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76. Particulates

Particulates, or particulate matter (PM), are tiny solid particles or liquid droplets suspended in the air. In road traffic, particulate emissions can come from vehicle exhaust, brake wear, tyre wear and road-surface wear, as well as dust that is disturbed by passing traffic.

Particulate matter is commonly classified by particle size. PM10 refers to particles with a diameter of up to approximately 10 micrometres, while PM2.5 refers to finer particles of up to approximately 2.5 micrometres. Vehicle emission standards, particulate filters and air-quality measures are used to reduce exposure to these pollutants.

Particulates
Smog over Connaught Place at sunset. (Delhi, India)
Wikimedia.org • wili hybrid • CC BY
What are particulates?

Particulates, or particulate matter, are very small solid particles or liquid droplets suspended in the air.

What are PM10 and PM2.5?

PM10 refers to particles with a diameter of up to approximately 10 micrometres. PM2.5 refers to finer particles with a diameter of up to approximately 2.5 micrometres.

Where do traffic particulates come from?

Road traffic can produce particles through engine exhaust, brake wear, tyre wear and road-surface wear. Passing traffic can also resuspend dust already present on the road.

Are diesel vehicles a source of particulates?

Yes. Combustion in diesel engines can produce very small soot particles. Modern diesel vehicles commonly use particulate filters to capture a large proportion of these exhaust particles.

What is a particulate filter?

A particulate filter is an exhaust-treatment device designed to trap particulate matter produced by an engine. Diesel particulate filters are commonly known as DPFs.

Do petrol engines produce particulates?

Yes. Petrol engines can also produce particulate emissions, particularly certain direct-injection engines. Appropriate emission-control systems may therefore include particulate filters.

Do electric vehicles produce particulates?

Fully electric vehicles produce no exhaust particulates from a combustion engine, but particles can still result from tyre wear, road wear and braking.

Are brake and tyre particles regulated?

Vehicle-emission regulation is increasingly addressing non-exhaust emissions. The European Euro 7 framework includes requirements concerning brake-particle emissions and tyre abrasion.

Is particulate matter the same as CO2?

No. Particulate matter consists of tiny airborne particles, while carbon dioxide is a gas. They are different types of vehicle emissions and are regulated for different environmental reasons.

How can vehicle particulate emissions be reduced?

Measures include effective particulate filters, cleaner vehicle technologies, correctly maintained emission-control systems and reductions in brake, tyre and road-wear emissions.

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