Several kinds of small meters are now available that can be carried or worn by a person to record magnetic field exposures automatically. The figure on the next page is an example of data collected with one of these meters. The magnetic field was measured every 24 seconds over a 24-hour period. For this person, field exposure at home was very low. These studies tend to show that appliances and building wiring contribute to the low-level background magnetic field exposure that most people receive.
People living close to large power lines tend to have higher overall field exposures.
However, as shown on the chart below, there is much individual variation among homes. A. Electric fields close to transmission lines are much stronger than the fields found near electrical appliances. However, remember that electric fields are greatly reduced in strength by objects like buildings, trees, and vehicles. Magnetic fields, on the other hand, are not blocked by most materials. Magnetic fields very close to electrical appliances are often stronger than the fields directly beneath power lines.