About a year ago, I received a phone call from a man who was looking for backup material for his son's science-fair project. The project asserted that exposure to a wireless local-area network (WLAN) would prevent living things from flourishing. The student had set up a wireless network in his home and then bought two of the same plants in seemingly identical condition. He placed one in an anechoic chamber while the other one was left in the open right next to it. To his eye, they both got the same amount of sun, water, etc. Yet the plant in the chamber (i.e., protected from the radio waves) was growing quickly while the plant out in the open was doing fine but had remained the same size. Of course, any number of things could have caused the results in what was certainly a creative but loosely performed experiment. Interestingly, however, a number of alarms have since been sounded over the potentially damaging effects of WLANs.
At the end of May, for example, the British Broadcasting Corp. (BBC) devoted an entire Panorama program to the safety of wireless networking in schools. According to the program, the density of electromagnetic (EM) fields near a laptop computer were approximately three times higher than those in the main beam of a typical base-station tower at a distance of 100 meters away. Obviously, radio signals will be denser the closer a person is to the transmitter. In addition, Wi-Fi is designed for short-distance radio links. The power levels that are transmitted are therefore very low. According to the UK's Health Protection Agency, sitting in a Wi-Fi hotspot for a year results in receiving the same dose of radio waves as making a 20-minute mobile-phone call.
As cellular networks, WLANs, and broadband networks like WiMAX merge together to cover every area of land, all living things will be exposed to an increasing amount of radio waves. Yet there is little proof that exposure to such waves—at the transmit power levels of current systems—will have any harmful effects. Some companies are developing technologies that limit such exposure as a precautionary measure. For instance, the scientists and engineers at Sarantel Ltd. (Wellingborough, UK) have developed antennas that focus the near-field region of an antenna from approximately 1 meter in diameter to 10 mm. With such an antenna, it is possible to develop wireless products that can be operated without interacting with the near-field EM radiation.
Whether or not such technologies are adopted, however, the consumer voice has spoken: WLANs are a success. For most, the convenience of being able to surf the Internet from anywhere in one's house or the backyard far outweighs any suspicions of the harmful effects of the network's radio waves. Like the cellular networks before them, WLANs seem to only get more popular—despite any bad press that they receive.