Power-Lines And Leukemia...

Electric currents generate magnetic fields, so living with electricity exposes people to those fields. Strong fields can disturb living cells in laboratory studies.

What about the weaker fields we experience if we live near power lines? Some data suggest that more children in these locations might develop childhood leukemia, a cancer of the blood cells.

We cannot do experiments that expose children to magnetic fields just to see if they will develop childhood leukemia.

It is hard to compare cancer rates among children who happen to live in more and less exposed locations, because leukemia is quite rare and locations vary in many ways other than magnetic fields.

It is easier to start with children who have leukemia and compare them with children who do not. We can look at many possible causes- diet, pesticides, drinking water, magnetic fields- to see where children with leukemia differ from those without. Some of the broad studies suggested a closer look at magnetic fields.

A careful look at magnetic fields took five years and cost $5 million. The researchers compared 638 children who had leukemia and 620 who did not. They went into the homes and measured the magnetic fields in the children's bedrooms, in other rooms, and at the front door. They recorded nearby power lines for the family home and also for the mother's residence when she was pregnant. Result: no evidence of more than a chance connection between magnetic fields and childhood leukemia

"No evidence" that magnetic fields are connected with childhood leukemia doesn't prove that there is no risk. It says that a careful study could not find any risk that stands out from the play of chance that distributes leukemia cases across the landscape.

Critics continue to argue that the study failed to measure some important variables, or that the children studied don't fairly represent all children. Nonetheless, a carefully designed observational study is a great advance over haphazard and sometimes emotional counting of cancer cases. (This was not an experiment; experiments actually test individuals in some way order to see how they respond. The goal of an experiment is usually to learn whether some treatment actually causes a certain response.)

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