CancerNet from the National Cancer Institute ****************************************************************************** * CANCER FACTS * * National Cancer Institute * * National Institutes of Health * ****************************************************************************** Extremely Low Frequency Field Exposure & Childhood Leukemia Collaborative Study of Extremely-Low-Frequency Electromagnetic Field Exposure & Childhood Leukemia The National Cancer Institute (NCI) and the Children's Cancer Group (CCG) are collaborating on a large-scale investigation to determine whether exposures to extremely-low-frequency (ELF) electromagnetic fields contribute to the development of acute lymphocytic leukemia (ALL) in children under age 15. ALL accounts for 85 percent of all childhood leukemias in the United States. ELF electromagnetic fields are the electric and magnetic fields created by electric charges in the 60-hertz (60 cycles per second) alternating current supplied to U.S. households. The 5-year study, directed by NCI's Epidemiology and Biostatistics Program, was initiated in September 1989 because of public concern and a need for more precise epidemiologic data. It is part of a larger CCG investigation evaluating the risk of ALL associated with a wide range of factors, such as prenatal exposure to x-rays, childhood and maternal diseases, maternal drug use, maternal smoking, parental occupations, household chemical exposures, and family genetic histories. For the ELF field evaluation, 600 children with ALL and 600 matched controls are being selected from the 1,800 cases and 1,800 controls (the latter identified by random-digit telephone dialing) who are participating in the comprehensive CCG study. The subjects, all under age 15, will include residents of 11 states: Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, New Jersey, Ohio, Pennsylvania, and Wisconsin. A dosimetry study was conducted to determine the best way to estimate children's ELF exposure levels. Children under age 9 wore monitors that recorded all ELF exposures during a 24-hour period. When results were compared with ELF field measurements made in homes, schools, and day care centers, the home measurements were found to correlate closely with actual cumulative ELF exposures, while school and day care center measurements contributed little to the overall ELF exposure history. Based on these findings, several types of home measurements were selected for use in the main ELF field study to characterize exposures for all cases and controls. The relationship between ELF radiation (from both household sources and electric power lines) and ALL is being examined by: - Measuring ELF radiation levels in four rooms in current and former homes of children with leukemia and matched controls; - Interviewing parents about their children's ELF exposures (including prenatal exposures) from electrical appliances; - Diagramming the location, type, and size of external power lines near residences; - Measuring the earth's magnetic field in two rooms to determine its possible influence on ELF field measurements; - Examining seasonal variability in ELF radiation levels within selected homes over a 1-year period; - Determining whether electric meter readings and utility company records can be used to approximate ELF radiation measurements in a home; and - Replicating the personal ELF radiation dosimetry study on selected control subjects in both younger (0-8 years) and older (9-14 years) age groups. Data on individual subjects will be used to estimate the amount of ELF exposure prenatally and throughout life. Estimates will be made for both the children who developed ALL and their matched controls. It will then be determined whether ELF exposure increases the risk of childhood ALL. This study will provide one of the first comprehensive and complete measures of ELF exposures in children's residences. In summary, children with newly diagnosed ALL and matched controls will have ELF field measurements made in current and former homes. For children with leukemia, measurements will be obtained closer to their date of diagnosis than was possible in previous studies. The possible role of ELF magnetic field exposures will be evaluated as part of a large-scale, comprehensive study of virtually all known or suspected causes of childhood ALL. Results from the study should be available in 1995. # # # The Cancer Information Service (CIS), a program of the National Cancer Institute, is a nationwide telephone service for cancer patients and their families, the public, and health care professionals. CIS information specialists have extensive training in providing up-to-date and understandable information about cancer. They can answer questions in English and Spanish and can send free printed material. In addition, CIS offices serve specific geographic areas and have information about cancer-related services and resources in their region. The toll-free number of the CIS is 1-800-4-CANCER (1-800-422-6237). Questions and Answers Collaborative Study of Extremely-Low-Frequency Radiation Exposure and Childhood Leukemia 1. What are extremely-low-frequency (ELF) electromagnetic fields? The electric and magnetic fields created by electric charges in 60-hertz alternating current are commonly referred to as extremely-low-frequency electromagnetic fields. Electric fields result from the strength of the charge, and magnetic fields arise from charge motion. An electric device that is plugged into a wall socket and activated generates both electric and magnetic fields. If the device is turned off and left plugged in, only the electric field remains, because no charges are in motion. The intensity of both kinds of fields drops off as distance from the source increases. ELF electromagnetic fields are considered nonionizing radiation, radiation that does not possess enough energy to remove electrons from atoms. Therefore, they cannot alter genes. The energy in ionizing radiation, such as x-rays and gamma rays, can break atomic bonds and cause chromosomal changes. ELF fields also differ greatly from microwaves, which are used to operate microwave ovens and radar: microwaves are nonionizing radiation of much higher frequencies (3 billion to 30 billion hertz). Findings on the biological effects of one form of radiation cannot necessarily be generalized to other forms of radiation of different wavelengths. 2. Have ELF fields been shown to cause or promote cancer? A small number of cell culture studies have indicated that ELF fields may cause biological effects in living tissues, such as interference with protein synthesis. However, these biological effects have not been proven hazardous. There is still no evidence that ELF fields cause or promote cancerous transformation of normal cells. Studies of laboratory animals exposed to ELF radiation have not shown any increased risk of cancer. Occupational studies of electrical workers have suggested an association with cancers, particularly leukemias and brain tumors. However, these studies are difficult to interpret because electrical workers are often exposed to chemicals, solvents, and other carcinogens. For example, a National Cancer Institute (NCI) case-control study of brain tumors found an elevated risk among persons who worked in the electrical and electronics industry. Risk of brain tumors rose with length of employment in the manufacturing or repair of electronic equipment but not among workers exposed to electric and magnetic fields. 3. What have previous epidemiologic studies of ELF fields and cancer shown? Human epidemiologic studies of ELF fields and cancer have been inconsistent and inconclusive. Findings from studies in Colorado and Sweden, which suggested a small increase of cancer in children and adults living near high-current power lines, were not confirmed in similar studies in Rhode Island, Washington, and England. A 1987 case-control study in Denver suggested a significant risk of childhood cancer associated with living near high-voltage power lines. However, the association was made using wire code configurations (diagrams showing increasing levels of current-carrying capacity) as a surrogate for ELF exposure levels. No consistent risk for childhood cancer was seen in homes where actual measurements were made. Similar findings were reported in a 1991 case-control study of childhood leukemia in Los Angeles. A study of leukemia in adults conducted by the University of Southern California did not find any connection between the occurrence of leukemia and the use of electric blankets. Findings on the relationship between appliance use and childhood cancer have been inconsistent. Two comprehensive reviews published in 1992 by the Oak Ridge Associated Universities and the National Radiological Protection Board (United Kingdom) on the health effects of ELF electromagnetic fields both concluded that the human data to date provide no firm evidence of a carcinogenic hazard from ELF exposure. 4. What advantages does the NCI-Children's Cancer Group (CCG) collaborative study have over previous examinations of ELF fields and childhood leukemia? ūThe study focuses on newly diagnosed cases. Previous studies have frequently involved ELF exposure estimates made as long as 20 years after the diagnosis of leukemia. Because families of the cases and controls had in many cases moved, many relevant homes were not measured for ELF radiation levels, and few opportunities existed for interviewing parents about other causal factors (such as pesticide exposures or medical x-rays). The NCI-CCG study uses a population of newly diagnosed (incident) ALL cases, allowing the researchers to make measurements and estimates of ELF exposures soon after the date of leukemia onset. Extensive ELF field measurements are obtained within and immediately outside residences. Parents are asked detailed questions about their child's lifetime appliance exposure and daily environment. ūThe study includes a strong measurement component. Previous studies have utilized incomplete ELF radiation measurements (such as measurements in only one home), surrogates for measurements, or no measurements at all. The NCI-CCG study includes ELF field assessment in nearly all current and former residences of subjects. Measurements used in previous studies, such as wire code configurations and the earth's magnetic field, are also included. ūThe study benefits from being part of a larger investigation. Previous studies of ELF radiation have varied greatly in their sample selection, methodologies, and analyses. Data interpretations, comparisons of results, and extensions of findings to larger populations are difficult. The NCI-CCG ELF radiation study utilizes leukemia cases and matched controls from 11 states participating in the nationwide CCG study. Like all subjects in the large-scale investigation, they are being evaluated for many other exposures and factors suspected of being associated with childhood leukemia. This will allow ELF exposure data to be analyzed with respect to data collected for other risk factors. For example, if a child with leukemia has been heavily exposed to ELF radiation and the mother received x-rays while pregnant, the researchers will adjust for the x-ray factor. The result will be a more accurate evaluation of the possible relationship between ELF and that child's leukemia. 5. How was the study design approved? How will the results be evaluated? The design of the study (protocol) was critically evaluated by internal committees in NCI's Epidemiology and Biostatistics Program. Because of the importance of clarifying any potential health hazards associated with ELF exposure from power lines near residences and from electrical appliances and wiring inside homes, a special advisory group was established to also review and approve the final protocol, help monitor the study, and evaluate the results. The advisory group consists of selected members of the NCI's Division of Cancer Etiology's Board of Scientific Counselors and other scientists with expertise in this area. In addition to the normal NCI internal peer review requirements for approval of scientific studies before they are submitted to journals for publication, the advisory group will review and comment upon the scientific validity of the final report. 6. What is the Children's Cancer Group? The CCG is an NCI-supported, multicenter network of pediatric oncologists, epidemiologists, and other cancer researchers from 38 institutions and affiliated hospitals throughout the United States. The CCG Operations Center is located at the National Childhood Cancer Foundation in Arcadia, California. Date Last Modified: 12/92 .