Even if cellular transmissions posed a low grade cancer threat, would we care? We're in contact with carcinogens all the time but obviously take the pragmatic view that probabilities are low and so long term that we quite knowingly continue. Just some of the common carcinogens in our environment - non-stick frying pans, cosmetics, most plastics, all alcoholic beverages, coffee, bubble bath, popcorn, anti-perspirant, bacon, baby powder, paint, petrol fumes, braaivleis etc etc
How many of these people who are so terrified of cellphone towers will happily expose themselves to dozens of carcinogens every time they park by the braai drinking beer and eating processed meat that came wrapped in plastic, having used firelighters doused in benzine/paraffin? Probably, these things will one day cause cancers in some of us, but do we really care?