The widely held view that even low levels of radiation damage health has no basis in hard science, a leading expert has said.
Radiation can cause serious health problems
Professor Zbigniew Jaworowski, former chairman of a United Nations committee on radiation effects, believes low levels may even be beneficial.
He told the BBC Today programme: "Low levels of radiation are probably essential for life itself."
However, the National Radiological Protection Board rejected the claim.
The standard measurement of radiation is set in terms of milliSieverts (mSv) per year. In the 1920s, the maximum dose regarded as safe was 700mSv.
By 1941, it was reduced to 70. By the 1990s, it became 20 for people exposed to radiation as part of their job, and 1 mSv for the general population.
Some people believe the maximum dose should be lower still.
Professor Jaworoski, now based at the Central Laboratory for Radiological Protection in Warsaw, Poland, said the background level of radiation was around 2.5mSv.
However, in some parts of the world background levels were as high as 700-800mSV.
He said a study in the Iranian city of Ramsar had shown people routinely exposed to 250mSv came to no harm.
"There were many generations of people living in these houses, and there was no evidence of any harm. One of the gentlemen living there was more than 100 years old."
Professor Jaworoski said the view that low levels of radiation were harmful was little more than an "administrative assumption".
His view was echoed by Lord Dick Taverne, chairman of the pressue group Sense About Science.
Writing in Prospect magazine, he said: "Far from safeguarding our health, current safety standards will almost certainly increase the incidence of cancer.
"A low dose of radiation seems to stimulate DNA repair and the immune system, so providing a measure of protection against cancer."
Dr Michael Clarke, of the NRPB, said the scientific consensus was that low level radiation probably did pose a small risk to health.
"The consensus is that every little bit does a little bit of harm, and you extrapolate from what you can see at high doses, down to low doses.
"A small exposure gives you a very small risk. Maybe over the years more science will show that DNA repair mechanisms are stimulated by low level radiation, but it is not clear at the moment."
However, Dr Clarke accepted that there was little hard evidence that low radiation levels do damage health, but he said it was difficult to tease out the effect from all the other potentially damaging factors.