Road traffic air pollution isn't just caused by exhaust fumes, says new report

A new study has suggested that almost half of air pollution caused by road traffic is not created by exhausts. The study, published in Atmospheric Environment, has found that a large proportion of road traffic pollution is created by issues like road surface wear, brake usage, and from particles dispersed into the air from the road by moving vehicles.

The study has resulted in the call for tighter control of pollution caused by non-exhaust sources. Professor Ranjeet Sokhi, the leader of the study from the University of Hertfordshire, said: "In terms of mass, non-exhaust sources can be more important than exhaust fumes, but legislative control has focussed on exhaust emissions.

"As exhaust regulations become stricter, non-exhaust sources become proportionately more important. Continuing to control exhaust emissions alone may not be enough to achieve legal air-quality standards."

Researchers looked at PM10 pollution particles - airborne particles that are less that ten millionths of a metre across - by taking samples from the Hatfield Tunnel on the A1 motorway in Hertfordshire. The focus on the PM10 particles is due to the fact that they are often linked with health problems such as heart disease.

The samples were analysed after being separated into their different chemical components, allowing for around 82 per cent of the pollutant particles to be traced back to their origins. This analysis revealed that only around 33 per cent of the road traffic pollution was caused by diesel and petrol exhaust fumes. Road wear accounted for 11 per cent of the pollution, as did brake wear. The amount of air pollution that came from vehicles whipping up particles from the road almost matched the level created by exhausts at 27 per cent.

Professor Sokhi said: "Other studies have looked at non-exhaust components of PM10, but those have mostly been done in open-air locations. We wanted to look at them in a more controlled environment, where the influence of the weather could be significantly reduced."