What Percentage of Air Pollution Is Caused by Cars?

There is no single universal percentage, because the share from cars varies by pollutant and location. Globally, passenger cars are responsible for about 8–10% of carbon dioxide (CO2) emissions, while in cities they commonly account for roughly 10–25% of nitrogen oxides (NOx) and about 5–10% of fine particulate matter (PM2.5). Road traffic as a whole (cars, vans, trucks, buses, two- and three-wheelers) typically contributes 30–70% of urban NOx and around 15–30% of urban PM2.5, with the car share being a subset that depends on fleet mix, fuel type, and emission controls.

The numbers at a glance

The figures below summarize typical ranges from recent assessments by agencies such as the International Energy Agency (IEA), World Health Organization (WHO), European Environment Agency (EEA), and the U.S. Environmental Protection Agency (EPA). They differ by pollutant (climate vs. health) and whether we look globally or at urban areas.

• Global climate pollution (CO2): Passenger cars contribute about 8–10% of total global CO2 emissions (roughly 45% of road-transport CO2; transport is about 23% of energy-related CO2, and road vehicles dominate that share).
• Urban nitrogen oxides (NOx): Road traffic often contributes 30–70% of city NOx; passenger cars typically account for about 10–25% of citywide NOx, and in some European cities with higher diesel car shares the car fraction can exceed 30%.
• Fine particulate matter (PM2.5): Traffic commonly contributes about 15–30% of urban PM2.5; passenger cars’ direct exhaust PM2.5 is usually low-single-digit percent where modern standards apply, but total car-related PM2.5 rises to roughly 5–10% when brake, tire and road dust are included. In cities with older fleets and weaker standards, the traffic share can be higher.
• Carbon monoxide (CO) and volatile organic compounds (VOCs): On-road vehicles are a major source in many cities; modern gasoline cars have cut CO/VOC emissions substantially where strict standards are enforced, but in cities with older fleets cars can still dominate these pollutants.

These ranges reflect broad, recent evidence and highlight that cars are a significant—but not exclusive—driver of air pollution. Heavy-duty trucks and buses, industry, power generation, buildings, agriculture, and household fuels can rival or exceed cars depending on the location.

Why there isn’t a single percentage

How much cars contribute to “air pollution” depends on what you measure, where you measure it, and when. The following factors explain the variability.

• Pollutant type: CO2 (climate) vs. NOx, PM2.5, ozone precursors (health). Cars’ relative contribution differs sharply across these.
• Urban vs. national averages: Cities with dense traffic see larger shares from vehicles than rural or national averages dominated by other sectors.
• Fleet composition: The split between passenger cars and heavy-duty diesel vehicles, plus the share of older vehicles, changes the outcome.
• Fuel and technology: Diesel vs. gasoline, presence of particulate filters, catalytic converters, and real-world compliance affect emissions.
• Non-exhaust sources: Brake, tire, and road dust emissions are growing in importance and are linked to total vehicle miles traveled and vehicle weight.
• Meteorology and geography: Weather patterns, altitude, and urban canyon effects can concentrate or disperse pollutants.
• Policy strength: Emission standards (e.g., Euro 6/7, U.S. Tier 3), inspection/maintenance, and low-emission zones materially reduce car emissions.

Taken together, these drivers mean a single global “percentage from cars” can mislead; more precise answers hinge on pollutant and place.

What current data shows by region and pollutant

Global climate pollution (CO2)

According to the IEA, transport produces about 23% of energy-related CO2 emissions, with road vehicles comprising roughly three-quarters of transport emissions. Passenger cars account for around 45% of road-transport CO2, putting them near 8–10% of total global CO2. This figure has edged down in markets rapidly adopting electric vehicles, but absolute transport emissions remain high as travel demand grows.

Urban health pollutants (NOx and PM2.5)

In the European Union, EEA inventories show road transport around 35–40% of NOx emissions in recent years, with passenger cars contributing roughly the high teens to about 20% of national totals on average—higher in diesel-heavy cities and busy corridors. For PM2.5, road transport contributes near 10–15% of primary emissions EU-wide, and non-exhaust sources (brake, tire, road dust) now exceed tailpipe PM in many cities.

In the United States, EPA national inventories indicate on-road vehicles contribute roughly one-quarter to one-third of NOx, with light-duty vehicles (cars and small SUVs) contributing a meaningful but smaller share than heavy-duty diesel trucks. Direct PM2.5 from modern gasoline cars is relatively low, but total traffic-related PM2.5—including non-exhaust—remains an important urban health burden near roads.

In many low- and middle-income cities, traffic is a leading source of NOx and a major contributor to PM2.5 along corridors, but citywide PM2.5 can be dominated by other sources such as household solid-fuel use, open burning, industry, power generation, and dust. Consequently, cars’ percentage contribution to total PM2.5 in such cities can be modest, even while roadside exposures are high.

How analysts estimate the “car share”

Source apportionment studies and emission inventories use a mix of measurements and models. Understanding their methods helps interpret the numbers.

1. Emission inventories tally emissions by sector and vehicle type using fuel use, mileage, and emission factors, then allocate to geographic areas.
2. Receptor/source apportionment measures chemical fingerprints in ambient air (e.g., NOx, black carbon, metals) to attribute shares to traffic, industry, etc.
3. Dispersion and chemical transport models simulate how emissions travel and transform, estimating contributions to concentrations and exposure.
4. Near-road monitoring reveals roadside peaks, which are higher than citywide averages and especially sensitive to vehicle mix and congestion.

Each approach has uncertainties—especially for non-exhaust PM and real-world driving—but together they provide consistent evidence for the ranges summarized above.

What will change the percentage over the next decade

Policies and technologies now in motion are reshaping cars’ share of air pollution. The items below are the highest-impact levers.

• Electrification: Rapid growth of battery-electric cars cuts tailpipe NOx, PM, CO, and VOCs to zero; lifecycle emissions then depend on the power grid.
• Stronger standards and compliance: Stricter emission rules (e.g., Euro 6/7, U.S. Tier 3/Low-NOx) and better real-world enforcement reduce NOx and PM.
• Non-exhaust controls: Regenerative braking, lighter vehicles, better tires, and street cleaning address brake, tire, and dust emissions.
• Mode shift and demand management: Public transit, walking, cycling, telework, and congestion pricing reduce vehicle miles traveled and exposure hot spots.
• Cleaner fuels and maintenance: Low-sulfur fuels, proper engine calibration, and inspection/maintenance keep emissions controls effective.

Where these measures scale up, the car share of both climate and health pollutants falls—sometimes rapidly—though heavy-duty vehicles and other sectors must also decarbonize to achieve clean air standards.

Bottom line

Cars are a meaningful contributor to air pollution, but the exact percentage depends on what you measure and where. A practical rule of thumb is: around 8–10% of global CO2 comes from passenger cars, while in cities cars often contribute about 10–25% of NOx and roughly 5–10% of PM2.5, with total road traffic accounting for substantially more. Local conditions can push these numbers higher or lower. Cutting emissions from cars—alongside trucks, industry, power, and buildings—is essential to meet clean air and climate goals.

Summary

There isn’t a single global figure for “how much air pollution cars cause.” Contemporary data suggest passenger cars produce about 8–10% of global CO2, roughly 10–25% of urban NOx, and around 5–10% of urban PM2.5, while all road traffic typically contributes 30–70% of city NOx and 15–30% of PM2.5. The actual share varies with pollutant, fleet, standards, and local sources, and it is expected to decline where electrification and strong emission policies expand.

Who air pollution 99%?

99% of the world’s population breathes polluted air, leading to life-threatening health concerns for millions. Monday’s Car Free Day is an opportunity to take #ClimateAction and show how cities can look & feel without cars. via UN Environment Programme.

What is the #1 source of air pollution on Earth?

Vehicle emissions, fuel oils and natural gas to heat homes, by-products of manufacturing and power generation, particularly coal-fueled power plants, and fumes from chemical production are the primary sources of human-made air pollution.

What is the #1 polluter on planet Earth?

China is the world’s biggest annual greenhouse gas polluter, responsible for nearly a third of global emissions, followed by the United States and India. While China leads in absolute annual emissions, the per capita emissions ranking changes, with countries like Qatar and the United States having higher per person pollution levels due to large individual energy consumption.
 
Absolute vs. Per Capita Emissions

• Absolute Emissions: Opens in new tabThis measures the total amount of pollution from a country. China emits the most carbon dioxide (CO2) annually. 
• Per Capita Emissions: Opens in new tabThis measures the pollution per person in a country. When looking at this metric, countries like the United States, Qatar, and Montenegro have higher emissions per person than China, which has a large population. 

Top Polluters by Annual Emissions

1. China: The largest annual emitter of greenhouse gases, accounting for roughly one-third of the world’s total. 
2. United States: The second-largest annual polluter. 
3. India: The third-largest annual polluter. 

Other Factors

• Historic vs. Current Emissions: Opens in new tabThe total historical contribution to climate change is another important factor to consider. 
• Efforts to Reduce Emissions: Opens in new tabDespite being the top polluter, China is making significant efforts to reduce its emissions by rapidly expanding renewable energy sources like wind and solar. 

What are the top 3 contributors to CO2 emissions?

The majority of this increase has resulted from increased fossil fuel consumption and industrial emissions. Agriculture, deforestation, and other land-use changes have been the second-largest contributors. Emissions of non-CO2 greenhouse gases (CH4, N2O, and F-gases) have also increased significantly since 1850.