Study Finds Tailpipe Emissions Are No Longer Cars’ Biggest Pollution Source

Researchers at Graz University of Technology have found that exhaust fumes are no longer the main source of air pollution caused by cars. While modern regulations have significantly cleaned up engines, other contributors now play a much larger role in harming the environment.

According to the study, tailpipe emissions now account for less than 10% of particulate pollution under typical driving conditions. The bulk of the problem comes from elsewhere: brake wear, tire abrasion, road surface erosion, and dust kicked up by passing vehicles.

With the introduction of the new Euro 7 standards in Europe in 2026, emissions from brakes are expected to drop by about 80% by 2040, thanks to improved materials and regenerative braking systems used in electric vehicles. Particulate emissions linked to engines themselves could fall by nearly 90%.

Tires, however, remain a tougher challenge. Reducing tire wear by more than 10–20% over a decade is difficult, since safety depends on maintaining strong grip. As a result, meeting air quality limits that are set to become twice as strict by 2030 may prove difficult.

An updated emissions model developed by the researchers—one that accounts for both exhaust and abrasive particles—shows that road dust and surface wear are likely to dominate vehicle-related pollution in the years ahead.