September 19, 2007
Persistent rumors suggest that Wi-Fi constitutes a threat to human health. Where there's smoke . . . right?
Around the world, fears persists regarding the possible health risks of Wi-Fi.
In recent reports, an Illinois school district stopped installation of a Wi-Fi network in response to parents health concerns. The German government has warned against Wi-Fi usage based on possible health risks. The president of a Canadian university banned the use of Wi-Fi on campus for the same reason.
What is the risk, if any? Should the Wi-Fi industry be concerned about backlash from a health-conscious public?
We asked Dr. Kenneth Foster, a researcher in the Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania. His paper, Radiofrequency Exposure from Wireless LANs, appeared in the March 2007 issue of the journal Health Physics.
Q: Is there is a Wi-Fi health risk?
A: I see no evidence of it, nor do major health organizations around the world. There are hazards that may exist above certain levels of exposure to radio frequency energy, so the United States sets limits well below those levels. In the case of Wi-Fi there are very wide margins around any exposure that is thought to be potentially dangerous.
Q: Are we sure those established limits negate all risk?
A: Human knowledge is not perfect, but this not entirely a new issue. People have been studying the possible health effects of radio frequency energy for generations now. From the present state of human knowledge there is no convincing evidence of any risk.
Q: Scenario: I am running my laptop at Starbucks. What is my risk compared to other radio frequency activities?
A: The amount of energy that access points emit is very tiny. I did a survey of wireless LANs lasts year and in all cases the signal strength was tiny compared to other sourcessuch as cell base stations. Most client cards in a laptop emit power that is substantially less that what a cellular phone emits.
At the same time, the speed of the interface is usually very high, but it only transmits in pulses, depending on bottlenecks in the system and handshaking protocols. It is not a continuous transmission. So you are looking at an access point that has the power of a cell phone, and is only transmitting for 1/1000th of the time. So the exposure is trivial compared to that of other sources.
Q: If these things are known, what is driving public concern?
A: Well, I personally am not afraid of this tiny source of radiation, when we live in a world surrounded by antennas, but other people may feel differently. It is a social attitude. People respond to possible risk in different ways. They may feel threatened by the technology itself, and that may lead them to perceive health concerns. It is not entirely a scientific matter but more a matter of personal attitude toward risk.
People hear that there are still unanswered questioned, and that makes them afraid, which does not always make sense. Is a bottle of Perrier safe? I personally have no concern. But is there scientific proof that there is no risk? Well, there is no such proof. There is no scientific proof of the absence of hazards in a bottle of Perrier. But that doesnt mean there are hazards.
Q: Have there been other cases of fear response in the face of new technology?
A: I have been in this field since 1971 and have heard the same stories and the same fears all that time. People have been concerned about radio broadcasting towers, military radar installations, video display terminals, power lines, and now it is Wi-Fi networks, Bluetooth, mobile phones. Each case is exactly the same. The public health authorities have conducted examinations and failed to find any evidence of a problem, and yet the activists insist that there is a terrible catastrophe that might happen to us. People raised the same question about light bulbs in the early 1900s.
Q: Governments and institutions around the world are warning against Wi-Fi risk and even discouraging its use. Should the industry feel threatened?
A: Virtually our entire society has decided that they find Wi-Fi useful, so overall I dont see this having much impact on the industry. If I were a Wi-Fi company I would be much more concerned about the coming of WiMAX and what it is going to do to the industry than I would be about this.