A controversial study holds to an earlier claim that mobile phone use does not increase a person's risk of developing a brain tumor.
The study, which was published in the British Medical Journal yesterday, argues that even after using a cell phone for more than a decade, a person's chances of getting a brain tumor are about the same as they would be without cell phone use. The study, which is an update to previous research that found no link between mobile phone use and cancer, examined the instances of brain tumors among long-term cell phone users in Denmark.
"In this update of a large nationwide cohort study of mobile phone use, there were no increased risks of tumours of the central nervous system, providing little evidence for a causal association," the study's authors write in their conclusion.
That finding, however, prompted a quick and vigorous rebuttal. After the study was published, researchers from the U.K., U.S., Australia, and elsewhere around the world said that the Denmark study was "seriously flawed" and should not be considered a definitive source for information on the risk of contracting a brain tumor after prolonged mobile phone use.
"From the way it was set up originally, this deeply flawed study was designed to fail to find an increased risk of brain tumors tied with cellphone use," Devra Davis, a cancer epidemiologist and president of Environmental Health Trust, said in a statement. "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.
"By extending an earlier analysis on the same group of cellphone users this new report provides unsurprising, biased and misleading conclusions," Davis continued. "It uses no direct information on cell phone use, fails to consider recent and rapidly changing nature and exposure to microwave radiation from cellphones, cordless phones and other growing sources, and 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."
It's that last element--leaving businesspeople out--that has caused the most outcry among researchers. But the study has also been criticized for not including cell phone data on users who might have only entered into mobile subscriptions since 1995.
"It ignores corporate subscribers (the heaviest users then) and the researchers have no data at all on cellphone use since 1995 so the extra 86 percent of the population who started to use a cellphone since 1996 were left in the 'non subscriber part of the population,'" Alasdair Philips, an expert in electromagnetic health at Powerwatch in the U.K., said in a statement.
The debate over whether mobile phones cause brain tumors has been hotly contested by those on both sides of the argument. In early July, a study from the International Commission for Non-Ionizing Radiation Protection Standing Committee on Epidemiology found that the "the accumulating evidence is increasingly against the hypothesis that mobile phone use can cause brain tumors in adults."
Less than two weeks later, a study was published in the American Journal of Epidemiology that concluded people who have used a cell phone for 11 to 15 years were just as likely to develop a brain tumor as those who have not.
But the World Health Organization said earlier this year that mobile phones can potentially cause cancer, and has listed handsets as a "carcinogenic hazard." Although the WHO stopped short of saying that there is definitely a link between cancer and mobile phones, several studies over the years have drawn that conclusion.
So, regardless of the study or the organization releasing them, at least for now, it appears there's no way to know for sure if cell phones do cause brain tumors. And with each new study, it's clear one side will inevitably try to debunk the other side's findings.