AS IF caving were not dangerous enough, regular cavers are also exposed to
high levels of the radioactive gas, radon. Formed naturally by the decay of
uranium in granite, it can build up to hazardous levels in enclosed spaces.
Researchers from University College Northampton and Princess Margaret
Hospital in Swindon measured radon in a popular system of caves in the Mendip
Hills in Somerset. They found that cavers who spend just 40 hours a year
underground could receive a radiation dose of as much as 4
millisieverts鈥攆our times the annual safety limit for members of the public
recommended by the UN (Journal of Environmental Radioactivity, vol 49,
p 235).
Guides and instructors spending 800 hours a year underground could receive as
much as 120 millisieverts鈥攆ive times the safety limit for radiation
workers. 鈥淚t is important that cavers are made aware of the radiation levels so
that they can decide to restrict their activities,鈥� says Malcolm Sperrin of
Princess Margaret Hospital, who is a keen caver.
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