Young children suffer more coughing attacks the nearer they live to a main road, according to researchers.
Children coughed more near main roads
Nearly 3,500 children living in Leicester were involved in the study.
A team from the University of Leicester focused on children aged between one and five.
They assessed the link between how much a child was exposed to microscopic particles produced primarily by diesel engines and what respiratory problems they had.
The study found cases of coughs increased by up to 3% for every 100 metres closer the children lived to a busy main road.
It claims particles pumped out by vehicles are an irritant on a child's airways.
It adds weight to past research which has established a link between air pollution and increased cases of asthma and other breathing problems.
Dr Jonathan Grigg, senior lecturer in paediatric respiratory medicine, said: "We know that small particles from diesel exhaust are one of the most dangerous air pollutants - since they can penetrate deep into a child's lungs.
"Our study into the health effects of living near road traffic has provided clear evidence that particles from vehicles are a significant irritant on the airways of young children."