Tire Particles Research Articles

Comparison of Methods for Sampling Particulate Emissions from Tires under Different Test Environments

Traffic-related emissions are strongly criticised by the public because they contribute to climate change and are classified as hazardous to health. Combustion engine emissions have been regulated by limit values for almost three decades. There is currently no legal limit for non-exhaust emissions, which include tire wear particle emissions and resuspension. As a result, the percentage of total vehicle emissions has risen continuously. Some of the particles emitted can be assigned to the size classes of particulate matter (≤10 µm) and are therefore of particular relevance to human health. The literature describes a wide range of concepts for sampling and measuring tire wear particle emissions. Because of the limited number of studies, the mechanisms involved in on-road tests and their influence on the particle formation process, particle transport and the measuring ability can only be described incompletely. The aim of this study is to compare test bench and on-road tests and to assess the influence of selected parameters. The first part describes the processes of particle injection and particle distribution. Based on this, novel concepts for sampling and measurement in the laboratory and in the field are presented. The functionality and the mechanisms acting in each test environment are evaluated on the basis of selected test scenarios. For example, emissions from external sources, the condition of the road surface and the influence of the driver are identified as influencing factors. These analyzes are used to illustrate the complexity and limited reproducibility of on-road measurements, which must be taken into account for future regulations.

Black microplastics in the environment: Origin, transport and risk of tire wear particles

With the continuous growth of vehicle per capita in recent years, tire wear particles (TWP) produced by tire wear on roads have been widely found in various environmental media, whose environmental behavior and effects have attracted extensive attention. After being produced, these microsized and nanosized TWP will drift into the atmosphere or enter the surrounding soil, rivers, and even into the ocean with rain and runoff. The existence of TWP significantly affects the composition of organic materials in the environment. Meanwhile, the release of heavy metals and organic additives from TWP will be harmful to organisms and human health. We summarized the sources and characteristics of TWP, their migration and diffusion in water, atmosphere, and soil environment. By analyzing the environmental impacts and ecological risks of TWP pollution, we proposed the key questions urgently to be solved and prevention measures.

A recent overview of the effect of road surface properties on road safety, environment, and how to monitor them.

Road pavements are exposed to traffic loading and external deterioration agents which both can compromise tire-pavement interactions, posing a threat to road safety. The surface wear generates crushed pavement materials or tire rubber wear particles which, combined with other contaminants, negatively impact the environment. In fact, these particles may remain on the road surface; adhere to tires; become airborne; or drain by rainfall to roadsides, waterways, lakes, and even open oceans. Therefore, the presence of road contaminants on road infrastructure pavements is a concern for both road safety and the environment. Although the condition of pavement, traffic intensity, airborne dust emissions, and roadside environments are significantly monitored by road practitioners, especially in urban areas, there is still a need to better evaluate the pollutants remaining on road surfaces. It is known that particles smaller than 40 μm can be trapped within micro-asperities and remain on road surfaces, while particles of larger sizes can be transported by rainfall. However, it is difficult to mobilize particles with sizes larger than 105 μm by storm water runoffs, which tend to remain on road surfaces. Hence, not only rainfall characteristics are responsible of particle's kinetics, but also particle's size and road surface roughness are important. Therefore, this paper presents an overview of road safety and environmental concerns around contaminants, highlighting the importance of the road surface characteristics in their behavior. Finally, the current methods to measure road surface characteristics and their application for environmental and safety issues are discussed.

Chronic toxicity of tire crumb rubber particles to mummichog (Fundulus heteroclitus) in episodic exposures

Microrubber (MR) encompasses all tire-related particles in the micro-scale and has recently drawn increased attention as a subclass of the broader group of microplastics. While tire particles entered the environment since the introduction of rubber tires for vehicles, the concern regarding tire wear particles (TWP) as an environmental contaminant is relatively new. Recent studies have examined physical and chemical toxicity of MR particles and leachates to a variety of organisms. However, there is a lack of information on the long-term effects of tire particle exposure under environmentally realistic conditions. The current study examined the chronic toxicity of crumb rubber (CR) particles to the estuarine fish species, mummichog (Fundulus heteroclitus) under episodic exposures at environmentally relevant concentrations. Immunohistochemistry (IHC) of fish gill, intestine, and liver was performed to assess CYP1A induction in these organs. Bile fluorescence was measured as an indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) from CR. DNA damage was measured through the formation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) together with other oxidative stress measures as lipid peroxidation (TBARS assay), free glutathione (GSH), and oxidized glutathione (GSSG) concentrations. Upregulation of CYP1A in gill, intestine, and liver was observed especially in gill filaments and general vasculature. Increased bile fluorescence demonstrated exposure to aromatic compounds, especially pyrene-like PAHs. Data for DNA damage indicated greater plasma 8-OHdG concentrations as a result of increased DNA repair. There was a decrease in malondialdehyde (MDA) production and an increase in total GSH at higher concentrations of CR. It appeared that under long-term repeated dosing, antioxidant systems in mummichog were upregulated to deal with exogenous stressors released by the CR particles. Combined, these data demonstrate that fish exposed to tire crumb rubber particles illicit significant biomarker responses under environmentally relevant CR concentrations, but induced antioxidant and detoxification pathways may prevent mortality and serious physiological effects in F. heteroclitus when exposed to environmentally relevant concentrations of CR.

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.

A Preliminary European-Scale Assessment of Microplastics in Urban Wastewater

Microplastics (MP) are not well defined from an analytical point of view and their measurement in the environment is still challenging. At the same time, their increasingly widespread presence is raising concerns for human health and ecosystems. In this contribution, we present a preliminary European-scale assessment of the environmental input of MP through urban wastewater and urban runoff. We quantify the emissions associated with urban wastewater based on the range of observed concentrations in wastewater treatment plants (WWTPs) effluents, and the emissions from tire wear particles (TWP) by assuming that a percentage of the particles generated on roads eventually reaches surface waters. In spite of the large uncertainties entailed in the calculation, it is apparent that TWP dominate the input of total plastic loads into European surface waters. The management of urban runoff, road runoff, and combined sewer overflows (CSO) is essential to control the emissions of MP from urban areas. On the other hand, WWTPs retain the majority of MP in the sewage sludge. The spreading of sewage sludge onto soil therefore represents a potential pathway of MP from urban wastewater into the environment.

Experimental and computational hazard prediction associated with reuse of recycled car tire material

The paper presents research on the emission of pollutants from used car tires in the form of microparticles. Due to the large amount of waste generated in the form of used car tires, a method is being sought to utilize this material as secondary raw material. More and more frequently, this waste is used in civil engineering. To do this, it is necessary to determine the environmental impact of this waste. 2 g of microplastic samples with fractions of 3000–8000, 1000–3000, 1000, and 600 µm were incubated in water protected from light. The influence of pH (3, 7, and 10), incubation time (1, 3, 5, 7, and 14 d) and temperature (20, 60, and 90 °C) on the degree of emission of selected phthalic acid esters and other tire components was investigated. Additionally, the influence of the decomposition of the analyzed material on the emission of methane and carbon dioxide at the temperature of 20 °C during 30, 180, and 360 days was investigated. The analysis of the amount of released substances was carried out using a gas chromatograph coupled with a mass spectrometer. Greenhouse gas analysis was performed using a gas chromatograph with a Barrier Discharge Ionization Detector. The research carried out confirmed that, depending on the environmental conditions, tire particles leach out, among others, phthalates, benzenediamine, phenol, benzothiazole, and benzene. Influence of particle size, pH value, incubation time, and temperature on the degree of emission of selected plasticizers was investigated. An innovative aspect of the research was the use of artificial neural networks to identify the validity of using machine algorithms in environmental research. An additional negative aspect of the implementation of tire particles in the water-soil environment is the emission of carbon dioxide and methane that are greenhouse gases.

Accumulation and depuration of microplastic fibers, fragments, and tire particles in the eastern oyster, Crassostrea virginica: A toxicokinetic approach

Along the South Carolina coast (U.S.) where the ecologically and economically important eastern oyster (Crassostrea virginica) forms extensive intertidal reefs, recent surface water surveys found that fibers, fragments, and microscopic tire particles represented 43.6%, 30.9%, and 17.7% of the total microplastics, respectively. The aim of this study was to characterize accumulation and depuration of these particles in eastern oysters. Oysters were exposed to purple polyethylene fibers, green nylon fragments, or micronized crumb rubber at a concentration of 5000 microplastics/L, and sacrificed after 0, 24, 48, and 96 h to characterize uptake. Following 96 h, remaining oysters were transferred to microplastic-free brackish water and sacrificed at 24, 48, and 96 h to characterize depuration. For fibers and fragments, levels increased in a nonlinear fashion reaching 1.61 ± 0.6 particles/g w. w. (mean ± SE) and 0.46 ± 0.1 particles/g w. w. after 96 h, respectively. Conditional uptake clearance rate constants (ku) were estimated to be 0.0084 and 0.0025 mL/g*h for fibers and fragments, respectively. For crumb rubber, levels increased in a linear fashion reaching 3.62 ± 0.8 particles/g w. w. after 96 h, and the ku value was estimated to be 0.0077 mL/g*h. Depuration was best described using a two-compartment (double exponential) model suggesting the presence of fast and slow compartments. Conditional depuration rate constants (kd) for the slow compartments were 0.0084, 0.0205, and 0.0048/h for fibers, fragments, and crumb rubber, respectively. These results demonstrate accumulation and depuration of microplastics in eastern oysters is size-and shape-dependent. Depuration, which is a common practice for shellfish safety, is an effective way to reduce microplastic loads in eastern oysters, but the minimum recommended time of 44 h would only reduce loads of these particles by 55.5–67.6%.

Toxicity assessment of tire particles released from personal mobilities (bicycles, cars, and electric scooters) on soil organisms

Tire particles are generated by the abrasion of tire treads on roads and are major contributors to microplastics in soil environments. Contamination by tire wear particles worsens annually as the use of personal mobilities increases. Tire particles (112–541 µm) were obtained from three types of personal mobility tires (bicycle, car, and electric scooter) and exposed to plants (Vigna radiata) and springtails (Folsomia candida) for 28 d to assess the toxicity of each tire-particle type. The laboratory-generated tire particles exhibit adverse effects depending on the origin of the tire or test species. Particles from bicycle or electric-scooter tires changed the soil’s bulk density and water holding capacity and adversely affected plant growth. Car tire particles had leached various organic compounds and induced detrimental effects on springtails (adult and offspring growth). We concluded that laboratory-generated tire particles (frow new tires) can affect the soil environment by changing soil properties and leaching chemicals; thus, causing adverse effects on soil organisms. Since this study found tire particle toxicity on soil organisms, it would be possible to compare the various contamination levels in areas near road soil and other clean soils.

Effect of treadwear grade on the generation of tire PM emissions in laboratory and real-world driving conditions

Tires generally wear out due to the friction between the tire and the road surface. Minimizing tire wear could reduce the non-exhaust particulate matter (PM) emissions from tires. Typically, tire treadwear grade can be used as an indicator of PM emissions from tires. Tires that wear out quickly will produce higher PM emissions than more durable tires. In this study, the effect of treadwear grade on the generation of tire PM emissions was investigated through laboratory and on-road driving measurements. In the laboratory measurements, a tire wear simulator installed in an enclosed chamber was used to eliminate artifacts caused by interfering particles during the generation and measurement of tire wear particles. For realistic on-road driving measurements, a mobile sampling vehicle was employed to sample road dust. The road dust was chemically analyzed using pyrolysis gas chromatography–mass spectrometry (GC–MS) to characterize the tire-road wear particles.Both measurements showed that the higher treadwear grade generated lower tire PM emissions due to the high strength of the rubber, except for the UTQG 700 tire. The UTQG 700 tire, which had the highest treadwear grade, produced higher PM emissions than the UTQG 350 and 500 tires because it readily formed the fine particles due to lamellar peeling rather than tearing or curling of tire treads. Notably, tire nanoparticles were observed in laboratory measurements due to the volatilization and nucleation of the sulphur (S) and zinc (Zn) compounds in the tire tread due to the frictional heat between the tire and paved road surface.

Tire wear particles as source for environmental contaminants – Suspect Screening for more than 70 leachables in the aquatic environment

Tire wear particles as source for environmental contaminants – Suspect Screening for more than 70 leachables in the aquatic environment

Applying Existing Particle Paradigms to Inhaled Microplastic Particles.

Ambient particulate pollution originating from plastic contaminates air, including indoor and urban environments. The recent discovery of ambient microplastic (MP) particles of a size capable of depositing in the thoracic region of the airway, if inhaled, has raised concern for public exposure and health impacts following lessons learned from other particle domains. Current microplastic exposure estimates are relatively low compared to total ambient particulate matter, but optimal analytical techniques and therefore data for risk and health impact assessments are lacking. In the absence of such an evidence base, this paper explores paradigms, metrics and dose-response curves developed in other particle domains as a starting point for predicting whether microplastic are of concern. Bio-persistence, presence of reactive sites and soluble toxicants are likely key properties in microplastic toxicity, but these are not measured in environmental studies and hence are challenging to interpret in exposure. Data from a MP inhalation study in rats is available but the study was conducted using conditions that do not replicate the known human health effects of PM2.5 or surrogate exposures: compromised, aged animal models are recommended to investigate potential parallels between MPs and PM2.5. One of these parallels is provided by tire wear particles (TWP), which form part of current ambient PM and are sometimes regarded as microplastic. A connection to epidemiological studies where PM filters are still available is recommended and consequently analytical advances are required. In summary, established particle domains and existing paradigms provide valuable insight and data that can be used to predict MP toxicity, and direct study design and key properties to consider in this emerging field.

Effects of Polyester Fibers and Car Tire Particles on Freshwater Invertebrates.

Microplastic ingestion has been shown for various organisms, but knowledge of the potential adverse effects on freshwater invertebrates remains limited. We assessed the ingestion capacity and the associated effects of polyester fibers (26–5761 µm) and car tire particles (25–75 µm) on freshwater invertebrates under acute and chronic exposure conditions. A range of microplastic concentrations was tested on Daphnia magna, Hyalella azteca, Asellus aquaticus, and Lumbriculus variegatus using water only (up to 0.15 g/L) or spiked sediment (up to 2 g/kg dry wt), depending on the habitat of the species. Daphnia magna did not ingest any fibers, but low levels of fibers were ingested by all tested benthic invertebrate species. Car tire particle ingestion rose with increasing exposure concentration for all tested invertebrates and was highest in D. magna and L. variegatus. In most cases, no statistically significant effects on mobility, survival, or reproductive output were observed after acute and chronic exposure at the tested concentrations. However, fibers affected the reproduction and survival of D. magna (no‐observed‐effect concentration [NOEC]: 0.15 mg/L) due to entanglement and limited mobility under chronic conditions. Car tire particles affected the reproduction (NOEC: 1.5 mg/L) and survival (NOEC: 0.15 mg/L) of D. magna after chronic exposure at concentrations in the same order of magnitude as modeled river water concentrations, suggesting that refined exposure and effect studies should be performed with these microplastics. Our results confirm that microplastic ingestion by freshwater invertebrates depends on particle shape and size and that ingestion quantity depends on the exposure pathway and the feeding strategy of the test organism. Environ Toxicol Chem 2022;41:1555–1567. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Chemical Leaching from Tire Wear Particles with Various Treadwear Ratings.

Physical friction between a tire and the road surface generates tire wear particles (TWPs), which are a source of microplastics and particulate matter. This study investigated the trends of chemical leaching from TWPs depending on the treadwear rating of the tire. A road simulator was used to produce TWPs from tires with various treadwear ratings. Liquid chromatography–tandem mass spectrometry was used to analyze the chemical leaching from TWPs, with a particular focus on benzothiazole and its derivative 2-hydroxy benzothiazole. However, chemical mapping via high-resolution tandem mass spectrometry detected another derivative: 2-mercaptobenzothiazole. The benzothiazole groups were observed to have different leaching tendencies, implying that using benzothiazole as a marker compound may lead to incorrect TWP quantitation. The results of this research also suggest that the ecotoxicological influence of TWPs can vary with the treadwear rating of a tire.

Genotoxic effects of chlorinated disinfection by-products of 1,3-diphenylguanidine (DPG): Cell-based in-vitro testing and formation potential during water disinfection

1,3-diphenylguanidine (DPG) is a commonly used rubber and polymer additive, that has been found to be one of the main leachate products of tire wear particles and from HDPE pipes. Its introduction to aquatic environments and potentially water supplies lead to further questions regarding the effects of disinfection by-products potentially formed. Using different bioassay approaches and NGS RNA-sequencing, we show that some of the chlorinated by-products of DPG exert significant toxicity. DPG and its chlorinated by-products also can alter cell bioenergetic processes, affecting cellular basal respiration rates and ATP production, moreover, DPG and its two chlorination products, 1,3-bis-(4-chlorophenyl)guanidine (CC04) and 1-(4-chlorophenyl)−3-(2,4-dichlorophenyl)guanidine (CC11), have an impact on mitochondrial proton leak, which is an indicator of mitochondria damage. Evidence of genotoxic effects in the form of DNA double strand breaks (DSBs) was suggested by RNA-sequencing results and further validated by an increased expression of genes associated with DNA damage response (DDR), specifically the canonical non-homologous end joining (c-NHEJ) pathway, as determined by qPCR analysis of different pathway specific genes (XRCC6, PRKDC, LIG4 and XRCC4). Immunofluorescence analysis of phosphorylated histone H2AX, another DSB biomarker, also confirmed the potential genotoxic effects observed for the chlorinated products. In addition, chlorination of DPG leads to the formation of different chlorinated products (CC04, CC05 and CC15), with analysed compounds representing up to 42% of formed products, monochloramine is not able to effectively react with DPG. These findings indicate that DPG reaction with free chlorine doses commonly applied during drinking water treatment or in water distribution networks (0.2–0.5 mg/L) can lead to the formation of toxic and genotoxic chlorinated products.

Pollution from Transport: Detection of Tyre Particles in Environmental Samples

Transport is one of the most important sources of environmental pollution. More and more information has shown that one of the greatest sources of emissions from transport are emissions related to the release of microplastics from tyres. This is one of the most underestimated sources of emissions into the environment. In this study, environmental samples are analysed for the presence of these particles. For this purpose, optical methods and spectroscopic methods are used. Fourier transform infrared (FTIR) spectroscopy is used to identify synthetic rubber, most likely derived from car tyres. A complementary confocal microscopy method is used to confirm the FTIR results. The soil samples and road dust from the areas with heavy traffic are tested. An average of 372 ± 50 fragments per kilogram dry weight are detected in the soil samples. In the case of samples from the road, this number is 515 ± 20 fragments per kilogram of dry matter. In the samples, most of the microplastics come from tyres, which confirms the scientists’ assumptions about the amount of emissions in the environment. More than 90% of the black fragments later identified as tyre-derived synthetic rubber are found in the samples. A greater number of microplastics are found in road dust samples than in the soil. This may be due to the direct influence of braking, which causes greater accumulation of samples at the emission source than at a short distance into the soil. There is also a noticeable difference in the size of the fraction. In the case of soils, a fraction below 50 µm accounts for the majority of cases. When one analyses road dust samples, one may observe that most of the fractions are between 50 and 200 µm. This may be due to the possibility of smaller emission particles over longer distances and the greater degradation process that occurs in soils. The microplastics from the road dust are less degraded than the microplastics from the soil.

Thermal conductivity of scrap tire rubber-sand composite as insulating material: Experimental investigation and predictive modeling

Scrap tire rubber of good thermal insulating properties can be reused with soils as a new sustainable construction material. While the heat conduction mechanism of this tire rubber-soil composite has not been fully understood. The present study investigated the thermal behavior of scrap tire rubber-sand composite for using it as an insulating material in thermo-active applications. Several series of thermal conductivity tests were conducted on scrap tire rubber-sand composite prepared with different sand/shredded tire particle size ratios, shredded tire mixing ratios, and degrees of saturation. A predictive model was developed within the framework of normalized thermal conductivity concept that could capture the experimental data. The results showed that addition of shredded tires leads to a considerable reduction in thermal conductivity of sand, indicating great potential of using recycled scrap rubber tires in the construction of insulation layers. With an increase in degree of saturation, the order of thermal conductivity increase was found to be: sand > scrap tire rubber-sand composite > shredded tires. The spatial distribution of solid particles changed from ‘rubber-connected insulation layer’ to ‘sand-encompassed conduction path’ with increasing sand/shreds tire particle size ratio. The normalized thermal conductivity exhibited a linearly increasing trend with shredded tire mixing ratio, and the increase rate mainly depended on degree of saturation and particle size ratio. The predicted thermal conductivity showed satisfactory accuracy for engineering design, as reflected by the absolute percentage difference being controlled under 25%. The validity of the prediction model was also demonstrated based on the experimental results reported in the published literature. Additional research is recommended to assess the effects of particle morphology on thermal conduction of the binary-solid particle system.

Plastic in the air?! - Spider webs as spatial and temporal mirror for microplastics including tire wear particles in urban air

Studies concerning quantities of microplastics (MP) including tire wear particles (TWP) contamination in air samples are scarce. Spider webs have been suggested as a cheap and easily accessible biomonitor particularly for inorganic contaminates. Here, we emphasize the potential of spider webs to gain insights in the spatial and temporal trends of MP in urban air. The samples, collected in a mid-sized German city, were processed with Fentons reagent and measured using pyrolysis-gas chromatography–mass spectrometry for specific, polymer related indicator compounds. All samples contained TWP and other MP. The latter are detected and quantified as pyrolysis products of a polymer backbone. The results were expressed as clusters (prefix “C”). Determined polymer contaminations ranged from 11.4 μg/mg to 108 μg/mg spider web sample. The dominant polymer was C-PET (Ø 36.0% of total MP) derived most likely from textile fibers. Additionally, there was evidence for traffic-related contaminations. In particular car tire tread (Ø 40.8% of total MP) and ⁎C-PVC (Ø 12.0% of total MP) were found, with the latter presumably originating from paint used for road markings. Truck tire tread, C-PE, C-PP, C-PS, C-PMMA, and C-PC were also frequently found, but in much lower abundance (Ø <6.4% of total MP). Differences in contamination levels could be plausibly related to the sampling locations.

Minimising Environmental Impacts of Tyre and Road Wear Particles

Minimising Environmental Impacts of Tyre and Road Wear Particles

Tire wear particle emissions: Measurement data where are you?

Tire wear particle (TWP) emissions are gaining more attention since they are considered to contribute a major share to the overall microplastic emissions and are suspected to be harmful to flora, fauna and humans. Hence, recent studies derived country-based TWP emissions to better understand the significance of the problem using either tire emission factors (EF) or a material flow analysis (MFA) of tires. However, all 14 country-based TWP emission studies found and published since the year 2000 base their calculation on other studies rather than own measurements. Therefore, we started to search for the actual TWP measurements which the 14 studies would rely on. As a result, we found a network of 63 studies which were used to derive TWP emissions in different countries and regions. Only in few cases (12%) TWP emission studies reference directly to a measurement study to derive TWP emissions, but mostly (63%) they rely on reviews or summarizing studies. Additionally, we could not obtain 25 studies in the analysed network. In total we found nine studies which actually measured TWP emissions. Out of these four studies originate from the 1970s, one analysed only light vehicles and one only considered buses. Thus, only three non peer-reviewed studies were considered to show trustful results which were cited a maximum of three times in the network. The obtained 14 country-based studies suggest TWP emissions of about 1.3 kg capita−1 year−1 for the EF approach and 2.0 kg capita−1 year−1 for the MFA approach (overall range: 0.9–2.5 kg capita−1 year−1). Consequently, we call for an urgent need to minimize uncertainties of TWP emission estimates to better understand the contribution of TWP to the overall microplastic pollution of the environment. A better understanding about quantities could also help to better address the risk of environmental pollution by TWP.