire constraints, and constant sustained driving factors had specific impacts on TRWP emissions.

Life stage-specific effects of tire particle leachates on the cosmopolitan planktonic copepod Acartia tonsa

Tire wear particles (TWP) are a major source of microplastics in the aquatic environment and the ecological impacts of their leachates are of major environmental concern. Among marine biota, copepods are the most abundant animals in the ocean and a main link between primary producers and higher trophic levels in the marine food webs. In this study, we determined the acute lethal and sublethal effects of tire particle leachates on different life stages of the cosmopolitan planktonic copepod Acartia tonsa. Median lethal concentration (LC50, 48 h) ranged from 0.4 to 0.6 g L-1 depending on the life stages, being nauplii and copepodites more sensitive to tire particle leachates than adults. The median effective concentration (EC50, 48 h) for hatching was higher than 1 g L-1, indicating a relatively low sensitivity of hatching to tire particle leachates. However, metamorphosis (from nauplius VI to copepodite I) was notably reduced by tire particle leachates with an EC50 (48 h) of 0.23 g L-1 and the absence of metamorphosis at 1 g L-1, suggesting a strong developmental delay or endocrine disruption. Leachates also caused a significant decrease (10-22%) in the body length of nauplii and copepodites after exposure to TWP leachates (0.25 and 0.5 g L-1). We tested a battery of enzymatic biomarkers in A. tonsa adult stages, but a sublethal concentration of 50 mg L-1 of tire particle leachates did not cause a statistically significant effect on the measured enzymatic activities. Our results show that tire particle leachates can negatively impact the development, metamorphosis, and survival of planktonic copepods. More field data on concentrations of TWPs and the fate and persistence of their leached additives is needed for a better assessment of the risk of tire particle pollution on marine food webs.

Long-term sublethal exposure to polyethylene and tire wear particles: Effects on risk-taking behaviour in invasive and native fish

Anthropogenic polymeric particles pollute even the most remote ecosystems and may compromise organisms' behaviour and movement skills. It is expected that invasive species cope better with pollutants than native species (i.e., pollution resistance hypothesis). In this study, invasive gibel carp (Carassius gibelio) and native crucian carp (Carassius carassius) were used as model organisms. Specimens were fed daily with food pellets (1 % body weight) added with 0.1 % polyethylene (PE), tire wear particles (TWPs) and control. Their behavioural parameters were compared before and after 14 and 60 days of exposure. Additionally, we evaluated burst swimming capacity after 60 days of exposure to the treatments. The fishes exposed to the PE and TWPs treatments showed significant trends toward increased boldness scores and, in the PE treatment, higher utilization of the open field, and both behavioural changes are associated with higher risk-taking. Invasive gibel carp had substantially better swimming performance than crucian carp, but the expected trend in relation to the treatments was not found. Fish exposed to sublethal doses of PE and TWPs showed signs of behavioural changes after two months of exposure that may affect risk-taking behaviour, which might impact species interactions with predators.

Sulfate radical-based advanced oxidation process effects on tire wear particles aging and ecotoxicity

Tire wear particles (TWPs) are widely distributed in natural water and pose as major pollutants in aquatic environments. In this study, heat-activated persulfate (HPT) and ultraviolet-activated persulfate treatments (UPT) were employed to investigate the influence of sulfate radical (SO4-•)-based advanced oxidation process (SAOPs) on TWP physicochemical properties and to clarify their ecotoxic effects in laboratory-level studies. Results showed that the specific surface areas of TWPs increased after UPT but decreased after HPT. In terms of chemical properties, the increase of oxygen-containing functional groups on the surfaces of TWPs was more evident in UPT than that in HPT. The atrazine (ATZ) adsorption capacity of TWPs after HPT and UPT was increased compared with the untreated TWPs. Atrazine adsorbed by TWPs was easily resolved and released in artificial intestinal fluid (1.89-2.08 mg/g) and artificial gastric fluid (1.60-2.04 mg/g) conditions. Acute toxicity experiments of Photobacterium phosphoreum and SEM-EDS detection results suggested that various heavy metals (e.g., Zn2+, Cu2+) in the TWPs would be released into the water system in SAOPs. ATZ released from TWPs that adsorbed ATZ herbicide, rather than TWPs themselves, had a negative effect on aquatic plant growth (e.g., C. vulgaris). The leaching solution of oxidized TWPs (after HPT and UPT) showed a more significant inhibition effect on the zebrafish survival compared with that of untreated TWPs, which was possibly caused by the generation of oxidation byproducts such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone.

Effect of bioturbation of the mitten crab on distribution of tire wear particles and their combined effect on sediment ecosystem

Tire wear particles (TWPs) are a major source of environmental microplastic pollution which gradually settle and accumulate in sediments after entering the aquatic environment, which can affect the behaviors of benthic organisms. Bioturbation of benthic species could affect the fate, impacts and potential risks of TWPs by altering the properties and structure of sediments. Therefore, in this study, the effect of TWPs on the burrowing activity of Chinese mitten crab (Eriocheir sinensis) was investigated. In addition, the effects of crab bioturbation on the distribution of TWPs and their additives were studied. The combined effects of TWPs and crab bioturbation on the microbial communities in the sediments were also explored. The results of this study showed that both TWPs and the leachate significantly inhibited the burrowing activity of crabs. TWPs in the surface layer of sediments were re-distributed by crab bioturbation and enriched mainly in the sediments near the burrow walls. Meanwhile, the heavy metals (i.e., Zn, Ca, Mg, Ba and Al) used as additives during the tire production in the burrow walls significantly increased as the accumulation of TWPs near burrow walls. In this study, TWP exposure decreased the bacterial diversity and abundance, as well as the functional genes related to carbon and nitrogen cycling process, but crab bioturbation increased them in the sediments of burrow walls by constructing a unique habitat. However, after TWPs entering into burrows, they were significantly decreased in the sediments near the burrow walls like the effects of TWPs, suggesting the negative effects of TWPs could play a dominant role in this combined system. Overall, this study is important for evaluating the distribution and effects of TWP pollution in the sediment ecosystem under biological factors such as bioturbation.

Exposure to 6-PPD Quinone at Environmentally Relevant Concentrations Inhibits Both Lifespan and Healthspan in C. elegans

N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD), one of the most common additives used in rubber, enters the environment due to significant emissions of tire wear particles. 6-PPD quinone (6-PPDQ) is an important derivative of 6-PPD after ozonization. With concentrations ranging from nanograms per liter to μg/L, 6-PPDQ has so far been identified in a series of water samples. Acute lethality of 6-PPDQ in coho salmon (LC50 < 1 μg/L) was lower than environmental concentrations of 6-PPDQ, highlighting the environment exposure risks of 6-PPDQ. It is becoming increasingly necessary to investigate the potential toxicity of 6-PPDQ at environmental concentrations. Here, we examined the effect of 6-PPDQ exposure on lifespan and healthspan and the underlying mechanism in Caenorhabditis elegans. Exposure to 6-PPDQ (1 and 10 μg/L) shortened the lifespan. Meanwhile, during the aging process, 6-PPDQ (0.1-10 μg/L) could decrease both pumping rate and locomotion behavior, suggesting the 6-PPDQ toxicity on healthspan. For the underlying molecular mechanism, the dysregulation in the insulin signaling pathway was linked to toxicity of 6-PPDQ on lifespan and healthspan. In the insulin signaling pathway, DAF-2 restricted the function of DAF-16 to activate downstream targets (SOD-3 and HSP-6), which in turn controlled the toxicity of 6-PPDQ on lifespan and healthspan. Additionally, in response to 6-PPDQ toxicity, insulin peptides (INS-6, INS-7, and DAF-28) could activate the corresponding receptor DAF-2. Therefore, exposure to 6-PPDQ at environmentally relevant concentrations potentially causes damage to both lifespan and healthspan by activating insulin signaling in organisms.

Disruption of dopamine metabolism by exposure to 6-PPD quinone in Caenorhabditis elegans

Caenorhabditis elegans is a useful model for examining metabolic processes and related mechanisms. We here examined the effect of exposure to N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) on dopamine metabolism and underling molecular basis in nematodes. The dopamine content was reduced by 6-PPDQ (1 and 10 μg/L). Meanwhile, dopamine related behaviors (basal slowing response and area restricted searching) were changed by 6-PPDQ (1 and 10 μg/L). Exposure to 6-PPDQ (1 and 10 μg/L) decreased expressions of genes (cat-2 and bas-1) encoding enzymes governing dopamine synthesis and cat-1 encoding dopamine transporter. Development of dopaminergic neurons was also affected by 10 μg/L 6-PPDQ as reflected by decrease in fluorescence intensity, neuronal loss, and defect in dendrite development. Exposure to 6-PPDQ (1 and 10 μg/L) altered expressions of ast-1 and rcat-1 encoding upregulators of cat-2 and bas-1. The dopamine content and expressions of cat-2 and bas-1 were inhibited by RNAi of ast-1 and increased by RNAi of rcat-1 in 6-PPDQ exposed nematodes. Using endpoints of locomotion behavior and brood size, in 6-PPDQ exposed nematodes, the susceptibility to toxicity was caused by RNAi of ast-1, cat-2, bas-1, and cat-1, and the resistance to toxicity was induced by RNAi of rcat-1. Therefore, 6-PPDQ exposure disrupted dopamine metabolism and the altered molecular basis for dopamine metabolism was associated with 6-PPDQ toxicity induction. Moreover, the defects in dopamine related behaviors and toxicity on locomotion and reproduction could be rescued by treatment with 0.1 mM dopamine.

Toxicity of 6PPD-quinone to four freshwater invertebrate species

The antioxidant N-(1,3-Dimethylbutyl)-N'-phenyl-p- phenylenediamine (6PPD) is used to protect the rubber in tires from oxidation, which extends the life of the tire. When oxidized, 6PPD is transformed into 6PPD-quinone (6PPDQ). 6PPDQ, along with other tire ingredients, can enter aquatic ecosystems through the transport of tire wear particles in runoff during a precipitation event. The mass mortality of coho salmon following precipitation events in urban areas lead to the discovery that 6PPDQ is the likely cause due to coho salmon's relatively high sensitivity to 6PPDQ. The assessment of 6PPDQ toxicity to other aquatic species has expanded, but it has focused on fish. This study investigated the toxicity of 6PPDQ to four freshwater invertebrate species, larval burrowing mayfly (Hexagenia spp.), juvenile cladoceran (Daphnia magna), file ramshorn snail embryo (Planorbella pilsbryi), and adult washboard mussel (Megalonaias nervosa). For all four species, the highest concentration of 6PPDQ tested did not result in significant mortality. This translated into the determination of the highest concentration that did not cause significant mortality (NOEC) for Hexagenia spp., D. magna, P. pilsbryi, and M. nervosa of 232.0, 42.0, 11.7, and 17.9 μg/L, respectively. The data from this study indicate that freshwater invertebrates are not as sensitive to 6PPDQ as some salmonid species (e.g., coho salmon Oncorhynchus kisutch). This study also analyzed 6PPDQ in road runoff from around the city of Guelph in Ontario, Canada. 6PPQ was detected in all samples but the concentration was two orders of magnitude lower than the NOECs for the four tested species of freshwater invertebrate.

Toxicity of tire particle leachates on early life stages of keystone sea urchin species

Particles from tires are a major fraction of microplastic pollution. They contain a wide range of chemical additives that can leach into the water and be harmful to aquatic organisms. In this study, we investigated the acute toxicity of tire particle leachates in early life stages of three keystone echinoderm species (Paracentrotus lividus, Arbacia lixula, Diadema africanum). Embryos were exposed for 72 h to a range of leachate dilutions, prepared using a concentration of 1 g L-1. Larval growth, abnormal development, and mortality were the measured endpoints. Furthermore, we estimated the activity of glutathione S transferase (GST) and the electron transport system (ETS) in P. lividus. Strong concentration-dependent responses were observed in all species, though with differing sensitivity. The median effect concentrations for abnormal development in P. lividus and A. lixula were 0.16 and 0.35 g L-1, respectively. In D. africanum, mortality overshadowed abnormal development and the median lethal concentration was 0.46 g L-1. Larvae of P. lividus were significantly smaller than the control from 0.125 g L-1, while the other two species were affected from 0.5 g L-1. ETS activity did not change but there was a non-significant trend of increasing GST activity with leachate concentration in P. lividus. Seven organic chemicals and eight metals were detected at elevated concentrations in the leachates. While we regard zinc as a strong candidate to explain some of the observed toxicity, it can be expected that tire particle leachates exhibit a cocktail effect and other leached additives may also contribute to their toxicity. Our results emphasize the importance of multi-species studies as they differ in their susceptibility to tire particle pollution. We found negative effects at concentrations close to projections in the environment, which calls for more research and mitigation actions on these pollutants.

Toxic effects of tire wear particles and the leachate on the Chinese mitten crab (Eriocheir sinensis)

Tire wear particles (TWPs) were considered as an important component of microplastic pollution in the aquatic environment. To understand the ecotoxicity of TWPs to crustacean, this study investigated toxic effects of TWPs and the leachate on the mitten crab Eriocheir sinensis and the accumulation of TWPs in the crabs. Although TWPs could be accumulated in various tissues (i.e., liver, gills and gut) of the crabs, exposure to TWPs or the leachate had no lethal effect on the crabs in this study. Lower concentrations of TWPs and the leachate exposure could stimulate the antioxidant defense system of the crabs, while higher concentrations could disrupt the stress defense system. In addition, the energy supply and metabolism of the crabs could also be affected by TWPs or the leachate. The transcriptomic profiles showed that the toxic mechanisms of TWPs and the leachate were not exactly the same. Similar to the results of biochemical analysis, several Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to oxidative stress and energy metabolism were significantly regulated by both TWPs and the leachate. However, TWPs could affect the expression of genes enriched in immune-related pathways, while the leachate regulated the enrichment of some other signaling pathways including FoxO signaling pathway, insulin signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, PPAR signaling pathway and neuroactive ligand-receptor interaction. Overall, our study could provide basic biological information for assessing the ecological risk of the TWP pollution in the aquatic environment and was useful to understand the potential toxic mechanisms of the TWPs and the leachate to crustaceans.

Acute toxicity of tire wear particles and leachate to Daphnia magna

Tire wear particles (TWP) are a new pollutant widely present in the environment, and have been identified as microplastics (MPs), which are receiving increasing attention due to their toxic effects on aquatic organisms. In this study, D. magna was used as test organism, and the leachate from TWP was prepared by hot water extraction for 30 (30-E) and 120 min (120-E). The acute toxic effects of particles and leachate on D. magna were studied under different exposure concentrations. The results showed that zinc and pyrene were the highest detected contaminants in the leachate. The 48 h-LC50 values for particles and leachate were determined to be 56.99, 461.30 (30-E), and 153.00 mg/L (120-E), respectively. Following a 48 h exposure period, the immobilization of D. magna exposed to the particles and their leachate were increased with the concentration increase. The physical damage of the gut was found to be a possible mechanism for particle-induced biotoxicity. The compounds leached from TWP were responsible for the acute toxicity of leachate. Particles usually demonstrated a greater degree of toxicity in comparison to their leachate, especially at environmentally relevant concentrations. Exposure to particles and leachate resulted in the inhibition of swimming speed, swimming acceleration, filtration rate, and ingestion rate in D. magna. Furthermore, thoracic limb activity was observed to be inhibited. The heart rate of D. magna was significantly increased by the presence of particles at a concentration of 200 mg/L and leachate at concentrations of 400 and 800 mg/L (120-E). The observed alterations in behavior and physiological endpoints may be related to oxidative stress and neurotoxicity in the organism. Reduced superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities indicated that D. magna may suffer from excessive oxidative stress, whereas the increase of acetylcholinesterase (AChE) activity may serve as a biomarker of susceptibility to evaluate the environmental risks of TWP and corresponding leachates as potential aquatic pollutants.. Therefore, a more comprehensive risk assessment of TWP in the environment is necessary.

Rising seas and roadway debris: Microplastic and low-density tire wear particles in street-associated tidal floodwater

Tidal flooding is increasingly common in low-lying coastal regions as sea levels rise. This type of flooding can occur on sunny days with no rainfall and may transport street-associated debris, such as microplastics (MPs) including tire wear particles (TWPs), to coastal systems. This research aimed to quantify MP abundance in tidal floodwater and investigate their fate. Three locations around Charleston, SC (USA) were sampled during 12 tidal floods, and their adjacent tidal creeks were sampled before and after 5 floods. Floodwater contained an average of 342 ± 60 MP/L. Most MPs in floodwater were low-density TWP (86.5 %). MP abundance in tidal creek surface water following flooding did not change, suggesting that MPs were not immediately transferred to coastal waterways but deposited in adjacent marsh sediment. Elucidating transport routes of MPs in coastal environments is critical to understanding and preventing this type of contamination in the face of a changing climate.

Lethal effect of leachates from tyre wear particles on marine copepods

With thousands of tons of Tyre Wear Particles (TWP) entering the aquatic environment every year, TWP are considered a major contributor to microplastic pollution. TWP leach organic compounds and metals in water, potentially affecting the marine food web. However, little is known about the toxicity of TWP leachates on marine copepods, a major food web constituent, and a key group to determine the environmental risk of pollution in marine ecosystems. In this study, we determined the lethal effect of TWP leachates on marine copepods after 24, 48, and 72-h of exposure to 0.05-100% leachate solutions prepared using a concentration of 5 g TWP L-1. The calanoids Acartia tonsa, Temora longicornis and Centropages hamatus, the cyclopoid Oithona davisae and the harpacticoid Amonardia normanni were used as experimental species. TWP leachates were toxic to all the studied species, with toxicity increasing as leachate solution and exposure time increased. Median lethal concentration (LC50, 72-h) ranged from 0.22 to 3.43 g L-1 and calanoid copepods were more sensitive to TWP leachates than the cyclopoid O. davisae and the harpacticoid A. normanni. Toxicity of TWP leachates was not related to the copepod body size, which suggests that other traits such as foraging behaviour or adaptation to contaminants could explain the higher tolerance of cyclopoid and harpacticoid to TWP leachates compared to calanoid copepods. Although field data on the concentration of TWP and their chemical additives are still limited, our results suggest that TWP leachates can negatively impact planktonic food webs in coastal areas after road runoff events.

Tire wear particles in different water environments: occurrence, behavior, and biological effects-a review and perspectives

As an important source of microplastics, the water ecological risk of tire wear particles (TWPs) has attracted widespread attention worldwide. However, the occurrence and behavior of TWPs and their biological effects in water environments have not been clearly analyzed. For example, most contemporary studies have focused on the evaluation of the aquatic toxicity of TWPs leachate, and little attention has been paid to the behavior process and potential risks of its surface properties in water environments. In addition, most studies rely on preparing TWPs under laboratory conditions or purchasing commercial TWPs for studying their water environmental behavior or exposure. These obviously cannot meet the requirements of accurate assessment of water ecological risks of TWPs. As thus, in addition to describing the occurrence, distribution, and (aging) transformation of TWPs in different water environments, we further tried to explain the potential water environment behavior process and multiple pathways leading to potential adverse impacts of TWPs on aquatic organisms from the perspectives of particle self-toxicity and release toxicity, as well as synergistic effects of TWPs and other substances are also discussed. The existing data, such as studies on the self-characteristics of TWPs, environmental factors, and subjects, are insufficient to comprehensively evaluate the recent changes in essential water ecosystem services and multifunctions caused by TWPs, implying that the impact of TWPs on water environmental health needs to be further evaluated, and the corresponding countermeasures should be recommended. In this context, the current review provides an outlook on future research on TWPs in aquatic environments.

Ubiquity of Amino Accelerators and Antioxidants in Road Dust from Multiple Land Types: Targeted and Nontargeted Analysis

Amino accelerators and antioxidants (AAL/Os), as well as their degradation derivatives, are industrial additives of emerging concern due to their massive production and use (particularly in rubber tires), pervasiveness in the environment, and documented adverse effects. This study delineated their inter-regional variations in road dust collected from urban/suburb, agricultural, and forest areas, and screened for less-studied AAL/O analogues with high-resolution mass spectrometry. 1,3-Diphenylguanidine (DPG; median concentration: 121 ng/g) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q; 9.75 ng/g) are the most abundant congeners, constituting 69.7% and 41.4% of the total concentrations of AAL/Os (192 ng/g) and those of AAO transformation products (22.3 ng/g), respectively. The spatial distribution across the studied sites suggests evident human impacts, reflected by the pronounced urban signature and vehicle-originated pollution. Our nontargeted analysis of the most-contaminated road dust identified 16 AAL/O-related chemicals, many of which have received little investigation. Particularly, environmental and toxicological information remains extremely scarce for five out of the 10 most concerning compounds prioritized in terms of their dusty residues and toxicity including 1,2-diphenyl-3-cyclohexylguanidine (DPCG), N,N''-bis[2-(propan-2-yl)phenyl]guanidine (BPPG), and N-(4-anilinophenyl)formamide (PPD-CHO). Additionally, dicyclohexylamine (DChA), broadly applied as an antioxidant in automobile products, had an even greater median level than DPG. Therefore, future research on their health risks and (eco)toxic potential is of high importance.

Urban runoff mortality syndrome in zooplankton caused by tire wear particles

Stormwater runoff from roadways is a global threat to water quality, aquatic organisms, and ecosystems. Tire tread wear particles (TWP) from roadway runoff may lead to urban runoff mortality syndrome (URMS) in some aquatic organisms. We tested the hypothesis that urban runoff from roadways can kill zooplankton. Both roadway runoff and TWP leachate were acutely lethal to a model species, the water flea Daphnia pulex. Life table experiments further revealed the lowered survival rates, intrinsic rate of increase, average life span, and net productive rate of D. pulex when exposed to roadway runoff and TWP leachate. The tire rubber antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) mainly contributed to the TWP toxicity. The toxicity of TWP and 6PPD extracted varied with time in nature. Cladocerans and rotifers were more sensitive to TWP and 6PPD than copepods. These results demonstrate the presence of URMS in zooplankton, which may cascade through food webs and affect aquatic ecosystems.

Identifying potential toxic organic substances in leachates from tire wear particles and their mechanisms of toxicity to Scenedesmus obliquus

Tire wear particles (TWPs) are increasingly being found in the aquatic environment. However, there is limited information available on the environmental consequences of TWP constituents that may be release into water. In this study, TWP leachate samples were obtained by immersing TWPs in ultrapure water. Using high-resolution mass spectrometry and toxicity identification, we identified potentially toxic organic substances in the TWP leachates. Additionally, we investigated their toxicity and underlying mechanisms. Through our established workflow, we structurally identified 13 substances using reference standards. The median effective concentration (EC₅₀) of TWP leachates on Scenedesmus obliquus growth was comparable to that of simulated TWP leachates prepared with consistent concentrations of the 13 identified substances, indicating their dominance in the toxicity of TWP leachates. Among these substances, cyclic amines (EC₅₀: 1.04-3.65 mg/L) were found to be toxic to S. obliquus. We observed significant differential metabolites in TWP leachate-exposed S. obliquus, primarily associated with linoleic acid metabolism and purine metabolism. Oxidative stress was identified as a crucial factor in algal growth inhibition. Our findings shed light on the risk posed by TWP leachable substances to aquatic organisms.

From prey to predators: Evidence of microplastic trophic transfer in tuna and large pelagic species in the southwestern Tropical Atlantic

Plastic pollution is present in most marine environments; however, contamination in pelagic predators, including species of economic interest, is still poorly understood. This study aims to access the macro- and microplastic contamination in tuna and large pelagic species and verify whether a trophic transfer occurs from prey to tunas captured by two fleets in the Southwestern Tropical Atlantic (SWTA). We combined different methodological approaches to analyse the intake of macro- and microplastics. In addition to examining the plastics in the fish' stomachs, we investigated the contamination in the prey retrieved from the guts of predators. A low frequency of occurrence (3%) of macroplastic was detected in the tuna and large pelagic species; conversely, we observed a high frequency of microplastic in the tuna's stomachs (100%) and prey analysed (70%). We evinced the trophic transfer of microplastics by analysing the ingestion rate of particles in prey retrieved from the tuna stomachs. In the 34 analysed prey, we detected 355 microplastic particles. The most contaminated prey were cephalopods and fishes of the Bramidae family. The most frequent microplastic shapes in both prey and tuna stomachs were foams, pellets and fibres (<1 mm). A variety of polymers were identified; the most frequent were styrene-butadiene rubber (SBR), polyamide (PA), polyethylene terephthalate (PET) and polyethylene (PE). Our findings enhance scientific knowledge of how the ecological behaviour of marine species can affect microplastic intake.

Chemical toxicity screening of tire particle leachates from vehicles and their effects on organisms across three trophic levels

Tire particles (TPs) generated on roads are a main contributor to microplastic environmental pollution. In this study, TP leachates from three vehicle types (bicycle, car, and electric scooter) were prepared. TP leachate toxicity impacts on three organisms (Vigna radiata, Daphnia magna, and Danio rerio) were analyzed, in addition to their chemical compositions. Zinc and benzothiazole were the most commonly detected compounds in all three leachate types. Growth inhibition of V. radiata, mortality of D. magna, and abnormality in D. rerio were observed as toxicological impacts. Overall, the lethal effects of TP leachates showed a significant, positive relationship with zinc and benzothiazole concentration. The results confirmed that TPs are complex contaminants, which release chemicals into the environment that affect both soil and aquatic organisms. These findings highlight the need for stricter control measures and environmental regulations to mitigate the ecotoxic effects of TPs and related contaminants across ecosystems and trophic levels.

A protocol for lixiviation of micronized plastics for aquatic toxicity testing

Plastics contain various types and amounts of additives that can leach into the water column when entering aquatic ecosystems. Some leached plastic additives are hazardous to marine biota at environmentally relevant concentrations. Disparate methodological approaches have been adopted for toxicity testing of plastic leachates, making comparison difficult. Here we propose a protocol to standardize the methodology to obtain leachates from microplastics (MPs) for aquatic toxicity testing. Literature reviewing and toxicity tests using marine model organisms and different types of MPs were conducted to define the main methodological aspects of the protocol. Acute exposure to leachates from the studied plastics caused negative effects on the early life stages of sea urchins and marine bacteria. We provide recommendations of key factors influencing MPs lixiviation, such as MP size (<250 μm), solid-to-liquid ratio (1-10 g/L), mixing conditions (1-60 rpm), and lixiviation time (72 h). The proposed methodology was successful to determine the toxicity of leachates from different micronized plastics on marine biota. Our recommendations balance feasibility and environmental relevance, and their use would help ensure comparability amongst studies for a better assessment of the toxicity of plastic leachates on aquatic biota.

Multi-endpoint effects of derelict tubular mussel plastic nets on Tigriopus fulvus

Microplastic debris from direct and indirect human activities is considered a major threat to the marine biodiversity mainly due to its abundance, durability, persistence, and ability to accumulate contaminants from the environment. Derelict tubular plastic nets of various colours (blue (BN), yellow (YN), green (GN), pink (PN), and white (WN) net), used to distinguish mussel farming owners, were collected by scuba-dive from the Mar Piccolo of Taranto (Ionian Sea). All nets were made of polypropylene. Investigations looked for potential acute (mortality) and sub-chronic (mortality, larval development and moult release number, and adult percentage after 5-9 days) effects on Tigriopus fulvus nauplii considering both whole plastics (microplastic (MP), 50 mg/L) and leachates (12.5-100%). Acute test determined a median lethal concentration (LC50) only for BN for both MPs (107 mg/L) and leachates (50.1%). The prolonged exposure (5 days) to microplastics did not affect the T. fulvus survival. After 9 days, YN and BN decreased of approximately 100% larval development.

Toxicity of tire wear particles and the leachates to microorganisms in marine sediments

Tire wear particles (TWPs), which are among the microplastic pollutants in the environment, can inevitably accumulate in coastal sediments. The present study comprehensively investigated the effect of pristine TWPs on bacterial community structure in coastal sediments and compared the effect of pristine TWPs and aged TWPs on nine strains of bacteria in sediments. In addition, the effect of the TWP leachate was studied with all the nine bacterial strains and the toxicity-causing substances in the leachate was investigated using Bacillus subtilis. Exposure to TWPs could lead to a shift in bacteria community and affect nitrogen metabolism in marine sediments. Aged TWPs were more toxic than pristine TWPs due to changes in particle surface characteristics. The leachate exhibited greater toxicity than TWPs as well, and Zn was identified to be the major toxicity-causing substance. The overall results of this study are important for understanding the effects of TWPs and the leachates on microorganisms in marine sediments.

Phenotypic toxicity, oxidative response, and transcriptomic deregulation of the rotifer Brachionus plicatilis exposed to a toxic cocktail of tire-wear particle leachate

Tire-wear particles (TWPs) are potential source of microplastic (MP) pollution in marine environments. Although the hazardous effects of MPs on marine biota have received considerable attention, the toxicity of TWPs and associated leachates remain poorly understood. Here, to assess the toxicity of TWP leachate and the underlying mechanisms of toxicity, the phenotypic and transcriptomic responses of the rotifer Brachionus plicatilis were assessed with chemistry analysis of a TWP leachate. Although acute toxicity was induced, and a variety of metals and polyaromatic hydrocarbons were detected in the leachate, levels were below the threshold for acute toxicity. The results of particle analysis suggest that the acute toxicity observed in our study is the result of a toxic cocktail of micro- and/or nano-sized TWPs and other additives in TWP leachate. The adverse effects of TWP leachate were associated with differential expression of genes related to cellular processes, stress response, and impaired metabolism, with further oxidative stress responses. Our results imply that TWPs pose a greater threat to marine biota than other plastic particles as they constitute a major source of nano- and microplastics that have synergistic effects with the additives contained in TWP leachate.