What pollution is caused by cars

Cars produce multiple kinds of pollution: harmful air pollutants from exhaust (like nitrogen oxides, particulate matter, and air toxics), greenhouse gases (mainly carbon dioxide), non-exhaust particles from brakes, tires and road dust, runoff that contaminates water and soil, and noise pollution. Electric vehicles sharply cut tailpipe emissions but still generate tire and brake particles, and their overall impact depends on how electricity and materials are produced. This article explains the main pollution pathways, their health and climate impacts, and what can reduce them.

Tailpipe air pollutants

Combustion engines emit a mix of gases and particles that affect local air quality and the global climate. These pollutants interact in the atmosphere, creating secondary smog and fine particles that can travel far beyond the road where they originate.

• Carbon dioxide (CO2): the dominant greenhouse gas from burning gasoline and diesel; accumulates in the atmosphere and warms the planet.
• Nitrogen oxides (NO and NO2, collectively NOx): irritate lungs directly and help form ground-level ozone and secondary particulate matter (PM2.5).
• Carbon monoxide (CO): a toxic gas that reduces oxygen delivery in the body; highest during cold starts and congested traffic.
• Volatile organic compounds (VOCs): include benzene, toluene, and formaldehyde; some are carcinogenic and many help form ozone and secondary organic aerosols.
• Particulate matter (PM2.5 and PM10): tiny soot and ash particles; ultrafine particles (smaller than 0.1 µm) can penetrate deep into the lungs and bloodstream.
• Black carbon: a component of soot from incomplete combustion, especially diesel; warms the climate by absorbing sunlight and darkening snow/ice.
• Ammonia (NH3): produced by exhaust after‑treatment systems; combines with NOx and acids in air to form ammonium nitrate PM2.5.
• Nitrous oxide (N2O): a powerful greenhouse gas from catalytic converters, with a global warming potential about 273 times that of CO2 over 100 years (IPCC AR6).
• Methane (CH4) and sulfur dioxide (SO2): generally minor for modern gasoline/diesel with low-sulfur fuels, but can matter where fuel quality is poor.
• Secondary pollutants: sunlight drives reactions of NOx and VOCs, producing ozone and secondary PM that peak downwind hours later.

Taken together, tailpipe pollutants drive smog episodes, chronic health burdens, and climate change. Modern emissions controls have cut many exhaust pollutants per vehicle, but total impacts depend on how much and where people drive.

Health and climate impacts of exhaust

Exposure to traffic pollution is linked to asthma, COPD, heart disease, stroke, adverse pregnancy outcomes, and cancers. The World Health Organization attributes millions of premature deaths annually to air pollution, with road traffic a major contributor in cities. NO2 and PM2.5 are key drivers of health risk near busy roads, and ultrafine particles and certain air toxics add to the hazard.

For climate, passenger cars contribute a substantial share of global energy-related CO2 emissions—on the order of one-tenth—once you account for their dominance in road transport. CO2 is the largest component, while black carbon, N2O, and life-cycle emissions from fuel and vehicle production add to warming.

Non-exhaust emissions: brakes, tires, and road dust

Even as engines get cleaner, particle pollution from vehicle wear and road surfaces has become the dominant share of traffic-related PM in many regions. These particles are mechanically generated and are not controlled by catalytic converters.

• Brake wear: friction releases metal-rich particles (iron, copper, antimony). Many jurisdictions are phasing out copper in brake pads to protect waterways.
• Tire wear: abrasion sheds synthetic rubber, fillers, zinc compounds and additives. A key additive, 6PPD, transforms into 6PPD‑quinone, which has been shown to be highly toxic to coho salmon in stormwater; tire particles also include inhalable PM.
• Road dust resuspension: vehicles stir up previously deposited particles (soil, de-icer salts, exhaust residues), adding to PM10 and PM2.5 levels along busy corridors.
• Electric vehicles (EVs): regenerative braking can cut brake dust substantially, but heavier curb weights can increase tire wear; non-exhaust emissions remain an issue for all vehicle types.

Because these particles are generated at the wheel–road interface, they persist regardless of propulsion system. Standards for tire abrasion and new materials are being developed to address this growing source.

Water and soil pollution from vehicles and roads

Pollutants from cars accumulate on road surfaces and wash into storm drains and waterways during rain, or settle into roadside soils. This diffuse runoff is a major urban water-quality challenge.

• Oils and fuels: drips and spills introduce hydrocarbons that are toxic to aquatic life.
• Heavy metals: copper and zinc from brakes and tires, lead and cadmium from legacy sources, accumulate in sediments and soils.
• Polycyclic aromatic hydrocarbons (PAHs): from exhaust and asphalt wear, some are carcinogenic and persistent.
• Tire-derived chemicals: 6PPD‑quinone in runoff has caused acute fish kills in parts of the U.S. Pacific Northwest during first-flush storms.
• Road salts and de-icers: elevate chloride levels in streams and groundwater, stressing ecosystems and corroding infrastructure.
• Detergents and solvents: from vehicle washing and maintenance can add surfactants and other toxics to stormwater.

Because storm sewers often discharge untreated to rivers, lakes, or coasts, roadway pollutants can bypass wastewater treatment entirely without dedicated stormwater controls.

Urban runoff pathways and mitigation

First-flush events carry high concentrations from roads to storm drains. Green infrastructure—such as bioswales, permeable pavements, and rain gardens—traps sediments and breaks down organics. End-of-pipe filters and settling basins capture tire and brake particles. Targeted controls near hot spots (highways, bridges) can markedly reduce pollutant loads to waterways.

Noise and light pollution

Beyond chemicals, road traffic generates environmental noise that affects health. Engine, tire, and aerodynamic noise elevate stress hormones, disrupt sleep, and are associated with heart disease. The WHO recommends average daily road-noise levels below about 53 dB (Lden) and night levels below 45 dB (Lnight) to limit harm. EVs are quieter at low speeds, but above roughly 30–40 km/h, tire–road noise dominates. To protect pedestrians, EVs add low-speed sound (AVAS), which slightly raises noise in certain contexts. Headlight glare and widespread nighttime illumination contribute to light pollution and safety concerns, though their environmental footprint is far smaller than air and water impacts.

How pollution varies by vehicle, fuel, and driving

The type of car, technology, fuel, and driving conditions greatly influence pollution levels. Key factors include engine type, after-treatment systems, maintenance, and driving patterns like cold starts and hard acceleration.

• Gasoline vs. diesel: Diesel engines historically emitted higher NOx and soot; modern diesel particulate filters (DPFs) and selective catalytic reduction (SCR) cut these if systems are well-designed and maintained.
• Cold starts and short trips: Emissions spike before the catalyst warms; VOCs and CO are especially high in the first minutes.
• High load and aggressive driving: Hard accelerations and towing increase fuel use and emissions of NOx and PM.
• Fuel quality and maintenance: Low-sulfur fuels enable better controls; malfunctioning sensors or filters can multiply emissions.
• Direct-injection gasoline: Can produce more fine particles; gasoline particulate filters (GPFs) mitigate this.
• Alternative fuels: CNG/LPG can reduce PM and some NOx but may raise methane slip; biofuels vary by blend and feedstock; hydrogen fuel-cell cars emit only water at the tailpipe.
• Electric vehicles: Zero tailpipe emissions; life-cycle emissions depend on the electricity mix and battery production. As grids decarbonize, EV life-cycle emissions continue to fall.
• Upstream emissions: Oil extraction, refining, and fuel transport add to gasoline/diesel footprints; electricity generation and battery manufacturing add to EV footprints.

Real-world performance can differ from lab tests; independent on-road measurements and robust compliance programs are crucial to ensure cleaner outcomes.

What can reduce car pollution

Cutting pollution from cars requires a mix of technology, policy, infrastructure, and behavior. Many measures deliver immediate health benefits while also reducing climate impacts.

• Drive less, shift modes: Expand reliable public transit, safe walking and cycling networks, and support telecommuting and trip consolidation.
• Cleaner vehicles and fuels: Electrify where feasible; improve fuel economy; deploy DPF/SCR/GPF systems; use low-sulfur fuels.
• Regulations and standards: Enforce stringent exhaust standards (e.g., U.S. Tier 3, Euro 6/VI and upcoming Euro 7), evaporative controls, and real-driving emissions tests.
• Tire and brake reforms: Develop low-abrasion tires, alternatives to 6PPD, and copper-free brake pads; adopt tire-wear limits and labeling; advance particle-capture technologies at the wheel.
• Urban traffic management: Low-emission and congestion zones, speed management, and pricing to cut stop‑and‑go traffic and idling.
• Better driving and maintenance: Eco-driving, regular maintenance, tire pressure checks, and avoiding unnecessary idling.
• Stormwater controls: Street sweeping, sediment traps, green infrastructure, and targeted filtration at high-traffic outfalls.
• Power-sector decarbonization and recycling: Clean grids amplify EV benefits; recycling batteries and metals lowers life‑cycle impacts.

Combined, these steps can substantially reduce health risks now and align road transport with climate goals over the coming decades.

Key numbers at a glance

These figures provide context for the scale and sources of car-related pollution, noting that values vary by country and city.

• Climate share: Transport produces roughly 23% of global energy-related CO2; road vehicles account for the majority of that, with passenger cars contributing on the order of 10% of total global CO2 (IEA).
• Urban NO2: Road traffic is the dominant source of NO2 in many cities; near major roads it can account for the majority of measured concentrations.
• PM from traffic: In regions with modern exhaust controls, non-exhaust sources (tires, brakes, road dust) now make up most of road-traffic PM2.5 and PM10.
• Tire wear: Each vehicle sheds from hundreds of grams to several kilograms of tire particles per year, depending on driving, speed, and vehicle mass; a fraction becomes airborne, the rest accumulates on roads and washes into waterways.
• Noise: Millions in Europe are exposed to road-traffic noise above WHO guideline levels, with measurable impacts on sleep and cardiovascular health.

While exact shares differ by fleet and policy, the pattern is consistent: cars affect air, water, soil, climate, and soundscapes—both near roads and far beyond.

Summary

Cars cause pollution in five main ways: tailpipe emissions that harm health and form smog; greenhouse gases that warm the climate; non-exhaust particles from brakes, tires, and road dust; runoff that contaminates waterways and soils; and pervasive noise. Technology and policy have curbed many exhaust pollutants, but non-exhaust particles and total climate impacts remain significant as traffic grows. Reducing driving, electrifying with cleaner power, tightening standards for exhaust and tire wear, improving urban design, and managing stormwater together offer the most effective path to cleaner air, safer water, and quieter streets.

What is the biggest pollutant from cars?

carbon monoxides
Across the U.S., vehicle emissions are the largest source of carbon monoxides (56% nationwide and up to 95% in cities) and nitrogen oxides (45% is attributed to the transportation sector). California’s transportation sector accounts for nearly 80% of nitrogen oxide pollution and 80% of the pollutants that cause smog.

What are the pollution caused by cars?

Car pollution involves harmful substances like carbon monoxide, nitrogen oxides, particulate matter, and volatile organic compounds (VOCs) released from burning fuel, which contribute to respiratory illnesses, smog, acid rain, and climate change. In the U.S., transportation is a major source of air pollution, with vehicles accounting for a significant portion of greenhouse gas and carbon monoxide emissions. To reduce car pollution, you can drive less, use public transportation, walk or bike, choose fuel-efficient or electric vehicles, and maintain your car regularly.
 
Types of Car Pollution and Their Sources

• Carbon Monoxide (CO): A toxic gas from incomplete combustion that reduces oxygen in the blood. 
• Carbon Dioxide (CO₂): A greenhouse gas that traps heat and contributes to global warming. 
• Nitrogen Oxides (NOx): Contribute to smog and acid rain, and cause respiratory issues. 
• Particulate Matter (PM): Tiny particles from exhaust, brake wear, and tire dust that can enter the lungs and bloodstream. 
• Volatile Organic Compounds (VOCs): Chemicals that form ground-level ozone and contribute to smog. 
• Sulfur Dioxide (SO₂): Emitted mainly by diesel vehicles and contributes to acid rain and respiratory problems. 
• Black Carbon: A component of particulate matter that absorbs sunlight, accelerating climate change. 

Health and Environmental Impacts

• Health: Opens in new tabCar pollution can cause or worsen respiratory diseases like asthma, lead to cardiovascular problems, increase the risk of cancer, and impact children’s development and academic performance. 
• Environment: Opens in new tabIt contributes to climate change by releasing greenhouse gases, forms acid rain, creates smog, and can destroy wildlife habitats. 

How to Reduce Car Pollution

• Drive Less: Opens in new tabOpt for walking, biking, carpooling, or public transportation instead of driving alone. 
• Drive Smarter: Opens in new tabChoose fuel-efficient vehicles, hybrids, or electric cars to reduce fuel consumption and emissions. 
• Proper Maintenance: Opens in new tabKeep your vehicle in good condition, including tires and engine, to ensure it runs efficiently and emits less pollution. 
• Avoid Idling: Opens in new tabDon’t let your car idle, as this wastes fuel and produces unnecessary pollutants. 

Do cars give off CO2 or CO?

Cars produce both carbon dioxide (CO2) and carbon monoxide (CO). Carbon dioxide is a result of complete fuel combustion and is a greenhouse gas, while carbon monoxide is a product of incomplete combustion and is a toxic, invisible gas. Modern catalytic converters significantly reduce CO emissions, but poorly tuned or older cars, or situations like a car running in an enclosed garage, can lead to dangerously high levels of carbon monoxide.
 
Carbon Dioxide (CO2) 

• What it is: A greenhouse gas that results from the complete burning of gasoline and diesel fuel in an engine.
• Effects: Contributes to climate change.

Carbon Monoxide (CO)

• What it is: A toxic, invisible gas produced when fuel doesn’t burn completely. 
• Effects: Harmful to human health and can be fatal in enclosed spaces. 

Why Cars Produce Both

• Complete Combustion: Opens in new tabWhen fuel burns perfectly with enough oxygen, the primary products are water vapor and carbon dioxide. 
• Incomplete Combustion: Opens in new tabIn reality, fuel combustion in a car engine is not always complete, especially at certain engine conditions or if the engine is poorly maintained, leading to the production of carbon monoxide. 

How CO emissions are reduced 

• Catalytic Converters: Modern cars are equipped with catalytic converters, which are designed to convert carbon monoxide into less harmful carbon dioxide before the exhaust leaves the vehicle.

When CO levels are dangerous

• Faulty Exhaust Systems: Opens in new tabLeaks in the exhaust system can allow carbon monoxide to escape before it’s converted by the catalytic converter. 
• Enclosed Spaces: Opens in new tabOperating a car in a closed area like a garage can lead to CO buildup, as there might not be enough oxygen for the catalytic converter to work effectively or for the gas to dissipate. 

What is pollution from cars called?

Car pollution is generally called vehicle emissions, a mixture of exhaust gases and particles that harm air quality and human health. Key pollutants include particulate matter (soot), nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and hydrocarbons, which contribute to issues like smog, acid rain, and the greenhouse effect.
 
Types of Pollution

• Exhaust Emissions: Gases and particles released from the vehicle’s engine as it runs. 
• Evaporative Emissions: Fuel vapors released from the fuel system and tank, even when the car is parked, especially in hot weather. 
• Abrasion Emissions: Particulate matter (PM) from the wear and tear of car parts, such as tires and brakes. 

Common Pollutants

• Particulate Matter (PM): Opens in new tabTiny particles, including soot, that can penetrate deep into the lungs, causing respiratory and heart problems. 
• Nitrogen Oxides (NOx): Opens in new tabGases that contribute to smog, acid rain, and can worsen respiratory issues like asthma. 
• Carbon Monoxide (CO): Opens in new tabA toxic, colorless gas resulting from incomplete fuel combustion that can be fatal. 
• Carbon Dioxide (CO2): Opens in new tabA greenhouse gas that, while not directly toxic, is a major contributor to climate change. 
• Hydrocarbons: Opens in new tabOrganic compounds that contribute to the formation of ground-level ozone (smog) and are a health hazard, according to Gasera Ltd. 

Impact of Car Pollution

• Reduced Air Quality: A major factor in air pollution, especially in cities with heavy traffic. 
• Health Problems: Exacerbates respiratory illnesses and can lead to serious heart and lung issues. 
• Environmental Damage: Contributes to smog, acid rain, and soil acidification. 
• Climate Change: Car emissions, particularly carbon dioxide, are a significant contributor to the global warming effect.