Before Professor Anthony Swerdlow began to explain the results of the Interphone study yesterday, he prefaced his remarks with something of an understatement. "This is a long-running and complicated issue," he warned.
Indeed it is, because what in effect scientists are trying to do in studying mobile phones and ill health is to prove a negative. They would like to reassure the public, if they can, that mobile phones pose no health risks, but they also know that it is scientifically impossible to say there are no risks attached to any one aspect of our daily lives.
By the time Professor Swerdlow began his explanation of the findings, a leak of the report had already resulted in newspaper headlines suggesting that half an hour a day on a mobile phone could increase the risk of brain cancer.
Professor Swerdlow explained why this was not true and why one statistical aberration within the study – the biggest of its kind – might lead some people to believe there was a risk of getting a brain tumour if you used your mobile phone regularly each day.
Over the past decade, there have been a couple of dozen studies looking at the health risk of mobile phones, in particular the risk of brain tumours. The vast majority have failed to establish an increased cancer risk, but one Swedish study did find a statistical association, which fell far short of linking cause and effect.
Establishing the risk of something, especially when the risk is very small, can be exceptionally difficult. Brain tumours are very rare and even if mobile phones increased the risk significantly, the total number would increase by only a few cases nationally.
Yet there is no evidence that mobiles do increase the risk, there is no evidence that the total number of brain tumours is increasing, and there is no evidence that an increasing use of mobile phones leads to a raised risk of brain cancer – a "dose response" seen in all other causes of cancer.
In short, there is nothing in this study showing that using mobile phones can lead to brain tumours. But, of course, this does not mean that science has answered the question we all want to know the answer to because this absence of evidence cannot yet be taken as evidence of absence.
Unfortunately, for us to get the sort of near-definitive answer we require in a risk-averse world, there need to be further studies over longer periods of time, with children as well as adults.
However, there must come a time when politicians – not scientists – decide that enough is enough, for the doubts over mobile phones to be put aside, and for money to be spent on more important matters.