Children who live close to major transport hubs are more at risk of dying of cancer, a study says.
Exhaust fumes were the primary cause of the increased cancer risk
University of Birmingham researchers found those living within 500 metres of a bus station were six times more likely to die of cancer.
The study also said railways and hospitals increased the risk. For all the sites, exhaust fume pollution was identified as the primary cause.
But experts said the findings should be treated with caution.
Researchers analysed details about the deaths of 22,500 children between 1955 and 1980 from cancers such as leukaemia, lymphoma, and brain and spinal cancers, the Journal of Epidemiology and Community Health reported.
They found carbon monoxide and 1,3-butadiene, both of which are produced by vehicle exhausts and particularly diesel engines, were the major cause of the increased risk.
But other chemicals, including nitrogen oxides and dioxins, were also cited in the report.
They calculated there could be a 12-fold increase in risk for children living near bus stations and emission hotspots.
Living in close proximity to hospitals increased the risk by 2.5 times, mainly because of the increased transport around the sites and the use of incinerators.
Railways and oil industry were also highlighted as increasing the risk.
About 1,500 new cases of childhood cancer are diagnosed each year in the UK, accounting for about 300 deaths annually.
Report author Professor George Knox said the exposure of a child in the womb and soon after birth to the pollutants were likely to be the critical period.
And he added more controls should be introduced.
"The dominant approach to control has been to specify maximum ambient air concentrations in work situations, but this is clearly not sufficient in the context of foetus/child exposure.
"Control and monitoring measures must be directed towards the sources."
But Ruth Yates, statistical information manager at Cancer Research UK, warned the research should be put into context.
"The results of this study should be interpreted with considerable caution and people should not be alarmed by its claims.
"Before we can be certain of any link between childhood cancer and exposure to pollution, research needs to include much more detailed information on people's levels of exposure than this study provides."