Power lines' link to leukemia still unconfirmed


April 05, 1994|By Dr. Genevieve Matanoski | Dr. Genevieve Matanoski,Medical Tribune News Service

With so many people living near high-tension wires, there has been a growing public concern about the possible risk of cancer from exposure to electromagnetic fields (EMFs).

Several articles have recounted stories of cancers in children who lived near high-power lines or went to school near power lines.

Late last year an additional study of the risks of cancer in children exposed to EMFs was reported from Sweden. The new data make this an appropriate time to revisit the controversy.

Q: What are the findings regarding EMF exposure and cancer in children?

A: There have been a number of studies on this subject. The best studies prior to the Swedish one were summarized in a British publication in 1992. This summary indicated a small increase in the risk of leukemia when the presumed exposure to EMF was based on the proximity of a residence to a high-power source or lines that might carry more current. Studies of brain cancer in children also seem to indicate an increased risk in association with EMF exposure. In all studies, when the scientists have actually measured the EMF exposures in the homes, the risk of the cancers is either very low or nonexistent.

The new Swedish study shows excess leukemias in relation to residence near power lines. What is different is that they have been able to estimate exposures in the past from information on the historical current loads in the lines. That measure was related to the risk of leukemia but not to the risk of brain cancer.

Q: How much are studies affected by guessing about an exposure rather than actually measuring it?

A: Every house has many characteristics. Proximity to a power line is only one. Therefore, if it were only the electric lines that were causing the problem, the risk should be increased if we measure the exposure directly. But that is not so. Some scientists have, however, pointed out that measurements of fields in homes today may not really reflect exposures in the past. The Swedish study, which based its measurements on past reported line loads, suggests that these scientists might be right. However, nothing is confirmed at the present.

We have a long way to go before we can determine whether there is any cancer risk from exposure to EMF. In the meantime, the recommendation of most scientists is that you practice "prudent avoidance." Since exposure drops rapidly with distance, try to maintain the maximum distance between yourself and a potential source.

Dr. Genevieve Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is a founding director of the school's Institute for Women's Health Research and Policy.

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