science

Non-exhaust emissions

Non-exhaust emissions is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Non-exhaust emissions rather than just read about it. In short: Non-exhaust emissions come from wearing down motor vehicle brake pads, tires, roads themselves, and unsettling of particles on the road. This particulate matter is made up of micrometre-sized particles and causes negative health effects, including respiratory disease and cancer.

Key takeaways

Non-exhaust emissions belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Non-exhaust emissions to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Non-exhaust emissions from memory before moving on to harder problems.

Reference excerpt

Non-exhaust emissions come from wearing down motor vehicle brake pads, tires, roads themselves, and unsettling of particles on the road. This particulate matter is made up of micrometre-sized particles and causes negative health effects, including respiratory disease and cancer. Very fine particulate matter has been linked to cardiovascular disease. Multiple epidemiological studies have demonstrated that particulate matter exposure is associated with acute respiratory infections, lung cancer, and chronic respiratory and cardiovascular disease. Researchers have also found correlations between exposure to fine particulate matter and fatality rates in previous coronavirus epidemics. Studies have shown that non-exhaust emissions of particles from vehicles can be greater than particles due to exhaust. The European Commission expects that "by 2050 non-exhaust emissions will constitute up to 90% of all particles emitted by road transport".

Types of emissions

Brakes Brake wear gets released into the air as particulate matter. Standard frictional brakes on a vehicle function by virtue of the friction between a brake pad and a rotating disc or drum when the two are forced together by application of pressure to the braking system. The frictional process causes abrasion of the brake pad and the surface of the disc or drum, leading to the release of particles, a substantial fraction of which become airborne.

Tyres Particles from car tyres pollute the environment and the air we breathe, whilst the long-term effects on our health and the ecosystem are unknown. These tyre wear particles are especially damaging due to the toxic chemicals that they are made from, which leach out of the particles into our rivers and oceans. These chemicals have a devastating impact on wildlife, and they accumulate into the food chain where they will ultimately pose a significant risk.

Rubber pollution gets released into the air. When in contact with the road, the surface of a tire is steadily abraded by contact with the road surface. This leads to the release of large quantities of small rubber particles which cover a wide range of sizes.

Road surface The road itself wears and releases particulate matter into the air. The friction between the tire surface and the road surface, which leads to tire abrasion, is also liable to abrade the road surface, especially where this is already fragmenting. Hence, road surface wear particles are also released into the atmosphere.

Road dust Particles on the road get thrown or blown into the air. Emissions from road dust suspension depend on a vehicle's speed, size, shape, porosity, amount of dust on road surfaces, and weather conditions. Considerable uncertainty remains regarding the amount of PM emitted by non-exhaust sources in real-world driving conditions and how this amount varies with the abovementioned factors.

Ways of reducing emissions Multiple scientists and regulators in the field have proposed more comprehensive regulation of tires. Lighter vehicles pollute less and reducing vehicle kilometers traveled is another method of mitigating non-exhaust emissions. Reducing demand for private vehicle travel can be accomplished by various measures that increase the relative attractiveness of public transport and non-motorized modes relative to private vehicles. These measures can consist of disincentives for private vehicle ownership and use, i.e., measures that raise their costs and inconvenience, as well as incentives for alternative modes (e.g., public transit, walking, and biking).

Electric and hybrid vehicles Electric vehicles and hybrid vehicles with regenerative braking do not emit the same level of brake wear, but as of 2022 were heavier than ICE vehicles so still give off more coarse (PM10) particles from re-suspended road particles, road wear, and tire wear.

Regulatory agencies and policies that target exhaust emissions Very few agencies are charged with implementing exhaust emission standards for non-exhaust emissions. Most policies target exhaust emissions and do not regulate non-exhaust particulate matter emissions. As of 2025, Euro 7 standards are still being argued about.

See also Air quality law European emission standards Exhaust gas Ontario's Drive Clean Partial zero-emissions vehicle Phase-out of fossil fuel vehicles Roadway air dispersion modeling United States vehicle emission standards Vehicle emission standard Vehicle inspection

References

Illustrations

Worked examples

Example 1 — a first encounter with Non-exhaust emissions

Start with the simplest possible case. Write down what Non-exhaust emissions claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Non-exhaust emissions before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Non-exhaust emissions ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Non-exhaust emissions

In research: Non-exhaust emissions appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Non-exhaust emissions in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Non-exhaust emissions is common in secondary-school and first-year university syllabi. It links to neighbouring topics Air pollution, Pollution, Transport and the environment, so understanding it makes those chapters shorter.
In everyday life: Look for Non-exhaust emissions outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Non-exhaust emissions in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Non-exhaust emissions means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Non-exhaust emissions out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Non-exhaust emissions in simple terms?

Why does Non-exhaust emissions matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Non-exhaust emissions?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Non-exhaust emissions.