Cell Phone Radiation - Maximum Exposure Levels

Cell Phone Radiation - what are the maximum exposure levels?

At cellular telephone frequency bands of 900MHz and 1.8GHz, the current U.K. NRPB investigation levels raised the U.K. permitted levels to 10 Watts per Kg in the head. The 1991 USA ANSI/IEEE C95.1 guidelines set the SAR at 1.6 W/Kg, and the CENELEC pre-standard states 2 W/Kg for the public. GSM Cellular-phones can deliver well over 2 W/Kg into head tissue during their output pulses, but they are said to comply because the average power is only about one-eighth of the pulse power (GSM & PCN digital phones), as up to eight calls share one channel using Time Division Multiple Access (TDMA) with each handset pulsing in one of eight time slots. Unlike the earlier analogue phones, the digital GSM ones emit a series of short pulses at a basic repetition rate of 217Hz. Pulsed microwaves have been shown to be more biologically active than continuous radiation of the same frequency and power level. Take an operating digital GSM mobile-phone near an ordinary medium wave radio and you will hear a buzzing noise.
These pulses are also picked up and detected by the cells inside the user’s and other nearby people's heads. In fact, up to 80% of the transmitted power can be absorbed by the user's head, which means that their brain cells are being “hit” by these radiation pulses two hundred and seventeen times every second. In addition, GSM digital phones and the new DECT cordless phones also both put high levels (several microtesla) of low frequency magnetic fields into the user’s head. These may be more responsible for the dementia (memory) effects than the pulsed microwaves. The newer American Code Domain Multiple Access (CDMA) system works differently and doesn't emit the sharp-edged low frequency magnetic pulses. The digital RF signal more resembles a noisy analogue signal and is also likely to be less bio-active.There is increasing pressure for Europe to replace the TDMA GSM system with a “third generation” CDMA system within the next ten years.

The NRPB, and others, average the power from a digital phone over 1 second, and so divide the pulse power by eight. They correctly argue that the tissue has time to cool down between pulses, and then go on to deduce that no damage will therefore take place. This is similar to saying that placing a hammer on a “cell” (an egg, for example) exerting a small steady force, will produce the same effect as hitting the egg, using eight times the force briefly once a second. As most practical engineers know, when trying to loosen a stuck nut and bolt, the effect of constant pressure on the spanner is FAR LESS than when tapping the spanner with a hammer.

In 1993, as the NRPB raised its permitted microwave levels, two military research bases in the USA reduced their permitted levels of radio frequency exposure (30 MHz to 100 GHz) from 100 W/m2 (10 mW//cm2) down to 1 W/m2 (0.1 mW/cm2 or 100 µW/cm2 ). This is because they acknowledged that there is now an overwhelming body of published evidence for the existence of non-thermal biological effects of high-frequency radiation. [16]