Not that this should be considered the final word on this, but a recent study by New Zealand’s Wellington School of Medicine has uncovered no increase in cancer rates since the introduction of cellphone service there in 1987:
The report concluded that incidence rates for malignancies arising in the head and neck, including those sites that hypothetically receive the highest levels of radio frequency radiation during cellular telephone use, have not changed materially since the introduction of cellular telephones to New Zealand. However, ecological studies of this nature are limited in many ways and the report authors, Angus Cook, Alistair Woodward, Neil Pearce, Cara Marshall called for a stronger study design to establish more exactly any elevation in risk.
The cellular industry better hope that there really isn’t an elevated risk of cancer from using cellphones because the resulting class action lawsuits would dwarf those filed against the tobacco companies.