Does cellphone use increase your risk of cancer?

More than four decades after the advent of the mobile phone, scientists are still trying to puzzle out the ways mobile device use might relate to a possible increased risk of cancer.

Scientists have been trying to assess if there is a link between cellphone use and cancer risk.

“[Cellphone use] is a rapidly changing field,” says Franco Momoli, a clinical epidemiologist at the Ottawa Hospital Research Institute. “It’s not easy to know what everything means in terms of evidence in the past and how it applies today.”

There are two types of radiation: ionizing radiation, the kind on the high end of the spectrum that can damage DNA cells and cause cancers, and non-ionizing radiation, the kind emitted from cellphones that cannot break down DNA cells, but produces heat. Cellular base stations, which connect to cellphones, produce radiofrequency (RF) fields, a non-ionizing form of electromagnetic radiation.

As of now, scientific consensus has found the amount of radiation emitting from base stations is well below Health Canada’s Safety Code 6 recommended exposure levels. Recent studies from Ottawa and Montreal communities that measured RF base station radiation found exposure levels significantly lower than Safety Code 6 recommendations.

Moreover, the RF exposure for cellphone users drops off dramatically with increasing distance from the handset. For example, the difference in RF exposure for someone holding a phone against their skull is much higher than if the person is texting, browsing the Internet or using a hands-free device. Still, for several decades now, scientists have been targeting RF field exposure and its potential health effects, with particular focus on the human head.

But Momoli, whose research focuses on RF fields and brain tumours, says he’s come across no plausible theories as to why RF field radiation would increase brain tumour risk.

“The trend in brain tumours, we haven’t really seen it,” he says. “Some people say those results are consistent with a long induction time, meaning exposure today might [take] years to have an effect on risk. 25 years later, and we’re only seeing the blips in brain tumour risks of major exposures such as Chernobyl. So radiation and its interaction with tissue is a complicated field. There’s so little we know.”

But as cellphone usage becomes more ubiquitous worldwide, most governments are pushing for further cellphone studies to chronicle any potential health effects from increased non-ionizing radiation exposure.

Numerous studies have been conducted across the globe, including several in Denmark, Sweden, Norway and Switzerland. Two of the largest studies on RF radiation and cancer risk, however, are the Interphone study from 2010, and the Mobi-Kids study, which began in 2010 and is still ongoing.

Interphone’s objective was to determine whether mobile phone use increases the risk of particular tumours, and whether RF cellphone energy is carcinogenic. It involved a decade-long set of case-control studies involving 13 countries and 7,416 tumour patients, with almost twice as many control patients (those without tumours used for comparison).

The research focused on four types of tumours in tissues that absorb mobile phone RF energy the most: in the brain (glioma and meningioma), the parotid (or salivary) gland and the acoustic nerve (which connects the ear to the brain).

But like so much of the research that’s been done, the study’s findings were confusing. Results suggested only people who used their cellphones the most and longest — for at least 10 years and on an average of 30 minutes or more per day — had an increased risk of brain tumours compared to people who don’t use cellphones. But the results also suggested that for people in lower cellphone use categories, tumour risk was substantially lower than those who used regular corded phones. This would suggest that, for most people, cellphones appeared to protect against tumours.

Another major issue with the study was how accurately people could recall their cellphone use, compared to what their mobile phone records read. “Heavy users tended to overestimate their use, and light users tended to underestimate. It was a complicated pattern of possible error,” says Momoli, who was involved in the research.

Momoli is also a principal investigator in the Mobi-Kids study, an international case-control project in 15 countries to assess the potential link between brain tumour risk in young people (10 to 24 years old) and “environmental risk factors,” including the use of cellphones. Similar to Interphone, Mobi-Kids compares those who have been diagnosed with a brain tumour against a matching control patient without a tumour.

Participants are also interviewed for detailed histories of their communication technology use, including WiFi, mobile and cordless phones. Questions include what cellphone brands were used, how many calls were made and for how long. Data will be pooled at the end of the studies, which are expected to be completed in around two years.

“Two different phone models can mean two vastly different types of exposure in the brain. How long you use it is of secondary concern,” says Momoli. “So the real target is to get estimates of how much energy is being deposited into the tissues of the brain.”

When younger people hold cellphones up to their heads, Momoli says energy goes deeper into the brain that it would with adults, who have thicker bone structures and larger ears.

“That’s the whole premise of the Mobi-Kids study. Kids are using phones and they might be at higher risk,” says Momoli. “Now the evidence of that is pretty weak, but it’s plausible.”

“Weak but plausible” findings seems to be the mantra for most of what’s been done on RF field and cancer risk research up until this point. Momoli says there is still a long way to go to find clear, telling evidence.

“Somebody once said we live in an ‘electromagnetic soup.’ We’re always being inundated by electromagnetic fields from light, radio, television, and now base stations and cellphones,” says Momoli. “The relative contributions of these things is imperfectly understood, and any health effects are even less understood.”