Brain cancer risk and electromagnetic fields (EMFs): Assessing the geomagnetic component

Cancer cluster studies in North Carolina identified several communities in which there existed an elevated risk of brain cancer. These findings prompt ed a series of case-control studies. The current article, which originated from the results of the 3rd of such studies, is focused on inclusion of the earth's own geomagnetic fields that interact with electromagnetic fields g enerated from distribution power lines. This article also contains an asses sment of the contribution of confounding by residential (e.g., urban, rural ) and case characteristics (e.g., age, race, gender). Newly diagnosed brain cancer cases were identified for a 4-county region of central North Caroli na, which the authors chose on the basis of the results of earlier observat ions. A 3:1 matched series of cancer cases from the same hospitals in which the cases were diagnosed served as the comparison group. Extensive geograp hic information was collected and was based on an exact place of residence at the time of cancer diagnosis, thus providing several strategic geophysic al elements for assessment. The model for this assessment was based on the effects of these two sources of electromagnetic fields for an ion cyclotron resonance mechanism of disease risk. The authors used logistic regression models that contained the predicted value for the parallel component of the earth's magnetic field; these models were somewhat erratic, and the elemen ts were not merged productively into a single statistical model. Interpreta tion of these values was difficult; therefore, the modeled values for the m odel elements, at progressive distances from the nearest power-line segment s, are provided. The results of this study demonstrate the merits of using large, population-based databases, as well as using rigorous Geographic Inf ormation System techniques, for the assessment of ecologic environmental ri sks. The results also suggest promise for exposure classification that is c ompatible with the theoretical biological mechanisms posited for electromag netic fields.