Investigation of the sources of residential power frequency magnetic field exposure in theUK Childhood Cancer Study

Abstract

There is an unexplained association between exposure to the magnetic fields arising fromthe supply and use of electricity, and increase in risk of childhood leukaemia. The UKChildhood Cancer Study (UKCCS) provides a large and unique source of information onresidential magnetic field exposure in the UK. The purpose of this supplementary studywas to investigate a sample of UKCCS homes in order to identify the particular sourcesthat contribute to elevated time-averaged exposure. In all, 196 homes have beeninvestigated, 102 with exposures estimated on the basis of the original study to be above0.2 µT, and 21higher than 0.4 µT, a threshold above which a raised risk has been observed. First, surveys werecarried out outside the property boundaries of all 196 study homes, and then,where informed consent had been obtained, assessments were conducted inside theproperties of 19 homes. The study found that low-voltage (LV) sources associatedwith the final electricity supply accounted together for 77% of exposures above0.2 µT, and 57% ofthose above 0.4 µT. Most of these exposures were linked to net currents in circuits inside and/or aroundthe home. High-voltage (HV) sources, including the HV overhead power linesthat are the focus of public concern, accounted for 23% of the exposures above0.2 µT, and 43% ofthose above 0.4 µT. Public health interest has focused on the consideration of precautionary measures thatwould reduce exposure to power frequency magnetic fields. Our study provides a basisfor considering the options for exposure mitigation in the UK. For instance, inelevated-exposure homes where net currents are higher than usual, if it is possible to reducethe net currents, then the exposure could be reduced for a sizeable proportion of thesehomes. Further investigations would be necessary to determine whether this is feasible.