Children who live near overhead power lines have an increased risk of getting leukaemia, according to new research published in the British Medical Journal.
Less than one in 100 homes are within 200m of a high voltage cable
About one child in 2,000 in Britain will develop leukaemia before they're 15 years old.
But scientists still don't know exactly what causes the illness and the report has caused some confusion.
The latest study published in today's British Medical Journal, says that leukaemia rates are significantly higher among children who live close to power lines.
But the report's authors say more work is needed to prove that the link is not coincidental or affected by other factors.
This morning, Breakfast asked: what does the study mean?
First we spoke to Professor Gerald Draper of the University of Oxford Childhood Cancer Research Group who is one of the report's authors.
He told Breakfast "We think it could be a coincidence, but it could mean something real. We really don't know, so it seemed t we ought to publish the results so that people could think about all possible explanations."
He added that the report had only been published today because some of the results had been leaked.
However, he did confirm earlier research which establish a "possible" link between power lines and the very small number of leukaemia cases very close by.
But he said cases found further away, at distances of 600m,could NOT be linked because the magnetic field would be very weak.
The Childhood Cancer Research Group looked at nearly 10,000 cases of childhood leukaemia, in those born from the early 1960s to the mid-1990s.
It found that children living within 200m of high voltage overhead lines ran a 70% greater chance of developing leukaemia than other children.
No excess risk was found for other forms of childhood cancer.
Researchers found that 64 children who'd developed leukaemia lived within 200m of an overhead power cable. That's around 5 cases more each year than they'd have expected.
Cause and effect
In the past, evidence suggested that low frequency magnetic fields, generated by high voltage cables, may be implicated in some way - a theory which hasn't been endorsed by the Childhood Cancer Research Group.
They point out there may be other factors at work, as overhead power lines are often found in less densely populated areas.
The social class of those involved is also higher than average in Britain.
It's possible that the findings are due to chance, or to other environmental factors - including social class, pollution, diet or housing. A definitive link between magnetic field, power lines and cancer has not been proven.
Our reporter Sarah Campbell spoke to residents in Beckton, East London, who live close to overhead power lines.
Campaigner, Eddie Gorman's son Paul, died from leukaemia in 1987, at the age of 14. He blames the electricity sub station at the bottom of their garden for his son's death.
He said: "We are saying to the government, don't add to problems that may be out there. Do not build homes - maybe hospitals - under these power lines."
But we also spoke to Dr David Grant, director of the Leukaemia Research Fund. He told us he thought the higher incidence of leukaemia near pylons was a coincidence.
He said: "If there is a link - and we think that there isn't - but if there is, it accounts for only one case in a hundred a year."
He also said that research was now suggesting that some form of assault on the immune system when a child was very young was a more likely cause.
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