HIGH-VOLTAGE OVERHEAD POWER-LINES IN EPIDEMIOLOGY - PATTERNS OF TIME VARIATIONS IN CURRENT LOAD AND MAGNETIC-FIELDS

In epidemiological studies of electromagnetic fields and health effect s, exposure classification is crucial. There is no generally accepted biophysical interaction mechanism, but many studies are based on the h ypothesis of a causal relationship with the strength of magnetic field . Some definition of the magnitude of exposure must be used, e.g., mea n magnetic flux density, the integral of magnetic flux and time, or a peak value. Magnetic fields around a particular power line depend on t he current load. The aim of the present study was to follow variations in line current load in the power supply system of the largest Norweg ian city on a yearly, monthly, daily, and diurnal basis. Fairly large variations in load were found, but increases in consumption were not n ecessarily reflected in current load on high voltage lines. The correl ation between outdoor temperature and current load varied widely, depe nd ing on the type of power station feeding the line in question. The registered time variations are large enough to interfere with epidemio logical classification of residences and testing of epidemiological hy potheses. (C) 1996 Wiley-Liss, Inc.