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).

Orion Engineered Carbons, a specialty chemical company, started commercial sales in Italy from the first new reactor for carbon black production to be commissioned in the European Union in over 40 years. 

The new 25-kiloton line at the facility in Ravenna, in the northern region of Emilia-Romagna, produces both specialty and technical rubber carbon blacks, primarily for the European market, the company said in a release. 

Corning Painter, CEO, Orion, said, “The new line offers customers seeking long-term solutions a unique strategic opportunity to align with a dependable plant that has been operating for more than 60 years in Europe.” 

Additional investments at the plant include a new co-generation facility to convert waste heat into electricity, generating up to 120 MWh of electricity per year. Seventy percent of the electricity is supplied to the national grid, serving about 30,000 households. Orion is a net exporter of electricity in Europe and worldwide. (TT)  

Shin-Etsu Chemical, a leading chemical company, plans to invest $702 million in its silicone portfolio, a key component of its functional materials business segment.

This latest investment follows a plan announced in February 2022, worth $562 million, to meet the surging demand for advanced functional silicone products. However, due to the continuous growth in need, especially for eco-friendly options that align with the global goal of carbon neutrality, the company has decided to expand the applications of its silicone products. The company will also focus on enhancing the advanced functionality of its product lineup and further developing environmentally friendly silicones.

In alignment with its newly announced silicones investment plan, Shin-Etsu Chemical will make investments not only in its central production hub in Japan, the Gunma Complex in Gunma Prefecture, but also in its Naoetsu Plant in Niigata Prefecture, Takefu Plant in Fukui Prefecture, and the Group company plant in Thailand, where silicone monomer and polymer production is conducted. The company will also invest further in existing silicone plants across other Asian countries, the United States, and Hungary. Simultaneously, Shin-Etsu Chemical will accelerate efforts to achieve carbon neutrality by embracing greener manufacturing processes.

Klean Industries Inc has announced that its partner Pyrolysis Hellas SA has completed Phase II of the Detailed Feasibility Study to design and build a tyre pyrolysis plant in Greece. Greek Authorities gave permits to its final Phase, the company said in a release. The company, while terming it as a significant milestone for the PHS project, claimed that it was the first tyre pyrolysis and carbon upgrading project in Greece to receive full authorizations.

Klean Industries Inc has announced that its partner Pyrolysis Hellas SA has completed Phase II of the Detailed Feasibility Study to design and build a tyre pyrolysis plant in Greece. Greek Authorities gave permits to its final Phase, the company said in a release. The company, while terming it as a significant milestone for the PHS project, claimed that it was the first tyre pyrolysis and carbon upgrading project in Greece to receive full authorizations.

Klean Industries Inc has announced that its partner Pyrolysis Hellas SA has completed Phase II of the Detailed Feasibility Study to design and build a tyre pyrolysis plant in Greece. Greek Authorities gave permits to its final Phase, the company said in a release. The company, while terming it as a significant milestone for the PHS project, claimed that it was the first tyre pyrolysis and carbon upgrading project in Greece to receive full authorizations.Klean Industries Inc has announced that its partner Pyrolysis Hellas SA has completed Phase II of the Detailed Feasibility Study to design and build a tyre pyrolysis plant in Greece. Greek Authorities gave permits to its final Phase, the company said in a release. The company, while terming it as a significant milestone for the PHS project, claimed that it was the first tyre pyrolysis and carbon upgrading project in Greece to receive full authorizations.

Each year, over 1.5 billion tyres are sold worldwide, representing more than 26 million metric tonnes, and just as many tyres each year also fall into the category of end-of-life tyres providing a large and partially untapped potential for resource and material recovery. Today, most traditional ELT treatment processes are not circular and do not result in any production of raw materials that are suitable to be reused in the tyre manufacturing industry. Without such ELT solutions in the EU, more than half of the EU end-of-life tyres and secondhand tyres are landfilled or are exported as tyre derived fuels for use into furnaces as an industrial fuel. The PHS project intends to reverse these trends and create a vibrant addition to advancements being made in the tyre recycling sector, the release said.

The PHS project is co-owned by Karabas European Hellenic Recycling. Currently, KEHR collects and recycles all types of scrap vehicle tyres and recycles them through traditional methods by shredding tyres into rubber granules, rubber powder & shock-absorbent surfacing slabs.

PHS has partnered with Klean Industries to build a modern tyre recycling facility that encompasses a state-of-the-art scrap tyre pyrolysis plant to recycle 20,000 TPA of waste tyres into valuable chemical products.

PHS proposes to construct and operate the Waste Tyre Pyrolysis Plant in Moulkia, a seaside town near Skala, Greece. It is located at an existing industrial site that is owned by KEHR, the release added. (TT)

ResiCare, an adhesive manufacturing subsidiary of Michelin, has found commercial use in Allin's plywood manufacturing unit, R'PLY. Allin and Michelin have been in collaboration since 2018.

The company claims that R'Ply is the first responsible plywood made using certified Poplar wood and integrating a ResiCare resin that is kinder to human health as well as the environment. The R’Ply is a high-performance plywood which can be used for multiple applications, according to the company. The plywood can be used for boat-building or in the building trade and will be available at certain DIY stores soon.

Michelin had set up a mobile ResiCare production unit at its Olsztyn site in May 2021. The company hopes to replace more than 80 percent of the usual adhesive used in its tyre textile reinforcement with the new ResiCare adhesive, which is free from any substances of very high concern for health (SVHC), by 2025. The company further plans to set up mobile production units similar to the one in Europe and Asia in the coming months. (TT)