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

 

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Birla Carbon, a leading global manufacturer and supplier of high-quality carbon materials, has been awarded the prestigious Platinum sustainability rating by EcoVadis, ranking it within the top one percent of all assessed companies globally. This honour recognises the firm’s enterprise-wide leadership in integrating sustainability across its operations, innovation and value chain.

The evaluation specifically commended its strong performance across four key areas: Environment, Labor & Human Rights, Ethics and Sustainable Procurement. This achievement is further validated by extensive third-party certifications, with over 75 percent of operations certified to international standards including ISO 14001, ISO 50001, ISO 45001, SA8000 and ISO 27001, underscoring the consistency and strength of its sustainability management systems.

John Loudermilk, President and CEO, Birla Carbon, said, “This Platinum rating reflects the steady progress we are making in embedding sustainability at the core of our business. Our growth strategy is geared towards delivering sustainability through innovation, operational excellence and responsible practices across our global footprint. We continually invest in sustainability and circularity-driven processes, keeping our operations sustainably efficient while creating long-term value for our customers, partners, communities and employees. Our sustainability strategy, Share the Future, serves as a roadmap to a sustainable future and guides our actions towards our aspiration of reaching net zero carbon emissions over the next 25 years. Being recognised among the top one percent of companies globally is a testament to the commitment of our teams worldwide.”

The Yokohama Rubber Co., Ltd. recently conducted an educational seminar for local natural rubber farmers in partnership with the Surat Thani branch of the Rubber Authority of Thailand (RAOT). This marked the 10th such event since the programme's inception in 2020, involving 50 local farm households. Attendees received complimentary fertiliser, developed with RAOT's expertise, as part of the ongoing support.

The seminar curriculum covered essential agricultural topics, including soil and plant nutrition, correct fertiliser application and methods to prevent contamination in natural rubber. To commemorate the 10th seminar, the programme was expanded to include guest speakers from local government, police and healthcare. These guests addressed broader community and safety issues, such as human rights for foreign and minority workers, road safety and occupational health. A particular focus was placed on practical well-being, with the local hospital director offering guidance on preventing injuries during tree tapping and managing encounters with poisonous insects.

Post-event feedback from participants was overwhelmingly positive. Many expressed that they gained new, systematic knowledge about cultivation practices, despite years of experience. Several noted that hearing directly from a rubber manufacturer reinforced the critical importance of purity in their product. Others found the health and safety advice immediately useful. The engaging delivery of the seminar was also highlighted, with one farmer mentioning a desire to recommend the valuable and enjoyable experience to peers.

This initiative is a direct implementation of a memorandum of understanding (MoU) signed between Yokohama Rubber and RAOT in January 2020. The MoU focuses on economic support for farmers and improving supply chain traceability, aligning with the company's Procurement Policy for Sustainable Natural Rubber. Hosted in the region where Yokohama’s Thai natural rubber processing subsidiary, Y.T. Rubber Co., Ltd. (YTRC), operates, the seminar exemplifies the policy's guideline to support small-scale farmers within the supply chain.

As a founding member of the Global Platform for Sustainable Natural Rubber (GPSNR), Yokohama Rubber is committed to advancing these principles. The company views such efforts as integral to creating shared value under its sustainability slogan, ‘Caring for the Future’, and contributes to broader United Nations Sustainable Development Goals through the promotion of sustainable raw material procurement.

In a significant event for India’s rubber sector, Minister for Ports, Co-operation & Devaswoms V N Vasavan inaugurated a ceremony for the transfer of innovative latex-based paint technology. This eco-friendly paint, a product derived from natural rubber, was developed by the Rubber Products Incubation Centre of the Rubber Research Institute of India. The technology was formally handed over to Kerala Paints Industries Private Ltd., with the Minister highlighting the event's historic nature for launching a sustainable product and stressing the importance of increasing domestic natural rubber consumption to improve grower returns.

Rubber Board Executive Director M Vasanthagesan outlined the centre's role in converting research into market-ready goods, reaffirming the Board's dedication to creating innovative, value-added rubber products. The gathering also heard remarks from several key figures, including Mahatma Gandhi University's K V Dayal, RRII Director Dr Debabrata Ray, RRII Senior Scientist Dr Shera Mathew and Kerala Paints' Managing Director Midhun P Pullumettel.

The Association of Natural Rubber Producing Countries (ANRPC) has released its Monthly NR Statistical Report for November 2025, providing an overview of key developments in the global natural rubber sector.

While a modest rise in global production of 1.3 percent is anticipated for the year, this follows a revised, lower output forecast for Indonesia. Concurrently, worldwide demand is projected to grow by a more subdued 0.8 percent, bolstered by an upward adjustment in Indonesia's own consumption figures.

Recent price pressures have emerged due to this combination of uncertain supply, influenced by unpredictable weather patterns and generally muted demand. However, there are sporadic positive indicators, including noticeable recoveries within the tyre sector across some regional markets.