We often use a variety of terms to describe different concepts. Below is a list of definitions to help stakeholders better understand the language that we use.
Non-exhaust emissions (NEE) from road traffic refers to particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage (DEFRA, 2019).
The term “road dust” might refer to particles from a wide range of organic and inorganic vehicular and non-vehicular sources that litter the road surface and may become airborne / mobile as a result of the movement of road traffic and weather events. Road dust may include, but is not limited to, TRWP.
Road wear particles
The term ‘road wear particles’ does not consider the tire-tread component of TRWP.
Tire and Road Wear Particles
Tire and road wear particles (TRWP) are tiny debris produced by necessary friction between tires and road surface. They are an approximately half-and-half mixture of tire tread and road pavement material. With a density of ~1.8g/cm3, TRWP are expected to sink in water. TRWP are distinct particle types, yet different – and often inaccurate – terms have been used to describe them, including:
The term ‘tire emissions’ has been used to describe the quantity of TRWP emitted per unit of distance travelled.
Tire particles have been referred to as microplastics. However, there is no globally accepted definition of microplastics. Our focus is not on whether TRWP may or may not be categorized as microplastics; it is on understanding the distribution of TRWP in the environment and their potential impact on human health and the environment.
Tire particles/tire wear particles
The terms ‘tire particles’ and ‘tire wear particles’ do not take account of the road-pavement-material component of TRWP.
“Pollution” has been defined as the addition of any substance or any form of energy to the environment at a rate faster than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form.
The research sponsored by the Tire Industry Project (TIP) contributes to scientific understanding of TRWP in the environment toward a better understanding of the relevance of terms like “tire pollution”.
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