Does using a mobile phone give you brain cancer? There was no answer to that question available from last night's BBC Panorama documentary on possible health risks from mobile phones.
No scientist is in a position to confirm that theory, not on the basis of the evidence available so far. Nor were the scientists quoted on the programme, Dr Lennart Hardell, from Sweden and Dr George Carlo, from the United States, making such a definitive link. They referred to two studies looking at the potential for health effects caused by the microwave radiation given off by mobile phone handsets.
Both scientists rightly urged caution and further study. They did not say if you use a mobile, you will die. Scientists have been looking at the possibility of risks for some years, but so far nothing conclusive has been discovered. The danger of exposure to intense radio waves is itself nothing new and is well documented, however. If you are too close to the source of the radiation then the waves have the potential to do harm, but as with toxic chemicals, the poison is in the dose. The question raised in last night's documentary is just that simple: does the radiation dose given off when using a mobile do you harm?
The mobile phone companies were yesterday quick to deny any risks, but they would say that, wouldn't they? Having installed hundreds of millions of pounds worth of transmission equipment, they don't want customers switching off or even reducing call duration, as suggested by Drs Hardell and Carlo. Like the cigarette companies, who still argue there is insufficient proof that smoking causes early death, the mobile companies argue there is no proof of risk. "If you look at the totality of evidence for any link between mobile phones and any human health effects, there is no cause for concern," according to the director of the Federation of the Electronic Industry in the UK, Mr Tom Wills-Sandford.
The question for the consumer is who do you trust. Who is right? And there is the even more difficult question, are we in a position to be able to answer these questions at all, or by extension, is there anything that we can do that carries no burden of risk.
Last night's documentary made much of Panorama's own analysis of the strength of radiation emitted by various brands of mobile phone, work conducted for it by the National Physical Laboratory. Some brands, it noted, emit 20 times more radiation than others, a meaningless statistic, however, because even the worst phone was more than 20 times below the legal safety limit for mobile radiation, as applied in the UK.
A far more appropriate question would have been why the UK limit is five times higher than that applying in the rest of Europe and is six times higher than that used in the US. Equally, why should there be any doubt about the safety level, why isn't it the same in all countries if we know so much about the safety or lack of it pertaining to mobile phone use?
This is why the two quoted scientists, or indeed any credible scientist, would first urge caution and then look for more research, more data that would answer the simple consumer question, is it safe. "The science we have today clearly shows that this is not black and white. That we have moved now into a grey area that suggests that there could be a problem that needs to be looked at very, very carefully," said Dr Carlo. "That grey area needs to be acknowledged."
Acceptance of a grey area is tantamount to saying, we don't know, we are trying to find out but we don't know. Scientists view that knowledge gap as a challenge and look for more research, while phone suppliers argue that the gap means that there is no proof.
This does not leave the consumer powerless. The best bet is to take some precautionary steps such as using a hands-free phone option or reducing the amount of time spent on the mobile. The next is to disregard the two poles in this argument, those that say there is no risk and those that say there is a terrible risk.
There are an estimated 300 million mobile phone users around the world. If mobile use was truly dangerous then with such a large sample it should have been very easy to decide if there is a major risk. On the other hand, the risk might be small and well hidden, making it very difficult to reach a conclusion.
It is then for each consumer to reach a decision on whether the risk is worth it. There is a clear and well-defined risk to driving the car to work each day, but we do it and ignore the risk. Electricity kills dozens of people each year but no one is saying that it should be banned from our homes. Each summer we wait for hot weather and a chance to barbecue but disregard the risk of food poisoning, which if severe can kill.
And as the consumer wrestles with the risks, scientists will continue their study of the dangers and attempt to push the balance of opinion in one direction or the other, wherever the truth lies.