The study was performed by researchers from the National Cancer Institute and the Children's Cancer Group and published in the July 2, 1997, issue of the New England Journal of Medicine. Using two methods to gauge a home's exposure to magnetic fields, the researchers found no increased risk of developing acute lymphoblastic leukemia (ALL), the most common type of childhood leukemia, in children residing in homes exposed to magnetic fields near electrical lines.

"The results of this latest, published research are clearly in line with our earlier conclusions that electromagnetic fields are unlikely to increase cancer risk," said Clark Heath, Jr., MD, vice president for epidemiology and surveillance research for the American Cancer Society. Dr. Heath, a respected expert on this issue, published a review of epidemiologic evidence on electromagnetic field exposure and cancer in the January/February 1996 issue of the ACS journal CA-A Cancer Journal for Clinicians. After reviewing the available research at that time, Dr. Heath concluded that the data were "weak, inconsistent, and inconclusive."

HOW THE STUDY WAS PERFORMED
To perform the study, researchers measured magnetic fields for 24 hours in the study participant's bedrooms and for 30 seconds in 3-4 other rooms and outside the front door of the current and former homes of the study participants (629 children with ALL under age 15 and 619 controls). These measurements were used to derive the average residential magnetic field levels for each home. Additionally, the researchers evaluated the distance and configuration of electrical lines near the residences and assigned a "wire-code" category for each home based on this information. Finally, the researchers measured magnetic fields in the homes where the families had lived while the mothers were pregnant with the children in the study.

WHAT THE STUDY FOUND
The study found no overall correlation between the level of EMF exposure and risk of childhood ALL, regardless of the measure of exposure used. There was a small increase in risk of ALL for children whose homes measured in the very highest range of magnetic fields. However, the number of children living in such homes was small in this study, making it hard to draw conclusions.

WHAT THE STUDY MEANS
This study was carefully constructed to overcome some of the weaknesses that have been present in previous studies on this issue. It used two methods to evaluate magnetic field exposure (direct measurements and wire coding) and it measured magnetic fields within 24 months after the date of diagnosis in the children with ALL, unlike earlier studies in which years or decades may have passed between the diagnosis of ALL and magnetic field measurements. Additionally, it is larger than any previous study of this topic and the people making the magnetic-field measurements and assigning wire codes were blinded to the subject's health (in other words, they did not know if the children in the houses they were measuring had cancer or not). Therefore, its results add important evidence to the debate over whether exposure to magnetic fields increases the risk of ALL.

In an accompanying editorial, Edward Campion, MD, deputy editor of the New England Journal of Medicine, points out that no previous study of this topic has measured EMF levels as thoroughly or in as many homes of children with leukemia. Dr. Campion indicated that, based on previous studies less carefully designed than the current one, some articles in popular magazines may have generated an unwarranted level of concern among people living near electrical lines. He also notes that EMF exposure levels due to electrical lines are far less than the exposure levels due to the earth's natural magnetic field or from riding on an electric-powered train.

Overall, this study found little evidence that living in homes with high magnetic fields or in homes close to electrical transmission or distribution lines is a significant risk factor for developing childhood ALL.

Linet MS, Hatch EE, Kleinerman RA, et al. Residential exposure to magnetic fields and acute lymphoblastic leukemia in children. N Engl J Med, 1997: 337(1); 1-7.

Campion EW. Power lines, cancer, and fear (editorial). N Engl J Med, 1997: 337(1);44-46.



Joann Schellenbach
National Director Media Relations
American Cancer Society
212-382-2169