Motor Vehicle Tyres as a Significant Source of Persistent Organic Pollutants Emission in Nigeria

Motor vehicle tyres are essential components of global rapidly expanding road transport sector, yet they constitute a major source of environmental pollution throughout their life cycle. This study presents a comprehensive assessment of Nigeria’s tyre flows for 40 years (1980–2020), associated waste generation, and the content/reservoir load of three hazardous rubber additives (N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, commonly called 6PPD; chlorinated paraffins, CPs; and polycyclic aromatic hydrocarbons, PAHs). This study provides the first systematic estimation of CP, 6PPD and PAHs flows and releases associated with end-of-life tyres (ELT) in the Nigerian environment. Using Nigeria’s case study on vehicle put-on-market datasets from our previous study, tyre configuration assumptions and replacement frequencies, approximately 776 million tyres (20,537 kilotons, kt) were used within the study period, while annual ELT generation amounted to 19 million units or 513 kt of ELTs. This stock of ELT (20,537 kt) contains total CPs of 267–1375 t and a substantial reservoir of 6PPD (~2000–82,000 t). The associated PAHs were estimated at 349–7332 t. The tyre particulate matter emission was estimated at 1.1–2.55 million tonnes. This study also estimated releases of these pollutants that are associated with tyre-wear particles (TWPs). For the 40 years period, the total estimated CP release ranges from ~14 t (low scenario) to ~171 t (high scenario); the 6PPD from ~110 t to ~10,216 t, while PAH releases varied from ~18 to as high as 911 t under different TWPs scenario. This has adverse human environmental health implications. This study recommends urgent implementation of a national ELT management framework.