|MadSci Network: Computer Science|
1) At what frequencies do cell phones transmit? There are two types of cell phones, regular cell phones which operate at frequencies of 800-900 MHz and Personal Communications Service (PCS) at 1850-1990 MHz. There is a cool picture of this in Bulletin 56 from the Federal Communications Commission Office of Engineering and Technology, which you can get on the web at http://www.fcc.gov/oet/info/documents/bulletins. It is figure 2. This bulletin covers electromagentic radiation [the technical name for this] from cell phones and many other sources, like power lines, TV stations and microwaves. There is also a web page for electromagentic radiation at http://www.fcc.gov/oet/rfsafety, but the bulletin explains it much better. 2) What is the energy levels that cell phones transmit? I was not able to find the actual energies that cell phones are able to transmit (although the output power is generally output 1 Watt). The energy that human tissue near the cell phones are allowed to absorb is less than 1.6 W/kg averaged over 1 g of tissue. (Putting it another way, 1 g of tissue is allowed to absorb 1.6 mW of energy near the cell phone). 3) Whether the energy coming from cell phones is dangerous is an open question. Concerns include cancer and heating of specific body parts (eyes and testis, because of limited blood flow). The way to evaluate this is to compare cancer rates in people who use cellular phones to those who do not. The problem with comparing people who use cell phones with those who do not is that these two groups of people are different. For example, the people who use cell phones might tend to live in cities while those who do not might live on farms. People who live on farms might have lower rates of cancer because they tend to eat a diet that is lower in fats and higher in fruits and vegitables. Then, the results showing that people who do not use cell phones have a lower rate of cancer have nothing to do with whether people use cell phones, but have to do with where they live. The point is, these studies are not so strait forward as they seem. Most of the studies relating to this is from studying energy that comes from electrical transformers and power lines near homes. Studies of this have not shown an increase in cancer from power lines and transformers, but the results are not conclusive. However, if there is an increase in cancer from power lines and transformers, the effect is small, and this is not a great risk. I have not read anything about studies of cell phones, but I think the risk is small. However, because cell phone have not been around long, it will be a while before cancers start to show up. So it appears that they do not cause cancer, but we realy do not know yet. Even if they do cause cancer, it appears that they will cause only a few cases a year. So buttom line is that cell phones are safe, but we cannot be sure they are completely safe. As far are heating of organs, the retina of the eye and testicle are the two most vulnerable organs. They are both vulnerable because they do not have large blood flows that can remove excess heat from radiation. However, this is not a large concern for cell phone usage, because FCC rules limit the amount of energy to safe levels. You asked if cell phones truly can be dangerous. Yes they can. Driving while using a cell phone is really dangerous. The rate of people crashing cars while driving using cell phones is like 2 or 3 times higher than when people are not using cell phones. So if you really are concerned about cell phone safety, don't talk and drive. I think far more people will be killed in car crashes caused by cell phones than by radiation from cell phones. I bring this up so you can put the risks of cell phones in perspective. You can get rid of most of the dangers of cell phones by not using them when concentration is important, like driving. As an aside, I add that using cell phones in hospitals is dangerous. The ventilators that breathe for really sick patients have been known to be reset by the radiation from cell phones. Talk about a dummer. So my answer is so long. Look on the bright side, the bulletin is even longer.
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