There have been no such incidents though you are right in your concern over the presence of a cell phone tower on your roof top. I would like to explain a few things to ease your concerning queries.
There are two types of radiations in our Electromagnetic (EM) spectrum, namely ionising and non-ionising.
RF radiation, UV radiation , visible light, IR radiation are types of non-ionising radiation. These radiations, together with ionising EM radiation (X radiation and gamma radiation) constitutes our EM spectrum.
Interactions between ionising radiations and biological material creates positively and negatively charged particles (ions), and thus have adverse effects.
Non-ionising radiations cannot create such particles and thus are less hazardous. As far as is currently known, RF radiation, for example, can only cause the molecules in biological material to vibrate and thereby generate heat.
for more information on types of radiation, please see the attached pdf. (taken from
PHYSICS at a Glance by Tim Mills)
also radiation impact is measured as in Watts/area, and as we move away from the BTS (base station). radiation level drops.
You have to know the difference between antennas and towers. It is the antennas that you need to keep your distance from and not the towers that hold the antennas.Though it would be concerning to know the maximum power to be transmitted by the antenna on tower. (depends on type of antenna, but it would be in very safe limits)
There is a good guide on this link :
http://www.fcc.gov/guides/human-exposure-rf-fields-guidelines-cellular-and-pcs-sites to understand more about power levels radiated at a cell site.
