Thermal Effects of Electromagnetic radiation

Thermal effects

 

 

 

Calculated specific absorbed radiation (SAR) distribution in an anatomical model of head next to a 125mW dipole antenna. Peak SAR is 9.5W/kg over 1 mg, average 0.008W/kg. (USAF/AFRL).

One well-understood effect of microwave radiation is dielectric heating, in which any dielectric material (such as living tissue) is heated by rotations of polar molecules induced by the electromagnetic field. In the case of a person using a cell phone, most of the heating effect may occur in the head surface, causing its temperature to increase by a fraction of a degree. The level of temperature increase is an order of magnitude less than that obtained during the exposure of head to direct sunlight. The brain’s blood circulation easily disposes of excess heat by instantaneously increasing local blood flow. However, the cornea of the eye does not have this temperature regulation mechanism. Premature cataracts is known as an occupational disease of engineers who work on high power radio transmitters at similar frequencies. Due to the low power of mobile phones, cataracts have not been reported to occur in users of these.

It has been claimed that some parts of the human head are more sensitive to damage due to increases in temperature, particularly in anatomical structures with poor vasculature, such as nerve fibers. More recent results from a Swedish scientific team at the Karolinska Institute (Lonn, Ahlbom, Hall and Feychting) have suggested that continuous use of a mobile phone for a decade or longer can lead to a small increase in the probability of getting acoustic neuroma, a type of brain tumor. The increase was not noted in those who used phones for less than 10 years. The study has been criticized for possible problems in data analysis such as recall bias. However, another study conducted by the Swedish National Institute for Working Life supported an increased risk of “malignant tumors on the side of the head the phone is used.” [1] Such long term heavy use involved phones of older higher power analog designs; that were first introduced to Sweden in 1984, earlier than many other countries.

http://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health