What to know about cellphones and cancer
When the World Health Organization — the world's leading health authority — declares that cellphones may cause a rare but often deadly form of brain cancer, consumers take notice. Making sense of the declaration is much trickier.
Photograph by: David Hancock, Getty Images
When the World Health Organization — the world's leading health authority — declares that cellphones may cause a rare but often deadly form of brain cancer, consumers take notice. Making sense of the declaration is much trickier.
Here's a primer on the new classification by the WHO's International Agency for Research on Cancer.
What is the new designation and how did the agency made it?
IARC's working group waded through the exposure data from cancer studies involving humans and experimental animals. The 31-member group, including two Canadian researchers, this week declared that radio-frequency electromagnetic fields from cellphones could be "possibly carcinogenic to humans" based on the increased risk forglioma, a malignant type of brain cancer, associated with wireless phone use.
What does that mean?
This category is used when there is limited evidence of carcinogenicity in humans and less than sufficient evidence in experimental animals. (Other categories in IARC's monographs include the more alarming "carcinogenic" and "probably carcinogenic." Less worrisome categories include "not classified as to its carcinogenicity" or "not carcinogenic.")
"It doesn't demonstrate or prove or absolutely condemn radio-frequency fields as causing cancer, but it's a first level of concern," says Jack Siemiatycki, an epidemiologist from the University of Montreal and a member of IARC's working group.
Daniel Krewski, the director of the McLaughlin Centre for Population Health Risk Assessment at the University of Ottawa, says: "This is quite a significant determination. 'Possibly carcinogenic to humans' does not mean it's absolutely sure that that's the case, but enough evidence has accrued that we should be concerned and do additional work to clarify the extent of the risk if one actually exists." Krewski also contributed to IARC's massive cellphone study.
What else is classified as "possibly carcinogenic"?
There are 266 agents classified in this group. Two food products are on the list: coffee (urinary bladder) and pickled vegetables. Other items deemed "possibly carcinogenic" include certain dry-cleaning chemicals, pesticides like DDT, diesel fuel, engine exhaust, lead, nickel and vinyl acitate.
What is the science behind all this?
Multiple studies were considered, but epidemiological data from IARC's massive INTERPHONE study, led by a Canadian researcher and involving 13 countries including Canada, were thought particularly relevant. The largest study ever conducted on cellphone use and brain cancers found no overall increased risk of cancer. But it did report that the heaviest cellphone users had a 40 per cent higher risk of a particular cancer: glioma. The data were collected up to 2004 and the highest category of heavy users was defined at that time as spending an average of 30 minutes per day on a cellphone over a 10-year period. (Cellphone use these days, of course, can run much higher than 30 minutes a day.)
What does a 40 per cent increased risk of glioma mean? Krewski concedes that 40 per cent "sounds high," but noted that it applies only to long-term, heavy users of cellphones, not the entire population.
As well, glioma rates normally vary by age, gender, region and other factors but are generally in the range of three to five cases per 100,000 population. Assuming that two-thirds of the Canadian population uses a cellphone, and only 10 per cent are heavy users, the increase would be hard to quantify in the general population.
What are the limitations of the science?
The University of Southern California's Jonathan Samet, chairman of IARC's working group, says there are "acknowledged gaps and uncertainties" in the current research, including the INTERPHONE project. In addition to a low participation rate, he says the INTERPHONE studies relied on people's recollections of cellphone use over the years, which he calls "inherently imperfect."
So are the data still valid?
Tumours can take 10 to 30 years to develop after the initial exposure, but cellphones have only widely been used since the 1990s. And the INTERPHONE data, collected until 2004, preceded the recent explosion of cellphone use, when consumers began dropping land lines altogether in favour of cellphones.
"Of course, as use patterns continue to grow, we can anticipate an ever larger population that is exposed for longer and longer," says Samet.
What's next?
Everyone agrees more research is needed. After that, things are muddy.
Siemiatycki says the classification "calls for attention to be given to the problem," but he's less definitive about whether that means industry, health agencies and governments should take action at this stage.
"I'm not really competent to make that call. It's a public health issue at that point," he says.
What is Health Canada saying?
At this stage, it's not conceding any increased danger.
"Health Canada's advice to Canadians remains the same. As long as exposures respect the limits set in Health Canada's radio-frequency (RF) exposure guidelines, the department has no scientific reason to consider exposure to low-level radio-frequency fields, such as those from cellphones or Wi-Fi, dangerous to the public," it says.
What should Health Canada should be saying?
Siemiatycki says he'd like to hear a change in tone and see action on the file.
"I'm not sure what they would have said (before the classification), but I guess today they would have to say they're really doing it, that they're really looking into it. They should either stimulate additional research or they should look at preventive strategies that might not be disruptive to people or to society, or to give warnings, I'm not sure. But they would need to look at this possibly in a more serious way than they did" before IARC's announcement this week.
Should I stop using my cellphone?
IARC isn't going that far, but director Christopher Wild says that, "given the potential consequences for public health of this classification and findings," additional research on long-term, heavy-use of mobile phones is vital. And "pending the availability of such information, it is important to take pragmatic measures to reduce exposure." Wild suggests using texting and hands-free devices or ear pieces, rather than ditching the cellphone altogether.
Should I take steps to minimize my risk?
It's your call, says Siemiatycki.
"People can respond to this according to their personal levels of concern, how they react to these kinds of possible hazards in society. So many things that we do carry some risk, whether it's driving on highways or whatever, and we make decisions constantly about risks that we're willing to take or not willing to take. For the time being, for the individual user, anyone who is concerned about this — and it's not unreasonable to be concerned about this — can have options for reducing their exposure to radio-frequency fields from mobile phones. The easiest is to use hands-free devices," said
Krewski says this makes sense. "Well, I think at this point, once the International Agency of Cancer Research identifies an agent as possibly carcinogenic to human, I don't know if we want to wait for the final definitive science to accrue. I think we should be a little bit careful. "
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