Almost everyone who uses a cellphone probably has a secret worry: Is it safe to place a small radio transmitter right next to my brain?
The most exhaustive study to date investigating whether mobile phones pose any risk is nearing completion, but the research, under way for almost eight years, may not settle the question.
The study, known as Interphone and organized by the International Agency for Research on Cancer, a United Nations watchdog, has investigated rates of four cancers found in the head and neck area in cellphone users from 13 countries, including Canada, for clues on whether the technology is dangerous.
The verdict: There is a hint in the data that cellphones may cause an elevated rate of brain tumours for long-term users of 10 years or more.
But it isn't clear whether the effect is real or the result of a design flaw in the study.
The researchers - about 50 from the various countries - have been arguing for the past 18 months over what the findings mean and how to explain them to the public. About one-third of the researchers are convinced there is a risk from using cellphones, about one-third give the devices a clean bill of health, and the remainder fall between the opposing camps, according to Louis Slesin, editor of Microwave News, a New York-based publication that tracks research into the biological effects of radio waves.
The study's lead author, Canadian epidemiologist Elisabeth Cardis, says the researchers have been trying to resolve their differences of interpretation and deal with the complexity of their findings, which are based on the study of about 6,400 cellphone users with cancer. She said the study is almost ready to be submitted to a peer-reviewed science journal, but couldn't offer a date when it would be made public.
"At this point, I don't know whether there is a real risk or not," said Prof. Cardis, who is based at the Centre for Research in Environmental Epidemiology in Barcelona and is an affiliated scientist at the University of Ottawa. "It's extremely important that we find out ... the correct answer, which is why we've spent a lot of time [on this] over the last year and a half."
With an estimated 3.3 billion cellphones in use worldwide, including many owned by teenagers and children - who may be more susceptible to cancer-causing agents - settling whether cellphones are safe has become an urgent public health priority.
But cellphone users can be forgiven for being a tad confused.
In May, the Toronto Public Health department recommended that children, especially preteens, use land lines whenever possible and limit the use of cellphones, contending that the safety of the phones has not been proven.
Yet other respected bodies dismiss such concerns. Health Canada says "there is currently no convincing evidence" cellphones cause serious health effects, such as cancer, according to its Web posting on the issue.
Public attention on the possible cellphone-cancer link also rises when prominent people, such as U.S. Senator Edward Kennedy, are diagnosed with brain tumours. He has a type of cancer that is being investigated in the Interphone study.
With experts so divided, there were hopes the Interphone study would lay the safety debate to rest.
The study, which began in earnest in 2000, is looking at four cancers that could have a connection to cellphones because they are found close to where radio waves from the devices would be absorbed in the body.
They are: glioma, an often fatal type of brain tumour (and the same kind that has stricken Mr. Kennedy); meningioma, a slow-growing, often benign, brain tumour; acoustic neurinoma, a cancer found in the inner-ear area; and salivary gland tumours.
These cancers are uncommon, so if there is any link to cellphones, the number of cases being caused by technology would be low. Breast-cancer incidence, for example, is about 16 times higher than brain tumours among Canadian women.
Because the cancers under investigation are rare, the researchers looked at rates across more than a dozen countries - including Japan, German, Britain and Australia - to get results that offered more chances of finding an effect.
