working in the communications industry, i can tell you that as long as you dont decide to stand directly in front of the Antennas you shouldn't be likely to have a problem.
far as i can tell, all the stories about phones and cancer come from people who fear technology and change.
people think "radiation", they think glowing in the dark and nuclear bombs.
as far as i know, you can use a mobile every day and never get aproblem. i know i spend several hours a day on my mobile, and the only problem is the people who are calling me
i dont know about the GRN bit, but i suppose it is something to do with the RF output being higher, maybe??? dont rightly know, but i will ask about and see what i can come up with..