For years some people have worried about the effects of electric and magnetic fields (EMF) on human health. People living near large power lines have wondered if high EMF emissions can cause leukemia or other cancers. Recently, these fears have extended to radiofrequency (RF) exposure from wireless technologies like cell phones, cell phone towers, and GPS devices. Scientists are continuing to learn more about the effects of EMF and RF exposure on the general population and on employees in certain occupations.
This article discusses the basics of EMFs and RFs, scientific studies on links between exposure and health problems, and recent trends in lawsuits over EMR and RF emissions.
Electric and magnetic fields (EMF) are produced by alternating electric currents found in electric transmission lines, plants that generate power, electric wiring, home and business appliances, cell phones, and other electric devices. Electric fields are measured in Volts per meter (V/m). Typical EMFs at home or on the job measure from 5 to 10 V/m, while levels under a power transmission line may measure as high as 10,000 V/m.
Radio frequency (RF) is one form of electromagnetic energy that is used in many types of wireless technologies -- including cordless phones, radar, ham radio, GPS devices, cell phones, and radio and television broadcasts.
Walls do not block electromagnetic fields, so EMF from outside sources like power lines or nearby electrical towers can enter homes and workplaces. However, because EMF levels decrease rapidly as you move away from the electric source, exposure levels from electrical lines, towers, and cell phone stations are usually very low for most people.
Concerns about EMF exposure from power lines were first raised in a 1979 study examining the incidence of leukemia in children living close to power lines. Some people believe that EMF exposure at high levels can also cause other types of cancers, reproductive problems, developmental problems, and mental depression. In recent years, concerns have been raised about the possible negative health effects of using cell phones or living or working near cell phone towers that emit RF waves.
In the 1990s, several well regarded national research organizations looked at the potential health problems associated with EMF exposure. In 1995, the American Physical Society reviewed reports and literature on EMF exposure and concluded that there was no consistent, significant link between cancer and power line fields. In 1999, the National Research Council (part of the National Academy of Sciences) examined evidence from the EMF-RAPID program (a government program established in 1992 to study EMF exposure) and concluded that it was very unlikely that EMFs in the normal domestic or occupational environment produce negative health effects, including cancer.
However, in 1999, the National Institute of Environmental Health Sciences (NIEHS) acknowledged that, because of the existence of "weak scientific evidence that exposure may pose a leukemia hazard," it could not entirely rule out the possibility that EMF exposure caused health problems. Although today most scientists believe that low-level exposure to EMFs does not cause health problems, researchers continue to study the issue. Many scientists do believe that people exposed to high levels of EMFs -- such as workers in certain occupations -- may develop health problems that are not linked to lower levels of EMF exposure.
Since 1985, the Federal Communications Commission (FCC) has adopted standards for safe levels of radio frequency (RF) exposure. Federal agencies -- such as the Environmental Protection Agency (EPA), Food and Drug Administration (FDA), and the Occupational Safety and Health Administration (OSHA) -- monitor and investigate issues related to RF exposure.
RF exposure from cell phone use. The FDA has acknowledged that it cannot entirely rule out the possibility of negative health effects caused by RF exposure from cell phone use. However, the agency maintains that, if a risk does exist, "it is probably small." The FDA provides recommendations to people who are concerned about RF exposure, including limiting cell phone use and using hands-free kits, which create a greater distance between the phone and the user (although experts caution that clipping the phone to a belt or clothing doesn't reduce exposure). To learn more about safety precautions for cell phone use, visit the FDA's Center for Devices and Radiological Health at www.fda.gov.
RF exposure from cell phone towers. Usually, antennas used for cellular and personal communication system (PCS) transmissions are found on towers, water tanks, or other elevated structures -- including rooftops and the sides of buildings. The FCC has adopted safety guidelines for evaluating RF environmental exposure, and federal health and safety agencies, such as the EPA, FDA, the National Institute for Occupational Safety and Health (NIOSH), and the Occupational Safety and Health Administration (OSHA) have also been involved in monitoring and investigating issues related to RF exposure. The FCC's limits for RF emissions on the ground near a cell tower are measured in milliwatts per square centimeter and is 1 mW/cm2 for PCS towers and 580-600 mW/cm2 for cellular towers. While RF emissions from cell phone towers usually result in ground-level exposure that is typically below the safety limits recommended by the FCC, RF emissions on the ground within 100-150 feet of a cell tower, or on a roof within 100 feet of a roof-mounted cell tower, can exceed FCC limits.
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