ELECTROMAGNETIC FIELDS AND ADULT MALIGNANT GLIOMA

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Malignant glioma, the most common primary malignant brain tumor in adults, is debilitating and rapidly fatal. Very little is known about its causes; residential studies in children and occupational studies in adults have suggested that extremely low-frequency electromagnetic field (EMF) exposures may be a factor. Studies of adult brain cancer have not yet undertaken an overall EMF exposure assessment incorporating residential, occupational, and other exposures. We are currently conducting a large, NCI-funded, population-based case-control study of malignant glioma in the San Francisco Bay Area. Cases (n equals approximately 550) are adults newly diagnosed with histologically confirmed malignant glioma from 8/1/91-7/30/94. Age-, sex-, and race-matched controls (n equals approximately 550) are obtained through random-digit dialing. Structured interviews ask questions pertinent to EMF exposure including detailed occupational histories to enable classification of occupational EMF exposures with duration; history and frequency of use of specific appliances (or other electric devices such as ham radios); and all addresses where subjects lived 15 years prior to study entry. In this proposed study, we will add a residential EMF exposure assessment consisting of (1) home spot measures using a pretested protocol for measurement with EMDEX meters, (2) characterization of power lines, transformers, and substations near the residence, and (3) Wertheimer-Leeper type wire-codes for the residence. Current residences (n equals approximately 1100) and all residences in the state of California of each subject for 15 years prior to study entry (n equals approximately 1870) will be considered. A 10% sample of all residences will be reassessed, blindly. Epidemiologic and industrial hygiene data will be used to develop EMF exposure matrices based on external residential wiring and other characteristics, occupation, and electric appliance use. Statistical analyses will test hypotheses that cases were more likely than controls to have lived in a residence with high current vs low current configuration wiring; that cases lived in residences with higher average EMF field strengths (or other metrics such as peaks, variance, or rate of change) than controls; and that cases had greater EMF exposure than controls based on each EMF exposure matrix and on a composite matrix. This will be the first study of adult brain cancer to combine information on EMF exposures from residential, occupational, and other sources as well as the first to provide residential EMF exposure information in addition to that contained in wire-codes.