Can talking on the phone heat up your head?
The Sunday Nation
Nairobi,
26 September 2010
After seeing last weeks article on mobile phone safety, one reader wrote this, “I have heard that the waves emitted by the phone while in use warm up the head just like the microwave oven. Is this true?”
If the waves had enough power, they COULD (and I emphasise “could”) heat up your head. But, as it is, they are too week.
Consider this: most microwave ovens emit about 700 watts (W) of radiation. At 1,000W, mine happens to be amongst the most powerful in the market. It boils a mug of water (about 250ml, or 250g) in 90 seconds (s). That is; it raises the temperature from about 20 to 100 degrees in that duration.
If it takes a 1,000W microwave oven 90s to raise the temperature of 250g of water by 80 degrees; it follows that it would heat up a kilo of the liquid by only 20 degrees in the same duration of 90s.
We get that answer by applying the principle of proportions: one kilo is four times 250g, therefore, we divide the initial temperature rise by four. That is, 80 divided by four, equals 20.
Now, the average human head weighs about 5kg and, like the rest of the body, water accounts for approximately 80% of the mass. Thus there is about 4kg of water in the head. (Shocking, isn’t it?)
Therefore; if you put a human head in the 1,000W microwave oven for 90s, its temperature would rise by only 5 degrees. Again, using proportions, one kilo rises by 20 degrees, thus four kilos should rise by 5 (20 divided by four).
But the power of the radiation from a mobile phone is NOT 1,000W. Most the gadgets emit about one watt of radiation during communication. So; if you talked for 90s (this is the average duration of most calls), what would be the resultant temperature rise in your head?
Well, since 1,000W rises it by 5 degrees, then it follows that one watt would heat it up by five thousandths of a degree. That is 5 divided by 1,000, or 0.005.
That is such a small change that the body’s cooling mechanism would deal with it in a matter of seconds. In fact, the head gets much more radiation than this when one is standing in the sun.
On the other hand, we might want to know what length of call would heat the head by one degree. Since 90s only gives 0.005 degree, then it would take 18,000 seconds to attain one degree. This is equivalent to five hours of continuous talking.
Still; aren’t there other effects apart from ionisation and heating? I don’t think so. After all, in the last 25 years since mobile phones entered the mass market, and with over 4 billion users currently, not a single case of ailment that can be linked to their use has ever been recorded.
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