UK Prioritises Tyre Additive Chemicals in Landmark Risk Screening Initiative

New risk spotlight on tyre additives

Tyre wear particles (TWP) are a significant source of microplastic pollution, releasing tens of thousands of tonnes into the UK environment annually. The study assessed 61 chemical substances—including phthalates, benzothiazoles, and phenylenediamines (PPDs)—commonly used to enhance durability and performance in tyres.

Using a combined hazard and risk-based approach, the Environment Agency ranked the substances based on environmental hazard classifications, production volumes, and predicted environmental concentrations (PECs) derived from a tyre-specific exposure model. Notably, 14 substances were categorised as 'of concern' and 29 as 'of potential concern'.

Phenylenediamines dominate high-risk rankings

Among the top-risk substances are DCBS, MBTS, and the widely used antiozonant 6PPD, along with its transformation product 6PPD-quinone (6PPD-Q). These compounds were found to present elevated risk characterisation ratios (RCRs) for freshwater sediment—highlighted as the most sensitive environmental compartment.

DCBS recorded an RCR exceeding 1,500 in worst-case scenarios. 6PPD-Q, now globally scrutinised due to links with salmon mortality in the US, ranked second in predicted environmental risk.

Compliance and regulatory implications

The report does not mandate immediate restrictions, but it identifies substances likely to face future regulatory scrutiny. The findings support targeted monitoring and more refined risk assessments. Industry professionals—especially in tyre manufacturing, chemical formulation, water management, and environmental compliance—are encouraged to review the substances flagged and evaluate their current use and alternatives.

While the report was designed as a prioritisation tool rather than a regulatory determination, its methodology mirrors frameworks under UK REACH, and future restriction proposals may follow.