Waves and waves of electromagnetic radiation streaming from a device positioned within inches of sensitive brain tissue. Sounds nasty, right? In fact, concerns about the connection between cancer and cellular phone use has led to a series of advisories and recommendations for hands-free attachments. Is there any substance to these concerns, poses the Montreal Gazette?

How popular are cellphones?

Since the introduction of cellphones in the early 1980s, their use has risen exponentially, to levels of about one phone per adult in some countries. In 2006, there were almost 17 million wireless subscribers in Canada, cutting across all income groups.

It's not just adults who can't resist the call; the increasing use of cellphones among children a makes an examination of possible health risks especially important.

What are people worried about?

Since their inception, cellphones have been a subject of debate, controversy -and conflicting scientific evidence. As far back as the 1930s, scientists have been concerned about potential damage caused by high-frequency electromagnetic fields (EMFs) -the kind that might be emitted by power lines or microwaves, for example. The concerns stem, in part, from similar but much higher energy radiation in the form of ultraviolet rays or X-rays that have been established to be carcinogenic. But when cellphones were introduced, little direct information on health risks was available, and the presumption was that the devices were safe. Since the radiation passes directly through the brain when phones are used without a hands-free device, the risk of brain tumours now is the chief worry.

Debate and controversy

The messages from government and health agencies have been inconsistent. On the negative side, in 2008, a health advisory from the city of Toronto -believed to be the first of its kind in Canada -suggested that teenagers and young children limit their use of cellphones to avoid the potential health risks of EMFs. On the reassuring side, the World Health Organization and the U.S. Food and Drug Administration (FDA) currently report no increased health risk associated with EMFs. And a National Cancer Institute program reports that, despite the dramatic increase in cellphone use, occurrences of brain cancer did not increase between 1987 and 2005; making it highly unlikely that cellphones are leading to an increased risk, at least in the short term.

 The study

CardisEetal. Brain tumour risk in relation to mobile telephone use: results of the INTERPHONE international case-control study. International Journal of Epidemiology May 17, 2010.

What kind of study was this?

INTERPHONE is the largest case-control study of mobile phone use and brain tumours ever undertaken. In a case-control study, researchers ask patients who have been diagnosed with brain cancer -the cases -about their use of cellphones while recruiting a number of otherwise similar healthy individuals -or controls -who do not have brain cancer and query them about their use of these devices.

It was conducted in 13 countries and involved more than 5,000 subjects, including more than 2,500 victims of brain cancer. Two kinds of brain cancer associations were examined: the possible connection with meningiomas, a generally curable kind of brain cancer, and with gliomas, a more malignant and life-threatening cancer. Hoping to understand the risks of long-term use, INTERPHONE recruited more mobile phone users -those who had used cellphones for at least 10 years -than any other study on this subject.

What were the results?

They were actually very surprising. Cellphone use was associated with a reduced risk of both types of brain cancer. Longer periods of cellphone exposure, in terms of time elapsed since starting to use a mobile phone, were also not linked with cancer risk. There was a suggestion, however, that cellphone users with several hundred hours of exposure might be at increased risk for the more dangerous gliomas as opposed to the other tumour of interest, meningiomas.

Can we believe the results?

It is not likely that these results are valid as presented. For instance, it makes no sense to believe that cellphones protect you from brain cancer and if those results are wrong, the single positive finding, related to high rates of use and brain cancer, should also be viewed with suspicion. The authors themselves suggest that there were biases in their study that led to these unexpected findings. To pass the test for an association between a potentially harmful environmental factor and an illness, there needs to be a biologically plausible connection between cellphones and brain cancer, as well as a connection between increasing exposure to electromagnetic radiation, or doses, and the risk of brain cancer; both of which are lacking in this example.

Why did they do the study if the results are unreliable?

Case control studies have played a crucial role in our understanding of what is harmful to our health. The connection between smoking and lung cancer, as well as the role of thalidomide, a pregnancy hormone in common use many decades ago, which resulted in disfiguring birth defects, came from this type of study; but the associations in those cases were far stronger than what is being suggested here. In other words, if a study like INTERPHONE was unable to connect cellphones to brain cancer, it's unlikely that further research will find any meaningful increase in risk.

What's the bottom line?

Fear mongering and paranoia will always raise doubts and concerns about this subject. As a result, it is not likely to be put to rest in the popular press and in some scientific circles anytime soon. However, if you're willing to believe insight from best available research evidence, you need not worry about developing brain cancer from using your cellular telephone; so feel free to make that call.

This material is designed for general educational purposes only and does not pertain to individual cases. It should not replace necessary medical consultations.