A comparison of natural levels of gamma radiation with death rates in the UK suggested that they might contribute to up to 19,000 of the UK's 560,000 deaths a year. Exposure to high levels are linked to anaemia, heart disease, respiratory infections, diseases of the nervous system and problems at birth.

The highest levels were found in Cornwall, South Humberside, Northumberland, Tyne & Wear, West Glamorgan and Derbyshire. With the exception of Cornwall, all of these counties also had a lower than average life expectancy. The researchers suggested that life expectancy in Cornwall was kept above the national average by the relative affluence of its population.

The study was originally set up to determine whether there were any links between natural radiation and motor neurone disease. It concluded that it was unlikely that it caused MND directly, but that it might contribute to 50 of the 1,200 deaths each year. It might be that natural radiation caused changes in DNA, making people more susceptible.

The findings of this study were strongly criticised by the National Radiological Protection Board (NRPB) but it did accept that some cancer deaths were probably due to natural radiation. David Sumner, an independent radiation specialist at the University of Glasgow in Scotland, put this figure at 1,000 from gamma radiation with a further 4,000 from radon gas and cosmic rays from outer space.

Gamma radiation is caused by minute particles of natural uranium in granite.