Children living in homes with high levels of radon gas or gamma radiation appear to be at no greater risk of developing cancer, a study showed yesterday.

Children living in homes with high levels of radon gas or gamma radiation appear to be at no greater risk of developing cancer, a study showed yesterday.

The research, involving 6,000 homes across Britain, found that levels of radon, a naturally occurring radioactive gas, were no higher in homes of children with cancer than those of healthy youngsters.

The quantity of gamma radiation in children's homes also seemed to be unrelated to their likelihood of developing cancer, according to results published in the British Journal of Cancer.

Concern about a possible link between childhood cancers and background radiation has been particularly acute in Devon and Cornwall, where levels of the radon, an invisible gas, are three to four times the national average.

But scientists from the UK Childhood Cancer Study, led by the cancer specialist Professor Sir Richard Doll, said that the results should be "reassuring" for parents. The scientists concluded in their report: "No evidence to support an association between higher radon concentrations and the risk of any of the childhood cancers was found."

The team, based at the University of Leeds, measured levels of radon and gamma rays in the bedrooms and living rooms of 2,226 children with cancer and 3,773 healthy children. The researchers divided the cancers into six groups and analysed them separately, to see whether radiation might influence some types of cancer but not others.

None of the six groupings, which included acute lymphoblastic leukaemia, brain tumours and Hodgkin's disease, showed a link to higher levels of radiation.

Scientists believe that ionising radiation can cause cancers at certain doses. But the study suggested that variations in radon and gamma rays from area to area were too small to make a difference.

Professor Doll, of Oxford University, said: "Although some areas have higher levels of radon or gamma radiation than others, the differences don't seem to be big enough to produce a detectable effect.

"That suggests background radiation is not playing as large a role as some people have feared." But he said that parents' fears about a possible link were unsurprising given that previous research had been inconclusive. "This study is the first in the UK to measure domestic levels of radiation and relate them to children's cancer risk, and it is pleasing to be able to ease those fears," he said.

Dr David Grant, the scientific director of the Leukaemia Research Fund, one of the funding bodies for the cancer study, said: "The first question parents often ask when their child is diagnosed with leukaemia is 'why?'

"People quite naturally turn to their immediate environment for answers, but it is reassuring to know that commonly encountered levels of radon gas and gamma radiation appear not to put children at risk."

Dr Michael Clark, the science spokesman for the National Radiological Protection Board, said a study in south-west England a few years ago had suggested a small increase in lung cancer among adults who were exposed to higher concentrations of radon gas. But it was revealed later that those with the disease were all smokers.

He said this study was more reliable. "This is the largest study of childhood cancer in the world. Scientists from many countries will take note of its findings."