Science Writing

Study finds traffic is main cause of small airborne particles that contribute to climate change

A recent study has found that urban traffic is a major source of the smallest airborne aerosol particles, which could pose health risks and are a factor in human causes of climate change.

Up until now, the source of these tiny particles, known as nanocluster aerosol particles or NCAs, has not been studied extensively. It was thought that the natural atmosphere, (namely, cloud formation) was a primary source of these particles. But the study found that in urban air, these tiny aerosol particles make up a significant part of the total number of particles and are a direct result of traffic emissions.

Researchers from Tampere University of Technology in Finland conducted the study, which took place in Helsinki and other parts of Europe. Scientists measured the particles in three locations: next to a road, in a street canyon and with a mobile laboratory — a van that took measurements as it drove on highways from northern Spain, through France, Luxembourg, Belgium, the The Netherlands, Germany, Denmark, Sweden and to Finland via ferry.

The highest concentrations of NCAs were found in tunnels and the concentrations matched the daily traffic patterns at the measurement sites. The study also implies that atmospheric processes, like cloud formation, are not necessary for the formation of a large number of NCAs.

These findings help to understand the atmospheric processes that affect climate change, urban air quality and public health. The full text of the study can be found at