What Percent of Pollution Do Cars Cause?

It depends on what kind of pollution and where you measure it, but a clear picture emerges: globally, passenger cars are responsible for roughly 10% of energy-related CO2 emissions; including all road transport raises that to about 15%. In the United States, cars and light trucks together account for about 16% of total greenhouse gas emissions. For city air pollution, road traffic typically contributes 30–40% of nitrogen oxides (NOx) and about 5–15% of primary fine particles (PM2.5), with higher shares near busy roads. Those figures vary by method, region, and year.

Why the percentage varies

“Pollution” spans climate-warming gases and health-damaging air pollutants, and the answer changes with scope (cars only vs. all road vehicles), geography, and the year of the inventory. Cars also pollute directly from exhaust and indirectly via fuel production, electricity generation for electric vehicles, brake/tire wear, and road dust.

By the numbers: current best estimates

The figures below summarize the most widely cited, recent estimates from major agencies, noting the scope and inventory year so comparisons are fair.

• Global climate impact (CO2): Passenger cars produce about 10% of global energy-related CO2 emissions. Transport overall is about 22–24% of energy-related CO2, and cars are roughly 40–45% of transport CO2 (IEA 2023–2024; IPCC AR6 2022).
• All road transport: Road vehicles (cars, vans, trucks, buses, motorcycles) account for roughly 15%–17% of global energy-related CO2 (IEA 2023–2024).
• United States: Transportation is about 28% of total U.S. greenhouse gas emissions; light-duty vehicles (passenger cars and light trucks/SUVs) are ~57% of transportation emissions—about 16% of total U.S. GHGs (EPA Inventory 2024, 2022 data).
• European Union: Passenger cars are responsible for roughly 12% of total EU CO2 emissions; road transport overall is about a quarter of energy-related CO2 in the EU (EEA 2023).

Taken together, cars alone typically contribute a single-digit to low-teens share of economy-wide climate emissions, while the broader road sector contributes in the mid-teens globally—and an even larger share within the transport sector itself.

Air pollutants in cities: NOx, PM2.5 and ozone precursors

Beyond climate impact, road traffic is a leading source of health-damaging air pollution in urban areas. The following figures reflect typical ranges reported by national and regional inventories; local hotspots can be higher.

• Nitrogen oxides (NOx): Road transport contributes around 30–40% of national NOx emissions in the U.S. and EU, and often 40–60% of measured NOx in dense urban centers (EPA National Emissions Inventory; EEA Air Pollutant Emissions, 2021–2023).
• Fine particles (PM2.5): Road transport contributes roughly 5–15% of primary PM2.5 at the national scale (lower in the U.S., higher in some EU countries), but roadside concentrations can be substantially higher due to proximity. Non-exhaust sources (brake, tire, and road dust) are a growing share as engines get cleaner (EEA 2023; EPA NEI).
• Volatile organic compounds (VOCs): On-road vehicles typically account for about 10–20% of anthropogenic VOCs, depending on the region and year; combined with NOx, these drive urban ozone formation (EPA NEI; EEA 2023).
• Ozone (O3): Not emitted directly by cars, but formed in the atmosphere from vehicle NOx and VOCs—meaning traffic is a major contributor to many cities’ smog episodes.

In short, cars and other road vehicles are dominant contributors to urban NOx and important contributors to PM2.5 and VOCs—key drivers of smog and cardiopulmonary health risks.

What determines the share from cars

Several factors push the percentage of pollution from cars up or down in any given place or year.

• Vehicle mix and usage: More SUVs and pickups, longer commutes, and higher traffic volumes raise emissions.
• Fuel economy and emissions standards: Stronger standards and inspection/maintenance programs lower both CO2 and smog-forming pollutants.
• Power sector mix for EVs: Electric vehicles cut tailpipe pollution immediately; their climate impact improves as grids add more renewables.
• Urban form and travel behavior: Compact, transit- and bike-friendly cities reduce per-capita driving and emissions.
• Technology turnover: Newer fleets with advanced aftertreatment (for NOx/PM) and higher efficiency reduce shares over time.

Because these drivers vary widely, the “percent from cars” is best understood as a range, not a single universal number.

How to reduce the share quickly

Evidence from cities and countries that have cut transport pollution points to a mix of technology, policy, and behavior shifts.

1. Accelerate EV adoption while cleaning the grid, prioritizing high-mileage vehicles (taxis, ride-hailing, delivery).
2. Tighten tailpipe standards (NOx/PM) and strengthen compliance and inspection to ensure real-world performance.
3. Shift trips to public transit, walking, and cycling; support with safe infrastructure and transit priority.
4. Raise fuel-efficiency and CO2 standards for new vehicles, including SUVs and light trucks.
5. Deploy low-emission zones, congestion pricing, and smart parking to cut stop-and-go traffic and exposure.
6. Address non-exhaust PM with regenerative braking, low-wear tires, street cleaning, and lower speed limits where appropriate.
7. Improve logistics and delivery efficiency (route optimization, consolidation, right-sizing vehicles).

Together, these steps can reduce both climate emissions and local air pollution from cars faster than any single measure alone.

Methods and sources

Percentages differ by boundary choices (energy-related CO2 vs. all GHGs, “cars” vs. all light-duty vehicles), inventory years, and whether non-exhaust sources are included. The figures above draw on the latest widely cited assessments.

• International Energy Agency (IEA), CO2 Emissions from Fuel Combustion and transport sector analyses (2023–2024): transport share of global energy-related CO2, road and passenger-car breakdowns.
• IPCC AR6 (2022), Working Group III: sectoral shares of global greenhouse gas emissions.
• U.S. EPA, Inventory of U.S. Greenhouse Gas Emissions and Sinks (2024, 2022 data): sector shares; transportation and light-duty vehicle contributions.
• U.S. EPA, National Emissions Inventory (latest available): NOx, VOC, PM2.5 contributions from on-road mobile sources.
• European Environment Agency (EEA) reports (2023): passenger car CO2 shares; road transport contributions to NOx, PM2.5, and VOCs in the EU.
• WHO syntheses on urban air quality and health for context on exposure and health impacts.

Because methodologies evolve, national and city inventories may report slightly different percentages; the ranges above reflect consistent, peer-reviewed sources.

Summary

There isn’t a single universal percentage for “pollution from cars,” but the contours are clear. Passenger cars account for roughly one in ten tons of the world’s energy-related CO2, with all road transport around the mid-teens. In cities, road traffic is a leading source of NOx and a meaningful contributor to PM2.5 and VOCs. The exact share depends on what you count and where, but technology, policy, and better urban design can drive those numbers down quickly.