Cancer and cellphones: The jury's still out
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.
The Canadian arm studied people with the cancers living in the Ottawa, Montreal and Vancouver areas.
Those with cancer were compared with controls: people who use the devices but don't have the disease, to determine whether there was any link.
When the results from the British and Nordic countries were pooled, researchers found "a significantly increased risk" of both glioma and acoustic neurinoma related to mobile phone use on the side of the head where the tumour developed, according to a study update posted on the IARC website earlier this month. The Israeli wing of the study has found a "possible relation" between heavy cellphone use and salivary gland tumours in the parotid gland, it said.
But Prof. Cardis said the risks may be overstated for technical reasons as a result of the study's design. One problem is that people who have recently been shocked by a cancer diagnosis may not be accurately reporting their cellphone usage. There have also been lower rates of participation in the control group. Both factors might skew the results to make cellphones appear more dangerous.
But raising more potential concern are the Interphone findings that corroborate recent data from Sweden, one of the first countries to adopt cellphones in a big way, in 1981. Researchers there are also finding elevated rates among long- term users - about double for both glioma and acoustic neurinoma after 10 years of use.
A researcher with the Swedish studies, Lennart Hardell, professor of oncology at University Hospital in Orebro, says that in light of his findings, he recommends people "reduce exposure as much as possible - use hands-free" settings on their cellphones.
"The evidence that we have on the phones at this point is worrisome," says Devra Davis, head of the University of Pittsburgh's Centre for Environmental Oncology.
But not all experts are as worried.
One of the Canadian Interphone researchers, Daniel Krewski, a professor at the University of Ottawa, doesn't try to minimize his exposure to cellphones. "I'm personally not taking any extra precautions," he says.
Because it is now unlikely that Interphone, one of the biggest and most expensive cellphone studies - about $15-million - will settle the safety question, Prof. Davis says there may be an easy way to figure out if there is any hazard: by running a study comparing people's cellphone billings with their medical records. If industry billing records were made available, then researchers "would have the answer in a few years."
Radio wave exposure
Cellphones emit a type of energy known as radio-frequency waves.
Up until the development of cellphones, many researchers weren't worried about them.
They have been considered benign because they are much less powerful than ionizing radiation, the type produced by X-rays: radiation so energy-laden it's able to break chemical bonds and cause damage to genetic material. Exposure to it is unequivocally linked to cancer.
With radio waves being much less powerful, their worst effect has been the ability to cause things to heat up, much like a very weak microwave oven.
The Canadian regulatory exposure limit to energy from portable radio transmitters in cellphones is a maximum of 1.6 watts per kilogram. It's equivalent to a small amount of heating that can't be perceived by those using the devices.But in recent years, there has been mounting evidence that radio waves pack a biological punch.
According to Daniel Krewski of the University of Ottawa, radio-frequency radiation can influence the rate at which elements such as calcium and sodium cross cell membranes. It's also able to change the production rates of an important enzyme, ODC, or ornithine decarboxylase which is involved in regulating cell growth, among other effects.
But Prof. Krewski says that while biological activity of radio-frequency radiation is now considered proven, it's "not of known health significance."
Because the energy of radio waves drops off rapidly with distance, those worried about cellphones can reduce their exposure by using hands-free modes or ear pieces, reducing call lengths or using a land line.
Cellphone towers also give off radio-frequency radiation, but because of their greater distance from people, the exposure is much smaller than transmissions from phones themselves.
(I take exception to the last statement - many apartment dwellers and office workers live directly underneath cell towers, the towers are also built very close to and inside residential areas, exposing some people 24/7)