How Much of the World’s Air Pollution Comes From Cars?

There isn’t a single, fixed global percentage because “air pollution” covers different pollutants, but the best evidence suggests passenger cars account for roughly 7–10% of global carbon dioxide (CO2) emissions and only a small, highly variable share of health-damaging urban air pollutants; in many big cities, traffic can drive 10–30% of fine particulate (PM2.5) and 20–50% of nitrogen oxides (NOx), with the portion attributable specifically to cars depending on how many vehicles are diesel, fuel quality, and local regulations.

Why There Is No One Number

“Air pollution” is an umbrella term. Climate pollution (CO2) is measured globally and consistently, but health-related pollutants (PM2.5, NOx, VOCs, ozone) vary by place and time, and are influenced by local fleets, fuels, weather, and enforcement. Studies also differ on whether they count all road vehicles or just passenger cars, making a single global percentage inherently misleading.

What the Best Global Numbers Say

Climate pollution (CO2) from cars

Multiple international datasets converge on a narrow range. Transport produces about one-fifth to one-quarter of energy-related CO2 emissions; road vehicles generate around three-quarters of transport emissions; and passenger cars account for roughly 40–45% of transport emissions. Combined, this puts passenger cars at approximately 7–10% of total global CO2 emissions as of recent assessments by agencies such as the International Energy Agency and Our World in Data.

Health-damaging air pollutants (PM2.5, NOx, ozone precursors)

Globally averaged, passenger cars contribute a much smaller share to primary PM2.5 than to CO2, because heavy-duty diesel trucks and non-transport sources (industry, power, agriculture, households) dominate PM2.5 and its precursors. However, in dense urban areas—especially where diesel use is common and emission standards or enforcement are weak—road traffic can be one of the largest local sources of NOx and a significant contributor to PM2.5. Within that traffic contribution, the proportion from cars versus trucks and buses varies widely by city and region.

How the Share from Cars Changes by Place

The contribution of cars to local air pollution depends on several practical factors that differ across countries and cities.

• Fleet makeup: Cities with many diesel cars and older vehicles see higher NOx and PM from cars; places with newer gasoline cars and strict standards see lower shares.
• Heavy-duty influence: Trucks and buses, especially diesel, often dominate NOx and PM2.5 within the road sector, reducing the fractional share from passenger cars.
• Fuel and maintenance: Low-sulfur fuels, effective inspection-and-maintenance programs, and particulate filters can sharply cut car emissions.
• Urban form and traffic: Congestion, stop-start driving, and cold starts increase emissions; compact, transit-oriented cities can reduce the per-capita burden.
• Meteorology and geography: Weather and topography influence how pollutants accumulate or disperse, affecting measured shares at ground level.

Taken together, these factors explain why estimates range from cars being a modest contributor in some regions to a major neighborhood-level source near busy roads in others.

What This Means for Policy and Daily Life

Cutting pollution from cars delivers both climate and health gains but must be paired with broader actions on trucks, industry, power generation, agriculture, and household fuels. Electrifying passenger cars, tightening emission standards, improving fuel quality, expanding public transit, and managing traffic can significantly reduce NOx and PM2.5 in cities while also lowering CO2.

Summary

There is no single global percentage for “how much air pollution is caused by cars.” The most defensible framing is twofold: passenger cars contribute about 7–10% of global CO2 emissions, while their share of health-damaging urban air pollution varies widely—often a small fraction globally but locally significant, commonly on the order of 10–30% of PM2.5 and 20–50% of NOx in traffic-heavy cities, with precise figures dictated by local fleets, fuels, and policies.

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 percentage of air pollution is caused by cars?

Cars, along with the entire transportation sector, are a major source of air pollution, but their exact percentage of total air pollution varies. In the U.S., transportation is the largest source of greenhouse gas emissions, responsible for about 28-31% of the total, with light-duty vehicles (cars, trucks, and SUVs) being the largest contributor within that sector. Cars and trucks also contribute significantly to local air pollutants like nitrogen oxides and particulate matter, which directly impact human health at street level.
 
Greenhouse Gas Emissions

• U.S. Transportation Sector: Opens in new tabaccounts for roughly 28-31% of all U.S. greenhouse gas (GHG) emissions, making it the largest contributing sector. 
• Light-Duty Vehicles: Opens in new tabPassenger cars, trucks, and SUVs are the biggest source of GHG emissions from the transportation sector, making up about 57.5% of it. 

Local Air Pollutants (PM2.5, NOx) 

• Tailpipe Emissions: Cars, trucks, and other vehicles release pollutants like nitrous oxide (NOx) and fine particulate matter (PM2.5) directly at street level. 
• Impact on Human Health: These tailpipe emissions are a significant concern for public health because they are breathed in by people at ground level. 
• Specific Contributions: On-road vehicles contribute a significant portion of local pollutants; for instance, they can account for up to 45% of nitrogen oxides (NOx) and one-third of volatile organic compounds (VOCs) in some areas. 

Global Context 

• Globally, SUVs alone accounted for over 20% of the increase in energy-related CO2 emissions in 2023.
• If SUVs were their own country, they would rank as the fifth-largest contributor to global CO2 emissions.

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. 

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.