That is intersting. I didn't read the entire article from the Cancer link, but was curious then, which towers do give off the high amounts of radiation? I have heard that some do. Interesting question...
Probably the highest levels of EMF you encounter would come from commercial television stations. Some UHF stations radiate an ERP (effective radiated power) 1,000,000 watts. In fact one of the reasons for the switch to digital TV is it is more efficient. The previous analog stations went as high as 3.4 million watts. Digital reduces this need.
The strongest transmissions though are military radar installations. These can go several million watts, but only in brief pulses. Plus they are usually confined to areas where not many people are around, thus minimal exposure. Remember EM Fields diminish according to the inverse square law of physics. The farther away from the source you are the weaker the field becomes.