[EMF-Link] [ HomePage | Search | What's New | Comments | Up One Level ] Questions and Answers About EMF Electric and Magnetic Fields Associated with the Use of Electrical Power. January 1995. Human Health Studies ---------------------------------------------------------------------------- Q. Are there high cancer rates in some neighborhoods close to electric power facilities? A. Scientists call unusual occurrences of cancer in an area or in time a "cancer cluster." In some cases, a cancer cluster has served as an early warning of a health hazard. For most reports of cancer clusters, however, the cause is never determined, or the perceived cluster is not really an unusual occurrence. Concerns have been raised about seemingly high numbers of cancers in some neighborhoods and schools close to electric power facilities. In recent years, three state health departments have studied apparent cancer clusters near electric power facilities. A Connecticut study involved five cases of brain and central nervous system cancers in people living near an electrical substation. The local rates for these types of cancer were found to be no different from statewide rates. Examination of cancer rates at various distances from the substation also failed to show evidence of clustering. In North Carolina, several cases of brain cancer were identified in part of a county that included an electric power generating plant. An investigation showed that brain cancer rates in the county, however, were actually lower than statewide rates. Among staff at an elementary school near transmission lines in California, 13 cancers of various types were identified. Although this was twice the expected rate, the state investigators concluded that the cancers could have occurred by chance alone. CLUSTERS As an analogy, think about how an uncommon family name might be distributed at homes located throughout a city. Would it be unusual to find neighborhoods where two or three unrelated families with this same name live in the same small area? Statistically, this may be shown to be expected due just to chance. While four or more such families may be very unlikely due to chance, this does not mean that it is impossible. One possible cause (other than chance) for some such "name clusters" is that the families are part of the same ethnic group and they choose to live close together. For perceived neighborhood cancer clusters, however, health agencies generally never find a common environmental cause. It is also apparent that the definition of a "cluster" depends on how large an area (neighborhood) is included . [Image] Cancer cases (x's in graphic) in a city may show patterns that appear to be "clusters." They may seem to suggest a common environmental cause. Usually such patters are due just to chance. Further, delineation of a cluster is subjective - where do you draw the circles? ---------------------------------------------------------------------------- [Home Page] Copyright (c) 1994-1996, Information Ventures, Inc. EMF-Link@infoventures.com http://infoventures.com