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Beginning in 1979, some studies suggested that magnetic fields (EMFs) may increase the risk for ALL while others have found no evidence for risk. EMFs are produced by power lines, electrical wiring and household electrical appliances.
Researchers from NCI in collaboration with the Children's Cancer Group (CCG), a network of pediatric oncologists and other researchers across the U.S., published an earlier report** in July 1997 that showed little evidence that the EMF from high current power lines or from high levels of magnetic fields measured in the home were associated with an increased risk of ALL in children.
The current study, also a collaboration between NCI and CCG, is the first large study of childhood ALL and electrical appliances. The researchers compared the exposure to household electrical appliances of 640 children diagnosed with ALL to the exposure of 640 matched controls — children of the same age, race and place of residence without the disease. (The same cases and controls were used in the two NCI/CCG studies). The data are based on the mothers' responses to a detailed questionnaire about their appliance use during pregnancy as well as their child's use. TVs, electric blankets, microwaves, hair dryers, stereo systems, heating pads and computers were some of the appliances included in the study. No measurements were taken of magnetic fields associated with the actual appliances used.
The authors were unable to draw a clear conclusion from the data. Although the data showed some association between appliance use and leukemia, there was no consistent pattern of increasing risk with increasing exposures. The scientists speculate that the magnetic fields from electrical appliances are unlikely to increase the risk of childhood ALL.
The contribution of home appliances to a person's total EMF exposure is thought to be small because most appliances are used for short periods of time and EMF exposures are elevated only close to the appliance. It is more difficult to assess the contribution of appliances to EMF exposures than that of power lines and building wiring. This is because for each appliance, the magnetic field varies greatly with distance, and frequently neither the distance of the person from the appliance nor how often an appliance is on or off can be reconstructed accurately from interviews.
These preliminary findings are part of a more comprehensive study being conducted by the CCG looking for possible causes of childhood ALL. In the larger study, many risk factors other than EMF are being evaluated in more than 1,900 children diagnosed with ALL between 1989 and 1993. These include exposures of children to infectious agents in the home or neighborhood, exposures of parents to radiation or chemicals at work, medications used by the mother during pregnancy, alcohol use, and lifestyle of the parents. Results are expected in two years.
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*The study is titled "Association Between Childhood Acute Lymphoblastic Leukemia and Use of Electrical Appliances During Pregnancy and Childhood." The authors are Elizabeth E. Hatch, Martha S. Linet, Ruth A. Kleinerman, Robert E. Tarone, Richard K. Severson, Charleen T. Hartsock, Carol Haines, William T. Kaune, Dana Friedman, Leslie L. Robison, and Sholom Wacholder. Epidemiology, May 1998.
**The study is titled "Residential Magnetic Field Exposures and Childhood Acute Lymphoblastic Leukemia." The authors are Martha S. Linet, Elizabeth E. Hatch, Ruth A. Kleinerman, Leslie L. Robison, Willian T. Kaune, Dana R. Friedman, Richard K. Severson, Carol M. Haines, Charlene T. Hartsock, Shelly Niwa, Sholom Wacholder, and Robert E. Tarone. NEJM, July 3, 1997.
Questions and Answers About the National Cancer Institute/Children's Cancer Group Study of the Magnetic Fields Associated With Electrical Appliances and the Risk of Childhood Acute Lymphoblastic Leukemia.