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Do we really know enough about cellphones causing cancer? Some answers to common questions about how mobile phone radiation affects us.

tech reviews Updated: Jun 11, 2011 22:51 IST

The debate about cellphone safety was reignited yet again last week when the World Heath Organisation (WHO) declared that it was “possible” that the phones could cause cancer. This is the first time a major health organisation has suggested such a link, and it was promptly disputed by many scientists, who have been saying for years that there is scant evidence to suggest this and that it is biologically implausible. Here are some answers to common questions about the issue.

What is the source of the latest claim?
The International Agency for Research on Cancer, which acts as an advisor to the WHO, has evaluated more than 900 factors that may contribute to cancer, assigning each of them to one of five classification groups. It has found that 107 are carcinogenic to humans, including asbestos, estrogen and tobacco, and 59 are “probably carcinogenic,” including the human papillomavirus linked with cervical cancer and night-shift work.

In addition, 266 agents — including certain industrial chemicals, coffee and now cellphones — are “possibly” carcinogenic. The panel has been unable to reach a conclusion on 508 agents, calling them “not classifiable”; these include chlorinated drinking water, fluorescent lighting and tea.
Only one — a nylon-manufacturing chemical found in drinking-water supplies — was declared “probably not carcinogenic.”

What is the cancer threat based on?
Cellphones give off a weak form of energy called non-ionising radiation, and the WHO panel said it performed an exhaustive review of numerous studies of this type of radiation in animals and humans.
The human studies are all observational, showing only an association between cellphone use and cancer, not a direct causal relationship. Some of the research suggests links to three types of tumours: cancer of the parotid, a salivary gland near the ear; acoustic neuroma, a tumour that essentially occurs where the ear meets the brain; and glioma and brain tumour.

All these tumors are rare, so even if cellphone use does increase risk, the risk to any individual is still very low.
The largest and longest study of cellphone use is called Interphone, a vast research effort in 13 countries, including Canada, Israel and several in Western Europe. The results, published in The International Journal of Epidemiology last year, found no overall link between cellphone use and brain tumors. But the investigators reported that study participants with the highest level of cellphone use had a 40% higher risk for glioma.
Another study, in The American Journal of Epidemiology, published data from Israel finding a 58% higher risk of parotid gland tumours among heavy cellphone users.

If the research has found “possible” links between cellphones and cancer, why do scientists dispute that?
The research is plagued by methodological problems. Over all, the Interphone study suggested that cellphone users are less likely to get cancer. Nobody believes that cellphones protect you from cancer, so the finding is considered an anomaly, attributable to biases and errors in the data. Critics say you can’t pick and choose. If one finding must be dismissed because of faulty data, then so must the others.

Moreover, if cellphones caused brain tumours, we should have seen a worldwide increase in brain tumors pandemic as the phones became ubiquitous. “If you look at brain cancer around the world over 25 years that cellphones have been in use, there’s no suggestion at all of any increase in rates,” said Dr Meir J. Stampfer, a professor at the Harvard School of Public Health and a consultant to the cellphone industry. “This is not a health risk.”

But cellphones do emit radiation. Doesn’t radiation cause cancer?
The non-ionising radiation given off by cellphones is too weak to break chemical bonds or damage DNA. Scientists have said repeatedly that there is no known biological mechanism to explain how it might lead to cancer or other health problems.

But this year, a US National Institutes of Health finding showed that less than an hour of cellphone use can speed up brain activity in the area closest to the antenna. The study offered a hypothetical mechanism for harm from low levels of non-ionising radiation: Perhaps it sets off free radicals or an inflammatory response in the brain.

What about the internet video showing cellphones popping popcorn?
In the video, four cellphones are pointed at a pile of kernels that start popping. It’s just a viral marketing campaign by the maker of Bluetooth headsets.

Are Bluetooth earpieces safer than putting a cellphone to the ear?
Bluetooth is a technology that allows electronic devices to communicate wirelessly. To do so, the device emits very low levels of radiation. Nobody has conducted research looking at their health effects. Even though the device emits less radiation than a cellphone, it goes directly inside the ear, closer to the brain. Short of not using a cellphone, the lowest exposure would come from using the speaker phone or a wired headset or ear buds.

That said, any risk from the electromagnetic fields emitted by a Bluetooth device is negligible, according to William G. Scanlon, professor of wireless communications at Queen’s University Belfast in Northern Ireland.

If everyone says the risk is low, what’s all the fuss about?
But it’s important to remember that all of the people studied so far began using cellphones as adults. With an entire generation having now been exposed to cellphones since childhood, nobody knows the health effect of a lifetime of exposure.

“We’ve hit the point where children are going to use a cellphone or something like a cellphone for most of their lives,” said Dr Jonathan Samet, a professor of preventive at the University of Southern California and the chairman of the WHO panel that suggested the cellphone-cancer link. “We do need to understand if there is a risk of cancer or anything else.”