An expert opinion has been given by John Marison- 'Can Cell Phones Really Cause Brain Cancer'? John Marison is Chief of the Division of Oncology at The Children's Hospital in Philadelphia (CHOP). Read his opinion.

"This has received a lot of press, and this is one in a series of press releases about the potential of cell phones to cause cancer. What I want to say is: There is nothing at all to be worried about. As a cancer researcher and someone who spends a lot of time thinking about what might cause cancer, I applaud the World Health Organization for pulling together a report and asking for more information and data to be able to study this. I think that the way in which that has been spun in the media -- that cell phones can cause cancer or that there is a concern among experts that cell phones cause cancer -- is overblown. What I really want to drive home is that there is nothing at all to be concerned about.

When we think about what causes cancer, one of the first questions we need to ask ourselves is: Is it plausible? Is there a realistic or even little bit of an explanation of a cause and effect? Cell phones are used very commonly; there is a concern that cancer incidences might be increasing, so it is natural to think that these devices that we spend a lot of time with these days might have a harmful effect.

For a long time, people thought that cigarettes, which became a very common part of everyday life, were not harmful and, despite some increasing concern for a long time, people denied that. So, are cell phones similar to the cigarette or to tobacco? The answer is no. Smoking causes irritation that has a carcinogenic effect, and there is a biologically plausible explanation for how smoking could cause harm.

Radio waves that come from a cell phone are low energy. Very good research has shown that it is a million times lower, literally a million times lower, than the energy that is necessary to damage DNA genetic material and cause mutation and cancer. There is no known biologically plausible way that these devices and the frequency of energy that they emit, which is the same as that which comes from the radio waves that bombard us every day as we listen to our radios, can damage DNA.

Could there be another reason? There is no reason that can be surmised, and, more importantly, there have been dozens and dozens of studies in test tubes, in animal models, and -- most importantly -- in human beings that have all refuted the hypothesis that these things can hurt you.

The World Health Organization evaluated a very, very large study that looked at thousands and thousands of cell phone users. There was the inability to definitely say that these devices were not associated with cancer in this very large group of patients because it is a complicated thing to study and relied on phone interviews and not actual real observations. The World Health Organization released a cautionary statement to say that we just need more information. That does not mean that cell phones cause cancer. There is nothing that we might need to change in our everyday lives, and I applaud the effort to get more data, but we have nothing to be concerned about".