Parents should use covers on their prams to protect them from air pollution, experts have warned.
Scientists have tested the pollution levels inside prams to assess how youngsters are affected.
They discovered that in the mornings when infants are on the school run with their older siblings exposure levels are higher.
“Young children are far more susceptible to pollution than adults, due to their immature and developing systems and lower body weight,” said Dr Prashant Kumar, at the University of Surrey and who led the new research.
“These findings provide an insight for families who walk to and from nursery and primary schools with young children. Essentially, children could be at risk of breathing in some nasty and harmful chemical species.”
“One of the simplest ways to combat this is to use a barrier between the in-pram children and the exhaust emissions, especially at pollution hotspots such as traffic intersections, so parents should use pram covers if at all possible,” he said.
The study has been published in the journal Environmental Pollution.
The researchers placed detectors in prams on 64 journeys to and from schools in Guildford at drop-off and pick-up times.
It revealed that pollution levels were higher at rush hour in the mornings.
The study said: “Fine particles show larger health impacts compared to their larger counterparts and at the young age children are more susceptible to particulate pollution, suggesting a clear need for precautionary measures to limit their exposure during their transport along the busy roadsides."
A recent World Health Organisation report said that 570,000 children under the age of five died every year from illnesses that could be linked to pollution.
Bus stops and traffic lights were the worst places for being exposed to the tiny particles from exhaust fumes and tyres that can get into the bloodstream.
Particulate pollution is estimated to cause a total of 29,000 early deaths in adults each year in the UK.