Magnetic Fields And Leukemia

June 16, 1997

NEW YORK (Reuters) - People who have a high level of exposure to magnetic fields at work and at home have more than three times the risk of leukemia as those with lower exposures, a new study suggests. There was no link between brain tumors and exposure to magnetic fields, according to the report.

However, the number of people included in the study was relatively small, and the researchers estimated occupational exposure to magnetic fields based on job title, noted lead author Dr. Maria Feychting, of the Institute of Environmental Medicine at the Karolinska Institute in Stockholm, Sweden.

Magnetic fields produced by electrical generation have been investigated for more than a decade, with studies often having conflicting results. The Washington, D.C.-based National Academy of Sciences announced last November that there is "no conclusive and consistent evidence" that electromagnetic fields (EMFs) are linked to cancer or other health threats, after analyzing more than 500 studies. That report looked at home exposure to electric and magnetic fields generated by common appliances such as shavers, hairdryers, and video display terminals. That report did not include high level exposure on the job, such as levels that electric industry workers may be exposed to.

"Our data provide some support for the hypothesis of an association between occupational magnetic field exposure and leukemia," Feychting reported in the current issue of Epidemiology. "Workers in occupations exposed to magnetic fields were at higher risk of acute myeloid and chronic lymphocytic leukemia than workers in unexposed occupations."

The study included 325 people with leukemia, 223 with central nervous system tumors (such as a brain tumor), and 1,091 healthy individuals - who all lived within 300 meters, or roughly 980 feet, from powerlines for at least one year during the period 1960 to 1985. The researchers estimated the study subjects' exposure to magnetic fields at work by looking at their occupation listed on a census taken every five years.

Those with high levels of exposure at work had 1.7 times, or 70% higher risk for certain types of leukemia, acute myeloid or chronic lymphocytic leukemia. Those with high exposure at home had 1.3 times, or a 30% increase in risk for the cancer compared to those with lower exposure. Those with high exposure at work and at home had 3.7 times the risk of such leukemias, though there was no increase in risk for central nervous system tumors.

"The most obvious limitation of this study is the small number of subjects, which renders some of the relative risk estimates unstable," Feychting wrote. "There are also limitations in the methods used for exposure assessment."

There is "little evidence" that exposure to magnetic fields at home can cause cancer in adults, the authors wrote. Although the study included a small number of people, it did find an association between leukemia and high exposure to magnetic fields at both home and work.

"Few people have an extremely high exposure," they concluded. "Despite this scarcity of highly exposed people, the focus on this contrast has further corroborated the association between magnetic field exposure and cancer in adults."

SOURCE: Epidemiology (1997;8:384-389)

Copyright 1997 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon.