Every time a tyre rotates against a road surface, microscopic particles of tyre rubber and asphalt are shed — this is tyre and road wear, and it is now recognised as the largest single source of microplastic pollution in UK waterways. TRWP are not merely inert rubber fragments: tyre rubber contains vulcanisation chemicals, PAHs from carbon black, zinc compounds (up to 1–2% of tyre mass), benzothiazoles, and the antioxidant 6PPD, whose ozone-reaction product (6PPD-quinone) is acutely lethal to coho salmon and is now suspected of wider aquatic toxicity. On land, TRWP accumulate in roadside soil and are transported into garden soils, food-growing areas, and water courses by rainfall runoff.
Where it's found
Road vehicle tyres and road surfaces jointly produce TRWP wherever vehicles travel. Busy roads, roundabouts, and junctions where braking and acceleration are frequent generate the highest particle loads. Roadside soils within 10 metres of busy roads accumulate TRWP to levels detectable in earthworms, insects, and soil microbiota. Stormwater drains collect TRWP-contaminated runoff and deliver it directly to rivers, estuaries, and coastal waters. Atmospheric transport carries the finest TRWP fractions (PM2.5 and smaller) considerable distances from roads.
Routes of exposure
Inhalation of airborne TRWP fractions near busy roads — the finest particles become airborne and contribute to ambient PM2.5 and PM10 concentrations in urban and suburban environments. Ingestion via consumption of food grown in roadside-contaminated soil or via seafood and fish that have accumulated TRWP-derived chemicals from aquatic environments. Dermal contact with roadside soils for children playing near verges. Secondary dietary exposure via 6PPD-quinone and benzothiazoles entering the food chain through contaminated water and aquatic food sources.
Health concerns
The particle-mediated toxicity of TRWP fractions is similar to other microplastic-associated harms — physical particle burden on lung tissue, transport of adsorbed chemicals to systemic circulation. The chemical hazards specific to TRWP include: zinc toxicity to aquatic organisms at concentrations found in road runoff; 6PPD-quinone acute toxicity to salmonid fish (and plausibly broader aquatic taxa); benzothiazoles as suspected endocrine disruptors; PAHs from carbon black as mutagens. Human epidemiological evidence linking TRWP exposure specifically to health outcomes is limited by the difficulty of separating TRWP from co-occurring traffic pollution.
Evidence
TRWP as a major microplastic source is well established — mass balance and tracer studies confirm it is the dominant microplastic entering UK waterways. The discovery of 6PPD-quinone as the cause of coho salmon mass mortality events in Washington State (2020–2021) dramatically elevated scientific interest. The aquatic toxicity of 6PPD-quinone is robustly demonstrated in fish models. Human health effects of TRWP exposure are at an early evidence stage — there is currently no published human cohort study attributing health outcomes specifically to TRWP exposure, though mechanistic evidence of concern from the chemical constituents is substantial.
Who's most at risk
Urban residents living within 50 metres of high-traffic roads; children playing in roadside green spaces and gardens near busy roads; people eating seafood from estuaries receiving high road runoff loads; cyclists and pedestrians breathing near-road air at peak traffic times; communities adjacent to road construction, grinding, and resurfacing works.
Regulatory status
RegulationTRWP is not currently regulated as a distinct pollutant category in UK or EU law. Tyre rubber compound restrictions exist under REACH for individual substances (e.g., PAHs in tyre rubber are restricted under Annex XVII), but TRWP as a mixture category has no emission standard. The European Chemicals Agency (ECHA) has initiated regulatory risk assessment of TRWP. 6PPD-quinone is being evaluated under REACH. Urban drainage regulations (SuDS requirements under the Flood and Water Management Act) are the primary policy lever currently affecting TRWP reaching waterways.
How to reduce your exposure
Avoid growing vegetables in soil within 10 metres of busy roads unless beds are raised with clean imported compost — roadside TRWP accumulation in vegetable garden soil is measurable. Filter garden tap water if your supply comes from a reservoir receiving significant road runoff. Support local anti-idling enforcement and clean air zone policies that reduce total traffic volume and tyre wear. Choose routes away from high-traffic roads for children's outdoor play where possible.
The nutrition connection
Zinc from TRWP road runoff enters drinking water sources — zinc is an essential micronutrient but elevated zinc displaces copper absorption (both compete for the same intestinal transporter, ZIP4) and can induce copper deficiency anaemia at chronically high intakes. The PAH component of TRWP has the same dietary interaction as other PAH sources — adequate cruciferous vegetable intake upregulates detoxification enzymes. The aquatic contamination route means people who eat substantial quantities of estuary-caught shellfish and fish may have higher TRWP-derived chemical exposure than non-seafood consumers.