Cell phones, also called cellular, wireless, mobile telephones, and smartphones, are hand-held personal telecommunications devices. They have built-in antennas that use radiofrequency (RF) energy, a type of non-ionizing electromagnetic radiation. Along with rapidly evolving phone technologies and the tremendous rise in smartphone usage, concerns about potential health effects of the technology have grown.
Since first becoming widely available in the 1990s, cell phones have become ubiquitous, an essential part of life for billions of users worldwide. The antenna inside the body of a cell phone sends and receives low-power RF waves to and from a nearby cell tower or base station that relays the signal through a network of stations. The phone converts sound into RF waves and RF waves into sound.
RF waves are a form of energy with wavelengths that fall between those of AM/FM radio and television waves and microwaves as used in microwave ovens. When turned on, cell phones operate at frequencies between 800 and 2,700 megahertz with maximum power of 0.1–2 watts. Smartphones are used for data as well as calls, and as of 2018, companies were using more advanced technology that combines two or more RF bands for larger bandwidth and faster speeds. RF exposure from cell phones is defined by the specific absorption rate (SAR)—the rate of RF energy absorption per unit body mass. RF exposure guidelines have been developed for workers and for the general public. These guidelines are based primarily on protecting users from acute injury from tissue heating by RF waves, since this is the only proven potential physiological effect of RF waves. The Federal Communications Commission (FCC) requires that all cell phones sold in the United States have SAR levels no higher than 1.6 watts per kilogram (W/kg) of body weight.
Various factors, other than the phone's SAR, affect the amount of RF energy that the body absorbs from a cell phone. These factors include the design and technology of the phone and the extent and type of cell phone usage. RF exposure falls off rapidly with increasing distance from the phone's antenna. For example, RF exposure is much lower when the phone is 12–16 in. (30–40 cm) away from the body—as when accessing the Internet, text messaging, using the phone on speaker mode, or using a hands-free device—compared to when the phone is held against the head. RF exposure also depends on the distance and path to the nearest base station. Greater distance from towers or being inside a building requires more energy. Obtaining a signal can also require more energy if cell phone traffic in the area is high. Cordless phones often operate at RFs similar to cell phones. However, since the range of a cordless phone is limited and requires a base connected to wiring, wireless phone signals are usually much less powerful than cell phone signals.
Studies have repeatedly shown that cell phone use while driving increases the likelihood of motor vehicle accidents and fatalities. Furthermore, it is not clear that hands-free cell-phone devices are any less of a risk, since studies have suggested that the danger may come as much from the distraction of talking on the phone as from handling the phone while driving or performing some other activity that requires one's full concentration. Texting while driving continues to be a major concern and extremely dangerous.
Although a variety of concerns have been raised about potential health effects of the RF waves emanating from cell phones, most studies have focused on whether cell phone use might increase the risk of cancerous or other tumors in the brain and other areas of the head and neck—the parts of the body that usually absorb the most RF energy from cell phones. Cancer develops because of changes in DNA, the genetic material of cells. Ionizing radiation, such as x rays and gamma rays, can break bonds in DNA and other chemicals in the body, increasing the risk of cancer. However, like FM radio waves, microwaves, visible light, and heat, RF waves from cells phones are a form of non-ionizing radiation that does not have enough energy to break chemical bonds or damage DNA. Furthermore, most of the RF energy from a cell phone is absorbed by the skin and other superficial tissues. Although at very high levels, as in microwave ovens, RF waves can heat body tissues, the energy levels in cell phones are much too low to raise temperatures in the human body.
Cell phones provide health benefits for many people. Rural and isolated populations have access to health advice through cell phones, and patients can maintain close contact with their healthcare providers. Smart phones increase access to health information and can display vital signs and upload patients' health statistics to providers on an ongoing basis.
Unfortunately, smartphones, along with other electronic devices, have a negative impact on environmental health. Cell phones fail or become obsolete at an ever-increasing rate, and most are discarded in landfills. Cell phones can contain lead, mercury, cadmium, and other heavy metals and toxic chemicals. According to the U.S. Environmental Protection Agency (EPA), one million cell phones represent more than 35,000 lb (16,000 kg) of copper; 772 lb (350 kg) of silver; 75 lb (34 kg) of gold; and 33 lb (15 kg) of palladium.
There is no solid evidence indicating adverse health effects from cell phone use; nor are there any theoretical reasons to suggest that there may be adverse health effects. However, with the vast majority of the world's population using cell phones for ever-increasing lengths of time, and given that cell phones have not been around long enough for any long-term effects to have necessarily become evident, some authorities believe that cell phones could potentially present public health concerns. For this reason, there are many ongoing studies looking for associations between cell phone use and health.
Hundreds of studies have looked for physiological effects from RF waves emitted by cell phones. Many have found no association between RF energy from cell phones and health problems. The very few studies that have reported effects have not been successfully replicated. Almost all laboratory studies indicate that RF waves do not damage DNA.
Multiple studies have compared cell phone use among people with and without brain tumors. Almost all of them have found no differences between the groups. For the most part, researchers have not been able to reproduce the results of the few studies that reported a possible link between cell phone use and an increased risk of tumors. Likewise, studies have not found an increased risk for brain tumors in workers exposed to RF energy.
Many studies have also looked for RF effects on electrical activity in the brain and on cognitive function, sleep, and heart rate and blood pressure. There is no consistent evidence of any health effects at RF levels below those that cause tissue heating. A small 2011 study reported that when subjects held an active cell phone to their ear for 50 minutes, brain tissues on that side of the head burned more glucose than tissues on the other side of the head. The increase in glucose metabolism correlated roughly with the amount of RF energy emitted by the particular phone. Since more glucose is normally used in whatever parts of the brain are in use, it is not clear whether this effect is of significance.
Despite the preponderance of evidence to the contrary, the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) classified RF fields as “possibly carcinogenic to humans,” in 2013 based on limited evidence of a possible increase in the risk of brain tumors from cell phone use. However, no other major agencies or organizations had classified cell phones as possibly carcinogenic. In 2016, however, scientists in the National Toxicology Program released preliminary findings of some cancers in rats exposed to full-body RF energy. The more the rats were exposed to higher intensities of RF energy, the more likely they were to develop rare forms of brain or heart cancer. The cancers were much higher in male rats than in females.
Agencies around the world have called for more research, given that smartphone use has increased and evolved rapidly. Furthermore, many cancers take years or decades to develop, and cell phones have only been in widespread use since the 1990s. Therefore, long-term studies in humans are needed and ongoing.
The FDA and the FCC suggest measures that cell phone users can take to reduce their exposure to RF energy:
SAR levels vary with the cell phone. In the United States, manufacturers must report the maximum SAR levels of their phones to the FCC, and this information may be listed in the phone's battery compartment. SAR values may also be available from the manufacturer's website. However, SAR values can be misleading, because they are based on the highest operating power of the phone, which does not represent normal exposure. Thus, the actual SAR value depends on a variety of factors. Commercial devices for reducing RF energy exposure have not been demonstrated to be effective.
Concerns have been raised about whether RF energy from cell phones can interfere with medical devices such as heart pacemakers. Cell phone use is often prohibited in hospitals and on airplanes, because the RF signals may interfere with some medical devices and with navigation systems on planes. The FDA has stated that cell phones do not pose a significant risk to most pacemaker users; however, refraining from placing the phone in a pocket close to the pacemaker is a simple precaution.
See also Cadmium ; Cancer ; Mercury .
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Federal Communications Commission, 445 12th St. SW, Washington, DC, 20554, Fax: (866) 418-0232, (888) 225-5322), firstname.lastname@example.org, http://www.fcc.gov .
National Toxicology Program, PO BOX 12233, MD K2-03, Research Triangle Park, NC, 27709, (984) 287-3209, http://ntp.niehs.nih.gov .
U.S. Food and Drug Administration, 10903 New Hampshire Ave., Silver Spring, MD, 20993-0002, (888) 463-6332, http://www.fda.gov .
Margaret Alic, PhD