A Danish study that monitored 350,000 cell phone users over an 18-year period found no link between mobile phone subscriptions and an increased risk of cancer.
The new study, conducted by the Danish Cancer Society and published in published in the British Medical Journal, is actually an update of an older study that adds five years of follow-up data running through 2007. It found no increased risk of tumors or other forms of cancer believed to be associated with cell phone use, even among those who held mobile phone subscriptions for more than a decade.
The study's approach has one clear weakness, however – it looks only at records of cell phone subscriptions, and not actual cell phone usage.
Devra Davis, a cancer epidemiologist and president of Environmental Health Trust, a group that actively campaigns for warning labels on cell phones, pointed out other flaws with the study:
“In order for any study of a relatively rare disease like brain tumors to find a change in risk, millions must be followed for decades," Davis explains in a lengthy critique of the study. She added that it "excludes those who would have been the heaviest users—namely more than 300,000 business people in the 1990s who are known to have used phones four times as much as those in this study.”
The authors of the study concede that their findings cannot be considered definitive and that a "small to moderate increase in risk for subgroups of heavy users or after even longer induction periods than 10-15 years cannot be ruled out" without larger studies.
The Danish study comes just months after World Health Organization research determined that cell phones should be considered "possibly carcinogenic." The international INTERPHONE study, released last year, also found no connection between cell phone use and cancer, but was widely criticized for being partially funded by the wireless industry.