Since 1979, public concern has been raised over the possible health effects of low frequency electromagnetic fields (EMF) emitted from power lines, transmitters, and common household items such as computers, television sets, electric blankets, microwave ovens, and more recently cellular telephones.
Thirteen studies pertaining to children, and five pertaining to adults have been conducted to evaluate household EMF exposure in relation to the risk of cancer. So far, the findings have yielded mixed results in children, while no association between adult cancer and EMF has been found. Furthermore, no correlations have been observed between "directly measured" residential EMF exposures and risk for either children or adults.
While occupational studies have suggested a link between EMF exposures and adult leukemia and brain tumors, only four of these investigations have included measurements, and findings have been inconsistent. Study of Extremely Low-Frequency EMF Exposure and Childhood Leukemia
The National Cancer Institute (NCI) and the Children's Cancer Group (CCG), a multicenter network of pediatric oncologists and other researchers from 38 institutions and affiliated hospitals in the United States, are collaborating on a large-scale investigation to determine whether exposure to extremely low-frequency EMFs contributes to the development of acute lymphocytic leukemia (ALL) in children under age 15. ALL comprises 85 percent of all childhood leukemias in the United States.
The EMF study, directed by Martha Linet, M.D., is part of a larger CCG investigation comprising more than 1,900 ALL cases and 1,900 controls. The study is designed to evaluate the risk of ALL associated with a wide range of factors, including maternal diseases and medication use during pregnancy, childhood diseases, and other exposures, such as parental occupation.
For the EMF evaluation, more than 600 children with ALL and more than 600 controls were selected from those participants in the larger group who resided in nine states: Illinois, Indiana, Iowa, Michigan, Minnesota, New Jersey, Ohio, Pennsylvania, and Wisconsin.
The relationship between EMF and ALL is being assessed by interviewing mothers about electrical appliance use during pregnancy and in childhood, and measuring EMF levels in four rooms within current and former homes of the participants. The scientists also diagramed the location, type, and distance to external power lines, and measured the earth's magnetic field in current and former homes to determine its possible influence on extremely low frequency EMF measurements.
Data on individual subjects will be used to estimate the amount of prenatal and lifetime EMF exposure. Estimates will be made both for the children who developed ALL and their matched controls. It will then be determined whether EMF exposure is correlated with increased risk of childhood ALL.
This study will provide one of the first comprehensive and complete measures of EMF exposures in households with children. Results of two personal EMF dosimetry studies on children aged 0 to 8 years in the greater Washington, D.C., metropolitan area and older control subjects (nine years and older) have been published. *Results from the larger study should be available late in 1996 or early in 1997. Risk Factors for Adult Brain Tumors
The causes of brain and nervous system tumors are largely unknown, but genetic factors and a variety of environmental exposures have been implicated to varying degrees. Epidemiologic studies have linked central nervous system cancers with certain rare genetic disorders and with a variety of environmental exposures, including physical, chemical, and biologic agents. Public concern over the possibility that hand-held cellular telephones may cause brain cancer, and the lack of identification of causes for most brain tumors, led to initiation of a comprehensive study of malignant and benign brain tumors to identify environmental and genetic causes for these serious but poorly understood diseases. NCI and extramural researchers will examine numerous factors that may affect brain cancer incidence, including occupational exposures, diet, vitamin supplements, use of home appliances and cellular telephones, reproductive and medical history, inherited susceptibility, and other factors.
The NCI case-control study, directed by Elizabeth Hatch, Ph.D., is being conducted at hospitals in Phoenix, Pittsburgh, and Boston. By the end of 1998, the researchers plan to enroll approximately 700 newly diagnosed brain tumor cases and an equal number of controls. The controls are patients admitted to the same hospitals with a variety of non-cancer diseases or conditions. Researchers are gathering information about possible risk factors through in-person interviews, self-administered questionnaires, and biochemical and molecular genetic analyses of blood samples. The occupational component of the study will improve on previous efforts to evaluate occupational risk factors for brain cancer by asking job-specific questions about tasks performed, specific chemicals and equipment used, and whether or not protective gear was worn.
Information will be obtained about use of cellular telephones, including the types of phones used (hand-held, car, transportable cellular phones or cordless phones) and frequency and duration of use. The researchers will also examine the consumption of foods and beverages containing N-nitroso compounds or their precursors and consumption of vitamins, fruits, and vegetables; medical and dental exposures to ionizing radiation; reproductive histories; exposures to viruses; and other preexisting medical conditions. Data collection began in 1994 and will finish at the end of 1998. Separate analyses will be conducted for different brain tumors.
Radar Exposure and CancerIn 1980, the National Academy of Sciences conducted a 20-year follow-up study of 20,000 U.S. Navy personnel to determine whether sailors exposed to high intensity microwave radiation (radar) during the Korean War were more likely to get cancer than sailors with no or minimal radar exposure. The study, was published in the July 1980 issue of the American Journal of Epidemiology, found no association between radar exposure and cancer. NCI and the National Academy of Sciences are conducting a 40-year follow-up study on this group of sailors. The study, under the direction of Frank Groves, M.D., of NCI, will be completed in 1998.
* Development of a Protocol for Assessing Time-Weighted-Average Exposures of Young Children to Power-Frequency Magnetic Fields-W.T. Kuane and M.S. Linet et al., Bioelectromagnetics 15:33-51 1994
Childhood Exposure to Magnetic Fields: Residential Area Measurements Compared to Personal Dosimetry-Diana R. Friedman, Elizabeth E. Hatch, Martha S. Linet et al, Epidemiology 7:151-155 1996
The National Institute of Environmental Health Sciences recommends that anyone concerned about the possible side effects of EMFs may do the following to reduce exposure:
Increase the space between a person and devices that may emit EMFs. Avoid standing too close to computers, microwave ovens, or TVS. Reduce the time of exposure to possible EMFs by turning off devices such as electric blankets when not in use. Avoid keeping such devices as electric alarm clocks too close to the bed. Discourage children from playing near high power lines or transformers. Avoid activities near EMF sources.
For more information on this subject call the National Institute of Environmental Health Sciences at: 800-NIEHS-94
The Cancer Information Service provides a nationwide telephone service for cancer patients and their families, the public, and health care professionals. The toll-free number is 1 800 4 CANCER (1 800 422 6237); services provided in English and Spanish. People with TTY equipment may call 1 800 332 8615.
This document is available through the NCI's CancerNet services on the Web (http://cancernet.nci.nih.gov) and through Cancer Fax (dial 301-402-5874 from the handset on your fax machine).