Compensation claims for an asbestos-related disease could cost billions of pounds, a court was told on Monday.
Ten test cases of people with pleural plaques - scars in the linings of the lungs caused by asbestos exposure - are being heard in Manchester.
But insurance firms are trying to block those with the condition from claiming damages for the disease altogether.
Claimants say the plaques rarely affect daily life but cause anxiety, and leave them susceptible to other illnesses.
They add that patients who know they have been exposed to asbestos could therefore contract more serious diseases in the future, such as mesothelioma, a terminal cancer of the lining of the lungs.
But insurance firms, which are thought to pay out £25m a year to sufferers, claim that the plaques are not injuries and that compensation should be stopped.
Antonio Bueno QC, representing one of the insurance firms fighting damages claims said "the figures involved are monumental".
'Risk of anxiety'
As well as thousands of existing cases, Mr Bueno said it was estimated that
the "numbers of people who have plaques who may not have come forward is
probably in the region of half a million".
It meant that the sums involved could "run into billions of pounds".
"Shorn of their trimmings, these claims are claims by the worried well," he said.
A great many people, "who in reality have nothing wrong with them at all",
were being compensated for harmless medical conditions "purely in respect of risk and anxiety".
'Markers of exposure'
Frank Burton QC, for the claimants, told the court last month that pleural plaques were "a marker of asbestos exposure" and "set time running" for sufferers.
He said: "Pleural plaques themselves do not cause conditions such as mesothelioma but are markers of asbestos exposure.
"A claimant told that he has a plaque feels worried and feels anxious.
"He has been told he has a condition and has been told that the fact that he has a plaque means that he has had enough asbestos exposure to put him at risk from those other diseases.
"The concern is an obvious one. It is a deterioration of health and a fear of
Typical awards for pleural plaques are £5,000, with the right to return to court if more serious asbestos-related illness occurs, or £10,000 on a full and final basis.
The High Court judge hearing the case is expected to reserve his judgment at the completion of legal