Recently, models on the fate of tyre wear particles (TWPs) have estimated that 18% of TWP emissions are transported from roads to freshwater bodies and approximately 2% are led out to estuaries and then marine habitats. What then happens to the remaining 16% of TWP emissions left in the freshwater compartment is not yet clear

 

The presence of tyre wear particles (TWP) in the aquatic environment is considered an emerging contaminant, and one that has gained increasing interest during the past few years. Although the presence of TWPs in the environment is given greater attention these days, TWPs have probably been present since the dawn of the pneumatic car tyre production in the late 19th century. The first scientific report of tyre dust identification along a roadside was published in 1961. Different perspectives have since been applied to this field of research and almost decade by decade shifted foci from degradation patterns to heavy metal release, to impacts of scrap tyres on the aquatic environment and leaching of chemicals from tyres. More recently, research within this field has been directed towards repurposing scenarios using crumb rubber in turf fields and playground material. Finally, in the 2010s, micronised tyre rubber has become grouped with other polymer debris and hence become part of the polymer landscape usually referred to as ‘microplastics.’ TWPs are considered to represent the majority of microplastics (or polymer debris) in the environment, and the newest calculation on the wear of tyres is estimated at 0.81 kg per person per year.

Now, looking at TWPs through the lens of microplastic pollution, research and information from the microplastics field are very well applicable to TWPs in many instances. With this new perspective of TWPs, increasing awareness of possible adverse effects in the environment follows - how do TWPs distribute in the different environmental compartments (soil, air, sediment, water and biota (living organisms)) and how do TWPs behave when exposed to different abiotic factors in these environmental compartments. For example, UV-radiation or pH, temperature and salinity differences could affect TWPs, but to what degree? A recent paper on this very subject concluded that particularly temperature and mechanical stress could influence the toxicity of TWPs. The focus of tyre production and function have seemingly always been directed towards maximising the three hallmarks: grip, wear and rolling resistance, and rightfully so, but somewhere along the road we forgot to consider where tyre abrasion actually disappears to. Luckily, some scientists already thought of this and today we can begin to lay the foundation to our collected TWP knowledge, based on the available scientific literature.

 

From roads to water

Research shows that the minority of TWPs end up in the airborne fraction (0.1-10%) and recently TRWPs have been assessed to contribute a low risk to human health in the particulate matter (PM) PM2.5 and PM10 range. So, where to find the remaining 90.0-99.9% of tyre debris emissions? Early research on particulate distribution showed a decreasing concentration of TWPs with increasing distance from the road. From there, TWPs are expected to wash off during rainfalls, transporting them to different environmental compartments. Recently, models on the fate of TWPs have estimated that 18% of TWP emissions are transported from roads to freshwater bodies and approximately 2% are led out to estuaries and then marine habitats. What then happens to the remaining 16% of TWP emissions left in the freshwater compartment is not yet clear and more research is needed to answer this question.

Aquatic organisms living in the water column or the sediment can interact with TWPs in their natural habitats during this particle transportation through freshwater to the marine environment. Although there are no scientific references on field observations of TWP ingestion by aquatic biota yet, few recent observations of this behaviour under controlled laboratory settings have been reported. In 2009 the first observation of the water flea, Daphnia magna, ingesting TWPs was described in the scientific literature and only two years ago the first photos were published showing ingestion of TWPs in the benthic amphipod Gammarus pulex following sediment exposure. Shortly thereafter photos of TWP ingestion in the amphipod Hyalella azteca and opossum shrimps from the mysidae family followed after water-only exposures, and most recently freshwater and marine fish species have been documented ingesting TWPs under laboratory conditions.

The recent focus on particulate effects of TWPs on biota is still in its infancy and the latest development in this field investigates the possible effects of both the particulate fraction and the leachate fraction. The leachate fraction is the suite of chemicals that leach out from TWPs to the surrounding water. Previously, tyre toxicity investigations in the aquatic environment revolved solely around the leachate fraction, which has been the primary focus over the last 30 years. Among the first papers the effect of whole tyre leachate was investigated showing worn tyre leachate to exhibit greater toxicity than leachate from a pristine tyre to rainbow trout. Furthermore, decreasing toxicity was observed with increasing salinity indicating that salinity either influences the leachability of toxic constituents or that an interaction of salts and toxic chemicals is present. Exposure of shredded tyre chips to different bacteria likewise showed a correlation between decreasing toxicity and increasing salinity, concluding that tyre leachate is likely to be a greater threat to freshwater habitats than to estuarine or marine habitats.

Toxicity pattern

Further testing of TWPs and leachate on a freshwater species recently showed a dissimilar toxicity pattern when comparing acute toxicity responses of TWPs or leachate. Here, the amphipod H. azteca was exposed to either TWPs in freshwater or the leachate fraction alone, i.e. with no particulates present. This showed that leachate was more toxic in lower concentrations, presumably because dissolved chemicals are more bioavailable. Although, at higher concentrations, the particle fraction of TWPs became more toxic. This phenomenon very well describes the complexity and discrepancies when working with TWPs in the aquatic environment. It is not just a question of determining toxicity of a single chemical under controlled settings, but rather investigating a mixture of many chemicals in changing ambient environments. This complex matrix of polymer and chemicals can be more or less bound to the particle, which in itself might have adverse effects. However, the particle could also function as a vessel, containing chemicals and making them more or less bioavailable depending on the surrounding environment. Discovering exactly which chemicals leach out under different exposure scenarios, and most importantly, what of that is actually bioavailable to aquatic living species is the more interesting question to answer.

Due to the amorphous nature of rubber, end-of-life tyres (ELTs) have been used as leachate collection material and been used to collect polycyclic aromatic hydrocarbons (PAHs) and metals from contaminated waters. This discrepancy between the different TWP uses that in some cases could deem toxic and have adverse effects but at the same time might serve to mitigate other environmental issues is a great conflict of contradictory traits. Now, we need to unravel exactly when these contradictory traits are possibly affecting aquatic environments negatively and when these traits might be used for our advantage.

 

So how do scientists quantify TWPs and chemical constituents or ‘biomarkers’ from TWP leachate in water? The quick answer is that no tried and tested procedure is more right than any other now, we simply do not have conformity or guidelines on how to do this. Especially when looking to find particulates from tyre debris, as this is not usually detected when investigating for other polymer debris e.g. microplastics. Therefore, it is expected that the total amount of microplastics has been underestimated due to the lack of data from TWPs, which make up a large part of the estimated microplastic load worldwide and have not been reported on a regular basis. A multitude of methods have been used to estimate TWP emissions by measuring the concentration of chemicals in samples, with more or less success over the years. The biomarkers that have been used to determine TWP concentration most successfully include quantification of benzothiazoles and zinc. Both chemicals are used as part of the vulcanisation process and are also ubiquitous in nature. They are used for manufacturing of other materials, but specific versions can be attributed mainly to tyre manufacturing and are thus the most reliable compounds to measure.

How this emerging field of tyre ecotoxicology will progress ultimately depends on cooperation between different stakeholders having a common goal to pursue. The one thing that we can probably all agree on, is the need for tyres and other rubber products in our society. How we then fill that need, and what future decisions we make to maximise our understanding of the possible negative implications of TWPs in the aquatic environment is of paramount importance. Our job now is to continue our research within this field and ultimately prevent excess and unnecessary pollution of the water bodies that we all depend on, in a manner that stays true to both the environment and our need for safe and reliable tyres. 

*The author is a PhD student in Environmental Biology at Roskilde University, Department of Natural Science and Environment, Denmark, with funds from Danish Environmental Analysis

 

References

1.        Thompson. Identification of vehicle tyre rubber in roadway dust. Am Ind Hyg Assoc 27, 488–495 (1966).

2.        Lassen, C., Hansen, S.F., Magnusson, K., Norén, F., Hartmann, N.I.B., Jensen, P.R., Nielsen, T.G., Brinch, A. Microplastics - Occurence, effects and sources of releases to the environment in Denmark. (Danish EPA, 2015).

3.        Boucher, J. & Friot, D. Primary microplastics in the oceans: A global evaluation of sources. (2017). doi:10.2305/IUCN.CH.2017.01.en

4.        Kole, P. J., Löhr, A. J., Belleghem, F. G. A. J. Van & Ragas, A. M. J. Wear and tear of tyres : A stealthy source of microplastics in the environment. Int. J. Environ. Res. Public Health 14, 1265 (2017).

5.        Kolomijeca, A., Parrot, J., Khan, H., Shires, K., Clarence, S, Sullivan, C., Chibwe, L., Sinton, D., Rochman, C. Increased Temperature and Turbulence Alter the Effects of Leachates from Tyre Particles on Fathead Minnow (Pimephales promelas). Environ. Sci. Technol. 54, 1750–1759 (2020).

6.        Unice, K. M., Panko, J.M.., Chu, J. & Kreider, M. L. Measurement of airborne concentrations of tyre and road wear particles in urban and rural areas of France, Japan, and the United States. Atmos. Environ. 72, 192–199 (2013).

7.        Kreider, M. L., Unice, K. M. & Panko, J. M. Human health risk assessment of Tyre and Road Wear Particles (TRWP) in air. Hum. Ecol. Risk Assess. 0, 1–19 (2019).

8.        Unice, K. M. et al. Characterizing export of land-based microplastics to the estuary - Part I: Application of integrated geospatial microplastic transport models to assess tyre and road wear particles in the Seine watershed. Sci. Total Environ. 646, 1639–1649 (2019).

9.        Unice, K. M. et al. Characterizing export of land-based microplastics to the estuary - Part II: Sensitivity analysis of an integrated geospatial microplastic transport modeling assessment of tyre and road wear particles. Sci. Total Environ. 646, 1650–1659 (2019).

10.      Wik, A. & Dave, G. Occurrence and effects of tyre wear particles in the environment - A critical review and an initial risk assessment. Environ. Pollut. 157, 1–11 (2009).

11.      Redondo-Hasselerharm, P. E., de Ruijter, V. N., Mintenig, S. M., Verschoor, A. & Koelmans, A. A. Ingestion and chronic effects of car tyre tread particles on freshwater benthic macroinvertebrates. Environ. Sci. Technol. acs.est.8b05035 (2018). doi:10.1021/acs.est.8b05035

12.      Khan, F. R., Halle, L. L. & Palmqvist, A. Acute and long-term toxicity of micronized car tyre wear particles to Hyalella azteca. Aquat. Toxicol. 213, 105216 (2019).

13.      Halle, L. L., Palmqvist, A., Kampmann, K. & Khan, F. R. Ecotoxicology of micronized tyre rubber : Past , present and future considerations. Sci. Total Environ. 135694 (2019). doi:10.1016/j.scitotenv.2019.135694

14.      LaPlaca, S. B. & van den Hurk, P. Toxicological effects of micronized tyre crumb rubber on mummichog (Fundulus heteroclitus) and fathead minnow (Pimephales promelas). Ecotoxicology (2020). doi:10.1007/s10646-020-02210-7

15.      Kellough, R. M. The effects of scrap automobile tyres in water. (1991).

16.      Day, K. E., Holtze, K. E., Metcalfe-Smith, J. L., Bishop, C. T. & Dutka, B. J. Toxicity of leachate from automobile tyres to aquatic biota. Chemosphere 27, 665–675 (1993).

17.      Abernethy, S. The acute lethality to rainbow trout of water contaminated by an automobile tyre. (1994).

18.      Hartwell, S. I., Jordahl, D. M., Dawson, C. E. O. & Ives, A. S. Toxicity of scrap tyre leachates in estuarine salinities: Are tyres acceptable for artificial reefs? Trans. Am. Fish. Soc. 127, 796–806 (1998).

19.      Hartwell, S. I., Jordahl, D. M. & Dawson, C. E. O. The effect of salinity on tyre leachate toxicity. Water. Air. Soil Pollut. 121, 119–131 (2000).

20.      Gunasekara, A. S., Donovan, J. A. & Xing, B. Ground discarded tyres remove naphthalene, toluene, and mercury from water. Chemosphere 41, 1155–1160 (2000).

21.      Edil, T. B., Park, J. K. & Kim, J. Y. Effectiveness of scrap tyre chips as sorptive drainage material. J. Environ. Eng. 130, 824–831 (2004).

22.      Lisi, R. D., Park, J. K. & Stier, J. C. Mitigating nutrient leaching with a sub-surface drainage layer of granulated tyres. Waste Manag. 24, 831–839 (2004).

23.      Aydilek, A. H., Madden, E. T. & Demirkan, M. M. Field evaluation of a leachate collection system constructed with scrap tyres. J. Geotech. Geoenvironmental Eng. 132, 990–1000 (2006).

24.      Alamo-Nole, L. A., Perales-Perez, O. & Roman, F. R. Use of recycled tyres crumb rubber to remove organic contaminants from aqueous and gaseous phases. Desalin. Water Treat. 49, 296–306 (2012).

25.      Alamo-Nole, L. A., Perales-Perez, O. & Roman-Velazquez, F. R. Sorption study of toluene and xylene in aqueous solutions by recycled tyres crumb rubber. J. Hazard. Mater. 185, 107–111 (2011).

26.      Parker-Jurd, F. N. F. Napper, I. E. Abbott, G. D. Hann, S. Wright, S. L. Thompson, R. C. Investigating the sources and pathways of synthetic fibre and vehicle tyre wear contamination into the marine environment (project code ME5435). (2019).

27.      Kumata, H., Yamada, J., Masuda, K., Takada, H., Sato, Y., Sakurai, T., Fujiwara, K. Benzothiazolamines as tyre-derived molecular markers: Sorptive behavior in street runoff and application to source apportioning. Environ. Sci. Technol. 36, 702–708 (2002).

28.      Klöckner, P., Reemtsmp, T., Eisentraut, P., Braun, U., Ruhl, A.S., Wagner, S. Tyre and road wear particles in road environment – Quantification and assessment of particle dynamics by Zn determination after density separation. Chemosphere 222, 714–721 (2019).

Germany's rubber industry continues to face significant headwinds, with fresh data from the German Rubber Industry Association (wdk) revealing a persistent downturn. The figures show employment falling for the fifth year in a row, while production levels have declined for the fourth consecutive year, underscoring the sector's struggle to regain its footing.

The association attributes this stagnation to waning enthusiasm for German rubber goods in both domestic and international markets. Michael Berthel, wdk Chief Economist, described a fundamental shift in procurement behaviour, even within Germany. He noted that purchasing decisions are now driven almost exclusively by price, a stark departure from the historical emphasis on quality and reliability. This change has opened the door to intense international cost competition, placing immense pressure on Germany's medium-sized suppliers. Berthel highlighted that prohibitive domestic costs related to energy, bureaucracy, taxation and labour make it nearly impossible for these firms to compete effectively. Consequently, many are compelled to relocate their investments abroad as a necessary escape from these local burdens, even though their preference would be to maintain and revitalise their operations within Germany after years of strategic transformation.

Against this backdrop, wdk President Michael Klein issued an urgent appeal to the federal government. He acknowledged that the broader struggles of German industry are well documented but stressed the immediate need for decisive political intervention. Klein called for concrete measures to stimulate demand and bolster the nation's competitive edge within Europe without further delay. He warned against allowing the rubber sector to decline quietly, emphasising its critical role in essential areas such as healthcare, infrastructure, security and mobility.

Punia Metox Private Limited has commenced production at a new manufacturing facility in Thottambedu, Tirupati, Andhra Pradesh, with operations starting on 12 February 2026.

The plant has an initial production capacity of 12,000 tonnes a year. Its structural design allows capacity to be doubled within four to six months, providing scope for rapid scale-up as demand grows, the company said.

Punia Metox said the facility has been equipped with modern technology to support operational and energy efficiency, safety, sustainability and consistent product quality. The company added that the plant has been designed to enable smooth and seamless operations from the outset.

The expansion forms part of Punia Metox’s strategy to align capacity growth with customer requirements and strengthen its position as a long-term supply partner. The company said the new unit reflects its focus on customer satisfaction, ethical business practices and value-based growth.

Cabot Corporation said it can now produce circular reinforcing carbons in the Asia-Pacific region after validating manufacturing capability at its plants in Cilegon, Indonesia, and Tianjin, China.

The materials are produced using tyre pyrolysis oil derived from end-of-life tyres and an International Sustainability & Carbon Certification (ISCC) PLUS mass-balance approach. With the addition of the two Asian sites, Cabot said it now has circular reinforcing carbon production capacity across Asia, Europe and the Americas.

Tyre manufacturers are pursuing targets to increase sustainable material use in tyre production, with many aiming for 40 per cent by 2030 and 100 per cent by 2050, the company said. Cabot’s circular reinforcing carbons are designed as a drop-in replacement for conventional carbon black, allowing manufacturers to increase sustainable content without affecting tyre performance.

Aatif Misbah, Vice-President and General Manager for sustainable solutions in Cabot’s reinforcement materials segment, said: “This achievement reflects our deep commitment to delivering sustainable solutions across Asia Pacific and globally. Scaling our circular reinforcing carbon capabilities helps strengthen our role as a trusted partner to the tire industry, while helping to drive meaningful sustainability progress. Looking ahead, we remain focused on supporting our customers’ evolving needs and helping enable a more sustainable future.”

Cabot’s facilities in Ville Platte, Louisiana; Mauá, Brazil; and Valasske Mezirici in the Czech Republic had previously demonstrated circular reinforcing carbon production capability. The products are ISCC PLUS-certified and marketed under the recovered category of Cabot’s EVOLVE Sustainable Solutions platform.

The company said it has 13 ISCC PLUS-certified sites supporting circular reinforcing carbon production across Asia, Europe and the Americas, along with two certified masterbatch and compounding sites in Europe.

The Rathi Group has formalised a partnership with the Indian Tyre Technical Advisory Committee (ITTAC) through a Memorandum of Understanding aimed at advancing technical collaboration on recovered carbon black (rCB). The agreement focuses on the responsible integration of rCB into tyre manufacturing, with an emphasis on detailed evaluation and enhancement of its material properties. This initiative will be driven through structured engagement between industry and academia, supported by ITTAC’s technical expertise.

The collaboration is facilitated by the Automotive Tyre Manufacturers’ Association (ATMA) and ITTAC, which have brought together leading technical experts, tyre manufacturers and research institutions on a unified platform. Their coordinated efforts are fostering a science-based approach to accelerate the assessment and adoption of circular materials within the tyre sector. This partnership is seen as a significant step in strengthening industry–academia linkages to advance sustainable practices.

Through this alliance, the Rathi Group aims to contribute to the evolving landscape of tyre-to-tyre circularity. The joint initiative underscores a shared commitment to developing innovative solutions that support environmental responsibility while maintaining technical performance standards in tyre applications.