Neurosurgeon Charlie Teo is, to many of his patients, the “angel” who cuts where other surgeons fear to go. He feels strongly about the possibility that using mobile phones might increase the risk of brain tumours. He too often sees the coincidence between the ear to which a mobile phone has usually been held and a tumour in the underlying brain.
Other causes of cancer have been identified through such coincidences. But coincidence doesn’t make association and association doesn’t mean causation. Teo recognises this and wants more and better research.
Stepping back for a moment, what is the evidence that exposure to radio waves when using a mobile phone causes cancer?
All relevant evidence published or accepted for publication up to June last year was reviewed by a multi-disciplinary expert panel convened by the International Agency for Research on Cancer, the World Health Organisation’s specialist cancer body. The experts’ bottom line was that RF-EMF (radiofrequency electromagnetic fields, or radio waves) is “possibly carcinogenic to humans”; that is, they possibly cause cancer.
There was some evidence in support of this conclusion from each of epidemiological studies in humans, experimental studies in whole animals and experiments in other biological systems, mainly cells.
Clearly, on this assessment, the scientific evidence linking mobile phone use to brain tumours is not strong. It is, nonetheless, easy to understand why Charlie Teo feels frustrated when the CEO of the Australian Mobile Telecommunications Association claims “expert opinion and the weight of evidence showed there were no adverse health effects from mobile phone use”.
Teo has rightly drawn attention to the major weakness of most epidemiological studies: they rely on users’ memory of how much they used their mobile phone. That memory is inaccurate and may be biased. Teo argues that this weakness “would be addressed definitively if the telcos would give access to phone usage records”.
He’s right again, and, happily, research based on personal recall (of information that telcos don’t collect) and mobile phone use records is now being done, with the European COSMOS study the best example.
This very large prospective cohort study (more than 160,000 participants have been recruited and the target is 250,000) is recruiting people 18 years and older, asking them about their mobile phone use to date and for their consent to ongoing access to their mobile phone use data from network operators.
At least 25 years of follow-up are planned. Associations with disease risks will be studied by linking cohort members to disease registries, and associations with symptoms such as headache and sleep quality will be evaluated by comparing responses to baseline and follow-up questionnaires.
It is studies such as this that will ultimately settle the question of mobile phone safety; but this answer is probably a decade or two away.
In the meantime, rigorous analyses of trends in brain tumour incidence in those who have used mobile phones most – young and middle-aged adults – are reassuring. There is, as yet, no upturn in brain tumour rates that can be plausibly linked to increasing use of mobile phones.
However, there are still comparatively few people who have used mobile phones heavily for more than ten years, and cancers can take a long time to develop after causative exposure begins. So the tumour trend space is one we must keep watching.