Childhood cancer in relation to distance from high voltage power lines - results may be entirely due to chance

Cancer Research UK comments on the BMJ paper "Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case control study."

Professor John Toy, Cancer Research UK's Medical Director, says:

"This study reports a very slight increase in the risk of childhood leukaemia for children born near power lines, but the researchers could not link this to the power lines themselves. These results may indeed be entirely due to chance.

"What this paper does not show is that power lines directly cause childhood leukaemia. This may seem confusing, but there may be other more common factors that exist in these areas that contribute to the apparent increased risk.

"The numbers of cases are small. This apparent very slight increase in risk would, if real, equate to five extra cases of childhood leukaemia in a total of around 400 that occur in a year.

"People who currently live or have lived near power lines in the past need not panic about this research. The triggers that cause childhood leukaemia are most likely a random course of events over which a parent has no control."

The causes of childhood leukaemia are still rather unclear. The theory that holds most weight with the majority of the scientific and medical community is that the disease is probably caused by two factors – an event that damages a baby's DNA before it is born, followed by an unusual pattern of infection later in childhood.

It should be noted that research has also suggested that early exposure to many infections as a baby – for example, a baby who attends day care and picks up a cold every so often – seems to offer some form of protection.

There are two main types of childhood leukaemia – acute lymphoblastic leukaemia (ALL) and acute non-lymphocytic leukaemia. There are around 400 cases of childhood leukaemia in England and Wales every year.

Survival rates for childhood leukaemia have improved substantially over the last ten years. For children diagnosed with the most common form of childhood leukaemia (ALL) between 1982-1986 the 5 yr survival rate was 70 per cent compared to 81 per cent for children diagnosed 1992-1996. Survival rates for the next most common form (acute non-lymphocytic leukaemia) rose from 30 per cent to 52 per cent over the same period.

A simple example of an association which is not causal would be if you cut your finger twice in a week and because both times you were wearing a blue shirt, concluding that it was the blue shirt that caused the accident. When actually the cuts were down to a number of factors – you were tired, you were watching the TV at the time and weren't concentrating or any number of factors that came into play at the moment of the accident.

It is possible to request the electro magnetic field to be measured in the home free of charge by contacting the relevant electricity supplier.

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