ALARMING research suggests that most childhood cancers are probably caused by exposure to pollution while babies are still in the womb.

A study carried out by scientists at Birmingham University found that children born within a 1km radius of an emissions hotspot were between two and four times as likely to die of cancer before the age of 16 as other children.

The researchers concluded that most cancers in children were probably the result of exposure before birth to industrial and environmental pollutants, most likely inhaled by the mother during pregnancy.

The study, which has implications for industrial areas in the North-East, said that being born close to emissions of a substance called 1,3-butadiene and carbon monoxide carried the highest risks.

While the commonest source of carbon monoxide is exhaust gases produced by motor vehicles, 1,3-butadiene is produced as a by-product several industrial processes found in the North-East.

According to Friends of the Earth, the largest source of butadiene emissions in the UK is the petrochemical complex on Teesside.

The author of the paper, Professor EG Knox, believes the results are so striking that urgent action should be taken to limit emissions.

He wrote: "Some countries are taking serious efforts to control emissions of 1,3-butadiene, while others have decided to await more information. The massive evidence on this substance, reported here, should allow no further delays."

In his paper, published in the Journal of Epidemiology and Community Health, Prof Knox calls for more research into childhood cancer to determine when an infant was exposed to chemicals and a search for solutions to the problem.

Substances such as carbon monoxide particulate matter and nitrogen oxides, associated with oil burning, particularly in engines and compounds such as benzene, benzapyrene and dioxins, are also cited in the research as potential hazards.

Animal research has already identified some of these compounds as cancer-causing carcinogens, the author said.

Prof Knox based his findings on a chemical emissions map for the UK, produced by the UK National Atmospheric Emissions Inventory in 2001, and details of all children in Britain who died from leukaemia and other cancers before their 16th birth- days, between 1953 and 1980.

To try to compensate for the time difference between the production of the map and the time covered by the deaths register, only children who died between 1966 and 1980 were included in the study.

Apart from the mother breathing in these substances, Prof Knox also believes that exposures in early infancy, through breast milk, or even before the child is conceived, could have an effect.

But Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "The evidence that most childhood cancers are 'probably down' to industrial and environmental pollutants is very thin.

"A wealth of information suggests that leukaemia, the most common type of cancer in children, may be a rare response to an unidentified but common infection."

Mary Taylor, a campaign officer with Friends of the Earth, said: "Teesside is still the largest source of butadeine emissions, which are known to be a carcinogen. In 1999 180 tonnes were released."

She acknowledged that most people in the UK would have been exposed to chemicals mentioned in the study, but said people living near the Teesside petrochemical complex "may have had an extra dose of butadeine, along with a lot of other chemicals".

She added: "We have to aim for zero emissions. Some communities, including those on Teesside, are getting more than their fair share of cancer-causing emissions."