Long-term variations in the exposure of the population of England and Wales to power-frequency magnetic fields

Abstract

This paper estimates the change in the average exposure of the population of England and Wales to power-frequency magnetic fields between 1949 and 1989. If magnetic fields are causally linked to disease with a linear exposure - response relationship, this quantity is related to the incidence rate of the disease. The exposure is divided into components attributable to a number of sources, principally residential background fields and fields from domestic appliances and the transmission system. The 1989 average exposures from these sources are estimated as 45 nT, 20 nT and 4.2 nT respectively. For each source, an understanding of how fields arise is combined with statistics on the use of electricity and demographic statistics to estimate the change in exposure from that source. These individual changes are then combined, weighted according to the average exposure from that source. The estimated increase in overall average exposure is by a factor of 4.5, which applies to the whole population and also just to children. This increase is slightly greater than the result obtained by the simpler method of taking average domestic electricity demand per consumer, and can be treated with more confidence. There are still numerous approximations involved, some of which are identified and discussed, with the conclusion that the estimated increase is probably an underestimate.