In addition to using "hands-free" devices, which keep mobile phones away from the head and body during phone calls, exposure is also reduced by limiting the number and length of calls. A person using a mobile phone 30–40 cm away from their body – for example when text messaging, accessing the Internet, or using a “hands free” device – will therefore have a much lower exposure to radiofrequency fields than someone holding the handset against their head. The power (and hence the radiofrequency exposure to a user) falls off rapidly with increasing distance from the handset. The handset only transmits power when it is turned on. Mobile phones are low-powered radiofrequency transmitters, operating at frequencies between 4 MHz with peak powers in the range of 0.1 to 2 watts. Radiofrequency waves are electromagnetic fields, and unlike ionizing radiation such as X-rays or gamma rays, can neither break chemical bonds nor cause ionization in the human body. Mobile phones communicate by transmitting radio waves through a network of fixed antennas called base stations. Given the large number of mobile phone users, it is important to investigate, understand and monitor any potential public health impact. In some parts of the world, mobile phones are the most reliable or the only phones available. In 2014, there is an estimated 6.9 billion subscriptions globally. In many countries, over half the population use mobile phones and the market is growing rapidly. ![]() Mobile or cellular phones are now an integral part of modern telecommunications.
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