RESIDENTIAL EXPOSURE TO MAGNETIC-FIELDS GENERATED BY 110-400 KV POWER-LINES IN FINLAND

In a specific case, the magnetic field generated in a building by a ne arby power line is usually easy to calculate, although the accuracy of these calculations is sensitive to the quality of source information. To be able to study public health dimensions of magnetic field exposu re (e.g., risk of cancer), it is necessary to evaluate the size and ex posure of the population at risk. Relatively little quantitative infor mation on public exposure to power-frequency magnetic fields of high-v oltage power lines is available. This report describes residential exp osure to magnetic fields from 110 kV, 220 kV, and 400 kV power lines i n Finland at the national level, including 90% of the total line lengt h in 1989. A geographical information system (GIS) was used to identif y the buildings located near the power lines. After determining the di stances between the lines and the buildings, historical data on load c urrents of these lines were used to calculate the magnetic fields. The residential magnetic field histories were then linked to the resident s by means of a computerized central population register. The data obt ained on personal exposure have also been utilized in a nationwide epi demiological study on magnetic field exposure of power lines and risk of cancer. The methods of exposure assessment and results of the numbe r of buildings near 110 kV, 220 kV, and 400 kV power lines, their aver age annual magnetic fields, and personal exposure to magnetic fields f rom these lines are described. We found that 15,600 residents lived in an average residential magnetic field greater than or equal to 0.1 mu T caused by power lines in 1989. The number of these residents increa sed fivefold during 1970-1989. We estimated that 0.3% of the populatio n was exposed in their residences to an annual average magnetic flux d ensity from 110 kV, 220 kV, and 400 kV power lines higher than 0.1 mu T, the level that the background magnetic flux density in general does not exceed in Finnish homes. Thus, the problem of magnetic field expo sure generated by high-voltage lines concerns only a relatively small fraction of the total population in Finland. However, the size and exp osure of the population at risk remain somewhat arbitrary in practical multisource situations, as the biological interaction mechanism, the concept of harmful dose, and, in particular, the significance of the d uration of exposure are unknown. (C) 1995 Wiley-Liss, Inc.