Comparison of residential power-frequency magnetic fields away from appliances in different countries.

The purpose of this paper is to review measurements of residential power-frequency magnetic fields made in different countries and to determine whether average magnetic fields away from appliances are higher in some countries than in others. The paper includes 27 studies reporting measurements of residential magnetic fields in samples of homes: 14 from North America, 5 from the United Kingdom, and 8 from other European countries. Various factors that might make the results from individual studies unrepresentative of average fields in the relevant country are identified and discussed. Because distributions of magnetic fields generally are approximately log-normal, they are summarised by their geometric means. The best estimate of the geometric means of long-term average background fields in the United States is 60-70 nT and in the United Kingdom approximately 36-39 nT. In other countries, there are insufficient studies to draw firm conclusions on average fields. Measurements of personal exposure are higher than measurements of background fields, perhaps because they include exposures from appliances and other sources in the home. The ratio of personal exposure to background field seems, on average, to be approximately 1.4.