https://secure.wikimedia.org/wikipedia/en/wiki/Mobile_phone_radiation_and_health
The effect mobile phone radiation has on human health is the subject of recent interest and study, as a result of the enormous increase in mobile phone usage throughout the world (as of June 2009, there were more than 4.3 billion users worldwide). Mobile phones use electromagnetic radiation in the
microwave range, which some believe may be harmful to human health. Other digital wireless systems, such as data communication networks, produce similar radiation.
A large body of research exists, both epidemiological and experimental, in non-human animals and in humans, of which the majority shows no definite causative relationship between exposure to mobile phones and harmful biological effects in humans.
The World Health Organization, based upon the majority view of scientific and medical communities, has stated that cancer is unlikely to be caused by cellular phones or their base stations and that reviews have found no convincing evidence for other health effects. Some national radiation advisory authorities have recommended measures to minimize exposure to their citizens as a precautionary approach.
https://secure.wikimedia.org/wikipedia/en/wiki/Cell_site#Cell_phone_tower_power_emission
The U.S. government agency, the FCC, says:
"For example, measurement data obtained from various sources have consistently indicated that "worst-case" ground-level power densities near typical cellular towers are on the order of 1 µW/cm2 or less (usually significantly less)."
That is 0.01 Watt per square meter. There is no temptation to use more power. The entire idea of a "cell" phone system is to create small "cells" that don't interfere with each other.
The average energy received over the entire earth is about 250 Watts per square meter over a 24 hour day, ignoring clouds. So, on a day with no clouds, the average electromagnetic energy received from the Sun is 25,000 times that received near a cell phone tower.
I'll repeat what I said earlier: the type of radiation emitted by cellphones can only have thermal effects on organic tissue. Ever felt your cellphone & ear feel warm after you've been talking to your girlfriend for too long? It's because heating tissue is the only kind of effect it can have. That's like standing outside in the summer sun for some time - your head will get hotter the longer you stand outside.