Car emissions are a major source of pollution. Cars and trucks emit twenty percent of all greenhouse gases emitted in the United States[1], which is the second largest greenhouse gas emitter in the world.

As of 2026, passenger cars and light trucks remain significant contributors to global environmental issues, accounting for approximately 10% of total global energy-related CO2 emissions. In the broader context of the transportation sector, private vehicles are responsible for more than 75% of transport-related emissions. In the United States, the impact is even more pronounced, with light-duty vehicles generating about 16% of total national greenhouse gas emissions. Beyond carbon dioxide, cars are also primary sources of urban air pollutants like nitrogen oxides (NOx​) and particulate matter (PM2.5​), which contribute to smog and respiratory health problems. While the rapid adoption of electric vehicles (EVs) is beginning to bend the curve—with many countries mandating a shift to zero-emission sales by 2035—the sheer volume of internal combustion engine vehicles currently on the road ensures that cars remain a central focus for global climate policy and urban air quality initiatives.