But how compelling is the evidence supporting such steps? Do we really need to change our behaviour, given the convenience of mobile communication? Should the telecommunications industry be compelled to incorporate EMR-shielding into mobile phones when this could compromise the technology's efficacy?

The arguments for and against intervention are now being presented to the medical physics community (Med. Phys. 35 5203). The point/counterpoint feature addresses the proposal: "There is currently enough evidence and technology available to warrant taking immediate steps to reduce exposure of consumers to cell-phone-related electromagnetic radiation."

The resolution is supported by Vini Khurana, staff specialist neurosurgeon at the Canberra Hospital and associate professor of neurosurgery at the Australian National University, Canberra, Australia. Having set up a web page devoted to mobile-phone risks (www.brain-surgery.us/mobilephone.html), Khurana is keen to communicate his precautionary message. "The physics community should be made aware of the emerging long-term epidemiological studies that point to a link between long-term cell-phone use and brain tumours," he told medicalphysicsweb.

His adversary in the debate is John Moulder, professor of radiation oncology and director of the Center for Medical Countermeasures against Radiological Terrorism at the Medical College of Wisconsin (Milwaukee, WI). "When patients ask radiologists and radiation oncologists about mobile phones, they generally turn to their medical physicists for answers. So medical physicists need to know more about issues like this than they can get from the mass media," Moulder said.

For and against
The opening statements and rebuttals from both participants focus on the strength and validity of the available scientific evidence. Khurana draws on an as-yet unpublished meta-analysis of 11 peer-reviewed epidemiology studies involving long-term (10 years or more) mobile-phone users, and an online BioInitiative Report written by an international working group of scientists, researchers and public health policy professionals.

Moulder questions these sources and cites conclusions from a series of peer-reviewed publications. Khurana parries by pointing to data that were left out of the peer-reviewed analyses being quoted by his sparring partner.

According to the epidemiological analysis presented by Khurana, mobile-phone users have a statistically significant higher chance (roughly twofold) of developing a glioma or acoustic neuroma on the side of the head preferred for phone use over a duration of prolonged use (at least 10 years). Moulder asserts that the epidemiological evidence for a causal association between cancer and RF energy is weak and unconvincing. He additionally notes that a causal link appears to be implausible from a biophysical point of view, and is not supported by animal studies.

Khurana highlights the conclusion of the BioInitiative report that further deployment of power lines, mobile phones and mast and WiFi systems should be subject to new safety limits and regulation. The need for such measures is refuted by Moulder, who notes that EMR exposure limits could reduce the range of mobile phones and increase the number of "dead zones".

So what's to be done? Individuals who are concerned about potential EMR damage can already take steps to limit their exposure. This point is made by both authors. Precautionary strategies include fitting a hands-free kit, using a landline instead of a mobile phone when one is available and avoiding lengthy calls.

Yet more studies may be needed to settle the debate over technological intervention, though. Although no animal studies have shown a significant link between cancer and EMR exposure, this question could be resolved in a larger research project, according to Moulder. "Such a study is underway in the US, under federal government funds. Answers from that study are probably at least three years away," he said.

A prospective study that followed groups of mobile-phone users and non-users for decades could strengthen epidemiological analyses, Moulder said. He believes that most epidemiological studies are inherently weak because they rely on individuals' memory of past mobile-phone usage.

Khurana agrees that there is scope to strengthen the weight of epidemiological evidence. "Any new study should look at heavy cell-phone users, for example, corporate users, for over 10 years, and compare this group's tumour incidence to minimal or rare users," he said.