5A (1) - Laserfiche WebLink

Home Browse Search

U.S. DEPARTMENT OF HEALTH AND HUFAM SERVICES actSheet National Institutes of Health Magnetic Field Exposure and Cancer: Questions and Answers Key Points • Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1). • Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1). • Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2). • Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3). • Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well - conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4). 1. 1 What are electric and magnetic fields? Electricity is the movement of electrons, or current, through a wire. The type of electricity that runs through power lines and in houses is alternating current (AC). AC power produces two types of fields (areas of energy) --an electric field and a magnetic field. An electric field is produced by voltage, which is the pressure used to push the electrons through the wire, much like water being pushed through a pipe. As the voltage increases, the electric field increases in strength. A magnetic field results from the flow of current through wires or electrical devices and increases in strength as the current increases. These two fields together are referred to as electric and magnetic fields, or EMFs. Both electric and magnetic fields are present around appliances and power lines. However, electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields can pass through buildings, humans, and most other materials. Since magnetic fields are most likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer. The focus of this fact sheet is on extremely low- frequency magnetic fields. Examples of devices that emit these fields include power lines and electrical appliances, such as electric shavers, hair dryers, computers, televisions, electric blankets, and heated waterbeds. Most electrical appliances have to be turned on to produce a magnetic field. The strength of a magnetic field decreases rapidly with increased distance from the source. 2. 1 Is there a link between magnetic field exposure at home and cancer in children? Numerous epidemiological (population) studies and comprehensive reviews have evaluated magnetic field exposure and risk of cancer in children (1, 2). Since the two most common cancers in children are leukemia and brain tumors, most of the research has focused on these two types. A study in 1979 pointed to a possible association between living near electric power lines and childhood leukemia (3). �19�tl�11� Page 1